Abstract: The growing attention of people to aesthetics has led to a greater demand for dental whitening treatments. Several solutions can be utilized to obtain the desired visual whiteness of teeth but, according to literature, at-home supervised treatments are the standard in dental bleaching. They require soft plastic trays to contain a whitening gel, with active chemical agents, and keep it in contact with the patient’s teeth. The fitting, comfort, and tightness of trays play a fundamental role in the treatment. Any gel leakage can compromise the effectiveness of the treatment and damage soft tissues. Commonly, the trays are ready-made or based on physical dental impressions and manually modified by the dental technician. These procedures have low repeatability and do not always ensure high accuracy. This work presents an automatic digital algorithm to design customized whitening trays. Starting from a digital scan acquisition of the patient’s dental arches, it generates the 3D models of the bespoke trays, in approximately two minutes per arch, ready to be produced by additive manufacturing and thermoforming technologies. The evaluation of the method involved 20 patients. The results emphasize that the custom trays were comfortable and ensured high levels of tightness and fitting.
Keywords: automatic product design | custom teeth trays | dental whitening | digital process
Abstract: This work aims at the development of a streamlined and robust CAD procedure to design load-bearing implants. The methodology used to reach this result is explained in the paper: 3D digital anatomy reconstruction of defective structures of the patient is performed with the help of a statistical shape model; subsequently, a CAD modelling tool based on implicit modelling (i.e., nTopology) is used to implement a repeatable semi-automatic procedure that can be performed by a competent user with little effort and limited manual operations. Once that the main shape of the implant is defined, lattice geometries are generated to improve mechanical properties of the implant. The procedure requires as inputs the reconstructed anatomy of the patient and a series of clinical indications on the type of implant that needs to be designed. The paper discusses the development of the whole procedure; achieved results, which include the application of the whole framework on multiple case studies, are presented. The procedure allows the design of a whole implant in 20 minutes circa.
Abstract: The huge possibilities generated by the introduction of rapid prototyping techniques in the medical field has paved the way for collaborations between physicians and engineers to produce personalized medical devices, tailored to the specific anatomy of the patient. Specifically, in the field of autologous auricular reconstruction, i.e. the reconstruction of the external ear using the patient's costal cartilage, the authors worked towards the development of new patient-specific intraoperative devices, to support the surgeon during the procedure. The surgical guide design was then supported by the development of automated techniques for their modelling. In this work, a new hybrid technique for the CAD modelling of surgical guides is proposed. The idea is not to totally eliminate the intervention of the physician in defining the shape of the surgical guides, but rather to simplify their interaction with design tools. The proposed method is based on the straightforward adaption of a two-dimensional template developed by evaluating various auricular biometric parameters to approximate ear structure. The template is coupled to a parametric automatic procedure that generates the surgical guides' CAD model. The template was created outside of commercial CAD modeling software packages to make the procedure more accessible, and it is managed using a well-designed graphical user interface. With specialized questionnaires to evaluate the surgeon's satisfaction, the interface was put to the test, and the results were positive.
Keywords: 3D Modelling | Autologous Ear Reconstruction | CAD | Microtia | Personalized Medicine | Reverse Engineering
Abstract: The design of a sailing yacht is mostly based on the traditional design techniques of trial-and-error which takes time and requires iterative corrections to reach the final result. Moreover, several design teams with different and complementary expertise are required. If the standpoint is the one of the designs of a pleasure yacht, most of the activities can be solved through the related standards. While, concerning regatta’s yacht, more deep investigations become mandatory and intensive application of digital design instruments is now a common practice in modern yacht design. In this paper, a parametric procedure has been set up aimed to design and numerically compare sailing hulls performances. The hull shape design follows the classical approach based on the definition of the main curves frame and the generation of a parametric surface. Preliminary information about the hull resistance can be quickly obtained with a dedicated module of the software. Once a satisfactory shape has been modeled, detailed investigations can be automatically executed with commercial fluid dynamics software. The procedure has been successfully applied to the design of a new boat belonging to a specific class-called 1001VELAcup R3- which is two people racing dinghy designed according to a box rule with limitations on materials, dimensions and total sail area. The availability of experimental data suggested the numerical investigation about the influence of the hull geometry on the sailing performances.
Abstract: Design For Assembly (DFA) aims at improving product design facilitating assembly phases via the application of evaluation metrics and design guidelines. However, DFA analyses are usually performed manually and the adoption of supporting tool is poor. This paper investigates the application of algorithms allowing to extract from CAD assembly models the required data to perform automated DFA analyses, thus providing a tool to support designers’ everyday works. In particular, attributes from geometric feature recognition algorithms, solids properties and assembly parts’ semantics are leveraged and mapped to the parameters required to accomplish DFA evaluations. The proposed approach is illustrated on a 3D printer for home use. At first, a manual DFA analysis has been performed on the product identifying product BOM, components properties, assembly cycle and times according to models in the literature. Then, the CAD model of the printer has been processed with some geometric algorithms to verify the possibility to extract the required data to be used as input to the DFA analysis. The test case has demonstrated the feasibility of the approach, even if some design considerations and improvement directions still need the critical evaluation of the designer.
Keywords: Assembly semantics | Design For Assembly | Feature recognition | Part recognition
Abstract: Lattice structures are receiving a renewed interest in many areas such as biomedical and industrial fields, due to the capabilities of additive manufacturing technologies which allow for the fabrication of very complex shapes. Currently, several methods and tools are described in the scientific literature and some commercial software are introducing dedicated packages to reduce designer efforts for lattice structure design and optimization. However, by using commercial CAD/CAM tools in the fabrication of components filled by lattice structure, several critical issues remain and need to be taken into consideration. This work aims at manufacturing variable-density lattice structures via fused deposition modeling deriving the density map from a grayscale or color image. In the proposed approach, the shell-based lattice model is not achieved by CAD tools, but only during the CAM process, while the lattice relative density is computed by editing the G-code, modifying the extrusion flow according to the local grayscale of a volumetric CAD model, defined from an image. The main advantages are related to the absence of a graded lattice geometric model and the consistency of the toolpath. The method is tested on various images and patterns, and can find applications in artworks, embedded information on components, and functional 3D printed parts, such as the replication of the density map of a bone derived from a DICOM grayscale image.
Abstract: Composite sandwich panels with honeycomb, corrugated, tetrahedral, trapezoidal, 3D periodic and hybrid lattice cores have long been studied for their use in various industrial fields. In this study, several numerical analyses were conducted in ANSYS APDL environment in order to analyze the effect of a novel bi-directional corrugated core configuration on the flexural performance of a CFRP sandwich panel. In particular, the sandwich core is obtained by repeating a regular unit cell in two different directions to form a three-dimensional lattice structure. In order to determine the optimal values of the geometrical parameters of the core unit cell and to evaluate how the layout of the composite laminate could affect the mechanical performances of the structure, a numerical study was conducted by using the Group Search Optimizer (GSO) algorithm, a metaheuristic animal-inspired optimization algorithm used to solve various real-world problems. The obtained results show that the GSO algorithm is very effective to optimize the main geometrical parameters of the composite sandwich panel with the novel bi-directional corrugated core. More generally, the implemented procedure provides an open framework to solve complex optimization problems that are very difficult to solve using exact methods, making the GSO algorithm particularly attractive for many industrial applications.
Keywords: ANSYS | Finite element analysis | Group search optimizer | Numerical optimization
Abstract: In this work a Reverse Engineering based approach has been implemented aiming to reconstruct the 3D shape of a strongly damaged and no longer usable impeller of a submersible centrifugal pump. After obtaining the 3D model, new designs of the impeller were investigated in terms of structural stability and corrosion resistance by changing the geometry and the material. Obtained results show the used approach can be very useful both to reproduce, by Additive Manufacturing, no longer available spare parts, so allowing to extend the useful life of old machineries and to reduce costs resulting from plant shutdowns, but also to improve the performances of old designs, making use of different materials and new manufacturing processes.
Abstract: Nowadays, 10–34% of patients undergone Total Knee Arthroplasty (TKA) continues to have pain and reduced mobility. New technologies in TKA have been developed to reproduce the native anatomy, respecting the natural joint line, by means of customized implants or following the kinematic alignment. In this context, the present research aims at defining a method to create customized implants. In particular, three different situations have been studied. The first condition is the healthy knee, that is used as reference for further analysis. For the second situation, an off-the-shelf prosthesis has been virtually implanted, following the kinematic joint line. In the third solution, a custom-made knee implant has been created. In all the three cases, FEA has been performed to study how load transmission and stability change after TKA. To reach the goal, high resolution Magnetic Resonance (MR) images of a healthy knee have been employed. Three-dimensional models of the knee have been reconstructed through a segmentation process, starting from DICOM images. Hence, the three situations have been studied. Distribution of pressure and stress are comparable in the two solutions, since they both maintain the natural joint line. Improving the kinematic function is crucial to increase patient satisfaction. According to the patient’s anatomy, the surgeon can choose between the standard and the personalized prosthesis. The studied customized approach allows to overcome the limits of conventional TKA since it permits to create geometries, which accommodate a variety of anatomical variations.
Abstract: Tracheomalacia (TM) is a tracheal weakening that causes the cartilage structure to collapse during breathing. The term tracheobronchomalacia (TBM) is used when the bronchi are also implicated in the disease. This illness can be treated in a variety of methods, including the insertion of stents in the cartilage-restricted region. Stents are commercially available in numerous sizes (diameter and length), different shapes and materials. The shape of the stent is chosen based on where the disease is located, while the size is derived from measurements on CT images or by endoscopic investigations. This task is extremely critical for the patient's health since improper stent can have serious and even deadly repercussions for the patient. Therefore, it is necessary to choose a stent that fits the patient's anatomy as closely as possible. To this end, it is possible to employ a three-dimensional model of the investigated anatomy and choose the most suitable type of stent following measurements made on the model itself. In this work, a method to assist physicians in the choice of the stent to be used in TM or TBM patients, is proposed. By analyzing the tracheobronchial tree and measuring successive cross-sections along the centerline of the lumen, the automated procedure allows to localize the diseased area and to identify the optimal shape and size of the stent to be implanted. Four case studies of paediatric patients were performed and the results were validated by a team of physicians specialized in the treatment of upper and lower airways.
Abstract: When dealing with craniofacial impairments, restoring the morphological condition is as crucial as restoring the functional ones to avoid psychosocial disabilities for the patient. For this aim, the accurate location of the midsagittal plane is essential for performing reliable symmetry analyses and guiding effective surgery planning. To provide a fully automatic and landmark-independent approach, capable of providing a midsagittal plane for craniofacial skeleton even from anatomical models with high asymmetries, an innovative method, called MaWR-method, was developed by the authors in a previous work. This paper further investigates the MaWR-method by evaluating its capacity to produce a successful outcome even in the worst-case scenario that may be considered in maxillofacial surgery, namely panfacial fractures. In all the test cases considered in this work, the method proved robust and reliable in its original design. It provided a consistent result requiring no user involvement, even when dealing with extreme asymmetries because of extensive and complex fractures.
Abstract: The optimization of a galvanic process is a crucial task for many manufacturers in the field of electro-deposition industry. This is true for companies operating in the high fashion field, in which expensive materials are used and reducing material waste is crucial. In this paper, the estimation of the wet surface of small metal parts is treated. In fact, considering a single piece, the amount of material required to guarantee a desired plate thickness is directly proportional to its outer surface. Starting with a rapid overview on other methods to come up with this task, the attention in principally oriented to surface estimation by means of optical scanning. A preliminary test session has been carried out and two main issues arose. The first one is related to resolution and accuracy: due to pieces small dimensions and details, high performances are required to achieve valid results. The second and principal issue is related to the high reflectivity of pieces, even before electroplating. With the aim of avoiding the use of matting paint (which is difficult to remove), the attention has been focused on commercial solution dedicated to jewellery and dentistry fields. Three devices (based on white and blue LED structured light) have been tested on high reflective and specular pieces. From the analyses, only the one based on blue LED technology was able to retrieve high reflective surfaces without matting. Minor issues arose in case of specular surface. The device has been considered suitable for the task.
Keywords: 3D optical scanners | 3D reconstruction | Blue LED structured light | Galvanic | Reverse engineering
Abstract: The orbital walls and floor are common sites of facial bone fracture and may cause severe functional impairment. The complex geometry of the bony orbit makes anatomical reconstruction extremely challenging, with main issues related to the implant’s correct shaping, positioning, and orientation inside the orbital cavity. This study proposes an innovative medical device to place patient-specific implants in fractured eye sockets properly. The device must be used with the developed improved version of a tailored implant shaping mould. The design of the orbital implant positioner followed specific clinical and technical requirements and specifications investigated through the Quality Function Deployment method. The device has been conceived to be simple, economical, capable of managing deantigenated bones or titanium meshes for orbital floor and wall, and reusable multiple times. The positioner consists of two handles hinged together and adequately coupled by a spring to allow the grasping and placing of the implant. Positioner and mould have been manufactured in polyamide using the Selective Laser Sintering technique. The system accuracy assessment resulted in promising outcomes. The mould can precisely shape the implant with a lower than 0.1 mm deviation. The implant positioner can place the implant with a rotation angle around the orbital rim of barely 7.1° and 1.2 mm deviation in the mediolateral direction (no deviations in the anteroposterior and superior-inferior directions occur)
Keywords: Computer-aided design | Craniomaxillofacial surgery | Implant design | Medical devices | Rapid prototyping
Abstract: These authors presented an automatic computer-based method for morphological feature segmentation and recognition for thoracic and lumbar human vertebrae in a previous paper. The method analyses high-density discretized models by segmentation and recognition rules codifying the vertebra morphology information, which does not change between different subjects. The methodology has been demonstrated to be valid and repeatable in segmenting and recognizing morphological features of vertebrae. The proposed one gives repeatable and reproducible results concerning the traditional manual methods. Nonetheless, the method has been tested only on human lumbar and thoracic vertebrae without distinctive pathologies. This paper aims to extend this methodology for much wider use by analyzing single vertebrae affected by common defectiveness in archaeological and medical fields. The results of the experimentations, analyzed by a skilled anthropologist and radiologist, show that the method correctly segments the analyzed morphological features, also for thoracic and lumbar vertebrae with defectiveness: in particular, defects that alter the shape of features or the symmetry of the vertebra, determine the absence of a feature, or heavily change the spatial distribution of the anterior part respect to the posterior one, have been analyzed.
Keywords: 3D medical image analysis | Feature recognition | Thoracic and lumbar vertebrae analysis | Vertebrae analysis computer-based methods
Abstract: Snap-fit joints represent a simple, economical and straightforward way of joining two different components. The design of the snap-fit joint is usually performed evaluating peak stresses that must be tolerated by the material without incurring into failure or plastic deformations; in addition, the force needed to join and disassemble parts is estimated in relation to ergonomic issues. Finally, the retention force, that is the force required to start disjoining parts, needs to be estimated. The evaluation of peak stresses or insertion/retention/removal forces is commonly performed through finite element method, having identified the respective deformed configuration. A different approach has been here followed considering that it is not trivial to identify the most critical condition in a full joining/disjoining cycle, when complex geometries are being considered. In detail, the snap joint has been modelled as a multibody model including a flexible body, which replicates the part that undergoes major deflections during the process. The model has been validated against experimental force – time curves, recorded for an existing joint, and it has been used to optimize a parametrised snap-fit design. As a result, the joining force has been reduced up to −84%; the disassembly force has been reduced up to −86% and the retention force has been incremented up to +7%. On the whole, a numerical framework to study these joints has been established, keeping the computational time reasonably low (about 40 min for the entire insertion and removal simulation).
Abstract: The work here presented is part of a wider research project aimed at extracting and using in industrial applications high level semantic information from 3D product models that are described by means of their boundary representation (B-rep). The specific focus of the paper is the recognition among the components of the CAD model of an assembly of those belonging to some categories of standard parts largely employed in mechanical industry. The knowledge of these components is crucial to understand the structure of mechanical products as they have specific meaning and function. Standard parts follow international standard in shape and dimensions, and also typical mounting schemes exist concerning their use in the product assembly. These distinctive features have been exploited as a starting point to develop a multi-step recognition algorithm. It includes a shape-based and a context-based analysis both relying on the geometric and topological analysis of a CAD model. As already anticipated by Voelcker in his visionary ability to anticipate open challenges, the shape of an object alone is not enough to understand its function. Therefore, context assessment becomes crucial to validate the recognition given by the shape-based step. It allows to uniquely recognize components in mechanical CAD models, by confirming correct results, refusing the false positives, as well as choosing the correct one when the assignment is multiple.
Keywords: 3D part recognition | Assembly analysis | CAD model processing | Standard part
Abstract: This paper presents a Generative Design Method (GDM) for highly customised Cultural Heritage applications concerning the exhibition and conservation of pottery. As a fundamental requirement, archaeological finds must be preserved in their structural integrity. Additionally, when present, the exposition supports must be aesthetically pleasant meaning that they must be non-invasive in the field of view of the observer. Furthermore, each artefact presents a unique geometry, hence its supporting structure must be designed accordingly. The proposed GDM considers these requirements, adopting a synergy of CAD, CAE, and optimisation tools. It is developed through two phases. The first phase, P1, concerns with the structural integrity of the fragment. In this phase, a Parametric Modelling approach is chosen for its ease of use both in the Finite Element Analysis evaluations of artefacts and in the design and optimisations of feasible supporting structures. The output of the phase P1 is the optimised configuration of the functional elements of the support ('Ci ') which are the interface region between the support itself and the fragment of pottery. They represent the input of the second phase, P2, that aims to generate lightweight concepts for the complete supporting structure considering the optimal 'Ci ' configuration. During this phase, an aesthetics criterion (related to the minimisation of the support's visibility) is also considered to achieve non-invasive supporting structures. Doing so, the GDM provides informed decisions in the early stages of the design activities with a simulation driven approach oriented to manufacturing. In this way, users are able to focus on design requirements since the concept's variants are generated by means of an optimised configuration of standardised components ('Ci') and obstacle geometries.
Abstract: Digital human modeling and gait analysis are essential for improving hip replacement surgery (HRS). In this study, Convolution Neural Networks (CNN) are used as a machine learning method to extract the most accurate stick-model from videos captured on a simple camera to represent gait and body components. We developed and tested multiple approaches to create an equitable skeleton model from an image. This process consists of two main parts: defining the joint locations using a CNN network in different architectures, and defining the connections into the final skeletons. A CNN has been trained, validated, and tested using the OpenPose software, which combines two different networks that have been tested on three data-sets for learning and evaluation. The results were satisfactory, but MobileNetV1 was evaluated for optimization of OpenPose computations and definitions. Several hyper-parameters were investigated to provide better representations. As a result of utilizing OpenPose methodology in conjunction with heavily optimized network design and post-processing code, and implementing MobileNet, the proposed solution has provided improved accuracy ratios.
Abstract: Blind and visually impaired people are mostly excluded in enjoying visual artwork yet. Even if the effectiveness of tactile supports has been proven in previous studies, these are difficult to realize, since they are commonly handmade. In this paper, a set of computer-aided interactive tools for a semi-automatic reconstruction of tactile bas-relieves is proposed. Starting from the digital picture of a painting, this set make it possible to retrieve a 2.5D reconstruction of a scene in the form of flat-layered bas relief, which means that the scene is reconstructed solely by means of geometric primitives such planes, cylindrical surfaces, conical surfaces and generic (curve) surfaces. Tools have been specifically thought to obtain tactile bas-relieves of architectural scenes. Unlike typical handmade crafting, the proposed tools do not require specific user skills or training. In fact, user is only asked to select points (i.e., to detect a vanishing point) or segments of the picture to obtain a specific surface. Tools have been designed, optimized, and adopted to realize the tactile bas-relief of the painting Piazza San Francesco (unknown artist, Museo Civico di Arte Antica - Pistoia), within the research activities related to ARTE project (Augmented Readability Tactile Exploration), co-founded by Cassa di Risparmio di Pistoia e Pescia.
Keywords: Blind | Shape from single image | Tactile bas-relief
Abstract: Additive manufacturing (AM) methods have a growing application in different fields such as aeronautical, automotive, biomedical, and there is a huge interest towards the extension of their use. In this paper, lattice structures for AM are analysed with regards to stiffness and printability in order to verify the suitability for applications where the main requirement of efficiency in terms of stiffness has to be balanced with other needs such as weight saving, ease of manufacturing and recycling of the material. At this aim, lattice structures with high porosity unit cells and large cell size made of a recyclable material were considered with a geometrical configuration allowing 3D printing without any supports. The lattice structures considered were based on body-centred cubic (BCC) and face centred cubic (FCC) unit cell combined with cubic cell. Finally, a multi-morphology lattice structure obtained by mixing different unit cells is also proposed. The lattice structures were modelled and structurally analysed by means of finite element method (FEM), manufactured with a Fusion deposition modelling (FDM) printer and evaluated in relation to printability and dimensional accuracy. The results show that the proposed structure with mixed cells is potentially advantageous in terms of weight saving in relation to the mechanical properties.
Keywords: Additive manufacturing | Geometrical configuration | High porosity | Lattice structure | Supportless 3D printing
Abstract: The demand for orthodontic and aesthetic treatments, aimed at having healthier teeth and more beautiful smiles, is increasingly growing. The devices on which these treatments are based must be rigorously bespoke for each patient. This is amplifying the need to develop digitized workflows, ranging from scanning to Additive Manufacturing (AM). The present work proposes an alternative workflow for designing and manufacturing orthodontic aligners, also known as clear aligners, starting from the intraoral scanning of the patient’s dentition. Orthodontic aligners are an alternative to metal brackets to correct dental malocclusions and they are often preferred by the patients because of their lower impact on facial aesthetics and for their higher comfort. The orthodontic treatments based on the aligners utilize a series of aligners, each one with a geometry slightly different from the previous one. The use of the single aligners is aimed to apply a force to the teeth and gradually aligning them until the end of the treatment. The workflow we propose in the present study is based on the following three main stages: intraoral scanning of the patient’s dentition, design of the aligners through a semi-automatic algorithm, and the direct additive manufacturing of the aligners through VAT photopolymerization technique. The possibility to directly additive manufacturing the aligners allows us to rethink the current orthodontic treatments. The aligners geometry can be re-designed, with the possibility of locally manipulating the thickness. This approach would allow the regulation of the amount of force applied locally to the tooth, thus optimizing the treatment and its duration. A feasibility study of the proposed workflow is reported in the present paper, with a focus on the semi-automatic design algorithm and on the additive manufacturing process of the aligners.
Keywords: Additive Manufacturing | Bespoke Medical Devices | Dental Appliances | Design Algorithms for Medical Applications | DfAM
Abstract: The human hand is a versatile and complex body part. It permits difficult movements with various degrees of precision and force. Several causes can lead to upper limb damage, including musculoskeletal disorders and diseases like stroke. The impairment can affect daily living activities. Patients usually undergo rehabilitation therapy with medical personnel for a long time after the traumatic event. In most cases, they use off-the-shelf medical devices. However, the shape of the upper limbs can differ a lot among people. A bespoke rehabilitative device could provide better comfort and usability, but the design process can be challenging. This work aims to present a digital workflow to generate a 3D virtual reconstruction of the patient’s upper limb structure, to be used in the device design. Starting from a 3D scan acquisition of the patient’s upper limb, the algorithm allows the creation of a polygonal mesh of the arm and the hand by a semi-automatic procedure. The algorithm uses neural networks’ capability to automatically detect the upper limb’s landmarks to localize the joints’ coordinates. The joints’ positions can be used to build a virtual skeleton for a 3D model of a human arm. The mesh of the model is subsequently wrapped around the scan of the real arm. The output consists in the 3D rigged model of the patient’s upper limb with a manifold mesh that can be deformed using its virtual skeleton. The results have been assessed with patients who had sports injuries or strokes. The 3D deviations between the scan acquisition of the arm and the resulting model have been evaluated.
Keywords: 3D scan | 3D virtual reconstruction | automatic landmarks detection | neural network | upper limb rigged model
Abstract: In the field of optical 3D scanning for healthcare applications, low-cost depth cameras can be efficiently used to capture geometry at video frame rates. However, the complete reconstruction of anatomical geometries remains challenging since different scans, collected from multiple viewpoints, must be aligned into a common reference frame. This paper proposes a fully automatic procedure to align scans of the upper limb patient’s anatomy. A 3D optical scanner, obtained by assembling three depth cameras, is used to collect upper limb acquisitions. A relevant dataset of key points on the hand and the forearm geometry is then determined and used to automatically obtain a rough 3D alignment of the different scans. Hand key points are identified through a neural network, which works on RGB images captured by the depth cameras; forearm key points are recognized by directly processing the point clouds through a specifically designed algorithm that evaluates the skeleton line of the forearm. The approach was tested on forearm acquisitions, and the results were compared to alternative alignment methodologies.
Keywords: 3D optical scanning | automatic point clouds alignment | depth cameras | upper limb anatomy
Abstract: The treatment of burn scars is a much discussed and sensitive topic because an improper therapy can have a significant impact on the quality of people's lives. To accurately assess both the health of scars and the outcomes of treatment, the medical evaluation should be based on objective measurements of progression over time. To overcome the limitations of subjective assessment is to leverage, 3D scanning technologies can be used to acquire topological information about the lesions and extract a set of relevant statistical parameters describing them. Accordingly, the present work aims at addressing both efficiency and reliability of a preliminary method based on the objective investigation of the surface topography of burn scars by applying it on several patients of the Meyer Children's Hospital burns department. A commercial 3D scanner is used to acquire 3D data relative to the scars of five patients. By applying a method based on the computational analysis of scan data, a significant number of roughness-related parameters are retrieved. This information is used to create a coherent dataset that allows the severity of burn scars to be inferred objectively. The developed method facilitates the evaluation of treatment efficacy by assessing wound healing during follow-up visits.
Abstract: Additive Manufacturing (AM) is currently making the relevance of lattice structure solutions increasing, allowing the achievement of high performance/mass ratio, where performance stands for energy absorption, stiffness, and/or insulation. This paper undertakes lattice structure for lightweight design of a horse saddletree. Saddletree is the backbone of a horse saddle, and it is composed of different components. In particular, the spring steel reinforcements inside the saddletree make it the heaviest part of the horse saddle, involving also multiple processes of manufacturing and manual assemblies. This paper aims to lightweight an existing saddletree with a Voronoi lattice solution, reducing several manual assemblies. From the methodological point of view, the lightweight design has been based on a multi-scale approach, carried out via nTopology (static FEA on the original bulk design, implicit geometrical lattice generation from FEA result maps and Boolean operation among lattice results and bulk design implicit model). The original bulk design has been digitally acquired and modeled through Reverse Engineering techniques, so that a specific customized solution may be improved. A final weight reduction of 76.5% is achieved, providing an example of how topological optimization techniques coupled with AM (in particular Powder Bed Fusion technology) may reduce assembly efforts
Abstract: Describing and supplementing geometric shapes (parts) and layouts (assemblies) with relevant information is key for successful product design communication. 3D annotation tools are widely available in commercial systems, but they are generally used in the same manner as 2D annotations in traditional engineering drawings. The gap between technology and practices is particularly evident in plain text annotations. In this paper, we introduce a functional classification of text annotations to provide an information framework for shifting traditional annotation practices towards the Model-Based Definition (MBD) paradigm. In our view, the current classification of dimensions, tolerances, symbols, notes, and text does not stress the inherent properties of two broader categories: symbols and text. Symbol-based annotations use a symbolic language (mostly standardized) such as Geometric Dimensioning and Tolerancing (GD&T) to provide precise information about the implications of geometric imperfections in manufacturing, whereas notes and text are based on non-standardized and unstructured plain text, and can be used to convey design information. We advocate that text annotations can be characterized in four different functional types (objectives, requirements, rationale, and intent), which should be classified as such when annotations are added to a model. The identification and definition of a formalized structure and syntax can enable the management of the annotations as separate entities, thus leveraging their individual features, or as a group to gain a global and collective view of the design problem. The proposed classification was tested with a group of users in a redesign task that involved a series of geometric changes to an annotated assembly model.
Keywords: Annotations | Model-based definition | Text annotations
Abstract: Robot-Based Additive Manufacturing (RBAM) combines material deposition nozzles and robotic manipulators to increase the flexibility of cartesian/delta Additive Manufacturing (AM) systems. RBAM overcomes the traditional limit given by the planarity of the manufacturing layer and allows variable slice thickness to be realized. Also, RBAM enables the deposition of the material in multiple directions. In this context, volume decomposition algorithms are implemented to split a solid into several sub-volumes. Each sub-volume is sliced according to an optimal direction to perform support-free manufacturing and to avoid tool collisions. A novel algorithm for the volume decomposition of a given input geometry is presented. In particular, it allows several planar separation surfaces to be computed that are used to split a general input shape. The surfaces are defined by analyzing overhangs according to an initial slicing direction. The normal of the surfaces identifies the slicing direction of the related sub-volumes. The algorithm steps are iterated to reach the complete removal of overhangs. The approach is tested in some case studies to evaluate its applicability.
Abstract: Assembly sequence planning starting from CAD models turned out to be a relevant task in the industrial manufacturing field. To have a successful assembly sequence, the relations between the assembly's parts and the possible interferences during the assembly operations deserve to be investigated. In particular, the collision analysis is the phase in which the movement of each part along some directions is evaluated to assess if it is obstructed by any of the other parts, and according to which the precedence matrix is computed. A lot of work has been done to address the problem, however, existing algorithms need to be improved yet. Among the open issues, the following three result to be the most challenging: the combinatorial explosion of the problem complexity, the limited choice of the assembly directions, and the engineering meaning of parts that is not taken into account, or it is manually given in input by experts. In this paper, an automatic assembly sequence planning approach is introduced. The focus is on the collision detection and precedence analysis for engineering meaningful subassemblies, namely the axisymmetric. Information automatically extracted relying on geometric processing and engineering knowledge, such as parts features and semantic interpretation of mechanical components, is first exploited to identify the subassemblies and, then, to choose the feasible assembly direction, as well as to treat fasteners and deformable parts in a more realistic way. An industrial CAD model of a gearbox is selected as case study to illustrate the approach, also emphasizing the importance of axisymmetric subassemblies.
 Pullia M.G., Benedetto E., Dassa L., De Matteis E., Donetti M., Felcini E., Frisella G., Karppinen M., Kurfürst C., Mariotto S., Mereghetti A., Mirandola A., Pella A., Perini D., Piacentini L., Pivi M.T.F., Prioli M., Ratkus A., Rossi L., Sabbatini L., Savazzi S., Stock M., Tommasini D., Torims T., Uberti S., Vannozzi A., Vilcans J., Vretenar M.,
Explorative studies of an innovative superconducting gantry, Journal of Physics: Conference Series,
Abstract: The Heavy Ion Therapy Research Integration plus (HITRIplus) is an European project that aims to integrate and propel research and technologies related to cancer treatment with heavy ion beams. Among the ambitious goals of the project, a specific work package includes the design of a gantry for carbon ions, based on superconducting magnets. The first milestone to achieve is the choice of the fundamental gantry parameters, namely the beam optics layout, the superconducting magnet technology, and the main user requirements. Starting from a reference 3 T design, the collaboration widely explored dozens of possible gantry configurations at 4 T, aiming to find the best compromise in terms of footprint, capital cost, and required R&D. We present here a summary of these configurations, underlying the initial correlation between the beam optics, the mechanics and the main superconducting dipoles design: the bending field (up to 4 T), combined function features (integrated quadrupoles), magnet aperture (up to 90 mm), and angular length (30° – 45°). The resulting main parameters are then listed, compared, and used to drive the choice of the best gantry layout to be developed in HITRIplus.
Abstract: Additive Manufacturing has enabled the design of complex components in several technical fields. Considering turbomachinery components, additive manufacturing has unlocked the achievement of significant performances for dynamic rotoring components. The application of topology optimization methods is one of the main factors accelerating the technological development of this sector. This paper presents a procedure for the optimization of static turbomachinery components. The framework proposed compares the results obtained by introducing a lattice structure and a solid optimized shape. The procedure is presented with reference to a specific case study. To validate the proposed framework, the complete re-design of a thrust collar of a major Italian-based Oil&Gas company is carried out, demonstrating that the re-thinking of the component in terms of Topology Optimization is a straightforward approach to increase the overall performance of the produced part
Abstract: Background and objective: The ability to accomplish a consistent restoration of a missing or deformed anatomical area is a fundamental step for defining a custom implant, especially in the maxillofacial and cranial reconstruction where the aesthetical aspect is crucial for a successful surgical outcome. At the same time, this task is also the most difficult, time-consuming, and complicated across the whole reconstruction process. This is mostly due to the high geometric complexity of the anatomical structures, insufficient references, and significant interindividual anatomical heterogeneity. Numerous solutions, specifically for the neurocranium, have been put forward in the scientific literature to address the reconstruction issue, but none of them has yet been persuasive enough to guarantee an easily automatable approach with a consistent shape reconstruction. Methods: This work aims to present a novel reconstruction method (named HyM3D) for the automatic restoration of the exocranial surface by ensuring both the symmetry of the resulting skull and the continuity between the reconstructive patch and the surrounding bone. To achieve this goal, the strengths of the Template-based methods are exploited to provide knowledge of the missing or deformed region and to guide a subsequent Surface Interpolation-based algorithm. HyM3D is an improved version of a methodology presented by the authors in a previous publication for the restoration of unilateral defects. Differently from the first version, the novel procedure applies to all kinds of cranial defects, whether they are unilateral or not. Results: The presented method has been tested on several test cases, both synthetic and real, and the results show that it is reliable and trustworthy, providing a consistent outcome with no user intervention even when dealing with complex defects. Conclusions: HyM3D method proved to be a valid alternative to the existing approaches for the digital reconstruction of a defective cranial vault; furthermore, with respect to the current alternatives, it demands less user interaction since the method is landmarks-independent and does not require any patch adaptation.
Abstract: The standard method of design and manufacturing customised orthoses is still very time-consuming due to their often very complex shape. Different authors have tried to solve this problem but, unfortunately, the proposed approaches cannot be easily used in clinical practice because they require substantial interaction among medical staff and engineers or technicians. The aim of this work is to present the framework of a new design approach that could allow clinicians to easily model a customised orthosis, without a skilled technician develops the entire procedure. In particular, an automatic process based on Generative Design has been implemented. The obtained results have demonstrated that the implemented algorithm is simple to use and could allow also not-skilled users to design customised orthoses.
Abstract: 3D reconstructed models are becoming more diffused daily, especially in the Cultural Heritage field. These geometric models are typically obtained from elaborating a 3D point cloud. A significant limit in using these methods is the realignment of different point clouds acquired from different acquisitions, particularly for those whose dimensions are millions of points. Although several methodologies have tried to propose a solution for this necessity, none of these seems to solve definitively the problems related to the realignment of large point clouds. This paper presents a new and innovative procedure for the fine registration of large point clouds. The method performs an alignment by using planar approximations of roof features, taking the roof’s extension into account. It looks particularly suitable for the alignment of large point clouds acquired in urban and archaeological environments. The proposed methodology is compared in terms of accuracy and time with a standard photogrammetric reconstruction based on Ground Control Points (GCPs) and other ones, aligned by the Iterative Closest Point method (ICP) and markers. The results evidence the excellent performance of the methodology, which could represent an alternative for aligning extensive photogrammetric reconstructions without the use of GCPs.
Keywords: multi-UAV scanning registration | particle swarm optimization | point cloud registration | shape features recognition
Abstract: The traditional manual method of analysis of ceramic finds involves expert operators in long and routine activities whose results depend on their subjectivity, specialization, and professional experience. This implies that the analysis of sherds is carried out using few data affected by high uncertainty. These limitations are even more clear with fragments with small axially symmetric portions whose elements of the investigation are not axially symmetric, such as handles, spouts, decorations. In this way both the axis of symmetry of the original object and the reference planes and/or axes of the characteristic dimensions of the elements are identified with such approximations as to compromise subsequent analyses and comparisons. To overcome these limitations, in this paper a new computer-based procedure is proposed. As a case study, the analysis fragments of jugs/bowls with trilobed spouts found in the site of Amiternum, coming from 12th-13th century contexts are considered; their analysis is fundamental to analyze the site where they were found since there is no archival documentation about their use.
Abstract: The sweep features of constant radius are particularly significant for the purposes of the historical-archaeological investigation and classification of ancient artifacts. The paper focuses on the automatic recognition of this specific class of features from triangulated 3D models experimentally acquired from cultural heritage objects. This is not a trivial problem. The ancient artifacts, although repeatable, are unique handmade pieces with a geometry commonly characterized by complex and non-analytical shapes. Their surfaces are also usually damaged and worn, so that the related geometric properties are altered or lost. The methodology proposed here is inspired by the one previously developed by the authors for the automatic segmentation of fillets, rounds and grooves from high-density triangulated models of mechanical components. The paper, in particular, focuses on the aspects of this methodology that must be tuned to allow the recognition of the sweep features of constant radius from archaeological finds. The methodology has been implemented and finally applied to an archaeological find acquired by a laser scanner.
Keywords: 3D archaeology | 3D digital models | Computer methods in archaeology | Feature recognition | Laser scanning
Abstract: Total Knee Arthroplasty (TKA) is a widely performed surgical procedure, which is advised to treat knee osteoarthritis. However, the literature reported that 25% of the patients are unsatisfied by the functional outcomes after the intervention. The main causes seem to be the prosthesis malalignment and the anatomical mismatch between the prosthetic components and the different people anatomy. Even if there exist several commercial solutions, whose aim has always been to provide a reliable prosthesis with high survivorship, the most recent scientific literature is focusing its aim to improving the patients’ clinical outcome, kinematics and satisfaction. For this reason, three approaches have been experimented and then discussed with an orthopedic surgeon. Open-source software applications for 3D modelling have been exploited, such as 3D Slicer and Meshmixer. Starting from medical images, through the segmentation process, the 3D model of the knee has been reconstructed. For the first approach, standard off-the-shelf prosthesis have been used for the virtual planning of the intervention. To overcome the limits of this method, two more customized approaches have been experimented. The first one is based on the patient-specific resurfacing prosthesis that fits the patient’s anatomy, preserving the femur and maintaining the natural joint line. The third approach allows to create a customized prosthesis, that is a compromise between the two previous methods. Among the three previous procedures, the most suitable one can be chosen according to the patient’s anatomy, knee size and articular cartilage damage.
Keywords: 3D modelling | Customized knee prosthesis | Total knee arthroplasty planning
Abstract: Emerging production technologies, in particular Additive Manufacturing (AM), nowadays are extremely suitable for creating highly complex products, tending towards the concept of ‘complexity for free’, which is often associated with AM. However, there are no adequate guidelines to provide decision support for the correct selection of the most economically appropriate technology. Indeed, from literature it has been highlighted the need to develop a technology selection methodology based no longer on production volume but on product complexity. This paper investigates this need by presenting an approach to determine the geometrical (or shape) complexity index of a part, which, combined with the assembly complexity, represents the driver for helping to decide the best production technology (traditional or additive). The geometrical complexity index has been determined based on complexity judgments, provided by CAD modelling experts, for a sample of CAD models. In this way, it has been possible to define a preliminary complexity index model, strictly linked to the CAD model information. The results showed that the geometrical complexity metrics from the literature, if individually considered, are not comprehensive. However, a combination of them makes it possible to obtain an index that best reflects the subjective judgement of the experts. In addition, by combining the geometrical and assembly complexity with a cost analysis it is possible to obtain convenience zones for better selecting the production technology.
Abstract: This work proposes a geometric approach to inverse kinematics of hyper-redundant manipulators used for remote maintenance of nuclear fusion reactors. The approach is particularly suited to be adopted in real-time human-in-the-loop control strategies involving high-frequency control feedback and requiring safe interaction between the manipulator and the in-vessel environment. The capability of the inverse kinematic method to find a solution for a set of different robot end-effector poses, inside a toroidal environment, was tested on the HyRMan kinematics, i.e. the Hyper Redundant Manipulator developed in the framework of the Divertor Tokamak Test (DTT) project. The simulation tests were aimed at assessing performance of the proposed method in terms of accuracy in the end-effector positioning, computational burden, distance from obstacle, distance from joint angles and torque limits and success rate of the task execution. The achieved results were compared to the ones obtained through an iterative method proposed in literature, i.e. the one based on the computation of the Jacobian pseudo-inverse, demonstrating overall higher performance of the proposed approach and comparable ability to safely avoid obstacles and joint limits.
Abstract: A Cayley map for the special Euclidean group SE(3) is introduced to relate, for a soft continuum robot, the Lie algebra of internal deformations with the Lie group of rigid–body motions. This Cayley map is used for approximated and exact kinematic shape reconstruction of soft continuum robots, under the hypothesis of constant deformations. This map could be used for deriving computationally efficient interpolation schemes for soft robots, since it does not involve transcendental functions as those introduced by the exponential parametrization of soft robot kinematics.
Abstract: Today it is more and more mandatory for all commercial companies to comply with the principles and methodologies of Industry 4.0 and to achieve the related capabilities protecting their competitiveness and taking a leading-edge position on market as regards technologies. Specifically, the whole production and sale system must achieve the fundamental characteristics of Industry 4.0 approach, but specially the manufacturing companies must also change and update their management procedures, internal organization, resource training, assets and all production process to keep safe their current business capacities. This evolution process is even more critical for Small and Medium Enterprises (SME), that traditionally tend to be conservative and to protect their way of operation, usually characterized by a low level of automation. The work presented focuses on the design and integration of a semi-automatic welding cell of train bolster in a SME which is currently realizing a project aimed to the acquisition of Industry 4.0 capabilities, with special focus on manufacturing processes. Among them, one of the most important is the production of welded-steel critical structures, that the Company supplies to prime manufacturer of railway rolling stock systems. The experience gained during the activity, the criticalities due to the integration processes and the adopted design methodologies are here described. The work has been carried out consistently with the Systems Engineering principles, starting from the requirements elicitation and analysis to the systematic approach for the design and integration activities.
Keywords: CAD | Design methodologies | Industry 4.0 | Internet of things (IoT) | Systems engineering | Welding process
Abstract: This study presents an alternative process for designing and manufacturing customized trays for dental-whitening treatments. The process is based on a digitized approach consisting of three main stages: design of a reference model, its manufacturing by AM, and thermoforming of the tray. The aim of the study was to develop a high-performance tray, able to guarantee comfort, safety, and efficacy for whitening treatments. To evaluate the patient’s experience, some tests under real operating conditions were performed. Twenty people carried out a nighttime treatment of 14 days. Each patient was asked to assess the overall level of satisfaction and the comfort of the tray and its ability to retain the gel. Tooth whitening was also determined according to the VITAPAN scale. All patients involved in the study were satisfied and provided positive feedback about comfort and tightness of the tray. At the end of the treatment, 15 out of 20 patients achieved shade A1 on the VITAPAN scale. The mean improvement in color shades was about 7. These results confirmed the great potential of the proposed dental tray. Its use was proven to guarantee a high level of quality, flexibility, and customization of dental-whitening treatments, improving comfort, safety, and efficacy.
Abstract: In radiotherapy, the treatment of skin tumors requires the application of tissue-equivalent devices in order to avoid the skin-sparing effect, and thus maximize and equalize the dose on the target. In the common clinical practice these devices, called bolus, are standard pads that do not perfectly adapt to the geometry of the patient generating empty spaces at the skin-bolus interface. This phenomenon hinders an efficient planning of the dose to be administered due to the non-adherence and the unpredictability of the position of the air gaps. In this work a workflow for the production of patient-specific bolus in Ecoflex® 00–10 silicone rubber (soft, biocompatible and sterilizable material) is proposed. The process exploits modern Reverse Engineering and Additive Manufacturing technologies to guarantee an accurate compliance with the involved geometries. Significant improvement, with respect to flat boluses, in the adhesion of the medical device to the anatomical region were found through in-vitro testing using replicas of the involved anatomy. Repeatability tests of the positioning performed on the customized bolus led to satisfying results demonstrating the possibility of accurate and predictable treatment planning.
Abstract: Home-based rehabilitation is becoming a gold standard for patient who have undergone knee arthroplasty or full knee replacement, as it helps healthcare costs to be minimized. Nevertheless, there is a chance of increasing adverse health effects in case of home care, primarily due to the patients’ lack of motivation and the doctors’ difficulty in carrying out rigorous supervision. The development of devices to assess the efficient recovery of the operated joint is highly valued both for the patient, who feels encouraged to perform the proper number of activities, and for the doctor, who can track him/her remotely. Accordingly, this paper introduces an interactive approach to angular range calculation of hip and knee joints based on the use of low-cost devices which can be operated at home. First, the patient’s body posture is estimated using a 2D acquisition method. Subsequently, the 3D posture is evaluated by using the depth information coming from an RGB-D sensor. Preliminary results show that the proposed method effectively overcomes many limitations by fusing the results obtained by the state-of-the-art robust 2D pose estimation algorithms with the 3D data of depth cameras by allowing the patient to be correctly tracked during rehabilitation exercises.
Keywords: 3D model | Body tracking | Data fusion | Joints estimation | RGB-D camera
Abstract: In this paper an interactive computational methodology was developed assuming that shape and size optimization of flexible components can significantly improve energy absorption or storage ability in assembled systems with flexible components (AS-FC). A radial basis functions mesh morphing formulation in non-linear numerical finite element analysis, including contact problems and flow interaction, was adopted as optimal design method to optimize shape and size design parameters in AS-FC. Flexible components were assembled in finite element environment according to functional ISO-ASME tolerances specification; non-linear structural analysis with flow interaction analysis was performed. The results of the study showed that the proposed method allows to optimize the shape and size of the flexible components in AS-FC maximizing the system's ability to absorb or store energy. The potentiality of the method and its forecasting capability were discussed for the case study of an automotive crash shock in which the specific energy absorption was increased by over 40%. The case studied refers to a simple flexible component geometry, but the method could be extended to systems with more complex geometries.
Keywords: Crash shock absorber | ISO-ASME tolerances specification | Radial basis functions | Shape and size optimization | Specific energy absorption
Abstract: In the Cultural Heritage field, the choice of materials and exhibit structures is essential to properly house and support artifacts without causing damage or deterioration. This problem is even more evident in the case of finds made of stone for which, due to their weight, a proper selection and dimensioning of the relative supports is required. In fact, without adequate support, this can result in stress concentrations that could compromise the artifact's state of conservation. As a consequence, more often such exhibition supports are customized items, that are designed and manufactured to meet specific functional and artistic setup needs. In this context, the paper presents a design approach that combines topology optimization and additive manufacturing techniques to develop customized support structures which undertake the twofold purpose of preserving the artifact and making it available for the exhibition in the museum. The proposed approach has been assessed through the case study of a sandstone Ionic capital hosted in the Brettii & Enotri Museum in Cosenza (Italy). The proposed approach is therefore meant as a guideline for the design of customized exhibit supports especially in the case of sandstone artifacts with a complex shape or a conservation condition that requires specific attention.
Abstract: In this work, a Coarse-Grained Lattice Spring Model to characterize the mechanical behavior of human mesenchymal stem cells subjected to nanoindentation measurements is presented. The model simulated the action of adhesive structures acting on cells, necessary for attaching them to a substrate, and a nanoindentation process, performed by means of an atomic force microscope with a spherical tip. Cells were hypothesized to behave as elastic materials and the model included several subcellular components such as cell cortex and cytoskeleton. The lattice spring model was integrated within an optimization algorithm that iteratively compared the force-indentation curve numerically predicted to the data experimentally obtained, until a best fit condition was reached. The computed mechanical properties of the cell were compared to those obtained via the Hertz contact theory and finite element modelling, showing a good agreement. The proposed lattice spring model appears as a promising tool that can be used, with a very low computational cost, to characterize cell materials and other biological materials.
Abstract: Within the literature concerning modern machine learning techniques applied to the medical field, there is a growing interest in the application of these technologies to the nephrological area, espe-cially regarding the study of renal pathologies, because they are very common and widespread in our society, afflicting a high percentage of the population and leading to various complications, up to death in some cases. For these reasons, the authors have considered it appropriate to collect, using one of the major bibliographic databases available, and analyze the studies carried out until February 2022 on the use of machine learning techniques in the nephrological field, grouping them according to the addressed pathologies: renal masses, acute kidney injury, chronic kidney disease, kidney stone, glomerular disease, kidney transplant, and others less widespread. Of a total of 224 studies, 59 were analyzed according to inclusion and exclusion criteria in this review, considering the method used and the type of data availa-ble. Based on the study conducted, it is possible to see a growing trend and interest in the use of machine learning applications in nephrology, becoming an additional tool for physicians, which can enable them to make more accurate and faster diagnoses, although there remains a major limitation given the diffi-culty in creating public databases that can be used by the scientific community to corroborate and even-tually make a positive contribution in this area.
Abstract: The present paper presents the development of a novel procedure for the modeling of Surgical Cutting Guides (SCGs) exploiting an implicit modeling approach. As discussed in the text, this approach allows for a streamlined and efficient design of this type of medical device. A procedural approach based on the application of a series of a priori-known implicit modeling function allows the generation of personalized surgical guides starting from the i) patient’s anatomy and ii) clinical decisions made by the medical staff. The CAD procedure is detailed in the text; achieved results are discussed and compared with a traditional CAD modeling approach on three case studies.
Abstract: Dealing with the design of personalized medical devices, mass production is not an option that can be hypothesized. Indeed, a cumbersome production process must be considered in such cases, mainly to account for a delicate design phase that needs to take into consideration, as input, an anatomy that vary each time. This article discusses the development of a statistical tool able to support the design of patient-specific devices. By expanding the classical formulation of the Statistical Shape Model (SSM) with the introduction of multiple levels of information within the same model, the authors have experimented with the concept of an “enhanced SSM”. While the traditional SSM only provides information on the variations that a class of shapes can manifest, the eSSM may include more levels of information. The article discusses two possible mathematical formulations of such statistical tool. Its application to the design of custom-made pelvic implants is discussed. Such application scenario is described starting from the generation of the eSSM for the pelvis. The features of interest considered in this paper are the centers of the acetabular regions of the pelvis, the segmentation of the anatomy in a series of semantical regions that must be considered when developing a load-bearing implant. Finally, the conclusions of this research are drawn and discussed together with possible future development of eSSMs.
Abstract: The panel method is a potential-flow numerical approach that shows valuable performances to solve aerodynamic problems in the preliminary design stages. It shows a lower computational effort compared with Computational Fluid Dynamics, wind tunnel tests or ‘on the field’ experiments. However, the 3D surface discretization in rectangular panels is tedious and must be often carried out manually from scratch. Moreover, the panel method can’t be used to compute the overall drag force due to strong assumptions. To solve these two challenging aspects, the authors propose a voxel-based fluid dynamic approach integrating its programmed functions within a panel method. Voxelization is used to automatically distribute coherently the panels along the external surface of a 3D model in an automated way. A parametric study is included to demonstrate how the voxel resolution affects the aerodynamic results and provide guidelines for future research. Overall drag is estimated using corrections for both the skin friction and the form drag sources. The Ahmed body case study is included and demonstrates a good agreement between the voxel-based fluid dynamics approach and the literature benchmarking values, but with lower computational efforts. Further studies involving more complex shapes should be performed to better understand the performances and limitations of the approach.
Keywords: Ahmed body | Automotive | CAD | Conceptual Design | Panel method | Voxelization
Abstract: The Panel method is an approach for the estimation of the lift of 3D models which is faster than CFD. This can be useful especially in the conceptual design stage where several configurations should be evaluated in a reduced time with a limited computational cost. However, the meshing of the 3D body surface with rectangular panels can be a time-consuming activity because the designer should define from scratch a cloud of points that matches the external surfaces of the tested object to obtain consistent panelling. Therefore, a voxelization-based methodology has been developed to obtain the panels’ position, speeding up and automating the model preparation process. The obtained discretization has been integrated into a panel method available in the literature. Four case studies, of increasing complexity, have been analyzed to investigate the capability of the innovative voxel-based panel methodology. A parametric study has been carried out to study the effect of the voxel grid dimension on the accuracy of the results. Benchmarking values of lift coefficient obtained from literature or xFoil software have been used to evaluate the precision that can be achieved with this approach. The results show a good agreement between the voxel-based panel method and the literature when the overall pressure distributions and aerodynamic coefficient values are considered. Higher errors are noticed with drag.
Abstract: Mitral regurgitation is a common valvular disorder. Transcatheter edge-to-edge repair (TEER) is a minimally invasive technique which involves holding together the middle segments of the mitral valve leaflets, thereby reducing regurgitation. To date, MitraClip™ is the only Food and Drug Administration (FDA)-approved device for TEER. The MitraClip procedure is technically challenging, characterised by a steep learning curve. Training is generally performed on simplified models, which do not emphasise anatomical features, realistic materials, or procedural scenarios. The aim of this study is to propose a novel, 3D printed simulator, with a major focus on reproducing the anatomy and plasticity of all areas of the heart involved and specifically the ones of the mitral valve apparatus. A three-dimensional digital model of a heart was generated by segmenting computed tomography (CT). The model was subsequently modified for: (i) adding anatomical features not fully visible with CT; (ii) adapting the model to interact with the MitraClip procedural equipment; and (iii) ensuring modularity of the system. The model was manufactured with a Polyjet technology printer, with a differentiated material assignment among its portions. Polypropylene threads were stitched to replicate chordae tendineae. The proposed system was successfully tested with MitraClip equipment. The simulator was assessed to be feasible to practice in a realistic fashion, different procedural aspects including access, navigation, catheter steering, and leaflets grasping. In addition, the model was found to be compatible with clinical procedural imaging fluoroscopy equipment. Future studies will assess the effect of the proposed training system on improving TEER training.
Abstract: Medical image segmentation, especially for biological soft tissues, is an issue of great interest. The aim of this study is to evaluate the segmentation performance of a commercial and an open-source software, to segment aortic root and coronary arteries. 3D printing stereolithography technology was used to generate ground truth models, which were then re-acquired by means of a micro-CT scanner. Measurements from the printed and reconstructed models with both the software were compared, in order to evaluate the level of agreement. In the second phase of this study, Computational Fluid Dynamics (CFD) simulations were conducted, to compare the outputs between the models segmented with the two software. The goal was to understand how differences in the segmentation process propagate in CFD results. Results showed that both software guarantee satisfactory segmentation performance, with average geometrical differences between reconstructed and physical models in the order of a few percentage points. However, when we consider thin details, as a sharp stenotic region, the commercial validated software seems to be more accurate in replicating the real anatomy. We also realized how apparently negligible geometrical differences, varying the employed software, can turn into enormous variations of hemodynamic parameters, such as velocity and wall shear stress, which place in the centre the delicate role the segmentation process holds. This evidence is crucial in the biomedical field and especially in a coronary arteries study, where CFD simulations can be exploited as a starting point for surgery considerations.
Abstract: Additive manufacturing technologies are increasingly taking place in the medical field, enabling the creation of graspable patient-specific anatomical models. Because of their potentiality in improving the understanding of complex anatomies and their shown effectiveness for residents' training, devices testing and planning of innovative surgical interventions, 3D printed models have been incorporated also into cardiac surgery and interventional cardiology. To offer valid and reliable support, however, these printed models are often required to be flexible, with an adequate mechanical response, especially when they aim at replicating soft tissues. The goal of this paper is to provide a high-quality and robust template of a patient-specific whole heart model, obtained starting from a Computed Tomography dataset and exploiting a material jetting printer. Due to the significant shape complexity and the variability in compliance featuring the human heart, the selection of the materials have been diversified, taking into account different model wall thicknesses. Thanks to the capability of the material jetting technology, the 3D model of the heart has been printed with two different material assignments, designed to get highly realistic feedback and reduce the gap between the real heart and the printed ones. Eventually, an accuracy evaluation of the printed model has been performed, by means of a laser 3D scanner. Some further considerations about time and costs required to produce the model are part of the paper, together with a discussion about potential areas of improvement, from materials characterization to the need of speeding up and automating the segmentation procedure.
Abstract: In this work a new approach for the creation of Articulated Total Body (ATB) models for person-specific multi-body simulations is presented, with the main aim of overcoming limitations related to classical multi-ellipsoids ATB models, based on regression equations having only the weight and the height of the subject as input. The new methodology is based on a Statistical Shape Model (SSM), morphable according to up to 24 input parameters: the SSM was obtained from Principal Component Analysis (PCA), applied on a wide database of 3D human scans (CAESAR). The so obtained geometry can be segmented automatically to generate body segments with the respective inertial properties (mass, principal moments of inertia, and centres of mass location). The routine has been tested on a random set of 20 male subjects and the classical multi-ellipsoids models were compared to these in terms of inertial properties and 3D external geometry: the highest differences were registered at the abdomen and the thighs for what concerns the mass (60%), principal moments (75%) and centres of mass (50 mm) properties; the trunk, the shoulder and the calves are the most critical areas for the external geometry (average distance between the anthropomorphic and ellipsoids models equal to 50 mm). A contribution has been made to build person-specific multibody models. This is a valuable method since approximations made by multi-ellipsoidal models have resulted to be relevant at specific body areas, and personalised models can be a support to design and to forensic analyses.
Keywords: 3D parametric human model | Articulated total body | Forensic biomechanics | Multibody analysis | Principal component analysis (PCA)
Abstract: Worldwide, stroke is the third cause of disability. The majority of people affected by this disease cannot perform activities of daily living. Bringing the therapy to the patients' home is complex, and in literature, there are still open challenges to face. Starting from therapists' and patients' needs, this paper describes a possible solution: HANDY, a rehabilitative active hand exoskeleton for post-stroke patients. With a desktop application, they perform three different types of exercises: passive, active and based on activities of daily living. They can also control the exoskeleton themselves in a serious-game approach with a leap motion controller. We evaluated our method with patients at the Villa Beretta rehabilitative center. Preliminary results from the session about comfort, usability and willingness to utilize the system are promising.
Abstract: Currently, the growing need for highly customized implants has become one of the key aspects to increase the life expectancy and reduce time and costs for prolonged hospitalizations due to premature failures of implanted prostheses. According to the literature, several technological solutions are considered suitable to achieve the necessary geometrical complexity, from the conventional subtractive approaches to the more innovative additive solutions. In the case of cranial prostheses, which must guarantee a very good fitting of the region surrounding the implant in order to minimize micromotions and reduce infections, the need of a product characterized by high geometrical complexity combined with both strength and limited weight, has pushed the research towards the adoption of manufacturing processes able to improve the product’s quality but being fast and flexible enough. The attention has been thus focused in this paper on sheet metal forming processes and, namely on the Single Point Incremental Forming (SPIF) and the Superplastic Forming (SPF). In particular, the complete procedure to design and produce titanium cranial prostheses for in vivo tests is described: starting from Digital Imaging and COmmunications in Medicine (DICOM) images of the ovine animal, the design was conducted and the production process simulated to evaluate the process parameters and the production set up. The forming characteristics of the prostheses were finally evaluated in terms of thickness distributions and part’s geometry. The effectiveness of the proposed methodology has been finally assessed through the implantation of the manufactured prostheses in sheep.
Keywords: Custom prosthesis | In vivo tests | Single point incremental forming | Superplastic forming | Ti‐6Al‐4V ELI
Abstract: Analyzing an assembly and recognizing how the components can mate with each other in order to satisfy the functionality for which they have been designed is not a trivial task. Teaching such a problem to engineering students requires they are familiar with a set of components and how much larger or thin can be the errors intrinsically related to the technologies employed in their production. A set of steps are necessary to reasoning about the right identification of a chain of dimensions that influences a functionality. Then can be useful to have a table where collect the data, especially when the number of parts is relevant. The paper presents a new format for the table that can be used in all kinds of problems that may occur in design: analysis, analysis with constraints, and synthesis. The way how to employ such a table and the steps to solve each problem is discussed with known examples.
Keywords: Modeling | Tolerance analysis and synthesis | Tolerance stack-up
Abstract: The partial element equivalent circuit method is a well-known numerical technique that is used to solve Maxwell’s equations in their integral equation form. The application of the PEEC method to modeling domains with non-orthogonal three-dimensional geometries requires the computation of the interaction integrals to be performed numerically, thus slowing down the overall computation. This work presents a new technique that allows improving the computation of the interaction integrals of the PEEC method for non-orthogonal geometries under the quasi-static hypothesis. To this purpose, a voxelization approach that automatically decomposes non-orthogonal volumes in elementary parallelepipeds is used, allowing the implementation of closed-form formulas for the interaction integrals and completely avoiding numerical integration. The proposed approach is applied to three example problems exhibiting very good accuracy and excellent speed-up compared to the standard one using the numerical integration.
Keywords: Equivalent circuits | Geometry | Integral equations | Integral equations | Magnetic circuits | Magnetic domains | magnetic fields | magnetic material modeling | Mathematical models | partial element equivalent circuit (PEEC) method | Standards | voxel
Abstract: Target design methodologies (DfX) were developed to cope with specific engineering design issues such as cost-effectiveness, manufacturability, assemblability, maintainability, among others. However, DfX methodologies are undergoing the lack of real integration with 3D CAD systems. Their principles are currently applied downstream of the 3D modelling by following the well-known rules available from the literature and engineers’ know-how (tacit internal knowledge). This paper provides a method to formalize complex DfX engineering knowledge into explicit knowledge that can be reused for Advanced Engineering Informatics to aid designers and engineers in developing mechanical products. This research work wants to define a general method (ontology) able to couple DfX design guidelines (engineering knowledge) with geometrical product features of a product 3D model (engineering parametric data). A common layer for all DfX methods (horizontal) and dedicated layers for each DfX method (vertical) allow creating the suitable ontology for the systematic collection of the DfX rules considering each target. Moreover, the proposed framework is the first step for developing (future work) a software tool to assist engineers and designers during product development (3D CAD modelling). A design for assembly (DfA) case study shows how to collect assembly rules in the given framework. It demonstrates the applicability of the CAD-integrated DfX system in the mechanical design of a jig-crane. Several benefits are recognized: (i) systematic collection of DfA rules for informatics development, (ii) identification of assembly issues in the product development process, and (iii) reduction of effort and time during the design review.
Abstract: Design for Manufacturing and Assembly (DfMA) is a consolidated engineering activity that suffers a real integration with 3D CAD systems. DfMA principles are currently applied downstream of the 3D modelling, by following the well-known rules available from the literature and company’s know-how. The paper provides a method to acquire, elaborate and represent DfMA rules sets to aid designers and engineers in developing mechanical products. This research work wants to define a general method able to couple DfMA design guidelines (knowledge-based design) with geometrical product features available by the investigation of the 3D model. The analysis of the 3D CAD model allows to anticipate manufacturing issues and to control manufacturing cost during product design. Moreover, a framework to embed this approach within a 3D CAD system is presented for future development in a software tool. Two case studies, a simple casing made of six parts and a centrifugal pump made of sixty-eight parts, highlight how the proposed method allows easy deployment of this approach in DfMA projects. Several benefits are recognized: (i) anticipation of manufacturing and assembly issues, (ii) reduction of manufacturing and assembly cost and, (iii) reduction of effort and time required by designers during the product development process.
Abstract: Burn injuries requires post-accident medical treatment. However, the treatment of burns does not end with first aid because scarred skin must be managed for many years, and in some circumstances, for life. The methods used to evaluate the state of a burn scar based, for instance, on Patient and Observer Scar Assessment Scale or similar ones, often lacks in univocally assessing the scarred skin’s state of health. As a result, the primary aim of this research is to design and build a prototype that can support the doctor during scar assessment, and eventually therapy, by providing objective information on the state of the lesion, particularly the value of skin pliability. The developed tool is based on the depressomassage treatment probe named LPG, currently used to treat burn scars in a number of hospitals. It consists of a non-invasive massage technique using a mechanical device to suction and mobilize scar tissue and is used as a post-operative treatment to speed up the healing process to make the mark of the scar less visible. The prototype is specifically designed to be manufactured using Additive Manufacturing and was validated comparing its performances against the ones of a certified instrument (i.e., the Romer Absolute ARM with RS1 probe). Validation was carried out by designing and developing a tool to put the RS1 probe in the same measurement conditions of the new prototype probe. Tests performed to assess the performance of the devised prototype show that the probe developed in this work is able to provide measurements with a sufficient degree of accuracy (maximum error ±0.1 mm) to be adopted for a reliable estimation of the pliability value in a hospital environment.
Abstract: This paper introduces a system that enable the collection of relevant data related to the emotional behavior and attention of both student and professor during exams. It exploits facial coding techniques to enable the collection of a large amount of data from the automatic analysis of students and professors faces using video analysis, advanced techniques for gaze tracking based on deep Learning, and technologies and the principles related to the Affective Computing branch derived from the research of Paul Ekman. It provides tools that facilitates the interpretation of the collected data by means of a dashboard. A preliminary experiment has been carried out to investigate whether such a system may help in assessing the evaluation setting and support reflection on the evaluation processes in the light of the different situations, so as to improve the adoption of inclusive approaches. Results suggest that information provided by the proposed system can be helpful in assessing the setting and the evaluation process.
Abstract: The role of 3D virtual reconstruction of lost heritage artefacts is acquiring ever-greater importance, as a support for archaeological research and art history studies, as well as a vehicle for the cultural and evocative involvement of the end-user. The main risk of virtual reconstruction is the lack of a faithful restitution but, conversely, very often the artefact conservation state does not allow a complete 3D reconstruction. Therefore, 2D sources, both textual and iconographic, represent a precious integration and completion of the existing 3D sources. This paper proposes an operating systematic workflow to integrate retrieved 2D and 3D sources and assess their compatibility for the virtual reconstruction of lost heritage artefacts using and integrating 3D survey and digital modelling. As a case study, we virtually reconstructed the lost equestrian monument of Duke Francesco III d'Este, 7 m high, built in 1774 in Modena, Italy, by the sculptor Giovanni Antonio Cybei and completely destroyed a little over 20 years later during the revolutionary uprisings. Following the proposed workflow, we integrate data coming from: a still preserved preparatory stucco model, paintings and engravings showing the missing details of the 3D model, a series of urban views returning the proportion and positioning of the monument (statue, pedestal and base), a fragment of the right foot providing the statue size and the appearance of the original white Carrara marble. The final 3D digital model shows a faithful correspondence to the 2D sources and guarantees an effective user’s fruition thanks to dedicated virtual applications. Besides the scientific and cultural goal, we highlight the evocative role of this work, which has contributed to the restitution of a monument that is unknown to most citizens and visitors.
Abstract: One of the main limitations in subject-centred design approach is represented by getting 3D models of the region of interest. Indeed, 3D reconstruction from imaging data (i.e., computed tomography scans) is expensive and exposes the subject to high radiation doses. Statistical Shape Models (SSMs) are mathematical models able to describe the variability associated to a population and allow predicting new shapes tuning model parameters. These parameters almost never have a physical meaning and so they cannot be directly related to morphometric features. In this study a gender-combined SSM model of the human mandible was setup, using Generalised Procrustes Analysis and Principal Component Analysis on a dataset of fifty mandibles. Twelve morphometric features, able to characterise the mandibular bone and readily collectable during external examinations, were recorded and correlated to SSM parameters by a multiple linear regression approach. Then a cross-validation procedure was performed on a control set to determine the combination of features able to minimise the average deviation between real and predicted shapes. Compactness of the SSM and main modes of deformations have been investigated and results consistent with previous works involving a higher number of shapes were found. A combination of five features was proved to characterise predicted shapes minimising the average error. As completion of the work, a male SSM was developed and performances compared with those of the combined SSM. The features-based model here proposed could represent a useful and easy-to-use tool for the generation of 3D customised models within a virtual interactive design environment.
Keywords: Features selection | Mandible | Morphometric measurements | PCA | Predicted shapes | Statistical shape model | Subject-specific model
Abstract: Compared to other additive technologies, Wire and Arc Additive Manufacturing (WAAM) offers high deposition rates, flexibility and a larger build volume as well as reduction of material waste. WAAM can be combined with a subtractive technology in hybrid robotic cells to further increase the application scope, thus producing products with improved surface finish where needed. However, there are some open issues that limit this process. So, the main goal of this paper is to review current research developments and provide a framework aimed at manufacturing parts by hybrid cells. A procedure is defined which moves from the evaluation of the designed shapes, their analysis to identify a proper manufacturing sequence until the elaboration of the instructions for the cell automaton controllers. Main WAAM issues are outlined to identify main research directions, and a test case is presented to highlight the process phases.
Keywords: Hybrid manufacturing | Process planning | Robotic cell | Wire and arc additive manufacturing
Abstract: Focus of this work is the recognition of the standard parts contained in a CAD assembly model, with the aim of enhancing the model semantics. Standard parts are components typically used in mechanical industry, which have a specificc engineering meaning and follow international standards. In particular eight categories of standard parts are considered, i.e. screws, nuts, O-ring, washers, circlips,keys, studs and pins. The provided algorithm relies on the geometric and topological analysis of the CAD model parts. A part is assigned to one of the categories if it satisfies the geometric requirements extracted for that specific category, based on engineering knowledge and design rules. In addition, if a part is recognized as standard part, besides the class of membership, further information is provided as result, namely its engineering dimensions.
Keywords: Assembly Semantics | CAD Model Processing | Part Classification | Standard Part Detection | Type Recognition
Abstract: Virtual or physical models of ancient machines are often used for museum exhibitions, documentaries and/or cinematographic works. Especially for high-fidelity models, complex activities are required, which actually lead the different stakeholders involved in the process to “design” an artifact (the model). As with any design process, the design of models of ancient machines can also benefit from the support of structured methods that guide the designers from the early “ideas” to the final design. This paper proposes a systematic approach specifically tailored for the interpretation and design of ancient machines, where a methodological tool is provided to manage both idea-generation and information-gathering activities. The method was applied to the design of a model of the delta wing conceived by Leonardo da Vinci (i.e., the glider represented in the Codex Madrid 1, Folio 64r), allowing to analyze and obtain an embodiment of the machine with the required fidelity level, thought to be realized in real scale.
Keywords: ancient machines | CAD | delta wing | design methods | design process | glider | Leonardo da Vinci | museum models | systematic design | technological heritage
Abstract: Introduction: In recent years, the scientific community focused on developing Computer-Aided Diagnosis (CAD) tools that could improve clinicians’ bone fractures diagnosis, primarily based on Convolutional Neural Networks (CNNs). However, the discerning accuracy of fractures’ subtypes was far from optimal. The aim of the study was 1) to evaluate a new CAD system based on Vision Transformers (ViT), a very recent and powerful deep learning technique, and 2) to assess whether clinicians’ diagnostic accuracy could be improved using this system. Materials and methods: 4207 manually annotated images were used and distributed, by following the AO/OTA classification, in different fracture types. The ViT architecture was used and compared with a classic CNN and a multistage architecture composed of successive CNNs. To demonstrate the reliability of this approach, (1) the attention maps were used to visualize the most relevant areas of the images, (2) the performance of a generic CNN and ViT was compared through unsupervised learning techniques, and (3) 11 clinicians were asked to evaluate and classify 150 proximal femur fractures’ images with and without the help of the ViT, then results were compared for potential improvement. Results: The ViT was able to predict 83% of the test images correctly. Precision, recall and F1-score were 0.77 (CI 0.64–0.90), 0.76 (CI 0.62–0.91) and 0.77 (CI 0.64–0.89), respectively. The clinicians’ diagnostic improvement was 29% (accuracy 97%; p 0.003) when supported by ViT's predictions, outperforming the algorithm alone. Conclusions: This paper showed the potential of Vision Transformers in bone fracture classification. For the first time, good results were obtained in sub-fractures classification, outperforming the state of the art. Accordingly, the assisted diagnosis yielded the best results, proving the effectiveness of collaborative work between neural networks and clinicians.
Keywords: CAD system | Deep learning | Femur fracture | Self-attention | Vision transformer
Abstract: Purpose: To evaluate the role of 3D models on positive surgical margin rate (PSM) rate in patients who underwent robot-assisted radical prostatectomy (RARP) compared to a no-3D control group. Secondarily, we evaluated the postoperative functional and oncological outcomes. Methods: Prospective study enrolling patients with localized prostate cancer (PCa) undergoing RARP with mp-MRI-based 3D model reconstruction, displayed in a cognitive or augmented-reality fashion, at our Centre from 01/2016 to 01/2020. A control no-3D group was extracted from the last two years of our Institutional RARP database. PSMr between the two groups was evaluated and multivariable linear regression (MLR) models were applied. Finally, Kaplan–Meier estimator was used to calculate biochemical recurrence at 12 months after the intervention. Results: 160 patients were enrolled in the 3D Group, while 640 were selected for the Control Group. A more conservative NS approach was registered in the 3D Group (full NS 20.6% vs 12.7%; intermediate NS 38.1% vs 38.0%; standard NS 41.2% vs 49.2%; p = 0.02). 3D Group patients had lower PSM rates (25 vs. 35.1%, p = 0.01). At MLR models, the availability of 3D technology (p = 0.005) and the absence of extracapsular extension (ECE, p = 0.004) at mp-MRI were independent predictors of lower PSMr. Moreover, 3D model represented a significant protective factor for PSM in patients with ECE or pT3 disease. Conclusion: The availability of 3D models during the intervention allows to modulate the NS approach, limiting the occurrence of PSM, especially in patients with ECE at mp-MRI or pT3 PCa.
Keywords: 3D modeling | Augmented reality | Prostate cancer | Robotic surgery | Surgical margins
Abstract: Exhausting manual labor is still predominant in the industrial context. It typically consists in manipulating heavy parts or working in non-ergonomic conditions. The resulting work-related musculoskeletal disorders are a major problem to tackle. The most-affected body section is the the lumbar spine. Recently, exoskeletons have been identified as a possible non-invasive solution to reduce the impact of low-back pain. State-of-the-art prototypes have been optimized to: follow unconstrained human kinematics, (partially) relieve the load on assisted joints, and allow anthropometric adaptation. Yet, this technology still has limited adoption. Manufacturing optimization may address the following limitations: bulky/heavy resulting designs, complex assembly and maintenance, high manufacturing costs, long procedures for adaptation and wearing, and psychological effects (e.g., cognitive load and usability). In this contribution, the aforementioned issues are tackled improving a previous low-back exoskeleton prototype. In particular, kinematic analysis, Finite-Element-Method, and topological optimization have been combined to obtain a lightweight prototype, testing different materials (Nylon, carbon-fiber reinforced PC/ABS, etc.). We applied both Design for Assembly and Design for Manufacturability. The resulting exoskeleton prototype is described in the paper, ready for end-user field tests.
Abstract: In the last years, the precision and personalized medicine is pushing the biomedical research efforts towards the direction of implant surgery requiring only 1-step approach: this goal has been achieved after the introduction of resorbable implants. The resorbable prosthetic support is indicated for temporary prosthetic applications, such as bone fractures fixation, or all those conditions usually treated with metal implants then removed with a second surgery, just after the healing of the bone defect. Biodegradable, bioactive and customizable implants for the treatment of bone fractures, both efficient in bearing the functional loads, and showing good biocompatibility and degradation properties matching the bone tissue healing, are still lacking. These premises have led to consider Magnesium (Mg) and its alloys as very promising candidates for the development of temporary, resorbable implants. However, the very high corrosion rate of Mg is the main problem, not yet solved. The material needs to be properly treated/coated, as well as manufactured, in order to design the most suitable duration of the temporary prosthesis permanence in situ. An innovative and interdisciplinary approach has been developed within the M.Era-Net ISIDE project and it is here briefly detailed with a special focus on the highlighted application fields.
Abstract: Geometric and dimensional deviations are the main contributors on quality and cost of products. Specifically, the selection of tolerance types and the appropriate allowable range plays a central role for an effective development process. Nevertheless, the trade-off between expected performances and target costs requires skills and interaction of many areas of engineering design, especially in the early design phases. Despite many tolerance-cost optimization practices are proposed by the research community several limitations still hamper the industrial application: among them, data and parameters sharing, flexibility to application complexity, and integration of simulation tools are the main ones. Focusing on a systematic framework, an integrated modelling and simulation environment is required to take full advantage of the concurrent use of engineering software. The present paper contributes to this aim by suggesting a Computer-Aided framework that integrates Geometric Dimensioning and Tolerancing simulations and manufacturing cost estimations in a multi-disciplinary optimization environment. Advanced tools are the cornerstones of the suggested framework, enabling easy identification of the main operational steps and providing the automation of the optimization. To be validated and demonstrate the effective applicability, the framework has been applied for the tolerance-cost optimization of an archetypal case study of an automotive engine assembly. The simulation models have been integrated within the optimization, providing several configurations of tolerances from which identify the optimal one. The analysis of optimization results allows to assess the efficiency of the method, highlighting further improvements to extend its robustness, flexibility, and application range.
Abstract: The study of the spine range of motion under given external load has been the object of many studies in literature, finalised to a better understanding of the spine biomechanics, its physiology, eventual pathologic conditions and possible rehabilitation strategies. However, the huge amount of experimental work performed so far cannot be straightforwardly analysed due to significant differences among loading set-ups. This work performs a meta-analysis of various boundary conditions in literature, focusing on the flexion/extension behaviour of the lumbar spine. The comparison among range of motions is performed virtually through a validated multibody model. Results clearly illustrated the effect of various boundary conditions which can be met in literature, so justifying differences of biomechanical behaviours reported by authors implementing different set-up: for example, a higher value of the follower load can indeed result in a stiffer behaviour; the application of force producing spurious moments results in an apparently more deformable behaviour, however the respective effects change at various segments along the spine due to its natural curvature. These outcomes are reported not only in qualitative, but also in quantitative terms. The numerical approach here followed to perform the meta-analysis is original and it proved to be effective thanks to the bypass of the natural variability among specimens which might completely or partially hinder the effect of some boundary conditions. In addition, it can provide very complete information since the behaviour of each functional spinal unit can be recorded. On the whole, the work provided an extensive review of lumbar spine loading in flexion/extension.
Abstract: Automated segmentation of brain tumors is a difficult procedure due to the variability and blurred boundary of the lesions. In this study, we propose an automated model based on Bendlet transform and improved Chan-Vese (CV) model for brain tumor segmentation. Since the Bendlet system is based on the principle of sparse approximation, Bendlet transform is applied to describe the images and map images to the feature space and, thereby, first obtain the feature set. This can help in effectively exploring the mapping relationship between brain lesions and normal tissues, and achieving multi-scale and multi-directional registration. Secondly, the SSIM region detection method is proposed to preliminarily locate the tumor region from three aspects of brightness, structure, and contrast. Finally, the CV model is solved by the Hermite-Shannon-Cosine wavelet homotopy method, and the boundary of the tumor region is more accurately delineated by the wavelet transform coefficient. We randomly selected some cross-sectional images to verify the effectiveness of the proposed algorithm and compared with CV, Ostu, K-FCM, and region growing segmentation methods. The experimental results showed that the proposed algorithm had higher segmentation accuracy and better stability.
Keywords: Bendlet system | feature set | image expression | segmentation | Shannon-cosine wavelet
Abstract: A 59-year-old woman was admitted to the emergency department for heart failure (HF), New York Heart Association (NYHA) IV, showing an anterior, evolved myocardial infarction (MI) with a wide apical left ventricular aneurysm (LVA), ejection fraction (EF) 24%, and global longitudinal strain (GLS) −5. 5% by echo. Cardiac magnetic resonance imaging (MRI) confirmed an apical LVA without thrombus, EF 20%, and a transmural delayed enhancement in the myocardium wall. Coronarography showed a three-vessel disease with occluded proximal left anterior descending (LAD) and proximal right coronary artery (RCA). Based on the cardiac CT scan, we decided to generate a three-dimensional (3D) print model of the heart, for better prediction of residual LV volumes. After LVA surgery plus complete functional revascularization, an optimal agreement was found between predicted and surgical residual LV end-diastolic (24.7 vs. 31.8 ml/m2) and end-systolic (54.1 vs. 69.4 ml/m2) volumes, with an improvement of NYHA class, from IV to I. The patient was discharged uneventfully and at 6- and 12-month follow-up, the NYHA class, and LV volumes were found unchanged. This is a second report describing the use of the 3D print model for the preoperative planning of surgical management of LVA; the first report was described by Jacobs et al. among three patients, one with a malignant tumor and the remaining two patients with LVA. This article focused on the use of the 3D print model to optimize surgical planning and individualize treatment of LVA associated with complete functional revascularization, leading to complete recovery of LV function with a favorable outcome.
Keywords: 3D printing model | CAD | heart failure | left ventricular aneurysm | surgical ventricular restoration
Abstract: In the last decades, the flourishing of Additive Manufacturing (AM) promoted innovative design solutions in many different sectors. Despite the numerous advantages of AM technology, there are still open challenges in the field. In Fused Deposition Modelling (FDM) structures the layer-by-layer manufacturing process induces anisotropy in the material properties of the structures. The correct characterization of the mechanical properties is fundamental in the design and development stages but at the same time difficult to achieve. The experimental approach can be extremely long and expensive. An alternative is the use of an accurate numerical approach and performing a Finite Element Analysis (FEA) of the geometry which is effectively printed. However, to the best of the authors' knowledge, there is not a common and well-established procedure to reconstruct the real geometry which is generated after the slicing process. In this paper, starting from the information provided by the G-CODE, an easy-to-use, and reproducible methodology to reconstruct the printed geometry is presented. The performance of the innovative approach is evaluated via qualitative observations by referring to several case studies. The results are thoroughly analysed, and future trends and research needs are highlighted.
Abstract: Nowadays, robot-based additive manufacturing (RBAM) is emerging as a potential solution to increase manufacturing flexibility. Such technology allows to change the orientation of the material deposition unit during printing, making it possible to fabricate complex parts with optimized material distribution. In this context, the representation of parts geometries and their subsequent processing become aspects of primary importance. In particular, part orientation, multiaxial deposition, slicing, and infill strategies must be properly evaluated so as to obtain satisfactory outputs and avoid printing failures. Some advanced features can be found in commercial slicing software (e.g., adaptive slicing, advanced path strategies, and non-planar slicing), although the procedure may result excessively constrained due to the limited number of available options. Several approaches and algorithms have been proposed for each phase and their combination must be determined accurately to achieve the best results. This paper reviews the state-of-the-art works addressing the primary methods for the representation of geometries and the subsequent geometry processing for RBAM. For each category, tools and software found in the literature and commercially available are discussed. Comparison tables are then reported to assist in the selection of the most appropriate approaches. The presented review can be helpful for designers, researchers and practitioners to identify possible future directions and open issues.
Abstract: The current study aimed to propose a Deep Learning (DL) based framework to retrieve in real-time the position and the rotation of an object in need of maintenance from live video frames only. For testing the positioning performances, we focused on intervention on a generic Fused Deposition Modeling (FDM) 3D printer maintenance. Lastly, to demonstrate a possible Augmented Reality (AR) application that can be built on top of this, we discussed a specific case study using a Prusa i3 MKS FDM printer. This method was developed using a You Only Look Once (YOLOv3) network for object detection to locate the position of the FDM 3D printer and a subsequent Rotation Convolutional Neural Network (RotationCNN), trained on a dataset of artificial images, to predict the rotations’ parameters for attaching the 3D model. To train YOLOv3 we used an augmented dataset of 1653 real images, while to train the RotationCNN we utilized a dataset of 99.220 synthetic images, showing the FDM 3D Printer with different orientations, and fine-tuned it using 235 real images tagged manually. The YOLOv3 network obtained an AP (Average Precision) of 100% with Intersection Over Unit parameter of 0.5, while the RotationCNN showed a mean Geodesic Distance of 0.250 (σ = 0.210) and a mean accuracy to detect the correct rotation r of 0.619 (σ = 0.130), considering as acceptable the range [r − 10, r + 10]. We then evaluate the CAD system performances with 10 non-expert users: the average speed improved from 9.61 (σ = 1.53) to 5.30 (σ = 1.30) and the average number of actions to complete the task from 12.60 (σ = 2.15) to 11.00 (σ = 0.89). This work is a further step through the adoption of DL and AR in the assistance domain. In future works, we will overcome the limitations of this approach and develop a complete mobile CAD system that could be extended to any object that presents a 3D counterpart model.
Abstract: Recently, estimation of the visual saliency map in car driving scenarios has received significant research interests. Visual saliency perception includes the processing of specific parts of the visual driving scene in which the subject (car driver) pays more attention (specifically the parts whose gaze is focused). This work makes further contributions to video saliency research with application on the sustainable assisted driver technologies. Ad-hoc Semantic Fully Convolutional Deep Network embedding Gradient-Reversal domain adaptation layer has been implemented to process the video frames captured by a commercial low frame-rate automotive-grade camera device hosted outside the vehicle. A parallel motion-magnified visual-to-physio drowsiness assessment of the car driver will complete the proposed full automotive solution. The collected experimental results confirmed the effectiveness of the proposed solution.
Keywords: ADAS | Deep Learning | physio-signal | Saliency
Abstract: Automotive industry is making rapid progress in the development of next generation cars with higher levels of autonomy and intelligent assistance. Although the general advanced driver assistance system (ADAS) architecture is widely discussed, limited interaction between driver and these intelligent solutions sometimes make these approaches inefficient. For these reasons, the authors triggered an investigation about driver's feedback in relation to the assistance inputs provided by the ADAS technologies. In this context, the goal of this proposal is the design of an intelligent system that learns from the analysis of the car driver eyes saccadic movements, the correlated level of attention towards the salient driving scene. With this approach, we enabled a visual-feedback system which learns the driver eye's fixing dynamic associated to the analyzed driving scene. Through ad-hoc enhanced motion magnification technique, the authors were able to amplify the mentioned saccadic dynamics in order to allow a downstream deep classifier to associate this physiological behavior with the corresponding level of the driver attention. The collected performances (over 97%) confirmed the effectiveness of the proposed method.
Abstract: Thanks to Laser Powder Bed Fusion (L-PBF) technology, SCALMALLOY® was the first aluminum powder material designed for Additive Manufacturing (AM), achieving a fine microstructure with high performance that is comparable to other cast materials. Despite the mechanical properties that can be achieved, there are some inherent factors that can impede components performance (i.e., surface roughness). Parts produced by L-PBF are usually characterized by rough “as-built” surfaces; hence, it is fundamental during the design phase to understand and consider how the quality of surfaces impacts on the part performance. This paper aims to provide a Computer-Aided Engineering (CAE) workflow to design components with different finishing regions in accordance with the functional distinction that exists among them. To achieve this goal, a comparison of the mechanical properties achieved for SCALMALLOY® specimens with and without post-processing is here assessed to fit proper material models for numerical simulation purposes. The material models, built with/from experimental data, are fit to functionally adapt the performance of 3D-printed objects inside CAE simulations like a Functionally Graded Material (FGM). A CAE design workflow is here applied to a case study, suitable to demonstrate how the methodology may support the integrated product–process design of structural parts reducing the cost of post-processing in AM. This approach may mitigate the performance decrease of “as-built” surfaces since the experimental results show a different fatigue endurance limit between the “as-built” and CNC machined specimens about of three times.
 Kyratzis D., Alemanno F., Altomare C., Barbato F.C.T., Bernardini P., Cattaneo P.W., De Mitri I., de Palma F., Di Venere L., Di Santo M., Fusco P., Gargano F., Loparco F., Loporchio S., Marsella G., Mazziotta M.N., Pantaleo F.R., Parenti A., Pillera R., Rappoldi A., Raselli G., Rossella M., Serini D., Silveri L., Surdo A., Wu L., Adriani O., Aloisio R., Ambrosi G., An Q.,
The Plastic Scintillator Detector of the HERD space mission, Proceedings of Science,
Abstract: The High Energy cosmic-Radiation (HERD) detector is one of the prominent space-borne instruments to be installed on-board the Chinese Space Station (CSS), around 2027. Primary scientific goals regarding this initiative include: precise measurements of cosmic ray (CR) energy spectra and mass composition, at energies up to the PeV range; contributions to high energy gamma-ray astronomy and transient studies; as well as indirect searches for Dark Matter (DM) particles via their possible annihilation/decay to detectable products. HERD is configured to accept incident particles from both its top and four lateral sides. Owing to its pioneering design, an order of magnitude increase in acceptance is foreseen, with respect to previous and ongoing experiments. The Plastic Scintillator Detector (PSD) constitutes an important sub-detector of HERD, particularly aimed towards anti-coincidence (discriminating incident photons from charged particles), while providing precise charge measurement of incoming cosmic-ray nuclei in a range of Z = 1-26. Main requirements concerning its design, include: high detection efficiency, broad dynamic range and good energy resolution. In order to select the optimal layout, two geometries are currently under investigation: one based on long scintillator bars and the other on square tiles, with both layouts being readout by Silicon Photomultipliers (SiPMs). Ongoing activities and future plans regarding the HERD PSD will be presented in this work.
Abstract: Since every structure in the human body can vary, customization is important to choose the most appropriate medical option according to the patient. Total knee arthroplasty (TKA) is a surgical procedure for the knee replacement that has a high rate of patient's dissatisfaction. Indeed, conventional prostheses are based on anthropometric data that accommodate common knees. However, mismatch can occur due to anatomical variations among the individuals. Thanks to the advances in imaging techniques and 3D modeling, it is possible to create customized knee implants starting from medical images. In this context, the present research proposes a methodology to design a customized knee implant taking into account clinical (e.g., prosthesis alignment and surgical cuts) and technical parameters (e.g., materials) that have a direct impact on TKA performance and patient's satisfaction. Changing these parameters, different scenarios have been modeled and simulated to understand the most suitable combination. Finite element analysis (FEA) has been employed to simulate and compare the proposed customized models, changing the different clinical and technical parameters. Stress induced by different combinations of the parameters has been evaluated to choose the optimal solution among the eight proposed scenarios. The optimum is reached with a physiological alignment, with six femoral facets and the ultra-high molecular weight polyethylene (UHMWPE) tibial insert. The implant design maintains the natural joint line and allows preserving more bone. The material is the parameter that mostly influences the stress distribution.
Abstract: The 6D pose estimation of an object from an image is a central problem in many domains of Computer Vision (CV) and researchers have struggled with this issue for several years. Traditional pose estimation methods (1) leveraged on geometrical approaches, exploiting manually annotated local features, or (2) relied on 2D object representations from different points of view and their comparisons with the original image. The two methods mentioned above are also known as Feature-based and Template-based, respectively. With the diffusion of Deep Learning (DL), new Learning-based strategies have been introduced to achieve the 6D pose estimation, improving traditional methods by involving Convolutional Neural Networks (CNN). This review analyzed techniques belonging to different research fields and classified them into three main categories: Template-based methods, Feature-based methods, and Learning-Based methods. In recent years, the research mainly focused on Learning-based methods, which allow the training of a neural network tailored for a specific task. For this reason, most of the analyzed methods belong to this category, and they have been in turn classified into three sub-categories: Bounding box prediction and Perspective-n-Point (PnP) algorithm-based methods, Classification-based methods, and Regression-based methods. This review aims to provide a general overview of the latest 6D pose recovery methods to underline the pros and cons and highlight the best-performing techniques for each group. The main goal is to supply the readers with helpful guidelines for the implementation of performing applications even under challenging circumstances such as auto-occlusions, symmetries, occlusions between multiple objects, and bad lighting conditions.
Keywords: 6D position estimation | Computer vision | Deep learning | RGB Input
Abstract: Purpose: This paper aims to enhance the visual quality of artificial above-ground structures, like pylons, masts, and towers of infrastructures and facilities, through a systematic design method for their morphological and structural optimization. Design/methodology/approach: The method achieves the functional and aesthetic goals based on the application of computer-aided tools. In particular, this is achieved according to three key steps: • Morphological development of landscape-related symbolism, environment, or culture and social needs. • Topology optimization of the design concept to reduce the structural weight and its visual impact. • Engineering of the resulting optimized structure. Practical implications: As a case study, the method is used for designing electricity pylons for the coastal territory of a Mediterranean European country, such as Italy. Citizens were involved during the identification phase of a symbolic shape for the concept development and during the final assessment phase. Research limitations/implications: The engineering phase has been performed by assembling standard lattice components with welded connections. Even if the use of this truss-like structure should lead to a minimum cost, the developed structure employs an additional 15%–20% of trusses and sheet metal covers the final cost is higher than a standard lattice pylon. Findings: The result is a structure with enhanced visual quality according to the international guidelines and fully complying with mandatory and functional requirements, such as regulatory and industrial feasibility, as well as those arising from social components. Originality/value: The method shows its potential in defining a custom design for lightweight structures with enhanced visual quality regarding the critical situation discussed here. The method considers both the subjective perception of citizens and their priorities and the landscape where the structures will be installed.
 Adriani O., Alemanno F., Aloisio R., Altomare C., Ambrosi G., An Q., Antonelli M., Azzarello P., Bai L., Bai Y.L., Bao T.W., Barbanera M., Barbato F.C.T., Bernardini P., Berti E., Bertucci B., Bi X.J., Bigongiari G., Bongi M., Bonvicini V., Bordas P., Bosch-Ramon V., Bottai S., Brogi P., Cadoux F., Campana D., Cao W.W., Cao Z., Casaus J., Catanzani E., Cattaneo P.W.,
Gamma-ray performance study of the HERD payload, Proceedings of Science,
Abstract: The High Energy cosmic-Radiation Detection (HERD) facility has been proposed as a space astronomy payload onboard the future China's Space Station. HERD is planned for operation starting around 2027 for about 10 years In addition to the unprecedented sensitivity for dark matter searches and cosmic-ray measurements up to the knee energy, it should perform gamma-ray monitoring and full sky survey from few hundred MeV up to tens of TeV. We present the first study of the HERD gamma-ray performance obtained with full simulations of the whole detector geometry. HERD will be a cubic detector composed with 5 active faces. We present a study conducted inside the HERD analysis software package, which includes a detailed description of the detector materials. In this work we present the HERD effective area, the point spread function and the resulting gamma-ray sensitivity.
Keywords: Cosmology | Gamma rays | Optical transfer function | Space stations
 Perrina C., Azzarello P., Cadoux F., Favre Y., Frieden J.M., La Marra D., Sukhonos D., Wu X., Adriani O., Alemanno F., Aloisio R., Altomare C., Ambrosi G., An Q., Antonelli M., Azzarello P., Bai L., Bai Y.L., Bao T.W., Barbanera M., Barbato F.C.T., Bernardini P., Berti E., Bertucci B., Bi X.J., Bigongiari G., Bongi M., Bonvicini V., Bordas P., Bosch-Ramon V., Bottai S.,
FIT: the scintillating fiber tracker of the HERD space mission, Proceedings of Science,
Abstract: The High Energy cosmic-Radiation Detection (HERD) facility is a space payload proposed to be installed onboard the China’s Space Station (CSS). The aims of HERD are the indirect detection of dark matter, the direct detection of cosmic rays towards the “knee” of the spectrum (∼ 1 PeV) and the monitoring of the full gamma-ray sky from 100 MeV. The HERD core is a calorimeter capable of accepting particles incident on its top and four lateral sides, each equipped with a sector of the scintillating fiber tracker: FIT. The FIT sectors host 7 tracking planes made of modules. The module, composed of a fiber mat and three arrays of silicon photomultipliers (SiPMs), is the elementary brick of FIT. Several FIT modules have been built and tested with particle beams at CERN. A FIT demonstrator, made of two partially instrumented tracking planes, has been assembled and sent through vibration tests. The results of the performed tests as well as the current design of FIT are presented in this contribution.
Keywords: Cosmology | Gamma rays | Scintillation | Space stations
 Velasco M.A., Bao T., Berti E., Bonvicini V., Casaus J., Giovacchini F., Liu X., Marco R., Marín J., Martínez G., Mori N., Oliva A., Pacini L., Quan Z., Tang Z., Xu M., Zampa G., Zampa N., Adriani O., Alemanno F., Aloisio R., Altomare C., Ambrosi G., An Q., Antonelli M., Azzarello P., Bai L., Bai Y.L., Bao T.W., Barbanera M., Barbato F.C.T., Bernardini P., Bertucci B., Bi X.J.,
The High Energy cosmic-Radiation Detector (HERD) Trigger System, Proceedings of Science,
Abstract: The High Energy cosmic-Radiation Detection (HERD) facility is a next generation spaceborne detector to be installed onboard the Chinese Space Station for about 10 years. HERD will address major problems in fundamental physics and astrophysics, providing precise measurements of charged-cosmic rays up to PeV energies, performing indirect searches for dark matter in the electron spectrum up to few tens of TeV and monitoring the gamma-ray skymap for surveys and transient searches. HERD is composed of a 3D imaging calorimeter (CALO) surrounded by a scintillating fiber tracker (FIT), a plastic scintillator detector (PSD) and a silicon charge detector (SCD). In addition, a transition radiation detector (TRD) is placed on a lateral side to provide accurate energy calibration. Based on this innovative design, the effective geometric factor of HERD will be one order of magnitud larger than that of current space-based detectors. The HERD trigger strategy is designed to accomplish the scientific goals of the mission, and is based on trigger definitions that rely on the energy deposited in CALO and the PSD. The trigger performances are evaluated using a detailed Monte Carlo simulation that includes the latest HERD geometry. In addition, alternative trigger definitions based on the event topology can be established thanks to the photodiode readout of CALO crystals. The feasibility of these topological triggers is also investigated and presented.
Keywords: Cosmology | Gamma rays | Intelligent systems | Monte Carlo methods | Space stations | Tellurium compounds | Topology
 Pacini L., Adriani O., Bai Y.-L., Bao T.-W., Berti E., Bottai S., Cao W.-W., Casaus J., Cui X.-Z., D’Alessandro R., Formato V., Gao J.-R., Li R., Liu X., Lorusso L., Lyu L.-W., Marin J., Martinez G., Pizzolotto C., Qin J.-J., Quan Z., Shi D.-L., Starodubtsev O., Tang Z.-C., Tiberio A., Vagelli V., Velasco M.A., Wang B., Wang R.-J., Wang Z.-G., Xu M., Yang Y., Zhang L.,
Design and expected performances of the large acceptance calorimeter for the HERD space mission, Proceedings of Science,
Abstract: The High Energy cosmic-Radiation Detection (HERD) is a future space experiment which will be installed on the China’s Space Station around 2027. The main goal of the experiment is the measurement of cosmic rays up to energies which are not explored by the instruments currently operating in space, in particular protons with energies up to PeV, nuclei up to hundreds of TeV per nucleon and electrons up to tens of TeV. HERD will consist of silicon charge detectors, anti-coincidence scintillators, scintillating fiber trackers, a transition radiation detector and a calorimeter. The latter is a homogeneous, deep, 3D segmented calorimeter made of about 7500 LYSO cubic crystals: thanks to this innovative design, it will achieve large acceptance, good energy resolution and excellent electron/proton discrimination. In order to increase both energy calibration capabilities and redundancy of the instrument, the LYSO scintillation light will be read-out by two independent systems: the first is made of wave-length shifting fibers coupled with imaged intensified CMOS cameras, and the second one consists of photodiodes with different active areas connected to a custom front-end electronics. Both read-out systems are designed to have a large dynamic range, up to 107, and a low power consumption. The design of the calorimeter is validated by several Monte Carlo simulations and beam test results obtained with detector prototypes. In this paper we describe the anticipated performances of the calorimeter and the current status of the double read-out system, and we discuss the recent developments of both the HERD prototype and the flight model design.
Keywords: Cosmic rays | Cosmology | Intelligent systems | Monte Carlo methods | Scintillation counters | Silicon detectors | Space stations
Abstract: The LIFE SNEAK project, started in September 2021, aims at the reduction of noise from road traffic that mainly affects densely populated urban areas where the noise and vibrations produced by the tram overlap with noise produced by road traffic. Applicative measures will be designed and tested in a pilot case of the city of Florence, such as low-noise and vibration surfaces with life cycle costs comparable to those of traditional surfaces, and measures to reduce tram noise aiming to obtain substantial reductions in noise and annoyance. In the first phase, specific attention was dedicated to the state-of-the-art analysis concerning prediction and monitoring of the level of noise and ground-borne vibrations in urban environments. Moreover, the impacts of road traffic and tramway in terms of noise and vibrations on people annoyance in urban context have been investigated to design appropriate questionnaires for citizens. In fact, the exploration of any combined effect of vibration and noise on annoyance is also suggested by recent guidelines for designing dedicated social surveys. In this paper the procedure to design a noise and vibration measurements and survey campaign oriented to support an evaluation of effective reductions in terms of both levels and annoyance is presented.
Keywords: Acoustic variables control | Life cycle | Roads and streets | Vibration measurement
Abstract: The paper illustrates the design of a new mechanical system for propeller blades pitch calibration in medium power wind turbines. The peculiarity of this system is its capacity of adjusting through a feedback control system, which allows the wind turbine to capture the maximum amount of energy from the wind. In this work an axial drive system was studied by means of racks capable of linearly adjusting the pitch of all wind turbine propeller blades in an intrinsically synchronous way, with an advantage over the traditional methods of propeller blades pitch calibration. For different wind speeds the system adjusts the blades angle of incidence in order to reduce the rotation speed and keep the system as close as possible to the pre-established design conditions generating maximum energy with a high efficiency. The manuscript examines the main analyses and simulations conducted during the design phase. These show that the proposed method allows to reach higher efficiencies with a greater intrinsic stability compared to the traditional pitch control mechanisms in medium power wind turbines. The experimental results on the first prototypes confirm the efficiency increase.
Keywords: Linearly Adjusting | Medium Power Wind Turbines | Pitch Calibration | Propeller Blades | Racks
Abstract: Additive manufacturing technologies allow for the direct fabrication of 3D scaffolds with improved properties for tissue regeneration. In this scenario, design strategies and 3D fiber deposition technique are considered to develop advanced scaffolds with different lay-down patterns, tailored mechanical and biological properties. 3D poly(ε-caprolactone) scaffolds are manufactured and surface-modified (i.e., aminolysis). The effect of surface modification on the mechanical and biological performances of the designed 3D scaffolds is assessed.
Abstract: Light-activated resins and composites are used in conjunction with a light curing unit and allow an on-demand process of polymerization. These kinds of materials usually represent the most popular choice in the restorative dental practice. Some works have already highlighted contemporary tendencies in the use of nondegradable scaffolds and mesenchymal stem cells in regenerative medicine. Accordingly, the aim of the current research is to develop 3D porous and light-activated composite structures with optimized functional properties. Preliminary mechanical and biological tests are carried out.
Keywords: composite structure design | computer-aided design | design for photo-curing 3D printing | mechanical and functional properties
Abstract: The paradigm of Industry 4.0 allows to increase the efficiency and effectiveness of the production. Companies that will implement advanced solutions in production systems will increase their level of competitiveness and will be able reach high market shares. The present paper is focused on the development of advanced digital solutions to be implemented on a close power loop test bench designed to test high power transmissions for naval unit. In particular, the test configuration consists of a back-to-back connection between two identical mechanical reducers. Since the efficiency of these systems are very high, it is not necessary to use large electric motors, thus managing to contain the operating costs of the testing phase. The particular test bench allows to size the electric motor simply based on the dissipated power by the kinematic mechanisms. By means of suitable sensors installed on the test bench it is possible to extrapolate countless technical data. The implementation of Industry 4.0 enabling technologies allows to evaluate the increase in efficiency compared to traditional systems in terms of reduction of noise and vibrations, efficiency of lubrication, reduction of consumption, installation and maintenance cost of the entire system.
Keywords: Cad modeling | digital transformation | Experimental tests | Industry 4.0 | Internet of things | Shipyard 4.0 | Sustainability | Test bench
Abstract: Background and objective: Because of the three-dimensional distribution of morphological features of human vertebrae and the whole spine, in recent years, to make more precise diagnoses and to design optimized surgical procedures, new protocols have been proposed based on analysing their three-dimensional (3D) models. In the related literature, processes of segmentation and morphological features recognition are essentially performed by a skilled operator that selects the interesting areas. So, being affected by the preparation and experience of the operator, this produces an evaluation that is poorly reproducible and repeatable for the uncertainties of a typical manual measurement process. Methods: To overcome this limitation, in this paper a new automatic method is proposed for feature segmentation and recognition of human vertebrae. The proposed computer-based method, starting from 3D high density discretized models of thoracic and lumbar vertebrae, automatically performs both the semantic and geometric segmentation of their morphological features. The segmentation and recognition rules codify some important definitions used in the traditional manual method, considering all the vertebra morphology information that is invariant inter-subject. Results: The automatic method proposed here is verified by analysing many real vertebrae, both acquired using a 3D scanner and coming from Computerized Tomography (CT) scans. The obtained results are critically discussed and compared with the traditional manual methods for vertebra analysis. The method has proven to be robust and reliable in the segmentation and recognition of morphological features of vertebrae. Furthermore, the proposed automatic method avoids the blurring of quantitative parameters get from vertebrae, resulting from poor repeatability and reproducibility of manual methods used in the state-of-the-art. Conclusions: Starting from the automatic segmentation and recognition here proposed, it is possible to automatically calculate the parameters of thoracic or lumbar vertebrae used in archaeology, medicine, or biomechanics or define their new ones.
Keywords: 3D medical image analysis | Computer methods for vertebra analysis | Shape segmentation | Thoracic and lumbar vertebrae | Three-dimensional measurement
Abstract: Design process is usually based on past experiences and best practises which compose the company know-how. The challenge is to identify common patterns in the design solutions generated for different design problems. The present paper focuses on the identification of product patterns by using a graph-based approach. It deals with the designing of automotive gearboxes and with the development of an approach and a software tool aimed to support preliminary design and CAD modelling activities in gearbox designing. The approach is applied to two different architectures of manual transverse gearboxes characterized by two and three shafts. It aims at the identification of common design features through the detection of the directed graphs matching. A Matlab software tool for gearbox preliminary design is implemented according to the detected common features. The proposed approach and the developed software tool provide an effective way to keep and re-use company know-how, especially in the context of large automotive companies.
Keywords: CAD modelling | Graph theory | Graphical user interfaces | KBE | Product pattern
Abstract: Many industrial sectors face increasing production demands and the need to reduce costs, without compromising the quality. The use of robotics and automation has grown significantly in recent years, but versatile robotic manipulators are still not commonly used in small factories. Beside of the investments required to enable efficient and profitable use of robot technology, the efforts needed to program robots are only economically viable in case of large lot sizes. Generating robot programs for specific manufacturing tasks still relies on programming trajectory waypoints by hand. The use of virtual simulation software and the availability of the specimen digital models can facilitate robot programming. Nevertheless, in many cases, the virtual models are not available or there are excessive differences between virtual and real setups, leading to inaccurate robot programs and time-consuming manual corrections. Previous works have demonstrated the use of robot-manipulated optical sensors to map the geometry of samples. However, the use of simple user-defined robot paths, which are not optimized for a specific part geometry, typically causes some areas of the samples to not be mapped with the required level of accuracy or to not be sampled at all by the optical sensor. This work presents an autonomous framework to enable adaptive surface mapping, without any previous knowledge of the part geometry being transferred to the system. The novelty of this work lies in enabling the capability of mapping a part surface at the required level of sampling density, whilst minimizing the number of necessary view poses. Its development has also led to an efficient method of point cloud down-sampling and merging. The article gives an overview of the related work in the field, a detailed description of the proposed framework and a proof of its functionality through both simulated and experimental evidences.
Abstract: The aim of this work is to implement a new process for the design and production of orthopaedic devices to realize entirely by Additive Manufacturing (AM). In particular, a generative algorithm for parametric modelling of flexible structures to use in orthopaedic devices has been developed. The developed modelling algorithm has been applied to a case study based on the design and production of a customized elbow orthosis made by Selective Laser Sintering. The results obtained have demonstrated that the developed algorithm overcomes many drawbacks typical of traditional CAD modelling approaches. FEM simulations have been also performed to validate the design of the orthosis. The new modelling algorithm allows designers to model flexible structures with no deformations or mismatches and to create parametric CAD models to use for the production of orthopaedic devices through AM technologies.
Abstract: In this paper, a tool able to support the sailing yacht designer during the early stage of the design process has been developed. Cubic Rational Bézier curves have been selected to describe the main curves defining the hull of a sailing yacht. The adopted approach is based upon the definition of a set of parameters, say the length of waterline, the beam of the waterline, canoe body draft and some dimensionless coefficients according to the traditional way of the yacht designer. Some geometrical constraints imposed on the curves (e.g., continuity, endpoint angles, curvature) have been conceived aimed to avoid unreasonable shapes. These curves can be imported into any commercial Computer Aided Design (CAD) software and used as a frame to fit with a surface. The resistance of the hull can be calculated and plotted in order to have a real time estimation of the performances. The algorithm and the related Graphical User Interface (GUI) have been written in Visual Basic for Excel. To test the usability and the precision of the tool, two existing sailboats with different characteristics have been successfully replicated and a new design, taking advantages of both the hulls, has been developed. The new design shows good performances in terms of resistance values in a wide range of Froude numbers with respect to the original hulls.
Abstract: In this paper, a tool able to support the sailing yacht designer during the early stage of the design process has been developed. Quadratic and cubic Rational Bézier curves have been selected to describe the main curves defining the hull of a sailing yacht. The adopted approach is based upon the definition of a set of parameters, say the length of water line, the beam of the waterline, canoe body draft and some dimensionless coefficients according to the traditional way of the yacht designer. Some geometrical constraints imposed on the curves (e.g. continuity, endpoint angles) have been conceived aimed to avoid unreasonable shapes. These curves can be imported in any commercial CAD software and used as a frame to fit with a surface. The algorithm and the related Graphical User Interface (GUI) have been written in Visual Basic for Excel. To test the usability and the precision of the tool, two sailboats with different characteristics have been replicated. The rebuilt version of the hulls is very close to the original ones both in terms of shape and dimensionless coefficients.
Abstract: Building information modelling (BIM) plays a prominent role in a good deal of architecture, engineering and construction (AEC) works, envisaging a full transition to digitalization for the construction industry. This is also due to a number of national and international regulations regarding the design, erection, and management of civil engineering constructions. For this reason, full interoperability of software environments such as computeraided design (CAD) and computer‐aided engineering (CAE) is a necessary requirement, particularly when the exchange of information comes from different disciplines. Users, throughout the years, have faced CAD–CAE interoperability issues despite following the IFC neutral open file format. This inability to share data (CAD to CAD, CAD to CAE) often generates model-interpretation problems as well as a lack of parametric information and a disconnection of elements. This paper addresses issues and mapping mechanisms in the exchange of data for the purpose of defining a baseline for the current status of bidirectional data exchange between AEC CAD/CAE software via the IFC format. A benchmark study, covering three years of software releases is illustrated; the assessment of the software performance was made with reference to criteria associated with the software’s level of suitability for use of the structural models. Four classes of performance, depending on the accuracy of the data transfer and on the associated corrective actions to be taken, were adopted. This confirmed that at the moment, the implementation of the IFC standard by software manufacturers is geared towards an expert class of users. Further efforts are needed in order to ensure its application is adopted by a wider class, thus extending and regulating its use by national, regional, and local authorities.
Keywords: BIM interoperability | Building information modelling (BIM) | Computer‐aided design (CAD) | Computer‐aided engineering (CAE) | Data exchange | Industry Foundation Classes (IFC)
Abstract: Currently, there is a growing interest of industries in applying additive manufacturing (AM) technology for generating objects with high geometrical complexity and low weight, ensuring good performance, comparable to those ones of products realized by means of traditional techniques. Anyway, it is still usual to realize AM products without focusing on the morphology of the object, hence without exploiting all the advantages of the technique. Indeed, since the several suitable AM technologies, it should be useful to know the functional characteristics of the component for the best choice of the appropriate one and its constructive complexity. In this regard, the 3D modeling strategy is extremely crucial for a proper realization of AM products. The paper deals with a study of the geometrical complexity of dashboard components of a car, based on several techniques for evaluating the geometric complexity. The latter is a fundamental element for estimating the feasibility of AM in terms of production costs and the benefits with respect to traditional molding. In detail, the study focuses on comparing several geometrical complexity evaluation techniques in order to identify the one that simplifies the calculation and better approximates the most used in literature.
 Militello F., Aho-Mantila L., Ambrosino R., Body T., Bufferand H., Calabro G., Ciraolo G., Coster D., Di Gironimo G., Fanelli P., Fedorczak N., Herrmann A., Innocente P., Kembleton R., Lilburne J., Lunt T., Marzullo D., Merriman S., Moulton D., Nielsen A.H., Omotani J., Ramogida G., Reimerdes H., Reinhart M., Ricci P., Riva F., Stegmeir A., Subba F., Suttrop W., Tamain P., Teschke M., Thrysoe A., Treutterer W., Varoutis S., Wensing M., Wilde A., Wischmeier M., Xiang L.Y.,
Preliminary analysis of alternative divertors for DEMO, Nuclear Materials and Energy,
Abstract: A physics and engineering analysis of alternative divertor configurations is carried out by examining benefits and problems by comparing the baseline single null solution with a Snowflake, an X- and a Super-X divertor. It is observed that alternative configurations can provide margin and resilience against large power fluctuations, but their engineering has intrinsic difficulties, especially in the balance between structural solidity and accessibility of the components and when the specific poloidal field coil positioning poses further constraints. A hybrid between the X- and Super-X divertor is proposed as a possible solution to the integration challenge.
Keywords: Alternative divertor configurations | DEMO | Divertor design
Abstract: This paper introduces a novel upper limb robotic exoskeleton designed to assist industrial operators in a wide range of manual repetitive tasks, such as tool handling and lifting/moving of heavy items. Due to its reduced size and high maneuverability, the proposed portable device may also be employed for rehabilitation purposes (e.g. as an aid for people with permanent neuromuscular diseases or post-stroke patients). Its primary function is to compensate the gravity loads acting on the human shoulder by means of a hybrid system consisting of four electric motors and three passive springs. The paper focuses on the exoskeleton mechanical design and virtual prototyping. After a preliminary review of the existent architectures and procedures aimed at defining the exoskeleton functional requirements, a detailed behavioral analysis is conducted using analytical and numerical approaches. The developed interactive model allows to simulate both kinematics and statics of the exoskeleton for every possible movement within the design workspace. To validate the model, the results have been compared with the ones achieved with a commercial multibody software for three different operator’s movements.
Abstract: Beam-based Compliant Mechanisms (CMs) are increasingly studied and implemented in precision engineering. Straight beams with uniform cross section are the basic modules in several design concepts, which can be deemed as standard CMs. Their behavioral analysis can be addressed with a large variety of techniques, including the Euler–Bernoulli beam theory, the Pseudo-Rigid Body (PRB) method, the beam constraint model and the discretization-based methods. This variety is unquestionably reduced when considering nonstandard CMs, namely design problems involving special geometries, such as curve/spline beams, variable section beams, nontrivial shapes and contact pairs. The 3D Finite Element Analysis (FEA) provides accurate results but its high computational cost makes it inappropriate for optimization purposes. This work compares the potentialities of computationally efficient modeling techniques (1D FEA, PRB method and chained-beam constraint model), focusing on their applicability in nonstandard planar problems. The cross-axis flexural pivot is used as a benchmark in this research due to its high configurable behavior and wide range of applications. In parallel, as an attempt to provide an easy-to-use environment for CM analysis and design, a multi-purpose tool comprising Matlab and a set of modern Computer-Aided Design/Engineering packages is presented. The framework can implement different solvers depending on the adopted behavioral models. Summary tables are reported to guide the designers in the selection of the most appropriate technique and software framework. Lastly, efficient design procedures that allow to configure nonstandard beam-based CMs with prescribed behavior are examined with two design examples.
Abstract: This paper reports about the design of a bio-inspired compliant wrist, whose mobility (i.e. ulnar-radial deviation and flexion-extension) has been realized by employing two pairs of contact-aided Cross-Axis Flexural Pivots (CAFPs), actuated via remotely-placed servo-motors and tendon transmissions. The human wrist behaves differently when deflecting in clockwise or anticlockwise direction, both in terms of maximum angular deflection and passive stiffness. The device proposed hereafter aims at mimicking such natural asymmetry, while withstanding unexpected external loads. In order to fulfill these requirements, two contacts are included: (i) a pure rolling contact (named passive contact), achieved via a cam mechanism guiding the CAFP deflection and ensuring the wrist resistance to compressive loads; (ii) a purposely shaped contact pair (named active contact), acting on one beam of the CAFP so as to increase its stiffness. The design procedures and tools specifically developed for the wrist optimization are described. In the first step, a CAFP shape optimization is performed, followed by the synthesis of the active contact pair. In the second step, the centrodes are computed and then used to generate the passive contact profiles. At last, the third step focuses on the definition of the tendons routing. To prove the validity of the numerical models, a physical prototype of the wrist is produced and tested. Direct comparisons between simulations and experiments confirm the efficacy of the proposed design method.
Abstract: This paper considers the fitting of a CAD template model to tessellated data as strategy to implement a reverse engineering process that aims at the reconstruction of a parametric associative CAD model. The reconstruction methodology, called Template-Based CAD Reconstruction (TCRT), has been presented and fully discussed in a previous paper Buonamici et al. (J Comput Des Eng 5:145–159, 2018). The present paper focuses on the study of a fast and robust strategy to perform the fitting of the Template CAD Model to reference data. The study explores how different optimization strategies and evaluation metrics can affect a parametric CAD-fitting methodology. Two different optimization algorithms (PSO and GA) and three formulations of the objective function are tested to find the most effective combination. Reconstruction test cases are presented and discussed in the text.
Abstract: Home-based recovery is gradually being used to reduce health-care costs; however, with a shorter stay in the hospital, the risk of growing adverse clinical outcomes exists, mainly due to the lack of motivation in the patient and on the difficulties in performing a strict control by the doctors. This is particularly true for patients who went under knee arthroplasty or total knee replacement who should strictly follow the effective recovery protocols delivered by the doctors. The development of tools for measuring the functional recovery of the operated joint is therefore deemed crucial both for the patient to feel motivated in performing the right number of exercises, and for the doctor that can follow him/her up remotely. One of the most recognized methods for assessing the correctness of a series of recovery exercises, is to monitor the pose of the patient in real-time so as to evaluate its posture in his range of motion. Accordingly, in this paper a novel hybrid approach to 3D human pose estimation is proposed. A first estimation of 2D body pose of the patient in the scene is given, then the depth information coming from the RGB-D sensor is exploited to estimate the joints 3D coordinates. The proposed algorithm proved to overcome the main limitation of using a pure 3D skeleton tracking algorithm during physiotherapy rehabilitation.
Keywords: 3D | Body tracking | Data fusion | Joints estimation | RGB-D camera
Abstract: This paper presents the results of a survey carried out with students enrolled in the first two years of the BS in Engineering at three Italian university locations. The study is part of a wider range of methods, tools and aids for the improvement of teaching and learning of technical drawing at university level developed by the University of Brescia, Udine, and Cassino and Southern Lazio. In particular, this work analyses the results of questionnaires related to the basic technical drawing outcomes, taking inspiration from previous research work in this field. What emerges is a positive picture that shows students’ interest in 3D CAD modeling topics such as part or assembly construction, but also their interest in more traditional subjects like sketching and dimensioning.
Abstract: Colour and texture are two perceptual stimuli that determine, to a great extent, the appearance of objects, materials and scenes. The ability to process texture and colour is a fundamental skill in humans as well as in animals; therefore, reproducing such capacity in artificial (‘intelligent’) systems has attracted considerable research attention since the early 70s. Whereas the main approach to the problem was essentially theory-driven (‘hand-crafted’) up to not long ago, in recent years the focus has moved towards data-driven solutions (deep learning). In this overview we retrace the key ideas and methods that have accompanied the evolution of colour and texture analysis over the last five decades, from the ‘early years’ to convolutional networks. Specifically, we review geometric, differential, statistical and rank-based approaches. Advantages and disadvantages of traditional methods vs. deep learning are also critically discussed, including a perspective on which traditional methods have already been subsumed by deep learning or would be feasible to integrate in a data-driven approach.
Keywords: Colour | Deep learning | Texture | Visual recognition
Abstract: Background: Accurate segmentation of pulmonary nodules on computed tomography (CT) scans plays a crucial role in the evaluation and management of patients with suspicion of lung cancer (LC). When performed manually, not only the process requires highly skilled operators, but is also tiresome and time-consuming. To assist the physician in this task several automated and semi-automated methods have been proposed in the literature. In recent years, in particular, the appearance of deep learning has brought about major advances in the field. Methods: Twenty-four (12 conventional and 12 based on deep learning) semi-automated-'one-click'- methods for segmenting pulmonary nodules on CT were evaluated in this study. The experiments were carried out on two datasets: A proprietary one (383 images from a cohort of 111 patients) and a public one (259 images from a cohort of 100). All the patients had a positive transcript for suspect pulmonary nodules. Results: The methods based on deep learning clearly outperformed the conventional ones. The best performance [Sørensen-Dice coefficient (DSC)] in the two datasets was, respectively, 0.853 and 0.763 for the deep learning methods, and 0.761 and 0.704 for the traditional ones. Conclusions: Deep learning is a viable approach for semi-automated segmentation of pulmonary nodules on CT scans.
Keywords: Computed tomography (CT) | Deep learning | Lung cancer (LC) | Pulmonary nodules | Segmentation
Abstract: The knowledge of the mechanical properties is the starting point to study the mechanobiology of mesenchymal stem cells and to understand the relationships linking biophysical stimuli to the cellular differentiation process. In experimental biology, Atomic Force Microscopy (AFM) is a common technique for measuring these mechanical properties. In this paper we present an alternative approach for extracting common mechanical parameters, such as the Young's modulus of cell components, starting from AFM nanoindentation measurements conducted on human mesenchymal stem cells. In a virtual environment, a geometrical model of a stem cell was converted in a highly deformable Coarse-Grained Elastic Network Model (CG-ENM) to reproduce the real AFM experiment and retrieve the related force-indentation curve. An ad-hoc optimization algorithm perturbed the local stiffness values of the springs, subdivided in several functional regions, until the computed force-indentation curve replicated the experimental one. After this curve matching, the extraction of global Young's moduli was performed for different stem cell samples. The algorithm was capable to distinguish the material properties of different subcellular components such as the cell cortex and the cytoskeleton. The numerical results predicted with the elastic network model were then compared to those obtained from hertzian contact theory and Finite Element Method (FEM) for the same case studies, showing an optimal agreement and a highly reduced computational cost. The proposed simulation flow seems to be an accurate, fast and stable method for understanding the mechanical behavior of soft biological materials, even for subcellular levels of detail. Moreover, the elastic network modelling allows shortening the computational times to approximately 33% of the time required by a traditional FEM simulation performed using elements with size comparable to that of springs.
Keywords: Atomic force microscopy | Cell material characterization | Elastic network model | Meshless methods
Abstract: Principal components analysis is a powerful technique which can be used to reduce data dimensionality. With reference to three-dimensional bone shape models, it can be used to generate an unlimited number of models, defined by thousands of nodes, from a limited (less than twenty) number of scalars. The full procedure has been here described in detail and tested. Two databases were used as input data: the first database comprised 40 mandibles, while the second one comprised 98 proximal femurs. The “average shape” and principal components that were required to cover at least 90% of the whole variance were identified for both bones, as well as the statistical distributions of the respective principal components weights. Fifteen principal components sufficed to describe the mandibular shape, while nine components sufficed to describe the proximal femur morphology. A routine has been set up to generate any number of mandible or proximal femur geometries, according to the actual statistical shape distributions. The set-up procedure can be generalized to any bone shape given a sufficiently large database of the respective 3D shapes.
Keywords: 3D model generator | Comparative anatomy | Mandible anatomy | Mesh morphing | PCA | Proximal femur anatomy | Stochastic bone models
Abstract: Cranioplasty is a procedure performed to repair defects in the human skull bone by surgically reconstructing the shape and function of the cranium. Several complications, both intraoperative and postoperative, can affect the procedure’s outcome (e.g., inaccuracies of the reconstructed shape, infections, ulcer, necrosis). Although the design of additive manufactured implants in a preoperative stage has improved the general quality of cranioplasties, potential complications remain significant, especially in the presence of critical skin tissue conditions. In this paper, an innovative procedure to improve the chances of a positive outcome when facing critical conditions in a cranioplasty is described. The proposed approach relies on a structured planning phase articulated in a series of digital analyses and physical simulations performed on personalized medical devices that guide the surgeon in defining surgical cuts and designing the implant. The ultimate goal is to improve the chances of a positive outcome and a fast recovery for the patient. The procedure, described in extenso in the paper, was positively tested on a cranioplasty case study, which presented high risk factors.
Abstract: New technological and packaging solutions are more and more being employed for power semiconductor switches in an automotive environment, especially the SiC-and GaN-based ones. In this framework, new front-end and back-end solutions have been developed, and many more are in the design stage. New and more integrated power devices are useful to guarantee the performances in electric vehicles, in terms of thermal management, size reduction, and low power losses. In this paper, a GaN-based system in package solution is simulated to assess the structure temperature submitted to a Joule heating power loss. The monolithic package solution involves a half-bridge topology, as well as a driver logic. A novel integrated electromagnetic and thermal method, based on finite element simulations, is proposed in this work. More specifically, dynamic electric power losses of the copper interconnections are computed in the first simulation stage, by an electromagnetic model. In the second stage, the obtained losses’ geometrical map is imported in the finite element thermal simulation, and it is considered as the input. Hence, the temperature distribution of the package’s copper traces is computed. The simulation model verifies the proper design of copper traces. The obtained temperature swing avoids any thermal-related reliability bottleneck.
Abstract: The valve train plays a major role in the performance of internal combustion engines by controlling the combustion process and it is therefore one of the key aspects for increasing the efficiency of combustion engines. Considering the dynamics, the spring force must be high enough to reliably close the valve preventing from seating bouncing due to surge modes after the valve closure. On the other side, the spring force should be kept as low as possible in order to reduce the engine friction losses and consequently the fuel consumption. In the high-performance engines, the valve springs have to be designed and optimized for sustaining higher stresses with compact dimensions leading to critical material and manufacturing processes. This requires a reduction of moving masses and a strong focus on design and process optimization of the coil springs for reducing the mechanical load and the friction losses at low engine speed. At the same time, valve train should be reliable at high engine speed. The calculation of stresses and contact forces for moving parts under dynamic load is essential for durability analysis. A method to calculate the contact of moving masses is described and proposed to justify valve motions experimental results. To fully understand the failure mechanism of test bed reliability trials, the dynamic stresses have been calculated modeling the real springs’ shape. The contact forces have been reproduced considering the coil clash effects and the dynamic behavior of the flexible spring.
Abstract: BACKGROUND: One of the aspects that influences the sitting comfort is the distribution of the pressure applied to the skin by the seat surface. In the scientific literature, many studies show experimental activities in order to evaluate the influence of pressure distribution at the seat-human interface on the comfort evaluation. The main limitation in seat design is based on the difficulties to predict the contact pressures distribution without prototypes because of the complex interaction among body muscles, wearing, human's anthropometric characteristics, shape and materials of the seat. Moreover, the same human can assume different postures on the same seat, and different people, seated on the same chair, can assume different postures even if they have the same anthropometric percentile. OBJECTIVE: The aim of this study is to propose a mathematical model evaluating interaction loads between human segments and seat segments. METHOD: In this model, a human body represented by 8 segments is placed on a 6 segments seat with posture dependent on seat segments and on position of the coccyx on seat and feet on floor. Human segments can be configured in length and weight and friction between body and seat is considered. A model validation study based on an experimental comparison with contact pressures is also presented. RESULTS: The experiment showed that there is a remarkable recursion of some stress values of the articular joints of the pelvis, hip and knee. By imposing these values in the calculation model, it is possible to determine, for each chair configuration, which postures will be assumed by a person, and to make a preliminary assessment of the level of comfort possible.
Abstract: Driver inattention is the primary cause of vehicle accidents; hence, manufacturers have introduced systems to support the driver and improve safety; nonetheless, advanced driver assistance systems (ADAS) must be properly designed not to become a potential source of distraction for the driver due to the provided feedback. In the present study, an experiment involving auditory and haptic ADAS has been conducted involving 11 participants, whose attention has been monitored during their driving experience. An RGB-D camera has been used to acquire the drivers’ face data. Subsequently, these images have been analyzed using a deep learning-based approach, i.e., a convolutional neural network (CNN) specifically trained to perform facial expression recognition (FER). Analyses to assess possible relationships between these results and both ADAS activations and event occurrences, i.e., accidents, have been carried out. A correlation between attention and accidents emerged, whilst facial expressions and ADAS activations resulted to be not correlated, thus no evidence that the designed ADAS are a possible source of distraction has been found. In addition to the experimental results, the proposed approach has proved to be an effective tool to monitor the driver through the usage of non-invasive techniques.
Keywords: ADAS | CNN | DADA | Deep learning | Driver’s attention | RGB-D camera
Abstract: This paper describes a methodology to design and optimize a controllable pitch propeller suitable for small leisure ship boats. A proper range for design parameters has to be set by the user. An optimization based on the Particle Swarm Optimization algorithm is carried out to minimize a fitness function representing the engine’s fuel consumption. The OpenProp code has been integrated in the procedure to compute thrust and torque. Blade’s geometry and tables about pitch, thrust and consumption are the main output of the optimization process. A case study has been included to show how the procedure can be implemented in the design process. A case study shows that the procedure allows a designer to sketch a controllable pitch propeller with optimal efficiency; computational times are compatible with the design conceptual phase where several scenarios must be investigated to set the most suitable for the following detailed design. A drawback of this approach is given by the need for a quite skilled user in charge of defining the allowable ranges for design parameters, and the need for data about the engine and boat to be designed.
Abstract: Within the context of modern industries, additive manufacturing (AM) plays a critical role. Design for AM (DfAM) requires defining design actions related to the product's geometry under development. DfAM affects design choices such as the type of process, the material, the geometry, and the model's features. Knowledge-based engineering (KBE) is promising for integrating DfAM principles in the early phases of product development. Still, few limitations are noticed, such as the real interoperability between DfAM and 3D CAD systems, leading to the application of proper DfAM rules downstream of the 3D modeling. This paper aims to describe a method to formalize AM engineering knowledge used as a repository to develop a CAD-integrated decision support tool by acknowledging the current gap. The method uses, as input, geometrical data retrieved by the feature analysis of the 3D CAD model (feature recognition approach) and manufacturing information related to AM processes. The method will allow closing the gap between the design and production departments by creating a knowledge-based system. The outcome of this system does not concern the possibility of predicting the AM process parameters. The system will support engineers in delivering product designs compliant with AM processes. Based on this system, a CAD-integrated DfAM tool can be developed in the future.
Keywords: Additive manufacturing | Am | Cad | Design for additive manufacturing | Design rules | Design tool | Feature recognition | Knowledge-based system
Abstract: Medical images do not provide a natural visualization of 3D anatomical structures, while 3D digital models are able to solve this problem. Interesting applications based on these models can be found in the cardiovascular field. The generation of a good-quality anatomical model of the heart is one of the most complex tasks in this context. Its 3D representation has the potential to provide detailed spatial information concerning the heart’s structure, also offering the opportunity for further investigations if combined with additive manufacturing. When investigated, the adaption of printed models turned out to be beneficial in complex surgical procedure planning, for training, education and medical communication. In this paper, we will illustrate the difficulties that may be encountered in the workflow from a stack of Computed Tomography (CT) to the hand-held printed heart model. An important goal will consist in the realization of a heart model that can take into account real wall thickness variability. Stereolithography printing technology will be exploited with a commercial rigid resin. A flexible material will be tested too, but results will not be so satisfactory. As a preliminary validation of this kind of approach, print accuracy will be evaluated by directly comparing 3D scanner acquisitions to the original Standard Tessellation Language (STL) files.
Keywords: 3D printing | Heart model | Patient-specific modeling | Segmentation | Stereolithography
Abstract: Purpose: COVID-19 has spread rapidly worldwide since its initial appearance, creating the need for faster diagnostic methods and tools. Due to the high rate of false-negative RT-PCR tests, the role of chest CT examination has been investigated as an auxiliary procedure. The main goal of this work is to establish a well-defined strategy for 3D segmentation of the airways and lungs of COVID-19 positive patients from CT scans, including detected abnormalities. Their identification and the volumetric quantification could allow an easier classification in terms of gravity, extent and progression of the infection. Moreover, these 3D reconstructions can provide a high-impact tool to enhance awareness of the severity of COVID-19 pneumonia. Methods: Segmentation process was performed utilizing a proprietary software, starting from six different stacks of chest CT images of subjects with and without COVID-19. In this context, a comparison between manual and automatic segmentation methods of the respiratory system was conducted, to assess the potential value of both techniques, in terms of time consumption, required anatomical knowledge and branch detection, in healthy and pathological conditions. Results: High-quality 3D models were obtained. They can be utilized to assess the impact of the pathology, by volumetrically quantifying the extension of the affected areas. Indeed, based on the obtained reconstructions, an attempted classification for each patient in terms of the severity of the COVID-19 infection has been outlined. Conclusions: Automatic algorithms allowed for a substantial reduction in segmentation time. However, a great effort was required for the manual identification of COVID-19 CT manifestations. The developed automated procedure succeeded in obtaining sufficiently accurate models of the airways and the lungs of both healthy patients and subjects with confirmed COVID-19, in a reasonable time.
Abstract: The study of CAD (computer aided design) modeling, design and manufacturing techniques has undergone a rapid growth over the past decades. In medicine, this development mainly concerned the dental and maxillofacial sectors. Significant progress has also been made in orthopedics with pre-operative CAD simulations, printing of bone models and production of patient-specific instruments. However, the traditional procedure that formulates the surgical plan based exclusively on two-dimensional images and interventions performed without the aid of specific instruments for the patient and is currently the most used surgical technique. The production of custom-made tools for the patient, in fact, is often expensive and its use is limited to a few hospitals. The purpose of this study is to show an innovative and cost-effective procedure aimed at prototyping a custom-made surgical guide for address the cubitus varus deformity on a pediatric patient. The cutting guides were obtained through an additive manufacturing process that starts from the 3D digital model of the patient’s bone and allows to design specific models using Creo Parametric. The result is a tool that adheres perfectly to the patient’s bone and guides the surgeon during the osteotomy procedure. The low cost of the methodology described makes it worth noticing by any health institution.
Keywords: 3D Printing | CAD Modeling | Cutting guides | Pediatric orthope-dics | Preoperative simulation | Surgery and diagnostics
Abstract: This paper presents a study based on Design for Disassembly (DfD) applied to a hydraulic pump through the Disassembly Geometry Contacting Graph (DGCG) methodology. DfD is today very important to reduce the disposal or maintenance costs foreseeable already in the planning phase. One of the key points in reducing costs is reducing time for disassemble each component. Because of that, the disassembly time was considered respect to other fundamental and optimizable characteristics such as: Disassembly costs, operations to be performed, quantity of material, etc. All the operations have been evaluated using the time measurement units (TMUs). The objective of the paper is to minimize the disassembly times required for an operator to separate each single component from the other. The study of accessibility, positioning, strength, and basic time led to a comparison between different disassembly methods in order to produce the optimal sequence. In the end, the validation of the sequence was carried out in an Augmented Reality (AR) environment in order to predict the manual disassembly understanding the possible issues without the need of building the components. Using AR, it was possible to look at the assembly during the design phase in a 1:1 scale and evaluate the chosen sequence.
Abstract: The present paper is about a family car project that starts from a study of the characteristics of the type of car taken into consideration and from an analysis of the environment carried out through an historical research on the models on the market from the 30s to the mid-90s, and their classification. The market analysis was carried out by answering six questions from the QFD and by developing the tables of relative importance and interrelation through which the most important and the most independent requirements to be attributed to the innovative family project were obtained. The competitor analysis was made through a research on the models currently on the market, the development of the benchmarking, and the what/how matrix from which the final requirements and project objectives were determined. The brand was selected, the budget was drawn up over a 12-month period and the car’s product architecture was defined. The SDE was carried out through an aesthetic analysis of the existing models, the sketches for each type of style and the selection of the final sketches. The development of the product, instead, consisted in the prototyping of a 1:18 scale model of the car through 3D printing.
Abstract: Nowadays, the importance of the concept of “Urban Mining” is growing even more, which consists in searching for raw materials inside objects that have reached the end of their life, instead of “inside nature”. It can be commonly found especially in mechanical and electronic equipment valuable materials, which can be extracted and reused as secondary raw materials. The importance of Design for Disassembly (DfD), that is the central topic of this paper, is increasing because of it brings great advantages in terms of disassembly times of components that have reached the end of life. According to the Disassembly Sequence Planning (DSP), this paper presents an application of several methods derived from literature to a two-way valve, to find optimal disassembly sequences. Different sequences have been compared in terms of disassembly time consuming, by the conversion of operations into disassembly time using accredited methods found in literature. Finally, an application in Augmented Reality is proposed to simulate a practical evaluation of what has been theorised so far.
 Pagliari C., Frizziero L., Donnici G., Liverani A., Santi G.M., Papaleo P., Napolitano F., Leon-Cardenas C., Trisolino G., Zarantonello P., Di Gennaro G.L., Maredi E., Stilli S., Stallone S.,
Cad-aided preoperative simulation in complex orthopaedic surgery, Proceedings of the International Conference on Industrial Engineering and Operations Management,
Abstract: This work aims to present the application of mechanical modeling software in three dimensions in the medical field, analyzing the procedures used by the engineer to support the orthopedic surgeon in preoperative planning. The first step of the procedure involves CT examinations in patients selected for surgery: DICOM images are managed in post-processing to obtain multiplanar reconstructions of the bone lesion to be treated. The files are then optimized, made shareable and imported into CREO's work platform; this is part of a family of CAD software products for mechanical design, developed by PTC, and is the fundamental application dedicated to parametric modeling. The result will be a faithful representation of the anatomical part both before and after surgical procedure, screening all the intermediate phases. The doctor will assess different lines of action according to the results, than he will communicate them to the engineer who, consequently, will correct and regenerate the model. The method finds its power in the dialogue between engineer and doctor: In complex cases closer collaboration is needed while, for the evaluation of less demanding injuries, the exam could be assigned as a remote project which, once completed, is returned to the medical facility of competence.
Abstract: The life of industrial products is getting shorter due to the rapid evolution of technologies. Because of that, the creation of models that are interested in last part of the product’s life are becoming extremely relevant. In recent years, many investments have been made in the recycling of raw materials and the reuse of End-Of-Life (EOL) products in order to reduce the waste of resources. Strategies of Design for Environment (DfE) have been searched and, for this reason, the Design for Disassembly (DfD) has become a fundamental phase in the product life cycle with the subsequent creation of design techniques aimed precisely at disassembly. Using this methodology, the designer can study and plan the optimal sequence which should be based on countless factors and criteria because there is not a straightforward path or a single combination of operations to follow. This paper describes and compares multiple disassembly methods based on minimum disassembly time with reference to a worm gear reducer. In particular, the component was made entirely on CAD (SolidWorks) and the sequences were pplied in a virtual environment. In this way, it was possible to evaluate different algorithms and obtain the optimal disassembly sequence that minimize the overall disassembly time.
Abstract: Engineering design shows a growing interest in exploring cost analysis to anticipate manufacturing issues and integrate production aspects within the product development process. This research aims to highlight key elements (inputs, parameters, models) to accurately predict the cost of a forged part using a complete model, with important information that can be available during the design phase. For this purpose, a systematic literature review of existing engineering methodologies developed for cost analysis of forged parts (i.e., cost estimation, DtC, and ABC) was performed with characterizations of the different approaches for evaluating the most important topics related to this objective. As a result, the most important insights related to the aim of this review are provided: (i) among quantitative methods, analytical and parametric models are the most suitable approaches to develop a cost estimation, (ii) a cost model based on a linear equation supported by single or multiple variables seems to be the most accurate tool to establish a robust cost analysis in the design of forged components, and (iii) input parameters related to the material type and geometrical features are the most critical cost-drivers in the cost assessment. Moreover, this review contributes to identifying emerging applications and obsolete topics, providing the ground to investigate unexplored areas relevant to future research.
Keywords: CAD | CAE | Cost assessment | Cost model | Engineering knowledge | Forging | Material processing | Systematic literature review
Abstract: Welding is a consolidated technology used to manufacture/assemble large products and structures. Currently, welding design issues are tackled downstream of the 3D modeling, lacking concurrent development of design and manufacturing engineering activities. This study aims to define a method to formalize welding knowledge that can be reused as a base for the development of an engineering design platform, applying design for assembly method to assure product manufacturability and welding operations (design for welding (DFW)). The method of ontology (rule-based system) is used to translate tacit knowledge into explicit knowledge, while geometrical feature recognition with parametric modeling is adopted to couple geometrical information with the identification of welding issues. Results show how, within the design phase, manufacturing issues related to the welding operations can be identified and fixed. Two metal structures (a jack adapter of a heavy-duty prop and a lateral frame of a bracket structure) fabricated with arc welding processes were used as case studies and the following benefits were highlighted: (i) anticipation of welding issues related to the product geometry and (ii) reduction of effort and time required for the design review. In conclusion, this research moves forward toward the direction of concurrent engineering, closing the gap between design and manufacturing.
Keywords: CAD | Design for manufacturing and assembly | DFMA | Engineering design | Feature recognition | Knowledge-based system | Rule-based system | Welded structure | Welding
Abstract: The paper proposes a method to couple manufacturing knowledge in the context of casting with 3D CAD modelling and design. The approach allows formalizing tacit into explicit design knowledge, for aiding engineers during the development of metal casted components. It is based on three main pillars: (i) identification of geometrical features (3D CAD features) and parameters that can cause an issue during the manufacturing process, (ii) definition of a numerical threshold for feature parameters that guarantee the feasibility of the casting process, and (iii) representation of design rules within a CAD system to support product design review. The method is considered the starting point for future developing a software tool (CAD tool plug-in), here just presented. Two case studies are reported with the aim to show the advantages of the proposed method and tool in the identification of manufacturing issues early in the product development process. Results highlight how the CAD-based tool is a useful assistant to avoid design problems related to the metal casting process.
Abstract: The work carried out has the purpose of improving and optimizing various industrial technical operations, such as preventive maintenance, taken here as an example of application, using the Design for Disassembly (DfD) technique. Therefore, through four metaheuristic methods that have been chosen among the most widespread in the field (described below) to make a comparison between them, the optimal disassembly sequence is sought, if it exists, in terms of time and then costs in order to extract a target component without damaging the other mechanical parts of the assembly. The hypothesis that has been tested throughout this case study is “a responsible application of DfD, not only from the design process of a product but also during the disassembly procedure, can bring substantial benefits to the company”. Interaction with a hypothetical operator in charge of the work to be performed is implemented with the use of augmented reality. In fact, through an application programmed for an Android device (in this case, a mobile phone, hence a handheld device), the operator can be instructed step-by-step on the disassembly sequence in dynamics as an animation. Finally, two virtual buttons were added in augmented reality with which the operator can start and pause/resume the animation at any time to facilitate the understanding of the different steps established by the sequence.
Abstract: This work shows a preoperative simulation procedure with Computer Aided Design (CAD) 3D software for a patient suffering from Ollier's disease. This pathology is very rare and occurs in extremely different ways depending on the case. Consequently, it is difficult to establish a correct surgical strategy that can be applied in a similar way to all patients. Computer Aided Surgical Simulation (CASS) process uses advanced modeling technologies to reproduce bony anatomy and simulate the surgery. The starting point is represented by the 3D digital model of the bone obtained from tomographic images. Through CAD modeling software such as Creo Parametric and following surgeons directives, engineers can provide doctors with orthopedic simulation and expectation of achievable surgical outcome. If virtual surgical prediction doesn’t meet doctors requirements, model is regenerated and it is possible to seek for a better solution. CASS process allow for extensive surgical planning, enhancing accuracy in theatre and enriching the amount of medical information that is needed to perform complex orthopedic procedures. In conclusion, the possibility to recognize in advance the overall orthopedic situation and outcoming expectancy represent an extraordinary upgrade of current surgical state of the art, leading to minimally invasive surgeries and patient-specific solutions.
Abstract: The influence of the grain angle on the cutting force when milling wood is not yet detailed, apart from particular cases (end-grain, parallel to the grain, or in some rare cases 45°-cut). Thus, setting-up wood machining operations with complex paths still relies mainly on the experience of the operators because of the lack of scientific knowledge easily transferable to the industry. The aim of the present work is to propose an empirical model based on specific cutting coefficients for the assessment of cutting force when peripheral milling of wood based on the following input: uncut chip thickness and width, grain angle (angle between the tool velocity vector and the grain direction of the wood), density and tool helix angle. The specific cutting coefficients were determined by peripheral milling with different depths of cut wood disks issued from different wood species on a dynamometric platform to record the forces. Milling a sample into a round shape (a disk) allows to measure the cutting forces toward every grain angle into a sole basic diameter reduction operation. Force signals are then post-processed to carefully clean the natural vibrations of the system without impacting their magnitudes. The experiment is repeated on five species with a large range of densities, machining two disks per species for five depths of cut in up- and down milling conditions for three different tool helix angles. Finally, a simple cutting force model, based on the previously cited parameters, is proposed, and its robustness analysed.
Abstract: The increasing availability of 3D anatomical models obtained from diagnostic images exploiting Reverse Engineering techniques allows the application of statistical analysis in the quantitative investigation of anatomical shapes variability. Statistical Shape Models are a well-established method for representing such variability, especially for complex forms like the anatomical ones. Not by chance, these models are widely used for medical applications, such as guiding segmentation of the diagnostic image and virtual reconstruction of incomplete anatomic region. The application of a statistical analysis on a set of shapes representing the same anatomical region essentially requires that shapes must be in correspondence, i.e. constituted by the same number of points in corresponding position. This work aims to compare two established algorithms, namely a modified version of the Iterative Closest Point and the non-rigid version of the Coherent Point Drift, to solve the correspondences’ problem in the construction of a Statistical Shape Model of the human cranium. The comparison is carried out on the models using the standard evaluation criteria: Generalization, Specificity and Compactness. The modified version of the Iterative Closest Point delivers a better Statistical Shape Model in terms of Generalization and Specificity, but not for Compactness, than the Coherent Point Drift-based model.
Keywords: Computer-Aided Technologies | Correspondences’ problem | Reverse Engineering | Statistical Shape Analysis | Statistical Shape Model
Abstract: The growing interest in the auricular anatomy is due to two different strands of research: 1) in the medical field it is associated with autologous ear reconstruction, a surgery adopted following trauma or congenital malformations; 2) in surveillance and law enforcement the ear is used for human detection and recognition. Alternative systems of ear analysis can be differentiated for the type of input data (two-dimensional, three-dimensional or both), for the type of acquisition tools (3D scanner, photographs, video surveillance, etc.) and finally for the adopted algorithms. Although the segmentation and recognition of the ear from the face is a widely discussed topic in literature, the detection and recognition of individual anatomical elements has not yet been studied in depth. To this end, this work lays the foundation for the identification of the auricular elements through image processing algorithms. The proposed algorithm automatically identifies the contours of the main anatomical elements by processing depth map images. The algorithm was tested qualitatively and quantitatively on a dataset composed of 150 ears. The qualitative evaluation was performed with the collaboration of medical staff and the quantitative tests were performed using manually annotated ground truth data.
Abstract: The major breakthroughs in the fields of reverse engineering and additive manufacturing have dramatically changed medical practice in recent years, pushing for a modern clinical model in which each patient is considered unique. Among the wide spectrum of medical applications, reconstructive surgery is experiencing the most benefits from this new paradigm. In this scenario, the present paper focuses on the design and development of a tool able to support the surgeon in the reconstruction of the external ear in case of malformation or total absence of the anatomy. In particular, the paper describes an appositely devised software tool, named G-ear, which enables the semi-automatic modeling of intraoperative devices to guide the physician through ear reconstruction surgery. The devised system includes 3D image segmentation, semi-automated CAD modelling and 3D printing to manufacture a set of patient-specific surgical guides for ear reconstruction. Usability tests were carried out among the surgeons of the Meyer Children's Hospital to obtain an assessment of the software by the end user. The devised system proved to be fast and efficient in retrieving the optimal 3D geometry of the surgical guides and, at the same time, to be easy to use and intuitive, thus achieving high degrees of likability.
Abstract: This paper introduces an e-learning platform for the management of courses based on MOOCs, able to continuously monitoring student’s behavior through facial coding techniques, with a low computational effort client-side, and to provide useful insight for the instructor. The system exploits the most recent developments in Deep Learning and Computer Vision for Affective Computing, in compliance with the European GDPR. Taking as input the video capture by the webcam of the device used to attend the course, it: (1) performs continuous student’s authentication based on face recognition, (2) monitors the student’s level of attention through head orientation tracking and gaze detection analysis, (3) estimates student’s emotion during the course attendance. The paper describes the overall system design and reports the results of a preliminary survey, which involved a total of 14 subjects, aimed at investigating user acceptance, in terms of intention to continue using such a system.
Abstract: Obstructive sleep apnoea syndrome is characterized by an obstruction in the upper airway due to the pharyngeal collapse during sleep. Mandibular advancement devices have gained success and large popularity as a non-invasive treatment for OSAS. Nevertheless, the effects of mandibular advancement devices were poorly investigated in literature. To this aim the paper proposes a procedure to achieve a numerical simulation model useful to assess the stress/strain distribution on the temporomandibular joint and periodontal ligaments caused by the mandibular advancement. The findings suggest that the mandibular roto-translation induced by the MAD provoke high stress on the molars and premolar teeth.
Abstract: Obstructive sleep apnea syndrome (OSAS) is a sleep disorder that causes pauses in breathing or periods of shallow breathing during sleep. Mandibular advancement devices (MADs) represent a non-invasive treatment for OSAS that has had the highest development in recent years. Nevertheless, literature has not primarily investigated the effects of mandibular advancement. This paper presents a finite element method numerical simulation model for evaluating the stress/strain distribution on the temporomandibular joint (TMJ) and periodontal ligaments caused by advancement devices used for the treatment of OSAS. Results highlight that the mandible lift phase generates significant stress values on TMJ, which cannot be neglected for extended usage of MADs. Furthermore, mandible molar teeth are more loaded than incisor ones.
Abstract: This article reports on the results of research aimed to translate biometric 3D face recognition concepts and algorithms into the field of protein biophysics in order to precisely and rapidly classify morphological features of protein surfaces. Both human faces and protein surfaces are free-forms and some descriptors used in differential geometry can be used to describe them applying the principles of feature extraction developed for computer vision and pattern recognition. The first part of this study focused on building the protein dataset using a simulation tool and performing feature extraction using novel geometrical descriptors. The second part tested the method on two examples, first involved a classification of tubulin isotypes and the second compared tubulin with the FtsZ protein, which is its bacterial analog. An additional test involved several unrelated proteins. Different classification methodologies have been used: a classic approach with a support vector machine (SVM) classifier and an unsupervised learning with a k-means approach. The best result was obtained with SVM and the radial basis function kernel. The results are significant and competitive with the state-of-the-art protein classification methods. This leads to a new methodological direction in protein structure analysis.
Keywords: 3D face analysis | differential geometry | geometrical descriptors | machine learning | protein classification | support vector machine | tubulin
Abstract: This work aims to identify people psychological stress through the capture of micro modifications and motions within their facial expression. Exogenous and endogenous causes of stress, from environment and/or psychological conditions that could induce stress, have been reproduced in the experimental test involving real subjects, and their face expressions have been recorded by 2D and 3D image capturing tools to create a sample of emotional database. Successively, 2D and 3D analyses have been performed on recorded data according to the respective protocols, by deep learning and machine learning techniques, and a data driven model of the databases has been developed by neural network approach, to classify the psycho-behavioral answers to the different kinds of stress conditions induced on tested people. The ultimate aim of the study is to demonstrate the possibility to analyze data collected on participants from 2D shooting and 3D scans in a consistent way by means of deep learning and machine learning techniques, so that to provide a methodology to identify and classify some of the subtle facial micro-expressions of people involved in stressing activities.
Abstract: Facial Emotion Recognition (FER) is the automatic processing of human emotions by means of facial expression analysis. The most common approach exploits 3D Face Descriptors (3D-FD), which derive from depth maps by using mathematical operators. In recent years, Convolutional Neural Networks (CNNs) have been successfully employed in a wide range of tasks including large-scale image classification systems and to overcome the hurdles in facial expression classification. Based on previous studies, the purpose of the present work is to analyze and compare the abstraction level of 3D face descriptors with abstraction in deep CNNs. Experimental results suggest that 3D face descriptors have an abstraction level comparable with the features extracted in the fourth layer of CNN, the layer of the network having the highest correlations with emotions.
Keywords: Abstraction | CNN | Deep learning | Explainable AI | Facial Emotion Recognition | FER
Abstract: The ITER Radial Neutron Camera is a diagnostic whose objective is measuring neutron emissivity and fusion power density through an array of detectors placed in collimating structures. The RNC is composed of two subsystems (In-Port RNC and Ex-Port RNC), located in the Equatorial Port 01 of the ITER tokamak. Although the measurements from the RNC are required for ITER D-T phase, its In-Port components must be ready for Assembly phase 2. Consequently, the two subsystems will be delivered at different times. At the current status of the design the In-Port RNC interfaces must be defined, if not fully specified, in order to allow for the subsystem integration in the Port Plug. A thorough assessment of the interfaces of the subsystem with all the diagnostics, plants and services in the port has been made, taking into account the concurrent development of the Equatorial Port 01 and the progress in the design of some of the subsystem components that may affect the identification of interfacing Plant Systems. This paper deals with the process that led to definition of the internal and external interfaces of the In-Port RNC, highlighting the main issues and the solutions adopted to perform integration within the Equatorial Port Plug 01.
Keywords: Integration | Interfaces | Iter diagnostics | Radial neutron camera
Abstract: The eutectic alloy Lithium Lead (LiPb) enriched at 90 % in 6Li is the breeder material for one of the candidate European Breeding Blanket (BB) concepts. Currently under investigation for DEMO reactor, the Water Cooled Lithium-Lead (WCLL), and for the WCLL Test Blanket Module (TBM) that will be qualified in the ITER reactor. The LiPb alloy is used as tritium breeder, neutron multiplier and tritium carrier. The design of the LiPb loops is currently under study and the conceptual design of the main loop components has been completed. For this reason, it becomes mandatory to proceed with the integration of the LiPb loops in the EU DEMO Tokamak building, checking the consistency of the different systems design to be integrated in DEMO reactor building. CAD design and integration of the entire LiPb loops are shown taking into account the building areas assigned, the interfaces with the other systems and the requirement related to the LiPb loop functions. An initial layout of the pipework and the position of the main components have been defined on the basis of the following design requirements: (I) gamma radiation shielding of the components and the pipework; (II) target flow velocity of the LiPb; (III) thermal expansion of the pipes; (IV) possibility to drain the entire loop; (V) redundancy of the loops; (VI) remote maintenance; (VII) position in the building and dimensions of the storage tanks. The 3D model of the entire loops has been provided and integrated in DEMO Tokamak building pointing out the issues related to the interfaces with the other systems and with the building itself.
Keywords: Breeding blanket | CAD | DEMO | Integration | Lithium lead | Piping design | Water cooled lithium lead
Abstract: The Industry 4.0 framework is pushing the manufacturing systems towards a zero-defect production based on robot technologies. The increasing level of automation in the production lines is raising new challenges for designers that must face the latest requirements in terms of product quality and power consumption. Among the multitude of components of the industrial plants, Servo-Mechanisms (SMs) play a crucial role and govern important performance indices of both robots and automatic machines. During the execution of high dynamics tasks, the SMs performance is influenced by many factors, including motion law, acting load, temperature and degradation. The development of accurate models aiming at predicting and optimizing the SMs behavior may not be practicable without extensive experimental activities. Owing to these considerations, this work introduces a novel test rig for the accurate characterization of industrial SMs. The rig is designed by combining the advantages of the existing prototypes. It is equipped with high precision sensors and an active loading system that enable to test the SM in various working conditions. Also, the rig modularity facilitates the installation of newly commissioned components and the execution of static and dynamic experiments. The paper mainly focuses on the rig mechanical design and components selection criteria.
Keywords: Computer Aided Design | Design methods | High Precision Manufacturing | Industry 4.0 | Servo-Mechanism Test Rig
Abstract: Mechanical assemblies are very complex structures, made of many parts of various shapes and sizes with different usages. Consequently, it is challenging to manage them during all the manufacturing processes, from the design to the assembly and the recycling. Aiming to simplify the assembly structure and reduce the number of parts to deal with simultaneously, in literature many works exist on subassemblies identification starting from the CAD assembly model. However, the methods provided loose sight of many details associated with the parts, as well as the fact that the treated model represents a real mechanical assembly which respects precise engineering rules. At this regard, this work introduces a novel methodology to detect meaningful clusters in CAD assembly models. The logic applied relies on engineering knowledge, both of mechanical assemblies' components and of assembling techniques, and on the leveraging of the semantics of components. In particular, referring to general design rules, we have identified some heuristics to exploit to partition the assembly into different types of clusters, such as the symmetry along an axis and the presence of fasteners or welds. It results that the assembly's parts are meaningfully grouped, considering, at the same time, their shape, functionality, and type of contact.
Abstract: In industrial manufacturing, both in the design and the production phase, the management of modern mechanical assemblies is becoming demanding due to their increasing complexity. The use of stable subassemblies concept constitutes a better alternative, which allows to independently treat smaller groups of the assembly's parts, also to achieve a parallel production. At this regard, several methods for automatic subassemblies identifi-cation, starting from the assembly CAD model, have been provided. However, most of the methodologies proposed rely on human intervention, especially in the model processing to make available essential data, while other details are ignored. After giving the definition of stable subassembly, this paper focuses on the application of stable subassemblies identification to industrial CAD models and highlights the issues arising. With the aim of ensuring a reliable CAD model analysis, starting point of the identification, the possible real engineering situations, both related to assembling methods and modelling techniques, are presented. Ap-proaches to algorithmically address them are then described, with the help of two examples of mechanical assemblies.
Abstract: Purpose: The current study aimed to propose a Deep Learning (DL) and Augmented Reality (AR) based solution for a in-vivo robot-assisted radical prostatectomy (RARP), to improve the precision of a published work from our group. We implemented a two-steps automatic system to align a 3D virtual ad-hoc model of a patient’s organ with its 2D endoscopic image, to assist surgeons during the procedure. Methods: This approach was carried out using a Convolutional Neural Network (CNN) based structure for semantic segmentation and a subsequent elaboration of the obtained output, which produced the needed parameters for attaching the 3D model. We used a dataset obtained from 5 endoscopic videos (A, B, C, D, E), selected and tagged by our team’s specialists. We then evaluated the most performing couple of segmentation architecture and neural network and tested the overlay performances. Results: U-Net stood out as the most effecting architectures for segmentation. ResNet and MobileNet obtained similar Intersection over Unit (IoU) results but MobileNet was able to elaborate almost twice operations per seconds. This segmentation technique outperformed the results from the former work, obtaining an average IoU for the catheter of 0.894 (σ = 0.076) compared to 0.339 (σ = 0.195). This modifications lead to an improvement also in the 3D overlay performances, in particular in the Euclidean Distance between the predicted and actual model’s anchor point, from 12.569 (σ= 4.456) to 4.160 (σ = 1.448) and in the Geodesic Distance between the predicted and actual model’s rotations, from 0.266 (σ = 0.131) to 0.169 (σ = 0.073). Conclusion: This work is a further step through the adoption of DL and AR in the surgery domain. In future works, we will overcome the limits of this approach and finally improve every step of the surgical procedure.
Abstract: Assembly process of aeronautical skin panels deals with large, thin and compliant components, which are usually joined with rivets. A leading challenge is the control of part-to-part gaps prior to riveting operation, which must be maintained below tight design specification limits to avoid excessive pretensions of the rivets which, if exceeded, impair the durability of the whole skin assembly. Gaps are compensated by number of time consuming and costly manual inspection-repair quality loops, which involve measuring gaps, disassembling parts, adding be-spoke shims, re-assembling parts. This paper proposes a novel methodology to support the inspection-repair quality loops with the aim to model and optimise the shape of the shims with the ultimate goal of reducing/eliminating manual and trial-and-error measurements as per today best practice. The methodology will be discussed in two steps: (1) physics-based variation simulation to model generation and propagation of dimensional and geometrical variations (by using scanning data o morphing mesh model) during multi-stage assembly operations; (2) virtual shimming simulator to model and optimise shimming condition between parts being assembled. The proposed methodology is presented and validated using the assembly process of the vertical stabiliser for commercial aircrafts.
Abstract: The aim of the current work was to analyze the influence of the ferrule effect for hybrid composite endodontic post designs consisting of carbon (C) and glass (G) fiber-reinforced polyetherimide (PEI), in upper canine teeth. Starting from theoretical designs of C-G/PEI hybrid composite posts with different Young's moduli (Post A-57.7 GPa, Post B-31.6 GPa, Post C-graduated from 57.7 to 9.0 GPa in the coronal-apical direction) in endodontically treated anterior teeth, the influence of the ferrule effect was determined through finite element analysis (FEA). On the surface of the crown, a load of 50 N was applied at 45° to the longitudinal axis of the tooth. Maximum principal stresses were evaluated along the C-G/PEI post as well as at the interface between the surrounding tooth structure and the post. Maximum stress values were lower than those obtained for the corresponding models without a ferrule. The presence of a ferrule led to a marked decrease of stress and gradients especially for posts A and B. A less marked effect was globally found for Post C, except in a cervical margin section along a specific direction, where a significant decrease of the stress was probably due to local geometric features, compared to the model without a ferrule. The presence of a ferrule did not generally provide a marked benefit in the case of the graduated Post C, in comparison to other C-G/PEI posts. The outcomes suggest how such a hybrid composite post alone should be sufficient to optimize the stress distribution, dissipating stress from the coronal to the apical end.
Keywords: Computer-Aided Design | Endodontic post design | Finite element analysis | Polyetherimide composites | Reverse engineering
Abstract: Industry 4.0 promises to increase the efficiency of production plants and the quality of the final product. Consequently, companies that implement advanced solutions in production systems will have a competitive advantage in the future. The principles of Industry 4.0 can also be applied to shipyards to transform them into “smart shipyards” (Shipyard 4.0). The aim of this research is to implement an interactive approach by Internet of Things on a closed power-loop test bench equipped with sophisticated sensors that is specifically designed to test high-power thrusters before they are installed on high-speed crafts, which are used in passenger transport. The preliminary results of the proposed Internet of Things-platform demonstrates the efficacy of the decision-making support tool in improving the design of propulsion systems and increasing their efficiency compared to traditional systems.
Keywords: CAD modelling | Experimental tests | Industry 4.0 | Internet of Things (IoT) | Test bench
Abstract: Total elbow arthroplasty (TEA) is an effective and frequently used treatment for patients with debilitating elbow pathology. Total elbow prostheses have lagged behind those of the knee, hip and shoulder for different reasons, such as the high failure rate of the early designs. Concern remains regarding the longevity of TEA implants, especially in younger patients. The main cause of revision of the implant is usually related to the phenomenon of aseptic loosening mainly due to the cement-bone interface failure. Aim of this work is the biomechanical analysis of a new elbow prosthesis to investigate the mechanical behaviour at the cement-bone interface. For this reason, a musculoskeletal model has been developed by modelling the forces of the muscles and after FEM analyses have been performed. Obtained results confirm the validity of the implemented model and can provide guidelines for surgeons regarding the implant configurations with the aim to reduce the aseptic loosening.
Keywords: CAD | FEM | Reverse engineering | Total elbow arthroplasty
Abstract: Potteries are the most numerous finds found in archaeological excavations; they are often used to get information about the history, economy, and art of a site. Archaeologists rarely find complete vases but, generally, damaged and in fragments, often mixed with other pottery groups. By using the traditional manual method, the analysis and reconstruction of sherds are performed by a skilled operator. Reviewed papers provided evidence that the traditional method is not reproducible, not repeatable, time-consuming and its results have great uncertainties. To overcome the aforementioned limits, in the last years, researchers have made efforts to develop computer-based methods for archaeological ceramic sherds analysis, aimed at their reconstruction. To contribute to this field of study, in this paper, a comprehensive analysis of the most important available publications until the end of 2019 is presented. This study, focused on pottery fragments only, is performed by collecting papers in English by the Scopus database using the following keywords: "computer methods in archaeology", "3D archaeology", "3D reconstruction", "automatic feature recognition and reconstruction", "restoration of pottery shape relics". The list is completed by additional references found through the reading of selected papers. The 53 selected papers are divided into three periods of time. According to a detailed review of the performed studies, the key elements of each analyzed method are listed based on data acquisition tools, features extracted, classification processes, and matching techniques. Finally, to overcome the actual gaps some recommendations for future researches are proposed.
Keywords: 3D archaeology | 3D reconstruction | Automatic feature recognition and reconstruction | Computer methods in archaeology | Restoration of pottery shape relics
Abstract: Secondary features, such as fillets, rounds, chamfers and grooves, are simple transitions between primary features, generally introduced in order to remove the sharp edges created by the intersection of primary features. Being able to distinguish secondary from primary features is important in various application contexts, such as reverse engineering, automatic geometric inspection of real scanned objects, and for preparation of models for FEM analysis and CNC tool-path generation. The process for the recognition of secondary features from high-density tessellated models of real work-pieces is intrinsically complex for several reasons. This explains why, currently, there are no methodologies able to recognize automatically secondary features and the investigation on secondary features is mostly focused on B-Rep models. In a previous paper, the authors proposed a method for secondary features recognition from discrete geometric models synthetically generated. Here the methodology is extended to discrete geometric models experimentally acquired, for which the recognition is a very complex process, due to the object discretization, to its non-ideal geometry and to measurement errors.
Keywords: Blending features | Feature recognition | Fuzzy logic | Point cloud segmentation
Abstract: Sports equipment design is a young and evolving engineering discipline focused on the best simultaneous optimization of user and product as a system. In motorsports, in particular, the final performance during a race depends on many parameters related to the vehicle, circuit, weather, and tyres and the personal feelings of every single driver. Top teams in high-tech categories can invest huge amounts of money in developing simulators, but such economic commitment is not sustainable for all those teams that operate in minor but very popular categories, such as karts or mini-motorcycles. In these fields, the most common design approach is trial and error on physical prototypes. Such an approach leads to high costs, long optimization times, poor innovation, and inefficient management of the design knowledge. The present paper proposes a driver centred methodology for the design of an innovative mini racing motorcycle frame. It consists of two main phases: the drivers’ feelings translation into engineering requirements and constraints, and the exploration of the design solution space. Expected effects of the application of the proposed methodology are an overall increase in the degree of innovation, time compression, and cost reduction during the development process, with a significant impact on the competitiveness of small racing teams in minor categories.
Abstract: The aim of this work is the design of a new customised elbow orthosis completely realized by Additive Manufacturing and the development of generative algorithms for parametric modelling and creation of 3D patterns to be adapted to the CAD model. This work describes a method to perfect the design of a custom elbow orthosis. A reverse engineering approach has been used to digitalize the patient’s arm and the subsequent CAD modelling of the structure of the custom elbow orthosis has been performed. In particular, two algorithms have been implemented for the creation of 3D patterns and Voronoi tessellations. Subsequently, FEM analyses have been carried out to validate the design. Finally, a prototype of the elbow orthosis with Voronoi tessellation has been realized by means of the SLS technology. The results obtained have demonstrated that the implemented algorithm solved the problems found during CAD modelling with conventional software. Furthermore, the results of FEM analyses have validated the design choices. All this allowed realizing the prototype by AM technologies without problems. Moreover, the new proposed modelling approaches allows creating, in an interactive way, patterns on complex surfaces. The results of this research activity present innovative elements of originality in the CAD modelling sector, which can contribute to solving problems related to the modelling for Additive Manufacturing. Furthermore, another innovative characteristic of the device is the use of torsion springs that simulate the action of physiotherapists during exercises for patient rehabilitation.
Abstract: Tibial fractures are common injuries in people. The proper treatment of these fractures is important in order to recover complete mobility. The aim of this work was to investigate if screw positioning in plates for proximal tibial fractures can affect the stability of the system, and if it can consequently influence the patient healing time. In fact, a more stable construct could allow the reduction of the non-weight-bearing period and consequently speed up the healing process. For that purpose, virtual models of fractured bone/plate assemblies were created, and numerical simulations were performed to evaluate the reaction forces and the maximum value of the contact pressure at the screw/bone interface. A Schatzker type I tibial fracture was considered, and four different screw configurations were investigated. The obtained results demonstrated that, for this specific case study, screw orientation affected the pressure distribution at the screw/bone interface. The proposed approach could be used effectively to investigate different fracture types in order to give orthopaedists useful guidelines for the treatment of proximal tibial fractures.
Abstract: Purpose: The purpose of this paper is to implement a new process aimed at the design and production of orthopaedic devices fully manufacturable by additive manufacturing (AM). In this context, the use of generative algorithms for parametric modelling of additively manufactured textiles (AMTs) also has been investigated, and new modelling solutions have been proposed. Design/methodology/approach: A new method for the design of customised elbow orthoses has been implemented. In particular, to better customise the elbow orthosis, a generative algorithm for parametric modelling and creation of a flexible structure, typical of an AMT, has been developed. Findings: To test the developed modelling algorithm, a case study based on the design and production of an elbow orthosis made by selective laser sintering was investigated. The obtained results have demonstrated that the implemented algorithm overcomes many drawbacks typical of the traditional computer aided design (CAD) modelling approaches. The parametric CAD model of the orthosis obtained through the new approach is characterised by a flexible structure with no deformations or mismatches and has been effectively used to produce the prototype through AM technologies. Originality/value: The obtained results present innovative elements of originality in the CAD modelling sector, which can contribute to solving problems related to modelling for AM in different application fields.
Abstract: Tooth loss is a common pathology that affects many people. Dental osseointegrated implants are the ideal solution to restore normal functionality in partially or completely edentulous patients. The not perfect osseointegration and the fixture fracture are the main causes of failure for these kinds of implant. To avoid these drawbacks, several studies have been conducted to analyse the behaviour of dental implants. Aim of this work is to analyse the biomechanical behaviour of three different endosseous dental implants. For this purpose, a new numerical model has been developed to simulate different levels of osseointegration and to evaluate the stress values on the bone at different times. In this way, it can be investigated the possibility of anticipating the use of dental implants that usually is delayed three months after surgery. Obtained results confirm the validity of the proposed approach and can provide useful guidelines for dentists.
Abstract: In the last two decades, osseointegrated prostheses have been shown to be a good alternative for lower limb amputees experiencing complications in using a traditional socket-type prosthesis; however, restraining biomechanical issues, such as peri-prosthetic bone fractures or loosening, are present. To better understand and overcome these limiting issues, and thus reduce the number of implant failures, many studies have investigated the stress distribution on bone and implant during normal daily activities. The aim of this study was a biomechanical analysis of two different osseointegrated implants, a screw-type (OPRA) and a press fit system (OPL, Osseointegrated Prosthetic Limb), to evaluate the stresses generated in bone and prosthesis during a fall. In particular, four scenarios have been experimentally reproduced to determine the loads on the limb during different kinds of fall. For this purpose, a motion capture system and a force plate have been used. Numerical FEM (Finite Element Method) simulations have been performed to compare the behaviour of the OPRA and OPL systems in different fall scenarios. The obtained results showed that a fall backwards due to balance loss is the most stressful scenario among the ones analysed. As regards the comparison between OPRA and OPL devices, it emerged they have similar behaviours in terms of peak values of the stress, but the OPL implant generates larger high-stress areas in the distal femur as compared with the OPRA system.
Abstract: The current generation of transcatheter heart valves (THV), as the Edwards SAPIEN 3 Ultra (S3), is not specifically designed for mitral position implantation and has intrinsic design geometry that may make mitral implantation suboptimal. This study aimed to develop a computed-tomography (CT) based CAD workflow for the preoperative planning of transcatheter mitral valve replacement (TMVR) by evaluating the resulting obstruction in the left ventricular outflow tract (LVOT). Specifically, the computational framework to reconstruct heart anatomy and virtually deploy the THV into mitral valve annulus was developed and successively applied to the cases of two patients who experienced annuloplasty ring failure. Planimetric assessment of the cross-sectional area of the neo-LVOT was quantified at different anatomic levels of implanted THV. Findings revealed the importance of the proposed CAD modeling workflow to enable more informative pre-operative assessments of the risk related to the development of the neo-LVOT obstruction and even to guide the Heart Team regarding device selection, sizing and intended positioning for TMVR.
Abstract: Parallel-sided foil sections are used for centerboards and rudders in sailing dinghy classes and also for struts placed in a fluid flow. The objective of this work is to create a systematic series of parallel-sided sections to be used under different conditions, with an emphasis on the sailing dinghies 470, 420 and Optimist. The loss, and surprisingly the gain, in performance relative to 4-digit NACA sections are also investigated. A 2D Reynolds-averaged Navier-Stokes solver is used with the k-ω SST turbulence model and the gamma transition criterion. A verification study is carried out based on four grids of systematically varied density, and results compared with experimental data on a NACA 64-006 section. The parallel-sided sections are modeled with rational Bézier curves whose geometrical parameters permit to link the shape of the profile to physical variables, which are systematically varied. Three Reynolds numbers and two angles of attack are investigated. Systematic plots show the influence of the trailing edge angle and nose radius for the different section families, and the optimum combination is presented in a table. Physical explanations of the trends, and of the exceptions, are given in the paper, using flow visualizations as well as pressure and friction plots.
Abstract: One of the main challenges in the roadmap to the realization of fusion energy is to develop a heat and power exhaust system able to withstand the large loads expected in the divertor of a fusion power plant. The challenge of reducing the heat load on the divertor targets is addressed, within the mission 2 ‘Heat-exhaust systems’, through the investigation of divertor configurations alternative to the standard Single Null (SN), such as the Snowflake (SF), Double Null (DN), X and Super-X (SX) divertors. This paper focuses on a preliminary engineering assessment of the alternative configurations proposed for the EU DEMO reactor. Starting from the description of the optimized plasma shape developed for each configuration, the 3D geometrical description of the Magnet System and of the main Mechanical Structures (Vacuum Vessel and in-vessel components) is presented. Based on the 3D geometry, the compatibility of the location and dimensions of ports with Remote Maintenance needs is discussed and possible design optimizations are proposed both for the Magnets system and the mechanical structures design. Finally, the various configurations are compared with regard to the engineering and feasibility aspects.
Keywords: Alternative magnetic configurations | CAD | Conceptual design | DEMO | Divertor concept
Abstract: The design activities of an insulated Plasma Facing Components-Cassette Body (PFCs-CB) support has been carried out under the pre-conceptual design phase for Eurofusion-DEMO Work Package DIV-1 “Divertor Cassette Design and Integration” - Eurofusion Power Plant Physics & Technology (PPPT) program. The Eurofusion-DEMO divertor is a key in-vessel component with PFCs which directly interact with the plasma scrape-off layer. The PFCs have to cope with high heat loads, neutron irradiation and electromagnetic loads. The mechanical integrity of the PFCs and water cooling pipes can be jeopardized by high heat loads and by electromagnetic loads generated in a disruption event. In European-DEMO the possibility to estimate the heat load by measuring the relative thermocurrents is under investigation. In order to allow thermocurrents measurements, a divertor design option provides that PFCs are electrically insulated from CB. In this work authors aim to analyze the opportunity that the PFC-CB fixing system incorporates an electrical insulation system, thus acquiring also an important diagnostic role in the measurement of the thermocurrents and in the management of the current flows. The possible use of ceramic material (e.g. alumina) as the insulating layer between the support components is investigated.
Abstract: This paper reports about the virtual and physical prototyping of an antagonistic Variable Stiffness Actuator (VSA) to be used on robotic arms specifically realized for physical human-robot interaction. Such antagonistic actuation system, which comprises purposely conceived Compliant Transmission Elements (CTEs) characterized by a nonlinear relation between the deflection and the applied torque, allows to simultaneously control both the joint's position and stiffness. The CTE's beams geometry, namely slender spline beams, has been defined by means of an automatic routine leveraging on Matlab and ANSYS and allowing for the shape optimization of complex flexures. The synthesized springs are characterized by a predefined quadratic torque-deflection characteristic, which is shown to guarantee a precise stiffness modulation while avoiding the need for a joint's position sensor. After shape optimization, the CTE is fabricated via additive manufacturing and subsequently tested. The acquired data show a very good consistency with the numerical results, although highlighting a non-negligible hysteresis due to material damping. Therefore, in order to cope with such unavoidable effect along with other parameter uncertainties and unmodeled effects (e.g. static friction), a robust feedback controller is proposed, allowing for the simultaneous and decoupled regulation of joint position and stiffness. Finally, a VSA prototype is produced and tested. Experimental results confirm that the VSA behaves as expected.
Abstract: The paper describes a novel Clench-and-Release Device (CRD), which can be used to quickly replace the rear wheels of bikes equipped with disk brakes, while also being suitable for front wheels. Since a quick wheel replacement is a pressing demand during competitions, the CRD reduces time wasted in situations like flat tire replacement. At the same time, it can be useful also for amateur bikers, who desire a simple way to lock/release a wheel without the risk of getting dirty or being unable to properly align the brake’s disk and pads. In fact, thanks to the CRD, both brake and pinion packs are kept in place at all times and the chain remains engaged with the gears, even after wheel removal. Although similar devices can be found on the market, the proposed CRD provides an improved design since: (i) pinions and brake are placed on the same side with respect to the wheel symmetry plane perpendicular to the wheel axis of rotation; (ii) the front and the rear wheel share the same hub; (iii) manual operations are definitely easier; (iv) the wheels are compatible with different types of transmission; (v) the brake discs are more protected in case of crashing. A patent for the Italian region has been filed.
Keywords: Computer-aided design | Through axle shaft | User centered design | Wheel quick release | Wheels’ fast removal
Abstract: This paper reports the design of a monolithic long-stroke constant force compliant mechanism (CM). The device is suitable for applications requiring a predefined force magnitude at the contact interface, such as manipulation systems. Starting from a compliant slider-crank mechanism providing a constant force within a rather limited deflection range, the paper describes the shape optimization carried out with the aim of extending the CM available stroke. In the first design step, the pseudo-rigid body (PRB) method is used to synthesize a sub-optimal lumped compliance solution. Secondly, two improved beam-based alternatives are evaluated by means of an integrated software framework, comprising Matlab and ANSYS. These new embodiments make use of a variable thickness beam, whose shape and dimensions have been optimized so as to provide a constant reaction force in an extended range. In particular, straight and spline segments are respectively used for the first and second prototype. With reference to the lumped compliance configuration, the available stroke has been increased of amounts equalling to 467% in the straight segments version (namely, from 3 mm to 14 mm) and to 833% in the spline segments version (namely, from 3 mm to 25 mm). All the predicted behaviors have been validated via physical experiments on 3D printed specimens. The proposed multi-step design flow may also be applied to a large variety of CMs, starting from their PRB model.
Keywords: compliant mechanisms | constant force mechanisms | pseudo-rigid body method | shape optimization | software integration
Abstract: Planning prototyping strategies for conceptual design purposes is a crucial activity, which needs a clear understanding of the potentialities of the different typologies of prototype. Therefore, to prepare future designers, it is very important to provide the required information in design-related academic courses. However, prototypes and prototyping activities are often taught in specific courses with a major emphasis on the underpinning technologies, but with limited attention on design implications, especially about the fuzzy-front-end of the design process. The work presented in this paper aims at investigating about how students perceive the usefulness of prototypes during conceptual design activities, in order to provide first indications about the gap to be filled. To this purpose, two classes of students participated to an experimental session, and were asked to perform a conceptual design task individually. Subsequently, they participated to an on-line survey developed to gather information about the perceived usefulness of prototypes, in relation to the performed conceptual design activity. Several findings have been obtained from this work, but maybe the most impacting one concerns the different consideration that the two samples of students had about the fidelity of prototypes. Indeed, differently from what recently highlighted in current literature, it emerged that engineering students preferred low-fidelity prototypes. However, other unexpected evidences have been found, which highlight that at least for the considered institution, students still lack a comprehensive understanding of the design-related potentialities of prototypes.
Abstract: Background and objective:Tomographic sequences of biomedical images are commonly used to achieve a three-dimensional visualization of the human anatomy. In some cases, the number of images contained in the sequence is limited, e.g., in low-dose computed tomography acquired on neonatal patients, resulting in a coarse and inaccurate 3D reconstruction. Methods:In this paper, volumetric image interpolation methods, devised to increase the axial resolution of tomographic sequences and achieve a refined 3D reconstruction, are proposed and compared. The techniques taken into consideration are based on motion-compensated frame-interpolation concepts, which have been developed for video applications, mainly frame-rate conversion. Results: The performance of the proposed methods is quantitatively assessed by using sequences with a simulated low axial resolution obtained from the decimation of standard high-resolution computed tomography sequences. Real data with an actual low axial resolution have been used as well for a qualitative evaluation of the proposed methods. Conclusions:The experimental results demonstrate that the proposed methods enable an effective slice interpolation and that the achievable 3D models clearly benefit from the increased axial resolution.
Abstract: Pectus Arcuatum (PA) is a congenital chest wall deformity which produces a superior manubrial and sternal protrusion, particularly at the sternal angle. PA surgical correction to reduce the angle of the sternum always includes the removal of bone portion by means of horizontal sternal osteotomies, resection of deformed rib cartilage and finally stabilization of the anterior thoracic wall. Within this process an incorrect assessment of the sternotomy angle during the procedure may lead to the need for bone or cartilage grafts to fill the left voids. This problem has been addressed with a patient-specific cutting template, realized with Reverse Engineering and Additive Manufacturing techniques, which proved to be a key element to simplify the procedure and avoid the occurrence of this type of complications. In this work is presented and validated a procedure that, through common CAD operations, realizes in a completely automatic way the CAD model of the custom cutting template, so as to make non-expert users independent in the realization of the medical device.
Abstract: Generative design tools have recently become an interesting solution to tackle design problems in several technical fields. This article takes into consideration the specific field of mechanical design and aims at describing available generative design solutions capable of dealing with structural optimization problems. The study provides a practical description on the workflow and performances of a specific software system implementing a generative approach for the generation of a set of alternative solutions for a static structural design problem. The software analyzed is Autodesk’s Generative Design, hosted in Fusion 360. The article discusses the functioning of the software and its performances; an enhanced focus on the features oriented to the generation of manufacturable shapes is provided in the text. In order to provide a practical and effective procedure, a literature case study was selected to test the software.
Abstract: Computer Aided reconstruction of mechanical parts nowadays heavily relies on dedicated RE software systems and highly skilled users to be carried out effectively. This paper investigates this scenario in order to identify most limiting factors in the current framework. With this respect, several considerations of general validity are drawn while presenting the problem from a theoretical perspective. A significant test case reconstruction, discussed in depth in the manuscript, is used to provide a practical point of view on real applications and help the reader acquire a hands-on comprehension of the current situation.
Abstract: Total hip arthroplasty (THA) and total knee arthroplasty (TKA) have been recently heralded as the operations of the Century. Large improvements in mobility and patient-reported outcomes are typically observed compared with the small-to-moderate effects experienced with non-surgical interventions. Following surgery, physiotherapy-led exercise-based rehabilitation is often prescribed to yield better gait-related outcomes. Nevertheless, outpatient rehabilitation is expensive and heavily burden the national health service. When specific machines are not needed during the physiotherapy, patients, if assisted, can perform a home program. The purpose of this paper is to qualitatively investigate the applicability of a self-managed, home-based system for the automated evaluation of a home physiotherapy rehabilitation after TKA and THA. The system leverages the cost effectiveness and the versatility of a RGB-Depth camera system together with a commercial skeleton tracking system to analyse specific exercises. A novel computation of lower limb movements and related angles is proposed to evaluate the quality of the daily exercises. The laboratory experimental campaign, envisaged the analysis of the rotation angles of hips and knees; a lower limb schematic model is considered to estimate both knee and hip angles during ab/adductor and flex/extension movements. A novel real time calculation of the hip bone plane is proposed to assess the joint angles during specific exercises performance. A qualitative data analysis of each exercise has been performed. Results on the system usability in a domestic environment are reported as well as a visual comparison of the analysed output.
Abstract: In patients affected by craniosynostosis, i.e. a congenital cranial defect, diagnostic evaluation for a prompt surgical treatment is performed using low-dose three-dimensional computer tomography (CT), characterized by a poor spatial resolution (in terms of slice thickness). The limited number of CT images reduces the accuracy of the 3D reconstruction of the skull and leads to a coarser segmentation and modelling. In this paper, Motion Compensated Frame Interpolation (MCFI) techniques are applied for an effective axial interpolation of tomographic images sequences, with the main objective of obtaining a refined 3D reconstruction. The performance of the proposed method was assessed by using high-resolution CT sequences. After downsampling along the axial direction, the missing slices were recovered by using the proposed algorithm, to obtain an estimate of the original sequence. The experimental results show that the 3D models obtained from the downsampled/interpolated sequence are very close to those obtained from the original one thus providing a high-quality 3D skull reconstruction.
Abstract: The present paper presents the study of a semi-automatic CAD technique for the generation of ventilation holes on ABS AM-manufactured arm orthoses. A lighter device, good air and water transpiration and an increased patient’s comfort are the main advantages achievable by introducing openings on plastic casts. The proposed procedure relies on the adaptation of a reference pattern of holes, obtained integrating both structural and functional aspects, to each patient’s cast. The adaptation procedure maps the original pattern, respecting its proportions, on each target orthosis, thanks to a set of reference points automatically extracted. The generation of holes is performed relying on an advanced CAD environment (i.e. Siemens NX), where a series of CAD modeling operations, based on the data extracted by the mapping algorithm, have been studied and tested. The whole procedure has been tested on 5 orthoses to validate its efficacy.
Abstract: The interest in developing customized external orthopaedic devices, thanks to the advent of Additive Manufacturing (AM), has grown in recent years. Greater attention was focused on upper limb casts, while applications to other body’s parts, such as the neck, were less investigated. In this paper the computer aided design (CAD) modelling, assessment and 3D printing with fused deposition modelling (FDM) of a customized neck orthosis are reported. The modelling, based on anatomic data of a volunteer subject, was aimed to obtain a lightweight, ventilated, hygienic and comfortable orthosis compared to the produced medical devices generally used for neck injuries. CAD models with different geometrical patterns, introduced for lightening and improving breathability, were considered, specifically, a honeycomb pattern and an elliptical holes pattern. These models were structurally assessed by means of finite elements analysis (FEA). Furthermore, an innovative composite material was considered for 3D printing. The material, Hemp Bio-Plastic® (HBP), composed by polylactic acid (PLA) and hemp shives, offers different advantages including lightweight, improved superficial finish and antibacterial properties. The results obtained in terms of design methodology and manufacturing by 3D printing of a prototype have shown the feasibility to develop customized cervical orthoses, with potentially improved performance with respect to cervical collars available on the market also thanks to the use of the innovative composite material.
Abstract: In recent decades, increasing attention is being paid to the multidisciplinary approach that allows the performance of both a preventive conservation and a more invasive restoration action. In this context, the present study aims to acquire information and data from field surveys undertaken in San Domenico Church, Southern Calabria, in order to provide a tool for the recording and the inventory of damage and decay phenomena, and assess their causes and scale. The subsequent calculation of damage indices also provided useful information in order to allow the prioritization of conservation and preservation responses.
Abstract: In injection molding production, automatic inspections are needed to control defects and evaluate the assigned functional tolerances of components and dies. With the “Smart Manufacturing” approach as a point of view, this paper resumes part of a wider research aiming the integration and the automation of a Reverse Engineering inspection process in components and die set-up. The paper compares two fitting approaches for recognition of portions of cylindrical surfaces. Therefore, they are evaluated in the respect of an automatic voxel-based feature recognition of 3D dense cloud of points for tolerance inspection of injection-molded parts. The first approach is a 2D Levenberg Marquardt algorithm coupled with a first guess evaluation made by the Kasa algebraic form. The second one is a 3D fitting based on the RANdom SAmple Consensus algorithm (RANSAC). The evaluation has been made according to the ability of the approaches of working on points associated to the voxel structure that locally divides the cloud to characterize planar and curved surfaces. After the presentation of the overall automatic recognition, the cylindrical surface algorithms are presented and compared trough test cases.
Abstract: The aim of this study is to understand if the shape of a cell can affect the characterization process of the mechanical properties via nanoindentation measurements. The characterization of the cell material by atomic force microscopy, in fact, traditionally implements the Hertz contact theory that is based on hypotheses not satisfied in the contact Atomic Force Microscope tip/cell and that do not take into account the actual cell morphology. In previous experimental studies, the mechanical properties of colorectal cancer cells differently shaped (rounded or elongated cells) and sized were determined via nanoindentation measurements. Implementing the Hertz theory, the authors found that differences in mechanical properties exist between the different cell lines with different shape. At this point, the question that can be raised is the following. Is it possible to state that this difference depends on the differences intrinsically existing between the mechanical properties of the investigated cells? Or, this difference can be justified with the difference in cells shape? In other words, the differences seen with the Hertz theory can depend on the fact that the cell shape was not taken into account. To respond to this question, the nanoindentation process of the different colorectal cancer cells was simulated via the finite element method. The finite element models reproducing the cells morphology were integrated into a numerical optimization algorithm that cyclically perturbs the cell mechanical properties until the difference between the force-indentation curve retrieved numerically and that obtained experimentally becomes smaller than an a priori fixed ε value. Once this occurs, the optimization algorithm stops and gives in output the optimal cell material properties. Interestingly, we found that the mechanical properties obtained via the Hertz contact theory are significantly different with respect to those computed with the proposed approach. Furthermore, we found that the material properties of the rounded cells are intrinsically different with respect to those of the elongated ones. The proposed approach provides new insights on the cell mechanobiology and on the effect of cell shape on the specific tasks in cancer growth and invasion.
Keywords: Cell material characterization | Cell modelling | Cell shape
Abstract: The paper offers insights into people's exploration of creative products shown on a computer screen within the overall task of capturing artifacts' original features and functions. In particular, the study presented here analyzes the effects of different forms of representations, i.e., static pictures and videos. While the relevance of changing stimuli's forms of representation is acknowledged in both engineering design and human-computer interaction, scarce attention has been paid to this issue hitherto when creative products are in play. Six creative products have been presented to twenty-eight subjects through either pictures or videos in an Eye-Tracking-supported experiment. The results show that major attention is paid by people to original product features and functional elements when products are displayed by means of videos. This aspect is of paramount importance, as original shapes, parts, or characteristics of creative products might be inconsistent with people's habits and cast doubts about their rationale and utility. In this sense, videos seemingly emphasize said original elements and likely lead to their explanation/resolution. Overall, the outcomes of the study strengthen the need to match appropriate forms of representation with different design stages in light of the needs for designs' evaluation and testing user experience.
Keywords: Areas of interest | Creative products | Eye-Tracking | Human-computer interaction | Images | User experience | Videos
Abstract: The paper investigates the relationship between the forms through which products are represented and the outcomes of evaluations made by observers. In particular, the study focuses on perceived affordances of creative designs, meant as the capability of capturing original elements and corresponding functions, for products presented through static images or videos. Also thanks to the use of Eye Tracking, the experimental results show how dynamic effects that involve salient aspects of products, as well as creative features, are critical to observers' capability of capturing design intentions.
Keywords: design affordance | design creativity | design evaluation | forms of representation | product design
Abstract: This paper presents a methodological procedure, based on the anatomical reconstruction and constrained deformation, to design custom-made implants for forehead augmentation in people affected by Apert syndrome, experiencing a frontal bone deficiency. According to the anthropometric theory, a cranial landmarks identification procedure was applied to retrieve, from a repository, a healthy skull, used as reference geometry for implant modelling. Then, using constrained deformation and free-form modelling techniques, it was possible to design a patient-specific implant. At last, the implant was realised using a custom mould, specially designed according to the patient’s needs to provide an accurate fit of the defect site. The design procedure was tested on a patient suffering from Apert syndrome. Three implants were virtually modelled and 3D-printed for pre-surgical evaluation. Their shapes were 3D compared with a reference one (handcrafted by a surgeon) to test the accuracy. Deviations are negligible, and the customised implant fulfilled the surgeon’s requirements.
Keywords: Computer-aided design | Craniomaxillofacial surgery | Implant design | Medical devices | Rapid prototyping
Abstract: The availability of advanced tools able to model complex geometries along with the relaxing of the constraints related to the manufacturing technologies are heavily transforming the design approach in many fields, including healthcare. The focus of this paper is on the optimization of porous lightweight cellular geometries in the orthopedic implants design: lattice structures have proven to fulfill the biological, mechanical, and technological constraints required in designing load bearing devices. The aim is to collect the information provided by the related literature to describe the effects induced by the selection of parameters designing lattice gyroid structures for orthopedic implants.
Keywords: custom metal implant | design for additive manufacturing | gyroid | metallic lattice structures | triply periodic minimal surface
Abstract: Designing an acquisition system for 2D or 3D information, based on the integration of data provided by different sensors is a task that requires a labor-intensive initial design phase. Indeed, the definition of the architecture of such acquisition systems needs to start from the identification of the position and orientation of the sensors observing the scene. Their placement is carefully studied to enhance the efficacy of the system. This often coincides with the need to maximize the surfaces observed by the sensors or some other metric. An automatic optimization procedure based on the Particle Swarm Optimization (PSO) algorithm, to seek the most convenient setting of multiple optical sensors observing a 3D scene, is proposed. The procedure has been developed to provide a fast and efficient tool for 2D and 3D data acquisition. Three different objective functions of general validity, to be used in future applications, are proposed and described in the text. Various filters are introduced to reduce computational times of the whole procedure. The method is capable of handling occlusions from undesired obstacle in the scene. Finally, the entire method is discussed with reference to 1) the development of a body scanner for the arm-wrist-hand district and 2) the acquisition of an internal environment as case studies.
Keywords: 3D scanning | Body scanner | Computer graphics | Optical sensors | PSO | Sensor placement | Visibility analysis
Abstract: In recent years, breakthroughs in the fields of reverse engineering and additive manufacturing techniques have led to the development of innovative solutions for personalized medicine. 3D technologies are quickly becoming a new treatment concept that hinges on the ability to shape patient-specific devices.Among the wide spectrum of medical applications, the orthopaedic sector is experiencing the most benefits. Several studies proposed modelling procedures for patient-specific 3D-printed casts for wrist orthoses, for example. Unfortunately, the proposed approaches are not ready to be used directly in clinical practice since the design of these devices requires significant interaction among medical staff, reverse engineering experts, additive manufacturing specialists and CAD designers. This paper proposes a new practical methodology to produce 3D printable casts for wrist immobilization with the aim of overcoming these drawbacks. In particular, the idea is to realize an exhaustive system that can be used within a paediatric environment. It should provide both a fast and accurate dedicated scanning of the hand-wrist-arm district, along with a series of easy-to-use semi-automatic tools for the modelling of the medical device. The system was designed to be used directly by the clinical staff after a brief training. It was tested on a set of five case studies with the aim of proving its general reliability and identifying possible major flaws. Casts obtained using the proposed system were manufactured using a commercial 3D printer, and the device’s compliance with medical requirements was tested. Results showed that the designed casts were correctly generated by the medical staff without the need of involving engineers. Moreover, positive feedback was provided by the users involved in the experiment.
Abstract: The autologous ear reconstruction surgery, i.e. the reconstruction of the missing ear anatomy with autologous cartilage tissue in case of partial or complete absence of the auricular region, can be extremely complicated due to the unique shape and size of this anatomical region. Operations of sculpting and carving of the costal cartilage in order to realize the ear reproduction require a high degree of manual expertise and experience from the surgeon. The development of surgical aids that can provide the physician with guidelines during the reconstruction is being studied in the literature. However, state-of-the-art techniques do not represent the optimal solution and only partially help in the reconstruction process. They are based on two-or three-dimensional templates of the target anatomy, providing visual support, yet not helping in the actual reconstruction phase, or, in some cases, by providing active aid but not simplifying the procedure sufficiently. In this context, the option of creating custom cutting guides that could actively assist the surgeon both in the pre-operative planning phase and during the surgery was considered. The proposed approach involves the use of surgical guides adopted for the cutting and reconstruction of the individual anatomical elements involved. Through an iterative process carried out in collaboration with the surgeon the characteristics of the surgical guides have been defined. Subsequently, a method that can be applied systematically to model the cutting guides, ready to be printed with additive production techniques was defined. The procedure was designed with a view to a future semi-automatization of the entire process that could make the physician autonomous in the realization of the patient-specific guides.
Keywords: 3D Ear Templates | Autologous Ear Reconstruction | CAD modelling | Personalized Medicine | Reverse Engineering
Abstract: Bone tumor resections have to be carefully planned in order to avoid intralesional cuts and thus lower the recurrence rate. Until the present-day bone resections have been performed freehand, using anatomical landmarks as reference points to retrieve planned resection planes over the very patient. Such method is highly prone to failure to the detriment of the patient’s health, in fact survival rate for osteosarcomas is very low, ranging between 20% and 47%. The clinical outcome is highly dependent on the resections’ accuracy; several emerging techniques proved to dramatically increase cutting accuracy, as well as survival rate, in particular Patient Specific Instruments (PSIs) and custom 3D printed metal prosthesis. The main limitation to a massive spread of this method is the large manufacturing time due to a lack of communication between surgeons and engineers about the surgical approach and the design constraints. This paper aims to compare several general-purpose low-cost software and to provide surgeons with an effective and easy to use platform to visually share information in a natural manner with engineers thus providing as many design constraints as possible, speed up the design process and avoid unfeasible results. Two surgeons from Azienda Ospedaliera Universitaria Careggi tested and evaluated a series of software. From this preliminary investigation Forger, a digital sculpting and texture painting application for iOS, resulted as the most user friendly and intuitive application among the test group.
Keywords: Computer aided surgery | Concurrent design | Digital surgical planning | Human computer interaction
Abstract: Innovation on semiconductors technology requires enhancements of all actors like adhesion layers, barriers and metal stacks, beyond of semiconductor materials themselves. In general, metallic layers influence the whole die performances. The composition and the layout of these metal layers are fundamental for the signal transmission from the frame to the die and vice versa, and therefore their improvement contributes to the die development in terms of performances and reliability. In the present work, two pad structures have been benchmarked and analyzed under the structural strength standpoint. The experimental comparison among the different pads has been done through a flat punch nanoindentation to highlight the material strength and the crack propagation phenomena. Testing results have been compared to finite element models to analyze the stress through the different layers. The findings of the work demonstrate the validity of the methodology adopted and show the importance of the metallic connections layouts for the stress concentration and crack formation analysis.
Abstract: Additive Manufacturing is becoming a suitable production process for many industries: it is based on the idea of adding material layer by layer, in opposite to traditional manufacturing processes. This technology shows advantages as design flexibility, internal logistics minimization and product customization that make it perfect to produce customized parts and all the applications where low production rates occur. The production of spare parts for classic or luxury cars is a field where Additive Manufacturing can be adopted because of low demand and relevant costs to manage stocks keeping several different parts in the after-sales inventory. The photogrammetry technique has been investigated to obtain the 3D model of the component to be replaced and send it to decentralized production centers equipped with 3D printers. This approach can enhance by far the supply chain management for automotive spare parts.
Abstract: Nowadays, the contribution of the CAD modeling is not yet well exploited into the design of overhead lines. Even if some commercial tools are available, they are very similar to configuration tools with design rules related to reference normative. Sometimes, if 2D/3D CAD tools are employed, they are viewers or customized versions with specific features for the design of overhead lines. This situation limits the interoperability between the design of overhead lines and traditional software employed in the design of civil structures and infrastructures. Moreover, an information modeling approach is still lacking in current tools for the management of additional data about maintenance, cost, etc. In the context of overhead lines, the paper aims at showing an information modeling approach with a platform software which includes a configuration tool, a CAD module, an analytical-based solver, a costing tool, and a Finite Element Method solver. The CAD module is employed to define a 3D model including, as tag-objects, a set of information regarding the lifecycle design of overhead lines. Finally, a Finite Element Model solver enhances a second level of validation and enables advanced simulations.
Keywords: Computer-aided design | Configurations | Finite Element Model | Information Modeling | Overhead lines
Abstract: Design for Assembly is a strategy of design aimed at minimising product cost through design and process improvements. It led to a revolution in the manufacturing industry, resulting in reduced product costs, improved quality, shorter time to market, lower inventory, fewer suppliers and many other improvements. DFA is the method of design of the product for ease of assembly and in this context this paper presents an application of the strategy to a virtual case study represented by a two-way relief valve modelled by CAD. The aim of this paper was to test some DFA methods proposed by the literature and search for an efficient assembly of the virtual two-way relief valve reproduced by CAD, then verifying its assembly effectiveness. Some evaluation methods proposed by literature about the optimisation of design efficiency have been applied to the case study and this led to reconsider the design of some parts of the product. A final new design for the valve is proposed and the evaluation methods applied have been tested again on the new solution, in order to validate the results. A comparison between the original valve and the new version proposed by the authors has been made, in order both to check the feasibility of the new valve and in order to check the evaluation methods proposed.
Abstract: Environmental impact and recycling have been increasingly frequent topics in recent years. At the same time, the life cycle of products has increasingly become shorter, as the escalating competitive market requires new products in smaller pieces. From this perspective, the recovery of parts and products that are produced in this market system for subsequent reuse when they reach the end of their life cycle is essential. For these reasons, it has become critical that companies re-evaluate their product design with a view to the possible recovery of the parts that comprise their products and to create new products for the market. The following discussion was based on the study of design for disassembly (DfD), which is the analysis of industrial products aimed at optimizing disassembly in terms of time and costs. The application of the DfD to a case study of a gearbox has, among its main objectives, the search for the best disassembly sequence in terms of time and money. During the course of the study, augmented reality (AR) was used. Through the use of the Unity software and Vuforia package, it was possible to bring the gearbox back to AR and then simulate the disassembly sequence in AR.
Abstract: The work here described aims to offer a starting point for improving and making a generic maintenance process more efficient, first of all thanks to the use of a cutting-edge technology such as augmented reality, as a key tool that makes it possible and immediate to communicate to operators which are the fundamental stages of the maintenance process to be followed in the working area. Furthermore, thanks to the use of two methods applied in the context of the Design for Disassembly (later described), we also propose to search for all the possible sequences to get to the removal of a target component to be adjusted—in particular the optimal one (if it exists, in terms of time and costs) to be subsequently applied in an augmented reality “self-disassembly” model that can be viewed and followed by the operator, in a way that is still very little used today.
Abstract: This work aims to present an in-house low-cost computer-aided simulation (CASS) process that was recently implemented in the preoperative planning of complex osteotomies for limb deformities in children. Five patients admitted to the Unit of Paediatric Orthopaedics and Traumatology from April 2018 to December 2019, for correcting congenital or post-traumatic limb deformities were included in the study. Three-dimensional (3D) digital models were generated from Computed Tomography (CT) scans, using free open-source software, and the surgery was planned and simulated starting from the 3D digital model. 3D printed sterilizable models were fabricated using a low-cost 3D printer, and animations of the operation were generated with the aim to accurately explain the operation to parents. All procedures were successfully planned using our CASS method and the 3D printed models were used during the operation, improving the understanding of the severely abnormal bony anatomy. The surgery was precisely reproduced according to CASS and the deformities were successfully corrected in four cases, while in one case, the intraoperative intentional undersizing of the bone osteotomy produced an incomplete correction of a congenital forearm deformity. Our study describes the application of a safe, effective, user-friendly, and low-cost CASS process in paediatric orthopaedics (PO) surgery. We are convinced that our study will stimulate the widespread adoption of this technological innovation in routine clinical practice for the treatment of rare congenital and post-traumatic limb deformities during childhood.
Keywords: 3D modeling | Computer aided | Osteotomy | Paediatric orthopaedics | Preoperative planning | Surgery | Surgical simulation
Abstract: This work aims to analyze the characteristics and importance that design techniques for disassembly assume in the modern design phase of a mechanism. To this end, the study begins by considering a three-dimensional model of a gear motor, taken from the components of which the overall drawings are arranged and from the relief of those not available. Once the mechanism has been digitally reconstructed, the activity focuses on the study of the optimal disassembly sequence by comparing different methodologies, according to two evaluation criteria-minimizing the time taken and minimizing the number of tool changes necessary to complete the sequence. The main results of the work are (1) defining a standard methodology to improve disassembly sequence planning, (2) finding the best disassembly sequence for the specific component among the literature and eventually new methods, and (3) offering to the industrial world a way to optimize maintenance operations in mechanical products. Referring to the limitation of the present works, it can be affirmed that the results are limited to the literature explored and to the case study examined.
Keywords: CAD | Disassembly sequence planning | Globoid gear motor
Abstract: In the region of the cultural patrimony, operators use high-resolution orthophotos of paintings for the restoration, monitoring and electronic recording and exhibition purposes. Unfortunately, artworks that are to be restored and/or shown in digital museums are painted on canvas that are far from perfectly planar. Professional documents surrounding an artwork to be preserved in digital collections or museums can therefore be enhanced with information relating to the paintings' 3D structure. This paper proposes both the design of a portable low-cost device that enables the acquisition of 3D geometry of painting and the procedure for triangulation of 3D data. This process uses a set of fiducial markers to set and continuously control the mutual orientation of the laser source and the camera and works accordingly to the principle of laser-camera triangulation.
Keywords: 3D Laser Scanner | Cultural Heritage | Marker Detection | Pose Estimation | Reverse Engineering
Abstract: In brain tumor surgery, an appropriate and careful surgical planning process is crucial for surgeons and can determine the success or failure of the surgery. A deep comprehension of spatial relationships between tumor borders and surrounding healthy tissues enables accurate surgical planning that leads to the identification of the optimal and patient-specific surgical strategy. A physical replica of the region of interest is a valuable aid for preoperative planning and simulation, allowing the physician to directly handle the patient’s anatomy and easily study the volumes involved in the surgery. In the literature, different anatomical models, produced with 3D technologies, are reported and several methodologies were proposed. Many of them share the idea that the employment of 3D printing technologies to produce anatomical models can be introduced into standard clinical practice since 3D printing is now considered to be a mature technology. Therefore, the main aim of the paper is to take into account the literature best practices and to describe the current workflow and methodology used to standardize the pre-operative virtual and physical simulation in neurosurgery. The main aim is also to introduce these practices and standards to neurosurgeons and clinical engineers interested in learning and implementing cost-effective in-house preoperative surgical planning processes. To assess the validity of the proposed scheme, four clinical cases of preoperative planning of brain cancer surgery are reported and discussed. Our preliminary results showed that the proposed methodology can be applied effectively in the neurosurgical clinical practice both in terms of affordability and in terms of simulation realism and efficacy.
Keywords: 3D casting | 3D printing | Additive manufacturing | Brain | Cancer | Computer aided design | Neurosurgery | Physical simulation | Preoperative planning | Virtual planning
Abstract: Autologous ear reconstruction, i.e. the reconstruction of the outer ear from autologous cartilage tissue, is a very important surgery considering the psychosocial repercussions of an individual affected by microtia (i.e. the total or partial absence of the outer ear). The execution of this surgery can be very complex due to the unique characteristics of this anatomical region. In order to help the surgeon in the process of cutting and suturing, innovative surgical guides were designed that can transmit information about the shape and size of the anatomy to be reconstructed. This work lays the foundation for the creation of a semi-automatic and easy-to-use tool for the modeling of surgical guides. The goal is to make the hospital staff autonomous in the creation of instruments that can be used in pre-surgical simulation and during surgery.
Keywords: Autologous Ear Reconstruction | Bioengineering | Computer Aided Design | Medical Devices and Equipment | Microtia
Abstract: The most common clinical treatment for ear deformities or non-congenital abnormalities is the reconstruction of the missing geometry using autologous costal cartilage. The surgical procedure consists in cutting, sculpting and suturing harvested costal cartilage from the patient to recreate an ear shape which is symmetric to the contralateral ear. During chirurgical operation, surgeons needs an accurate 3D template as reference to reproduce the ear. For this purpose, reverse engineering and additive manufacturing techniques can be employed. Specifically, this works aims to develop a reliable, low-cost and user-friendly system, to acquire the healthy ear geometry in clinical environment avoiding head patient’s exposition to radiation (MRI, CT scan). An ideal acquisition setup and device have been selected to achieve accurate results. To this end, a casted model of an ear was created as reference, and the best setup was evaluated by comparing the obtained 3D reconstructions with it. Once the setup has been determined, the anatomies of five volunteers were acquired, to test the methodology on human subjects.
Keywords: 3D model | Ear | Microtia | Photogrammetry | RealSense D415
Abstract: Nowadays, smartphones and laptops equipped with cameras have become an integral part of our daily lives. The pervasive use of cameras enables the collection of an enormous amount of data, which can be easily extracted through video images processing. This opens up the possibility of using technologies that until now had been restricted to laboratories, such as eye-tracking and emotion analysis systems, to analyze users' behavior in the wild, during the interaction with websites. In this context, this paper introduces a toolkit that takes advantage of deep learning algorithms to monitor user's behavior and emotions, through the acquisition of facial expression and eye gaze from the video captured by the webcam of the device used to navigate the web, in compliance with the EU General data protection regulation (GDPR). Collected data are potentially useful to support user experience assessment of web-based applications in the wild and to improve the effectiveness of e-commerce recommendation systems.
Keywords: Affective Computing | Convolutional Neural Networks | Deep Learning | Gaze detection | User Experience
Abstract: The paper aims at providing an overview on the current automation level of geometric verification process with reference to some aspects that can be considered crucial to achieve a greater efficiency, accuracy and repeatability of the inspection process. Although we are still far from making this process completely automatic, several researches were made in recent years to support and speed up the geometric error evaluation and to make it less human-intensive. The paper, in particular, surveys: (1) models of specification developed for an integrated approach to tolerancing; (2) state of the art of Computer-Aided Inspection Planning (CAIP); (3) research efforts recently made for limiting or eliminating the human contribution during the data processing aimed at geometric error evaluation. Possible future perspectives of the research on the automation of geometric verification process are finally described.
Keywords: Automatic geometric verification | Computer-Aided Inspection Planning | Error evaluation | Feature Recognition | GPS standards | Model of specification for tolerancing | Partition
Abstract: Background: Sleep-Related Breathing Disorders are characterized by repeated episodes of complete or partial obstruction of the upper airway during sleep. Mandibular advancement devices represent a non-invasive treatment in reducing the number of respiratory events and in decreasing symptoms. The advancement extent of these devices is responsible for the mandibular roto-translation and its effects on the temporomandibular joint. Methods: This study defined a systematic method to assess the mandible roto translation that is caused by MADs according to a scan-to-CAD approach. Starting from a closed mouth position and simulating the oral appliance at different settings it was possible to define a local reference system that is useful for the evaluation of the mandibular roto-translation. This latter was then applied to evaluate the movements of the condyle and the mandibular dental arch. Results: MAD1 resulted in a reduced mouth opening and protrusion, while MAD2 enabled a higher degree of motion of the mandible useful for patients who need an important protrusion. Conclusions: The two devices present different dynamics. Results that are achievable employing this method can be directly used by practitioners in comparing MADs, as well as by researchers in evaluating MADs effects.
Keywords: Computer-aided design | Digital dentistry | Digital workflow | Mandibular advancement device | Obstructive sleep apnea syndrome
Abstract: This work proposes an innovative method for evaluating usersâ™ engagement, combining the User Engagement Scale (UES) questionnaire and a facial expression recognition (FER) system, active research topics of increasing interest in the humanâ"computer interaction domain (HCI). The subject of the study is a 3D simulator that reproduces a virtual FabLab in which users can approach and learn 3D modeling software and 3D printing. During the interaction with the virtual environment, a structured-light camera acquires the face of the participant in real-time, to catch its spontaneous reactions and compare them with the answers to the UES closed-ended questions. FER methods allow overcoming some intrinsic limits in the adoption of questioning methods, such as the non-sincerity of the interviewees and the lack of correspondence with facial expressions and body language. A convolutional neural network (CNN) has been trained on the Bosphorus database (DB) to perform expression recognition and the classification of the video frames in three classes of engagement (deactivation, average activation, and activation) according to the model of emotion developed by Russell. The results show that the two methodologies can be integrated to evaluate user engagement, to combine weighted answers and spontaneous reactions and to increase knowledge for the design of the new product or service.
Keywords: 3D simulator | CNN | Deep learning | Facial expression recognition | Human-computer interaction | User engagement scale | User-centered design
Abstract: The pre-concept design of the DEMO Vacuum Vessel is going on in view of the 2020 gate review; moreover the nuclear heat loads on the vessel inner shell were determined and found to be about one order of magnitude higher compared to ITER. A subsequent thermal-structural analysis of the vessel inner shell revealed high thermal stresses and a large temperature gradient through the inner shell thickness. Given the simultaneous occurrence of primary membrane stresses in the entire vessel inboard wall and, in proximity of the vessel ribs, high bending stresses due to the coolant pressure, a survey of all options within the design rules was required to identify the inter-dependencies of the individual stress limits (primary membrane, primary bending, thermal membrane plus bending). In order to face this kind of issues a detailed assessment on the design of the inboard wall of DEMO Vacuum Vessel has been conducted and is presented here. The current work evaluates both P and S type damages for the inboard wall of DEMO Vacuum Vessel in case of high nuclear heat load, vacuum vessel coolant pressure and toroidal field coil fast discharge. The elastic analysis method has been used to check the rules for prevention of both types of damage. The rules applied to prevent the aforementioned damages are compliant to Level A criteria, in case of negligible creep and negligible irradiation. In order to check the structural integrity of the inboard wall of DEMO VV against high thermal and mechanical loads, optimization structural analyses were performed and checked against the rules provided in the applicable design code (RCC MRx).
Abstract: In recent years, bone fracture detection and classification has been a widely discussed topic and many researchers have proposed different methods to tackle this problem. Despite this, a universal approach able to classify all the fractures in the human body has not yet been defined. We aim to analyze and evaluate a selection of papers, chosen according to their representative approach, where the authors applied different deep learning techniques to classify bone fractures, in order to select the strengths of each of them and try to delineate a generalized strategy. Each study is summarized and evaluated using a radar graph with six values: area under the curve (AUC), test accuracy, sensitivity, specificity, dataset size and labelling reliability. Plus, we defined the key points which should be taken into account when trying to accomplish this purpose and we compared each study with our baseline. In recent years, deep learning and, in particular, the convolution neural network (CNN), has achieved results comparable to those of humans in bone fracture classification. Adopting a correct generalization, we are reasonably sure that a computer-aided diagnosis (CAD) system, correctly designed to assist doctors, would save a considerable amount of time and would limit the number of wrong diagnoses.
Keywords: Bone fracture | CAD system | Deep learning | Neural network | Orthopedics | X-ray
Abstract: The optimization of the aeronautical assembly lines is one of the most challenging tasks in development of a new aircraft. To date the Aeronautical companies are founding project related to the optimization of the manufacturing processes, impacting on the reduction of the non-recurring costs. The work presented focuses on methods for the implementation of the determinate assembly approach in the case of manufacturing of aeronautical structures. The methods are based on the prediction of the coupling tolerances between airframe components in order to reduce the numbers of the features to be manufactured in assembly. All that to lead to a reduction of the non-recurring costs.
Keywords: Aeronautical products | Assembly process | CAD | Determinant Assembly | Determinate Assembly | Hole to hole | Statistical distribution | Tolerance prediction
Abstract: Nowadays, robots are heavily used in factories for different tasks, most of them including grasping and manipulation of generic objects in unstructured scenarios. In order to better mimic a human operator involved in a grasping action, where he/she needs to identify the object and detect an optimal grasp by means of visual information, a widely adopted sensing solution is Artificial Vision. Nonetheless, state-of-art applications need long training and fine-tuning for manually build the object's model that is used at run-time during the normal operations, which reduce the overall operational throughput of the robotic system. To overcome such limits, the paper presents a framework based on Deep Convolutional Neural Networks (DCNN) to predict both single and multiple grasp poses for multiple objects all at once, using a single RGB image as input. Thanks to a novel loss function, our framework is trained in an end-to-end fashion and matches state-of-art accuracy with a substantially smaller architecture, which gives unprecedented real-time performances during experimental tests, and makes the application reliable for working on real robots. The system has been implemented using the ROS framework and tested on a Baxter collaborative robot.
Keywords: Collaborative robotics | Deep learning | Industry 4.0 | Vision-guided robotic grasping
Abstract: Purpose: Suspected fractures are among the most common reasons for patients to visit emergency departments and often can be difficult to detect and analyze them on film scans. Therefore, we aimed to design a Deep Learning-based tool able to help doctors in diagnosis of bone fractures, following the hierarchical classification proposed by the Arbeitsgemeinschaft für Osteosynthesefragen (AO) Foundation and the Orthopaedic Trauma Association (OTA). Methods: 2453 manually annotated images of proximal femur were used for the classification in different fracture types (1133 Unbroken femur, 570 type A, 750 type B). Secondly, the A type fractures were further classified into the types A1, A2, A3. Two approaches were implemented: the first is a fine-tuned InceptionV3 convolutional neural network (CNN), used as a baseline for our own proposed approach; the second is a multistage architecture composed by successive CNNs in cascade, perfectly suited to the hierarchical structure of the AO/OTA classification. Gradient Class Activation Maps (Grad-CAM) where used to visualize the most relevant areas of the images for classification. The averaged ability of the CNN was measured with accuracy, area under receiver operating characteristics curve (AUC), recall, precision and F1-score. The averaged ability of the orthopedists with and without the help of the CNN was measured with accuracy and Cohen's Kappa coefficient. Results: We obtained an averaged accuracy of 0.86 (CI 0.84−0.88) for three classes classification and 0.81 (CI 0.79−0.82) for five classes classification. The average accuracy improvement of specialists was 14 % with and without the CAD (Computer Assisted Diagnosis) system. Conclusion: We showed the potential of using a CAD system based on CNN for improving diagnosis accuracy and for helping students with a lower level of expertise. We started our work with proximal femur fractures and we aim to extend it to all bone segments further in the future, in order to implement a tool that could be used in every-day hospital routine.
Keywords: Bone fracture | Convolutional neural network | Deep Learning | Orthopaedics | X-Ray
Abstract: Purpose: The current study aimed to systematically review the literature addressing the use of deep learning (DL) methods in intraoperative surgery applications, focusing on the data collection, the objectives of these tools and, more technically, the DL-based paradigms utilized. Methods: A literature search with classic databases was performed: we identified, with the use of specific keywords, a total of 996 papers. Among them, we selected 52 for effective analysis, focusing on articles published after January 2015. Results: The preliminary results of the implementation of DL in clinical setting are encouraging. Almost all the surgery sub-fields have seen the advent of artificial intelligence (AI) applications and the results outperformed the previous techniques in the majority of the cases. From these results, a conceptualization of an intelligent operating room (IOR) is also presented. Conclusion: This evaluation outlined how AI and, in particular, DL are revolutionizing the surgery field, with numerous applications, such as context detection and room management. This process is evolving years by years into the realization of an IOR, equipped with technologies perfectly suited to drastically improve the surgical workflow.
Abstract: In the original article, there was an error. A Conflict of Interest Statement was missed. A correction has been made to the Conflict of Interest section reporting the following detailed information.
Abstract: The aim of the research is to develop an azimuthing contra-rotating propeller for commercial applications with a power of 2000 kW. The thruster system is designed especially to be installed on high speed crafts (HSCs) for passenger transport with a cruising speed of about 35-40 knots. The topic is very useful because the azimuth thruster solutions currently do not find commercial applications in naval units for passenger transport. The latter are heavy, not very efficient from a hydrodynamic point of view and suitable for maximum cruising speed of about 18-20 knots. The study is interesting because among the advantages that these solutions provide are the possibility of transmitting very high torques and to guarantee a much longer life cycle. In more detail, the propulsion is realized by using a C-drive configuration, with a first mechanical transmission realized by using bevel gears mounted in a frame inside the hull, and a second transmission realized by bevel gears housed in a profiled hull at the lower end of a support structure. In the profiled hull will be installed the shafts of the propellers, in a contra-rotating configuration. In order to optimize the system before its industrial use, a close power loop test bench has been studied and designed to test high power transmissions. The test configuration allows to implement a back-to-back connection between two identical azimuthing contra-rotating propellers. Moreover, the particular test bench allows to size the electric motor simply based on the dissipated power by the kinematic mechanisms. Since the efficiency of these systems are very high, it is not necessary to use large electric motors, thus managing to contain the operating costs of the testing phase. The most significant disadvantage is the need to have two identical transmissions with consequent increase in installation costs. Through the back-to-back test bench it was possible to study the increase in efficiency compared to traditional systems.
Keywords: azimuthing contra-rotating propeller | CAD modeling | experimental test | finite element analysis | POD | Thruster
Abstract: The accurate location of the mid-sagittal plane is fundamental for the assessment of craniofacial dysmorphisms and for a proper corrective surgery planning. To date, these elaborations are carried out by skilled operators within specific software environments. Since the whole procedure is based on the manual selection of specific landmarks, it is time-consuming, and the results depend on the operators' professional experience. This work aims to propose a new automatic and landmark-independent technique which is able to extract a reliable mid-sagittal plane from 3D CT images. The algorithm has been designed to perform a robust evaluation, also in the case of large defect areas. The presented method is an upgraded version of a mirroring-and registration technique for the automatic symmetry plane detection of 3D asymmetrically scanned human faces, previously published by the authors. With respect to the published algorithm, the improvements here introduced concern both the objective function formulation and the method used to minimize it. The automatic method here proposed has been verified in the analysis of real craniofacial skeletons also with large defects, and the results have been compared with other recent technologies.
Abstract: In this paper, a topological optimization procedure has been applied on a real component of the deck of a sailing multi-hull in order to find the internal shape that best save the material used in the manufacturing process without a relevant loss of structural rigidity. The multi-hull boat is a 16 feet length catamaran equipped with an asymmetric foil on both centerboards and with a symmetric foil on both rudders. The task of the analyzed object is to act as a cylindrical support for the screw that drives the rotation of the centerboard. The process adopted to manufacture this object is the Fused Deposition Modeling (FDM) technique, because of its high versatility and its relative low-cost impact. The aim of this work is to verify the applicability of FDM to structural naval component subjected to demanding loads during navigation and, at the same time, to investigate on the robustness of a topology optimization strategy in creating new shapes that recent additive manufacturing are able to create.
Abstract: Among rising technology in medical field, methods and solutions of reverse engineering have a high impact as a new possibility for improving the traditional processes to design prosthesis and orthoses. Furthermore, reverse engineering solutions allows managing a big amount of patient's data, which can be also exploited for making the medical assessment during rehabilitation activities more objective and measurable. In particular, innovative technologies permit to manage big amount of data coming from several IT devices in order to better understand the correlation between technical aspects and human factors. These IT devices can be exploited through customized software applications, which are able to combine many data types (e.g. 3D scanners, motion capture systems and pressure sensors). In this research work, the attention is focused on the design of lower limb prosthesis around the digital human model of the patient. We present a virtual platform composed by an ad-hoc developed application for customizing the prosthesis according to patients' life style and medical knowledge as well as for visualizing pressure on patient's limb while evaluating his/her gait in a unique virtual knowledge-guided environment. Such applications are conceived to be usable by non IT experts, and all information are directly visualized on the digital human model of the amputee. The first part of the paper introduces the whole platform to design lower limb prosthesis using low-cost technologies. Then, the virtual gait analysis tool is described. Finally, tests and conclusion are discussed.
Keywords: 3D modelling | Health informatics | Marker-less motion capture system | Pressure data | User centered design
Abstract: This paper introduces a novel hybrid finite element (FE) formulation of shell element to enable assembly process simulation of compliant sheet-metal parts with higher efficiency and flexibility. Efficiency was achieved by developing both new hybrid quadrilateral and triangular elements. Quadrilateral element (QUAD+) was formulated by combining area geometric quadrilateral 6 (AGQ6) nodes and mixed interpolated tensorial components (MITC) to model membrane and bending/shear component respectively. Triangular element (TRIA+) was formulated by merging assumed natural deviatoric strain (ANDES) for membrane and MITC for bending/shear component. Flexibility was addressed by developing an open-source C++ code, enhanced by the OpenMP interface for multiprocessing programming. Tests and benchmarks were compiled and executed within Matlab using the MEX API interface. Extensive benchmark studies were accomplished to evaluate the performance of the proposed hybrid formulation and the shell formulations used in three FEM packages - ABAQUS, ANSYS and COMSOL- under static linear elastic condition with small strain assumption. It was observed that the proposed QUAD+ and TRIA+ elements performed better amongst the FE packages, especially when there was in-plane mesh distortion, with errors below 3%. It was also identified that the best efficiency is obtained by adopting dominant QUAD+ elements compared to the TRIA+ when working on complex geometries. This paper also contributes to present a wide set of benchmark studies required to verify new release of FE packages using shell element or evaluate the performance of new shell formulations.
Keywords: Benchmark study | Finite element modelling | Flexibility and efficiency | Sheet metal | Shell elements
Abstract: Mathematical modeling of soft robots is complicated by the description of the continuously deformable three-dimensional shape that they assume when subjected to external loads. In this article we present the deformation space formulation for soft robots dynamics, developed using a finite element approach. Starting from the Cosserat rod theory formulated on a Lie group, we derive a discrete model using a helicoidal shape function for the spatial discretization and a geometric scheme for the time integration of the robot shape configuration. The main motivation behind this work is the derivation of accurate and computational efficient models for soft robots. The model takes into account bending, torsion, shear, and axial deformations due to general external loading conditions. It is validated through analytic and experimental benchmark. The results demonstrate that the model matches experimental positions with errors <1% of the robot length. The computer implementation of the model results in SimSOFT, a dynamic simulation environment for design, analysis, and control of soft robots.
Abstract: The goal of this paper is to disseminate the main results achieved within the FlexARM project. The project deals with advanced modeling techniques and predictive control strategies for flexible mechanical systems intended to be used in remote tasks inside advanced nuclear fusion reactors. This article aims at underlying the main aspect of the FlexARM methodology and paves the way towards future research in the field.
Keywords: DEMO remote maintenance | Flexible mechanical systems | Modeling | Vibration control
Abstract: In the current pre-concept phase of the European DEMO, integration studies of the systems in the Upper Port area are being carried out. In DEMO, the Upper Port of the Vacuum Vessel is extraordinarily large to allow for the vertical extraction of the Breeding Blanket segments. This requires a number of components inside and outside the port to be integrated with tight space constraints: The Upper Port structure and its annexes, the adjacent Toroidal and Poloidal Field Coils, the Thermal Shields, the piping connection to the Vacuum Vessel Pressure Suppression System, the Shield Plug and its inserts, the feeding pipework of the in-vessel components and part of the Breeding Blanket supporting structures. Apart from functional aspects, the design of these components is driven by considerations of structural integrity, maintainability and irradiation shielding, which are mutually competing in many areas. Several studies were conducted on the design of the Upper Port and the required configuration of the components within. The present article describes the development approach, the studied options and the respective results, the identified issues as well as the proposed engineering solutions, in particular with respect to the mechanical design of the Upper Port and the integrated Shield Plug.
Abstract: In this work we present the latest progresses (September 2018) in the conceptual design of the main containment structures of DTT fusion reactor. The previous DTT baseline design is revised in terms of structural materials and overall reactor shape. The major change involves the vacuum vessel, which now foresees a welded double-wall stainless steel structure. The basic design includes eighteen sectors, with novel ports configuration for remote maintenance systems, diagnostics and heating equipment. New supports are designed for the first wall, which is conveniently segmented in view of assembly and remote replacement. The cryostat of the machine is conceived as a single-wall cylindrical vessel reinforced by ribs. The cryostat base is also in charge of supporting the vacuum vessel and the magnets system. A preliminary FEA analysis confirms that the main mechanical structure might withstand the design loads, in particular the ones resulting from possible plasma disruptions.
Abstract: The water-cooled lithium-lead breeding blanket is in the pre-conceptual design phase. It is a candidate option for European DEMO nuclear fusion reactor. This breeding blanket concept relies on the liquid lithium-lead as breeder-multiplier, pressurized water as coolant and EUROFER as structural material. Current design is based on DEMO 2017 specifications. Two separate water systems are in charge of cooling the first wall and the breeding zone: thermo-dynamic cycle is 295–328 °C at 15.5 MPa. The breeder enters and exits from the breeding zone at 330 °C. Cornerstones of the design are the single module segment approach and the water manifold between the breeding blanket box and the back supporting structure. This plate with a thickness of 100 mm supports the breeding blanket and is attached to the vacuum vessel. It is in charge to withstand the loads due to normal operation and selected postulated initiating events. Rationale and progresses of the design are presented and substantiated by engineering evaluations and analyses. Water and lithium lead manifolds are designed and integrated with the two consistent primary heat transport systems, based on a reliable pressurized water reactor operating experience, and six lithium lead systems. Open issues, areas of research and development needs are finally pointed out.
Abstract: This paper presents the recent progress in the pre-conceptual design activities for the EU-DEMO divertor Cassette Body, performed in the framework of the work package “Divertor” of the EUROfusion Power Plant Physics & Technology (PPPT) program. According to Systems Engineering Principles, the divertor CAD model is reviewed, considering the updates in the DEMO configuration model presented by the Programme Management Unit (PMU) in 2017. The design parameters affected by these changes and their impact on the divertor design and on the interfaced systems are analysed. Then, the paper focuses on the integration on the new cassette geometry of the divertor sub-systems. This includes the design of a “shielding liner” for cassette body and Vacuum Vessel protection, as well as the development of the cassette body-to-Vacuum Vessel fixation system. The design activities related to these main sub-systems are discussed in detail, in terms of CAD model and thermo-mechanical calculations.
Keywords: 3D CAD modelling | Divertor | Divertor fixation system | EU-DEMO | Shielding liner
Abstract: Kinematic modeling of continuum robots is challenging due to the large deflections that these systems usually undergone. In this paper, we derive the kinematics of a continuum robot from the evolution of a three-dimensional curve in space. We obtain the spatial configuration of a continuum robot in terms of exponential coordinates based on Lie group theory. This kinematic framework turns out to handle robotic helical shapes, i.e. spatial configurations with constant curvature and torsion of the arm.
Abstract: Compliant Mechanisms (CMs) are currently employed in several engineering applications requiring high precision and reduced number of parts. For a given mechanism topology, CM analysis and synthesis may be developed resorting to the Pseudo–Rigid Body (PRB) method, in which the behavior of flexible members is approximated via a series of rigid links connected by spring-loaded kinematic pairs. From a CM analysis standpoint, the applicability of a generic PRB model requires the determination of the kinematic pairs’ location and the stiffness of a set of generalized springs. In parallel, from a design standpoint, a PRB model representing the kinetostatic behavior of a flexible system should allow to compute the flexures’ characteristics providing the desired compliance. In light of these considerations, this paper describes a Computer-Aided Design/Engineering (CAD/CAE) framework for the automatic derivation of accurate PRB model parameters, on one hand, and for the shape optimization of complex-shape flexures comprising out-of-plane displacements and distributed compliance. The method leverages on the modelling and simulation capabilities of a parametric CAD (i.e. PTC Creo) seamlessly connected to a CAE tool (i.e. RecurDyn), which provides built-in functions for modelling the motion of flexible members. The method is initially validated on an elementary case study taken from the literature. Then, an industrial case study, which consists of a spatial crank mechanism connected to a fully-compliant four-bar linkage is discussed. At first, an initial sub-optimal design is considered and its PRB representation is automatically determined. Secondly, on the basis of the PRB model, several improved design alternatives are simulated. Finally, the most promising design solution is selected and the dimensions of a flexure with non-trivial shape (i.e. hybrid flexure) is computed. This technique, which combines reliable numerical results to the visual insight of CAD/CAE tools, may be particularly useful for analyzing/designing spatial CMs composed of complex flexure topologies.
Abstract: Position-controlled servo-systems mostly make use of electric rotary motors and gearboxes and, if necessary, a transmission mechanism to convert rotary into linear motion. Even so, especially in the field of automatic machines for packaging, it should be highlighted that most of the required movements are usually linear, so that Linear Electric Motors (LEM) should somehow represent a more convenient solution for designers. LEM can directly generate the required trajectory avoiding any intermediate mechanism, thus potentially minimizing the number of linkages/mechanical parts and, therefore, the undesired backlash and compliance that come along. On the other hand, particularly within small-medium enterprises, LEM may be rarely employed despite obvious advantages, mostly due to their high-cost as compared to rotary actuators and the lack of knowledge of the achievable performance. In light of these considerations, the present paper reports an industrial case study where an automatic machine for packaging, comprising distributed actuation and several tasks requiring a linear motion, has been completely redesigned employing different kind of LEM (i.e. iron-core and iron-less). Such machine architecture is compared to a “traditional” design where brushless gearmotors are coupled to linkage systems. The paper mainly focuses on the selection criteria for the LEM system and on the engineering tools employed during the different design stages. Qualitative and quantitative conclusions are finally drawn, which may provide useful hints for designers that are willing to actually employ LEM-based solutions in an industrial scenario.
Keywords: CAD/CAE | Engineering Design Methods and Tools for Industry 4.0 | High Precision Manufacturing | Modelling | Simulation
Abstract: Purpose: Pectus arcuatum is an anterior chest wall deformity that requires transverse wedge sternotomy. Determining and delivering the correct cutting angle are crucial for successful correction. This report describes the early clinical experience with a novel cutting template technology able to deliver the optimal cutting angle. Description: From patients’ computed tomographic scans, the optimal cutting angle is obtained using computer-aided design. A template comprising slots tilted at the right cutting angle and a safety block to avoid damaging the posterior periosteum is printed through additive manufacturing. Evaluation: The template allows surgeons to perform a precise wedge sternotomy, safely sparing the posterior periosteum in all patients, without complications. Postoperative chest roentgenograms and clinical photographs demonstrate optimal sternal realignment and cosmetic outcome. In this report, the mean operative time was 110 minutes. All patients were successfully discharged, with a mean length of stay of 4 days. Conclusions: Transverse wedge sternotomy aided by a computer-aided design–devised cutting template may reduce the technical challenge of this procedure, thereby increasing its safety and reducing operative times and hospital stay. Further research on long-term patient outcomes is necessary.
Abstract: Low-cost RGB-D cameras are increasingly being used in several research fields, including human–machine interaction, safety, robotics, biomedical engineering and even reverse engineering applications. Among the plethora of commercial devices, the Intel RealSense cameras have proven to be among the most suitable devices, providing a good compromise between cost, ease of use, compactness and precision. Released on the market in January 2018, the new Intel model RealSense D415 has a wide acquisition range (i.e., ~160–10,000 mm) and a narrow field of view to capture objects in rapid motion. Given the unexplored potential of this new device, especially when used as a 3D scanner, the present work aims to characterize and to provide metrological considerations for the RealSense D415. In particular, tests are carried out to assess the device performance in the near range (i.e., 100–1000 mm). Characterization is performed by integrating the guidelines of the existing standard (i.e., the German VDI/VDE 2634 Part 2) with a number of literature-based strategies. Performance analysis is finally compared against the latest close-range sensors, thus providing a useful guidance for researchers and practitioners aiming to use RGB-D cameras in reverse engineering applications.
Keywords: Active stereo | Depth camera | Device characterization | Performance comparison | RealSense D415 | Reverse engineering | VDI/VDE standard
Abstract: Pectus Arcuatum, a rare congenital chest wall deformity, is characterized by the protrusion and early ossification of sternal angle thus configuring as a mixed form of excavatum and carinatum features. Surgical correction of pectus arcuatum always includes one or more horizontal sternal osteotomies, consisting in performing a V-shaped horizontal cutting of the sternum (resection prism) by means of an oscillating power saw. The angle between the saw and the sternal body in the V-shaped cut is determined according to the peculiarity of the specific sternal arch. The choice of the right angle, decided by the surgeon on the basis of her/his experience, is crucial for a successful intervention. The availability of a patient-specific surgical guide conveying the correct cutting angles can considerably improve the chances of success and, at the same time, reduce the intervention time. The present paper aims to propose a new CAD-based approach to design and produce custom-made surgical guides, manufactured by using additive manufacturing techniques, to assist the sternal osteotomy. Starting from CT images, the procedure allows to determine correct resection prism and to shape the surgical guide accordingly taking into account additive manufacturing capabilities. Virtually tested against three case studies the procedure demonstrated its effectiveness.
Keywords: Biomedical devices | CAD | Design for additive manufacturing | Medical imaging
Abstract: Te design of bone scafolds for tissue regeneration is a topic of great interest, which involves diferent issues related to geometry of architectures, mechanical behavior, and biological requirements, whose optimal combination determines the success of an implant. Additive manufacturing (AM) has widened the capability to produce structures with complex geometries, which should potentially satisfy the diferent requirements. These architectures can be obtained by means of refned methods and have to be assessed in terms of geometrical and mechanical properties. In this paper a triply periodic minimal surface (TPMS), the Schwarz's Primitive surface (P-surface), has been considered as scafold unit cell and conveniently parameterized in order to investigate the efect of modulation of analytical parameters on the P-cell geometry and on its properties. Several are the cell properties, which can afect the scafold performance. Due to the important biofunctional role that the surface curvature plays in mechanisms of cellular proliferation and diferentiation, in this paper, in addition to properties considering the cell geometry in its whole (such as volume fraction or pore size), new properties were proposed. Tese properties involve, particularly, the evaluation of local geometrical-diferential properties of the P-surface. Te results of this P-cell comprehensive characterization are very useful for the design of customized bone scafolds able to satisfy both biological and mechanical requirements. A numerical structural evaluation, by means of fnite element method (FEM), was performed in order to assess the stifness of solid P-cells as a function of the changes of the analytical parameters of outer surface and the thickness of cell. Finally, the relationship between stifness and porosity has been analyzed, given the relevance that this property has for bone scafolds design.
Abstract: 3D models of submerged structures and underwater archaeological finds are widely used in various and different applications, such as monitoring, analysis, dissemination, and inspection. Underwater environments are characterised by poor visibility conditions and the presence of marine flora and fauna. Consequently, the adoption of passive optical techniques for the 3D reconstruction of underwater scenarios is a highly challenging task. This article presents a performance analysis conducted on a multi-view technique that is commonly used in air in order to highlight its limits in the underwater environment and then provide guidelines for the accurate modelling of a submerged site in poor visibility conditions. A performance analysis has been performed by comparing different image enhancement algorithms, and the results have been adopted to reconstruct an area of 40 m2 at a depth of about 5 m at the underwater archaeological site of Baiae (Italy).
Keywords: 3D reconstruction | Image enhancement | Underwater Cultural Heritage | Underwater imaging
Abstract: Reverse Engineering (RE) may help tolerance inspection during production by digitalization of analyzed components and their comparison with design requirements. RE techniques are already applied for geometrical and tolerance shape control. Plastic injection molding is one of the fields where it may be applied, in particular for die set-up of multi-cavities, since no severe accuracy is required for the acquisition system. In this field, RE techniques integrated with Computer-Aided tools for tolerancing and inspection may contribute to the so-called “Smart Manufacturing”. Their integration with PLM and suppliers' incoming components may set the information necessary to evaluate each component and die. Intensive application of shape digitalization has to front several issues: accuracy of data acquisition hardware and software; automation of experimental and post-processing steps; update of industrial protocol and workers knowledge among others. Concerning post-processing automation, many advantages arise from computer vision, considering that it is based on the same concepts developed in a RE post-processing (detection, segmentation and classification). Recently, deep learning has been applied to classify point clouds, considering object and/or feature recognition. This can be made in two ways: with a 3D voxel grid, increasing regularity, before feeding data to a deep net architecture; or acting directly on point cloud. Literature data demonstrate high accuracy according to net training quality. In this paper, a preliminary study about CNN for 3D points segmentation is provided. Their characteristics have been compared to an automatic approach that has been already implemented by the authors in the past. VoxNet and PointNet architectures have been compared according to the specific task of feature recognition for tolerance inspection and some investigations on test cases are discussed to understand their performance.
Abstract: In sheet metal forming, springback represents a major drawback increasing die set-up problems, especially for ultra-high strength steels. Finite Element Analysis is a well-established method to simulate the process during design, and multicriteria optimizations, for example, via surrogate models, are investigated in order to develop integrated design. Since to take into account also springback compensation die design may involve a large number of geometric variables, this paper presents a robust design formulation, based on the adoption of the shape function optimization, to describe springback in terms of weights directly associated to global shape variations of the die shape. Doing so, multicriteria optimization, which involves also die compensation, can be set up in a more intuitive approach, as requested in the preliminary steps of die design. After the introduction of the industrial problem, the mathematical formulation of the shape function optimization is presented together with its novel extension to Robust Design, which is based on the Dual Response Surface. Through a test case derived from the head part of a B-pillar, stamped from a Dual Phase sheet 1.5 mm thick, this novel extension investigates the effect of 6% variation from nominal values of initial yield stress and thickness. Results demonstrate the feasibility of the procedure, underlying that an optimal compensation may not be optimal in terms of process robustness.
Abstract: Interventions of ancient bronze statues restoration may last long periods, involving several activities from material and structural analysis to set-up of museum exhibitions, passing through reconstruction of fragments. In this paper, we describe procedures and methods used for evaluation of the current posture of “Principe Ellenistico”. In fact, the statue seems to present some inaccuracies, in the fragments assembly, made during the last restoration activity (one of this effect is clearly observed in the spear inclination). The final aims are: (1) evaluation of differences among the postures before and after the last restoration; (2) recognition of the original fragments embedded in a previous restoration; and (3) the study of a possible better positioning of them. Methods applied are related to feature recognition on acquired point clouds, image analysis through control points and algorithms to find centerline of the elements that could need to be repositioned. In the final part, a concept design for a new inner-support is presented, giving the possibility to avoid assembly inaccuracies. Future developments are presented as the prospect of additive manufacturing the support, firstly with a FDM prototype and then through SLM or similar technologies.
Abstract: The research reported in this paper applies an explicit non-linear FEA solver to simulate the interaction between a clamp and a hyper-elastic material that aims to mimic the biological tissue of the colon. More in detail, the paper provides new results as a continuation of a previous works aimed at the evaluation of this solver to manage contact and dynamic loading on complex, multiple shapes. Results concern with the evaluation of the contact force during clamping, thus to the assessment of the force-feedback. The analysis is carried out on two geometries, using the hyper-elastic Mooney-Rivlin model for the mechanical behavior of the soft tissues. A pressure is applied on the colon to simulate the surgical clamp, which goes progressively in contact with tissue surface. To assess FEA criticality, and, then, its feasibility, the stress-strain and the contact force are analysed according to geometrical model and thickness variation, leaving the pressure constant. Doing so, their effect on the force-feedback can be foreseen, understanding their role on the accuracy of the final result.
Abstract: Although the CAD parameters allow to update easily the geometrical model, the numerical models updating into Finite Elements (FE) software with different mesh result to be often heavy, due to the necessity both to create new mesh and to make usually time consuming and complex CAE calculations for updating the loading conditions. The aim of the present research is to devise a reliable methodology and at the same time to reduce computational burden in the shape optimization studies of mechanical components. In particular, an integrated Multibody (MB) and Mesh-Morphing (MM) approach was developed to perform shape optimization, in order to reduce maximum tensions. Using the RBF Morph ACT Extension plugin implemented in the commercial solver FEM ANSYS® Mechanical vers. 18.2 along with the commercial MB software MSC ADAMS® vers. 2017, shape optimizations can be obtained in a very short time, by acting directly at the mesh so updating node positions and mesh elements geometry without bringing different geometrical models of the component into the FE environment. To validate the methodology, a crankshaft for a high performance Internal Combustion Engine (I.C.E.) was chosen, as case study, to optimize the fillet zones between web and pin.
Abstract: To date, standard methods for assessing the severity of chest wall deformities are mostly linked to X-ray and CT scans. However, the use of radiations limits their use when there is a need to monitor the development of the pathology over time. This is particularly important when dealing with patients suffering from Pectus Carinatum, whose treatment mainly requires the use of corrective braces and a systematic supervision. In recent years, the assessment of severity of chest deformities by means of radiation-free devices became increasingly popular but not yet adopted as standard clinical practice. The present study aims to define an objective measure by defining a severity index (named External Pectus Carinatum Index) used to monitor the course of the disease during treatment. Computed on the optical acquisition of the patients’ chest by means of an appositely devised, fast and easy-to-use, body scanner, the proposed index has been validated on a sample composed of a control group and a group of Pectus Carinatum patients. The index proved to be reliable and accurate in the characterization of the pathology, enabling the definition of a threshold that allows to distinguish the cases of patients with PC from those of healthy subjects. [Figure not available: see fulltext.]
Abstract: The present paper proposes a methodology to design and manufacture optimized turbomachinery components by leveraging the potential of Topology Optimization (TO) and Additive Manufacturing (AM). The method envisages the use of TO to define the best configuration of the rotoric components in terms of both static and dynamic behavior with a resultant reduction of overall weight. Eventually, the topology-optimized component is manufactured by using appropriate materials that can guarantee valid mechanical performances. The proposed strategy has been applied to a 2D impeller used for centrifugal compressors to prove the effectiveness of a TO+AM-based approach. Although this approach has never been extensively used before to centrifugal compressors and expanders, its application on rotor and stator components might unlock several benefits: Tuning the natural frequencies, a reduction in the stress level, and a lighter weight of the rotating part. These objectives can be reached alone or in combination, performing a single analysis or a multiple analyses optimization. Finally, the introduction of AM technologies as standard manufacturing resources could bring sensible benefits with respect to the time to production and availability of components. Such aspects are essential in the Oil and Gas context, when dealing with new projects but also for service operations.
Abstract: Background: The integration of computer-aided design/computer-aided manufacturing (CAD/CAM) tools and medicine is rapidly developing for designing medical devices. A novel design for a 3D-printed patient-specific surgical template for thoracic pedicle screw insertion, using a procedure based on reverse engineering, is presented. Methods: The surgeon chooses the entry point on the vertebra. The optimal insertion direction and the size of the screws are defined via an algorithm on the basis of a patient-specific vertebra CAD model. The template features an innovative shape for a comfortable and univocal placement and a novel disengaging device. Results: Three spinal fusions were performed to test the template. Excellent results were achieved in terms of the accuracy of the screw positioning, reduction in surgery duration, and number of X-rays. Conclusions: A novel design for a customized, 3D-printed surgical template for thoracic spinal arthrodesis was presented, and improvements in terms of precision, duration, and safety were achieved without changing the standard procedure.
Keywords: 3D imaging | additive manufacturing | bone | computer-assisted surgery | imaged guided surgery | in vivo | modelling | pedicle screw fixation | screw direction optimization | spine | surgical template | thoracic | thoracic spinal arthrodesis | X-ray minimization
Abstract: Aim of this paper is to present a methodology useful to optimize the geometry of the blades of a small-size wind turbine which are obtained from a circular pipe: an optimal chord distribution and airfoil sweep can be obtained with a proper cutting path. A strong reduction in manufacturing costs and time can be achieved for blades which are a critical element in wind turbine systems, especially in case of renewable plants in developing countries. An algorithm has been developed to obtain the shape of the blades and wind turbine performances are computed by the Blade-Element Method, due to its low computational simplicity; the XFoil tool has been used to compute the aerodynamic of the blades. Heuristic algorithms have been applied to obtain a feasible design solution assuring the best efficiency of the wind turbine. Also structural considerations are kept into account to provide a feasible configuration able to withstand the forces acting on the rotating blades. Results obtained suggest that an optimal design of such a kind of blades can be obtained thanks to this methodology. The mathematical framework developed for the optimization is efficient and the heuristics algorithms allow the convergence to feasible configurations. The computing time is compatible with a practical application of the method also in industries.
Abstract: Nowadays, Building Information Modeling (BIM) is a common design approach to support the life cycle of projects in the field of Architecture Engineering Construction (AEC). New constructions’ projects require a BIM modeling to provide digital information within a 3D digital mockup. The main target is to reduce time and cost related to the elaboration of additional and not integrated documentation. This issue is also common in projects focused on the renovations of existing buildings. In fact, the BIM approach provides tools to improve interoperability between different software to integrate analysis and simulations within the architectural representation. The renovation projects require reverse engineering tools and methods for the 3D modeling of existing structures. One of the issues concerns the digital photogrammetric survey of glass surfaces. This paper proposes a design approach to support BIM phases for already existing structures with a test case focused on a hallway with a continuous glass wall.
Abstract: Anisotropic dimensional change on sintering may strongly affect the precision of parts produced by press and sinter. In previous work a design procedure accounting for anisotropic dimensional change of axi-symmetric parts (disks and rings) has been developed on the basis of experimental data. In this work the procedure has been applied to predict the anisotropic dimensional change of real parts produced in industrial conditions, providing that coaxial rings were identified in the geometry of the actual parts. Parts were highly different for material, complexity of geometry, green density and process conditions. Parts were measured in the green and sintered state and the measured dimensional changes were compared to the predicted ones, finding a good agreement. The procedure was also adapted to predict dimensional change of an oval feature, and highly satisfactory results were obtained.
Keywords: Anisotropy | Dimensional change | Powder metallurgy | Precision of PM parts
Abstract: Background: Autotransplantation of cryopreserved ovarian tissue is currently the main option to preserve fertility for cancer patients. To avoid cancer cell reintroduction at transplantation, amulti-step culture systemhas been proposed to obtain fully competent oocytes for in vitro fertilization. Current in vitro systems are limited by the low number and health of secondary follicles produced during the first step culture of ovarian tissue fragments. To overcome such limitations, bioreactor designs have been proposed to enhance oxygen supply to the tissue, with inconsistent results. This retrospective study investigates, on theoretical grounds, whether the lack of a rational design of the proposed bioreactors prevented the full exploitation of follicle growth potential. Methods: Models describing oxygen transport in bioreactors and tissue were developed and used to predict oxygen availability inside ovarian tissue in the pertinent literature. Results: The proposed theoretical analysis suggests that a successful outcome is associated with enhanced oxygen availability in the cultured tissue in the considered bioreactor designs. This suggests that a rational approach to bioreactor design for ovarian tissue culture in vitro may help exploit tissue potential to support follicle growth.
Keywords: Design | In vitro culture | Ioreactor | Ovarian tissue | Oxygen | Transport
Abstract: In an increasingly competitive business world, the “time to market” of products has become a key factor for business success. There are different techniques that anticipate design mistakes and launch products on the market in less time. Among the most used methodologies in the design and definition of the requirements, quality function deployment (QFD) and design for Six Sigma (DFSS) can be used. In the prototyping phase, it is possible to address the emerging technology of additive manufacturing. Today, three-dimensional printing is already used as a rapid prototyping technique. However, the real challenge that industry is facing is the use of these machineries for large-scale production of parts, now possible with new HP multi-fusion. The aim of this article is to study the entire product development process taking advantage of the most modern models and technologies for the final realization of a case study that involves the design and prototyping of an innovative multifunctional fan (lamp, aroma diffuser and fan) through the Multi Jet Fusion of HP. To begin with, issues related to the DFSS, the QFD and their application to identify the fan requirements are explored. Once the requirements have been defined, the modern CAD design systems and the CAE systems for the validation of the case study will be analyzed and applied. Finally, HP’s Multi Jet Fusion methodology and design rules for additive manufacturing will be analyzed in detail, trying to exploit all the positive aspects it offers.
Keywords: CAD | CAE | Design for additive manufacturing | Design for six sigma | FEA | Multi jet fusion | Product development | QFD | Rapid prototyping
Abstract: In an increasing number of aggressive enterprise world, “time to market” concerning products has come to be a solution element because of enterprise success. There are exceptional techniques so expect layout mistakes or open products concerning the need between much less time. Among the most used methodologies in the design and setting about stability the requirements, Quality Function Deployment (QFD) and Design for Six Sigma (DFSS) execute remain used. In the prototyping phase, such is feasible in imitation of tackle the rising science regarding additive manufacturing. Today, three-dimensional stamping is in the meanwhile used as a rapid prototyping technique. However, the actual challenge that enterprise is going through is the use of these machineries for large-scale production about parts, at last viable along current HP Multi fusion. The aim of this article is to study the interactive design and engineering applied to the entire product development process taking advantage of the most modern models and technologies for the final realization of a case study that involves the design and prototyping of an innovative multifunctional fan (Lamp, Aroma Diffuser and fan) through the Multi Jet Fusion of HP. To begin with, issues related to the DFSS, the QFD and their application to identify the fan requirements are explored. Once the requirements have been defined, the modern CAD design systems and the CAE systems for the validation of the case study will be analyzed and applied. Finally, HP’s Multi Jet Fusion methodology and design rules for additive manufacturing will be analyzed in detail, trying to exploit all the positive aspects it offers.
Keywords: CAD | CAE | Design for additive manufacturing | Design for Six Sigma | FEA | Multi jet fusion | Product development | QFD | Rapid prototyping
Abstract: This paper defines a systematic workflow for production cost estimation of sheet metal stamped components. The approach represents a solution toward the adoption of Design to Cost methods during early product design. It consists in a sequence of steps that, starting from a 3D CAD model with annotations (material, roughness and tolerances) and production information (batch and production volume) leads to the manufacturing cost through an analytic cost breakdown (raw material, stamping and accessory processes, setup and tooling). The calculation process mainly consists in a first step where geometric algorithms calculate the sheet metal blank (dimensions, shape, thickness) and specific product features (e.g. flanges, louvers, embossing, etc.). The following steps allow to calculate the raw material, the stamping process and the process-related parameters, which are the manufacturing cost drivers (e.g. press, stamping rate/sequence/force and die dimensions/weight). The manufacturing cost is the sum of the previous calculated items. Testing the approach for three different components, the average absolute deviation measured between the estimated and actual cost was less than 10% and such a result looks promising for adopting this method for evaluating alternative design solutions.
Keywords: Cost estimation | Design to cost | Feature recognition | Sheet metal stamping
Abstract: Recently, the approach that defines the total life cycle assessment (LCA) and the end of life (EoL) in the early design phases is becoming even more promising. Literature evidences many advantages in terms of the saving of costs and time and in the fluent organization of the whole design process. Design for disassembly (DfD) offers the possibility of reducing the time and cost of disassembling a product and accounts for the reusing of parts and of the dismantling of parts, joints, and materials. The sequence of disassembly is the ordered way to extract parts from an assembly and is a focal item in DfD because it can deeply influence times and operations. In this paper, some disassembly sequences are evaluated, and among them, two methods for defining an optimal sequence are provided and tested on a case study of a mechanical assembly. A further sequence of disassembly is provided by the authors based on experience and personal knowledge. All three are analyzed by the disassembly order graph (DOG) approach and compared. The operations evaluated have been converted in time using time measurement units (TMUs). As result, the best sequence has been highlighted in order to define a structured and efficient disassembly.
Abstract: Used in several industrial fields to create innovative designs, topology optimization is a method to design a structure characterized by maximum stiffness properties and reduced weights. By integrating topology optimization with additive layer manufacturing and, at the same time, by using innovative materials such as lattice structures, it is possible to realize complex three-dimensional geometries unthinkable using traditional subtractive techniques. Surprisingly, the extraordinary potential of topology optimization method (especially when coupled with additive manufacturing and lattice structures) has not yet been extensively developed to study rotating machines. Based on the above considerations, the applicability of topology optimization, additive manufacturing, and lattice structures to the fields of turbomachinery and rotordynamics is here explored. Such techniques are applied to a turbine disk to optimize its performance in terms of resonance and mass reduction. The obtained results are quite encouraging since this approach allows improving existing turbomachinery components’ performance when compared with traditional one.
Abstract: In the fashion field, the use of electroplated small metal parts such as studs, clips and buckles is widespread. The plate is often made of precious metal, such as gold or platinum. Due to the high cost of these materials, it is strategically relevant and of primary importance for manufacturers to avoid any waste by depositing only the strictly necessary amount of material. To this aim, companies need to be aware of the overall number of items to be electroplated so that it is possible to properly set the parameters driving the galvanic process. Accordingly, the present paper describes a simple, yet effective machine vision-based method able to automatically count small metal parts arranged on a galvanic frame. The devised method, which relies on the definition of a rear projection-based acquisition system and on the development of image processing-based routines, is able to properly count the number of items on the galvanic frame. The system is implemented on a counting machine, which is meant to be adopted in the galvanic industrial practice to properly define a suitable set or working parameters (such as the current, voltage, and deposition time) for the electroplating machine and, thereby, assure the desired plate thickness from one side and avoid material waste on the other.
Abstract: This paper presents a software based on an innovative Convolutional Neural Network model to recognize the six Ekman's universal emotions from the photos of human faces captured in the wild. The CNN was trained using three different datasets already labeled and merged after making them homogeneous. A comparison among different types of CNN architectures using the Keras framework for Python language is proposed and the evaluation results are presented.
Keywords: convolutional neural network | deep learning | emotion recognition
Abstract: In the era of the fourth industrial revolution the efficient sharing and exploitation of information are key success factors for companies. In order to maintain competitiveness and to answer to the requests for highly customized products, shoe last producers need to innovate their processes, by adopting digital technologies. The present paper proposes an innovative integrated approach for shoe last design and manufacturing. The process is enabled by CAD/CAM technologies, which allow to integrate the design and manufacturing phases, and by haptic technologies, which allow to interact with the virtual models to simplify the successive planning and manufacturing operations. The final aim is to support traditional companies in the implementation of the Industry 4.0 paradigm. The test case about marking operation confirms that the adoption of the proposed approach leads to a sensible improvement in the company operational efficiency, thanks to the reduction in the number of repetitive tasks.
Keywords: CAD/CAM technologies | Haptic interface | Industry 4.0 | Shoe last design
Abstract: Recently, robotics has increasingly become a companion for the human being and assisting physically impaired people with robotic devices is showing encouraging signs regarding the application of this largely investigated technology to the clinical field. As of today, however, exoskeleton design can still be considered a hurdle task and, even in modern robotics, aiding those patients who have lost or injured their limbs is surely one of the most challenging goal. In this framework, the research activity carried out by the Department of Industrial Engineering of the University of Florence concentrated on the development of portable, wearable and highly customizable hand exoskeletons to aid patients suffering from hand disabilities, and on the definition of patient-centered design strategies to tailor-made devices specifically developed on the different users' needs. Three hand exoskeletons versions will be presented in this paper proving the major taken steps in mechanical designing and controlling a compact and lightweight solution. The performance of the resulting systems has been tested in a real-use scenario. The obtained results have been satisfying, indicating that the derived solutions may constitute a valid alternative to existing hand exoskeletons so far studied in the rehabilitation and assistance fields.
Keywords: Biomechanical engineering | Hand exoskeleton | Kinematic analysis | Mechanism design and optimization | Mechatronics | Wearable robotics
Abstract: Purpose: The purpose of this paper is to describe an innovative Parametric and Adaptive Slicing (PAS) technique to be used for generating material addition paths along three-dimensional surfaces. Design/methodology/approach: The method is grounded on the possibility to generate layers starting from multiple reference surfaces (already available in the model or created on purpose). These are used for mathematically deriving a family of parametric surfaces whose shape and spacing (the layer thickness) can be tuned to get the desired aesthetic, technical and functional characteristics. The adhesion among layers is obtained guaranteeing a smooth transition among these surfaces. Findings: The examples described in the paper demonstrate that the PAS technique enables the addition of the material along non-planar paths and, hence, the elimination of the staircase effect. In addition, objects printed using this technique show improved mechanical properties with respect to those printed using standard planar layers. Research limitations/implications: As the method allows a local control of the material addition/deposition, it can be used to design the mechanical behavior of the objects to be printed. Originality/value: The technique proposed in this paper overcomes the limitations of currently available adaptive and curved layer slicing strategies, by introducing the possibility to generate layers with a non-constant thickness whose shape morphs smoothly from one layer to another.
Abstract: This study proposes a novel occlusions detection and restoration strategy. The aim is to success with 3D face recognition even when faces are partially occluded by external objects. The method, which relies on geometrical facial properties, is designed for managing two types of facial occlusions (eye and mouth occlusions due to hands). First occlusions are detected and (if present) classified, by considering their effects on the 3D points cloud. Then, the occluded regions are progressively removed, and finally, the non-occluded symmetrical regions are used to restore the missing information. After the restoration process, face recognition is performed relying on the restored facial information and on the localized landmarks. The landmarking methodology relies on derivatives and on 12 differential geometry descriptors. The discriminating features adopted for facial comparison include shape index histograms, Euclidean and geodetical distances between landmarks, facial curves, and nose volume. Obtained recognition rates, evaluated on the whole Bosphorus database and on our private dataset, ranging from 92.55 to 97.20% depending on the completeness of data.
Keywords: 3D face | Differential geometry | Face analysis | Face recognition | Feature extraction
Abstract: Surgical interventions for jaw reconstruction require the design and the production of surgical guides that allow the surgeon to operate quickly and accurately. In some cases, the reconstruction is performed by inserting a prothesis, thus operating exclusively on the jaw, while in other cases the reconstruction is performed by withdrawing and inserting part of the fibula in place of the original jaw bone. This project aims to develop a procedure that allows 3D modeling of the surgical guides necessary for surgical intervention. The idea is to find a surgical guide archetype, a starting shape for the surgeon so that the cutting planes can be oriented without the surgical guide having to be redesigned from scratch for every single patient. The first step of the procedure is the segmentation, performed applying the thresholding operation on the images provided by magnetic resonance MR in order to identify the region of interest (ROI). The second step is the reconstruction of the 3D model, so that a mesh is obtained from 2D images. Subsequently the mesh is post-processed and the cutting plans along which the surgeon will intervene are defined.
Keywords: 3D modeling | 3D reconstruction | Maxillofacial surgery | Surgical guides
Abstract: The optimization of the aeronautical structures manufacturing is one of the most challenging tasks in development of a new aircraft. Nowadays, aeronautical industries are supporting researches deal with the development of new assembly approaches which aim at increasing efficiency and reducing cost of the processes. The work here presented focused on definition of a Jig-less assembly procedure of the 'Integrated Main Landing Gearbox' (ITEM B). The project aims to develop a new generation of Lower Center Fuselage with an innovative landing system integrated in the fuselage itself. The ambition of ITEMB is the creation of a single integrated structure in composite material of the gear bay that reduces assembly costs, optimizing and integrating the entire design, construction and maintenance of the aircraft. The approach here described is based on the integration of different engineering disciplines, as such as the tolerance statistical prediction, the ergonomics, digital human modeling, manufacturing and measurement technologies. In particular, through an appropriate ergonomic analysis, an innovative assembly process of the gear bay was developed and optimized in a virtual environment pointing out the advantages and disadvantages with respect to a traditional assembly cycle. The assembly process is based also on the implementation of the assembly tolerance prediction.
Abstract: Aboveground biomass (AGB) is a parameter commonly used for assessing and monitoring primary productivity of grassland communities. Destructive AGB measurements, although accurate, are time-consuming and do not allow for repeated measurements as required by monitoring protocols. Structure-from-motion (SfM) photogrammetry has been proved to be a reliable tool for rapid and not destructive AGB estimations in grass systems. Three-dimensional (3D) models of fourteen 1 × 1 m2 pasture plots were reconstructed and AGB volume measured under several measurement settings. Volume-based AGB measures were regressed to AGB values resulting from destructive methods to identify the measurement settings that show the best fit. Furthermore, 3D models of four mountain pasture plots were reconstructed in May, July, and August. Models relative to the same plot were aligned and their relative difference measured to produce a diachronic canopy variation model (DCVM). On the measured volume (Vd), the coefficient of density (cρ) was applied to adjust the volume values (Vadj) in relation to variation due to different DCVM point densities. The measurement setting for AGB volume estimations strongly influenced their correlation with traditional AGB scores. The best fit was obtained selecting 1 mm grid cell size and minimum point height distance. Such options were then selected to measure the DCVM. Adjusted volumes were fully correlated with the average point distance. Three plots revealed higher rates of AGB in the spring compared to summer season, as justified by the summer aridity constraints affecting vegetation productivity in Mediterranean areas. In one plot, we found an anomalous seasonal pattern, showing an AGB reduction in spring, which can be correlated with grazing, that promoted a subsequent increment in summer. Our study indicates that image-based photogrammetric techniques allow for reliable non-destructive measurements of surface biomass in diachronic analyses, offering a valuable tool for evaluating occurrence, magnitude, and spatial patterns of variations of community primary productivity over time. Diachronic canopy variation model produced congruent patterns of inter-seasonal canopy variations proving to be a useful tool for analyzing local disturbance to vegetation canopy caused by grazing.
Keywords: biomass | coefficient of density | diachronic variation | local disturbance | non-destructive measurements | pasture community | photogrammetry | structure-from-motion
Abstract: The aim of the present work is disclosing a model suitable to provide a new tool for the synthesis of mechanisms and structures. Firstly, a framework will be introduced for the representation of a particular class of mechanisms: compliant mechanisms. For this purpose, the constitutive elements and the relations between the elements are organized in a taxonomy, similar to the ones used for the definition of ontologies. Ontologies have been taken as inspiration for the construction of the general schema for two main reasons: the first one is the need of consistency in the physical models, in order to obtain reliable results. The second reason is that one of the main features of ontologies is modularity, which means that they may be reused, and implemented for the creation of widest classifications. In the proposed framework, mechanisms result from the combination of the constitutive elements, according to a certain topology. The topologies are generated taking in account the defined feasible relations between elements. Once the mechanisms are defined, their behavior, in terms of mechanical response, is calculated and implemented in the schema as well. Finally, a classification of the evaluated mechanisms is provided, correlating the mechanical behavior of the mechanisms to the topological arrangement of their elements, or, in other words, their geometry. This classification may be synthetized in a table which may be query setting the mechanical response (set of deformation allowed or denied as response of a set of generalized forces). The result of the query is the indication of the topology of the mechanism that fits the mechanical response best. The proposed table is a design tool actually, suggesting the constructive form to the designer starting from a functional requirement. Moreover, considering the table of topologies and the physical model with which it was generated, they constitute a synthesis tool for that class of mechanisms, and, ultimately, a topology, and size optimization tool.
Keywords: Control | Modeling | Modeling and simulation | Optimization | Robotics
Abstract: Anterior cruciate ligament (ACL) deficiency can result in serious degenerative stifle injuries. Although tibial plateau leveling osteotomy (TPLO) is a common method for the surgical treatment of ACL deficiency, alternative osteotomies, such as a leveling osteotomy based on the center of rotation of angulation (CBLO) are described in the literature. However, whether a CBLO could represent a viable alternative to a TPLO remains to be established. The aim of this study is to compare TPLO and CBLO effectiveness in treating ACL rupture. First, a computational multibody model of a physiological stifle was created using three-dimensional surfaces of a medium-sized canine femur, tibia, fibula and patella. Articular contacts were modeled by means of a formulation describing the contact force as function of the interpenetration between surfaces. Moreover, ligaments were represented by vector forces connecting origin and insertion points. The lengths of the ligaments at rest were optimized simulating the drawer test. The ACL-deficient model was obtained by deactivating the ACL related forces in the optimized physiological one. Then, TPLO and CBLO treatments were virtually performed on the pathological stifle. Finally, the drawer test and a weight-bearing squat movement were performed to compare the treatments effectiveness in terms of tibial anteroposterior translation, patellar ligament force, intra-articular compressive force and quadriceps force. Results from drawer test simulations showed that ACL-deficiency causes an increase of the anterior tibial translation by up to 5.2 mm, while no remarkable differences between CBLO and TPLO were recorded. Overall, squat simulations have demonstrated that both treatments lead to an increase of all considered forces compared to the physiological model. Specifically, CBLO and TPLO produce an increase in compressive forces of 54% and 37%, respectively, at 90◦ flexion. However, TPLO produces higher compressive forces (up to 16%) with respect to CBLO for wider flexion angles ranging from 135◦ to 117◦ . Conversely, TPLO generates lower forces in patellar ligament and quadriceps muscle, compared to CBLO. In light of the higher intra-articular compressive force over the physiological walking range of flexion, which was observed to result from TPLO in the current study, the use of this technique should be carefully considered.
Abstract: The preservation status of an underwater cultural site can be determined as the combination of two primary factors, namely the site physical integrity, which results from the past and present interaction of the site itself with the biological/chemical agents located in the surrounding environment, and the exposure of the site to human-related threats. Methods to survey underwater archaeological sites have evolved considerably in the last years in order to face the challenges and problems in archaeological prospection, documentation, monitoring, and data collection.This paper presents a case-study of an archaeological documentation campaign addressed to study and monitor the preservation status of an underwater archaeological site by combining the quantitative measurements coming from optical and acoustic surveys with the study of biological colonization and bioerosion phenomena affecting ancient artefacts. In particular, we present the first results obtained in the survey and documentation campaign carried out during the spring - summer 2018 in the "Nymphaeum of Punta Epitaffio" located in the Marine Protected Area - Underwater Park of Baiae (Naples).
Keywords: 3D Imaging | 3D Mapping | Baiae Archaeological Park | Photogrammetry | Underwater Archaeology
Abstract: Objective: To investigate the influence of implant design on the change in the natural frequency of bone-implant system during osseointegration by means of a modal 3D finite element analysis. Methods: Six implants were considered. Solid models were obtained by means of reverse engineering techniques. The mandibular bone geometry was built-up from a CT scan dataset through image segmentation. Each implant was virtually implanted in the mandibular bone. Two different models have been considered, differing in the free length of the mandibular branch (‘long branch’ and ‘short branch’) in order to simulate the variability of boundary conditions when performing vibrometric analyses. Modal analyses were carried out for each model, and the first three resonance frequencies were assessed with the respective vibration modes. Results: With reference to the ‘long branch’ model, the first three modes of vibration are whole bone vibration with minimum displacement of the implant relative to bone, with the exception of the initial condition (1% bone maturation) where the implant is not osseointegrated. By contrast, implant displacements become relevant in the ‘short branch’ model, unless osseointegration level is beyond 20%. The difference between resonance frequency at whole bone maturation and resonance frequency at 1% bone maturation remained lower than 6.5% for all modes, with the exception of the third mode of vibration in the ‘D’ implant where this difference reached 9.7%. With reference to the ‘short branch’ considering the first mode of vibration, 61–68% of the frequency increase was achieved at 10% osseointegration; 72–79% was achieved at 20%; 89–93% was achieved at 50% osseointegration. The pattern of the natural frequency versus the osseointegration level is similar among different modes of vibration. Significance: Resonance frequencies and their trends towards osseointegration level may differ between implant designs, and in different boundary conditions that are related to implant position inside the mandible; tapered implants are the most sensitive to bone maturation levels, small implants have very little sensitivity. Resonance frequencies are less sensitive to bone maturation level beyond 50%.
Keywords: Bone properties | CAD | Dental materials | Endosteal implants | Finite element analysis | Implant stability | Material properties | Osseointegration | Reverse engineering
Abstract: Objectives: To assess conceptual designs of dental posts consisting of polyetherimide (PEI) reinforced with carbon (C) and glass (G) glass fibers in endodontically treated anterior teeth. Methods: 3D tessellated CAD and geometric models of endodontically treated anterior teeth were generated from Micro-CT scan images. Model C-G/PEI composite posts with different Young's moduli were analyzed by Finite Element (FE) methods post A (57.7 GPa), post B (31.6 GPa), post C (from 57.7 to 9.0 GPa in the coronal–apical direction). A load of 50 N was applied at 45° to the longitudinal axis of the tooth, acting on the palatal surface of the crown. The maximum principal stress distribution was determined along the post and at the interface between the post and the surrounding structure. Results: Post C, with Young's modulus decreasing from 57.7 to 9.0 GPa in the coronal–apical direction, reduced the maximum principal stress distribution in the restored tooth. Post C gave reduced stress and the most uniform stress distribution with no stress concentration, compared to the other C-G/PEI composite posts. Significance: The FE analysis confirmed the ability of the functionally graded post to dissipate stress from the coronal to the apical end. Hence actual (physical) C-G/PEI posts could permit optimization of stress distributions in endodontically treated anterior teeth.
Abstract: Objective: To assess the influence of implant thread shape and inclination on the mechanical behaviour of bone-implant systems. The study assesses which factors influence the initial and full osseointegration stages. Methods: Point clouds of the original implant were created using a non-contact reverse engineering technique. A 3D tessellated surface was created using Geomagic Studio® software. From cross-section curves, generated by intersecting the tessellated model and cutting-planes, a 3D parametric CAD model was created using SolidWorks® 2017. By the permutation of three thread shapes (rectangular, 30° trapezoidal, 45° trapezoidal) and three thread inclinations (0°, 3° or 6°), nine geometric configurations were obtained. Two different osseointegration stages were analysed: the initial osseointegration and a full osseointegration. In total, 18 different FE models were analysed and two load conditions were applied to each model. The mechanical behaviour of the models was analysed by Finite Element (FE) Analysis using ANSYS® v. 17.0. Static linear analyses were also carried out. Results: ANOVA was used to assess the influence of each factor. Models with a rectangular thread and 6° inclination provided the best results and reduced displacement in the initial osseointegration stages up to 4.58%. This configuration also reduced equivalent VM stress peaks up to 54%. The same effect was confirmed for the full osseointegration stage, where 6° inclination reduced stress peaks by up to 62%. Significance: The FE analysis confirmed the beneficial effect of thread inclination, reducing the displacement in immediate post-operative conditions and equivalent VM stress peaks. Thread shape does not significantly influence the mechanical behaviour of bone-implant systems but contributes to reducing stress peaks in the trabecular bone in both the initial and full osseointegration stages.
Keywords: Bone properties | CAD | Dental materials | Endosteal implants | Finite element analysis | Material properties | Osseointegration | Plateau implants
Abstract: A new method for secondary features segmentation, performed on high-density tessellated geometric models, is proposed. Four types of secondary features are considered: fillets, rounds and grooves. Sharp edges are also recognised. The method is based on an algorithm that analyses the principal curvatures. The nodes, potentially attributable to a fillet of given geometry, are those with a certain value for the maximum principal curvature. Since the deterministic application of this simple working principle shows several problems, due to the uncertainties in the curvature estimation, a fuzzy approach is proposed. In order to segment the nodes of a tessellated model belonging to secondary features of a given radius, an appropriate set of membership functions is defined and evaluated based on some parameters, which affect the quality of the curvature estimation. A region-growing algorithm connects the nodes pertaining to a same secondary feature so that, for a given radius, one or more secondary features may be recognized. The method is applied and verified in some test cases.
Keywords: Computational geometry | Features extractions | Fuzzy logic | Mechanical engineering computing | Region growing algorithm
Abstract: In this paper, a new method for axis detection of discrete thin-walled axially symmetric surfaces is presented. This method is based on the property of thin-walled axially symmetric surfaces that the minimum path of a point on the external wall to the internal wall is on a straight line passing through the axis. This working principle, since it does not require the evaluation of differential geometrical properties, makes the method robust to noise. The proposed method has been applied in a very critical application area: axially symmetric archaeological pottery fragments, for which the evaluation of the axis is complex because of manufacturing error and of modification of the surface properties due to the action of time and weather. The trueness of the proposed method is compared with those of the five methods presented in the literature in the analysis of real sherds of various dimensions and conditions. The proposed method demonstrates greater robustness than these methods and is shown to be promising to improve the number of sherds that can be successfully analyzed.
Keywords: 3D archeology | Axis estimation | Computer | Geometric inspection | Methods in archaeology
Abstract: Despite the widespread use of reverse total shoulder arthroplasty, the fundamental effects of implant configuration on certain biomechanical outcomes have not been completely elucidated especially for the most innovative prostheses. Aim of this work is to investigate the behaviour of a new reverse shoulder prosthesis, characterized by a humeral tray with a variable offset, designed to increase the range of motion and to reduce the impingement. The purposes of this study were to evaluate the effect of reverse shoulder implant design parameters on the deltoid muscle forces, required to produce abduction, and on the shoulder range of motion, in order to provide a more systematic understanding of the fundamental effects of humeral component positioning on the implant performances. The study has been implemented using virtual prototypes of the shoulder-prosthesis assembly. The shape of the prosthesis has been digitally acquired via a 3D scanner and the CAD models of all the components have been created. Through CT images, 3-dimensional models of the shoulder bones have been reconstructed and assembled with the prosthesis components. Numerical FEM models have been set up in order to evaluate how the abduction force changes depending on the humeral tray offset. Using the virtual prototypes of the shoulder-prosthesis assembly, a range of motion analysis has been carried out by setting up a collision detection analysis in a 3D parametric modeling environment. Different humeral tray positions were investigated and four different motions of the arm were simulated. Obtained results have demonstrated that a suitable positioning of the humeral tray can offer significant biomechanical advantages in terms of range of motion and abduction force.
Abstract: In this paper we derive the analytic solutions for the statics of cantilever soft arm under external loading. The main motivation behind this work is the development of manageable and ready-to-use mathematical models of soft robotic arm for various purposes. We formulate the problem exploiting the Lie group structure of the arms' configuration space. This allows using the powerful mathematical tools from differential geometry. The model builds upon the theory of Cosserat rods: The mechanics-based perspective used to describe the kinematics and statics allows including into the model the large deformations due to axial, shear, torsion and bending effects. The position fields of the manipulators' shapes are analytically integrated and validated with respect to exact solutions and experiments.
Abstract: This paper presents a novel instant 3D whole body scanner for healthcare applications. It is based on photogrammetry, a digital technology which allows to reconstruct the surface of objects starting from multiple pictures. The motivation behind this work is the development of minimally invasive procedures for instant data acquisitions of anatomical structure. The scanner provides several features of interests in 3D body scanning technologies for the healthcare domains: (i) instant capture of human body models; (ii) magnitude of accuracy in the order of 1 mm; (iii) simplicity of use; (iv) possibility to scan using different settings; (v) possibility to reconstruct the texture. The system is built upon a modular and distributed architecture. In this paper we highlight its key concepts and the methodology which has led to the current product. We illustrate its potential through one of the most promising 3D scanning healthcare applications: the data acquisition and processing of human body models for the digital manufacturing process of prostheses and orthoses. We validate the overall system in terms of conformity with the the initial requirements.
Keywords: 3D reconstruction | Body scanning | Healthcare | Human body measurements | Human body visualization | Photogrammetry | Proshetics and orthotics
Abstract: Kinematic modeling of continuum robots is challenging due to the large deflections that these systems usually undergone. In this paper, we derive the kinematics of a continuum robot from the evolution of a three-dimensional curve in space. We obtain the spatial configuration of a continuum robot in terms of exponential coordinates based on Lie group theory. This kinematic framework turns out to handle robotic helical shapes, i.e. spatial configurations with constant curvature and torsion of the arm.
Abstract: Background and objective: The purpose of the present paper is to pave the road to the systematic optimization of complex craniofacial surgical intervention and to validate a design methodology for the virtual surgery and the fabrication of cranium vault custom plates. Recent advances in the field of medical imaging, image processing and additive manufacturing (AM) have led to new insights in several medical applications. The engineered combination of medical actions and 3D processing steps, foster the optimization of the intervention in terms of operative time and number of sessions needed. Complex craniofacial surgical intervention, such as for instance severe hypertelorism accompanied by skull holes, traditionally requires a first surgery to correctly “resize” the patient cranium and a second surgical session to implant a customized 3D printed prosthesis. Between the two surgical interventions, medical imaging needs to be carried out to aid the design the skull plate. Instead, this paper proposes a CAD/AM-based one-in-all design methodology allowing the surgeons to perform, in a single surgical intervention, both skull correction and implantation. Methods: A strategy envisaging a virtual/mock surgery on a CAD/AM model of the patient cranium so as to plan the surgery and to design the final shape of the cranium plaque is proposed. The procedure relies on patient imaging, 3D geometry reconstruction of the defective skull, virtual planning and mock surgery to determine the hypothetical anatomic 3D model and, finally, to skull plate design and 3D printing. Results: The methodology has been tested on a complex case study. Results demonstrate the feasibility of the proposed approach and a consistent reduction of time and overall cost of the surgery, not to mention the huge benefits on the patient that is subjected to a single surgical operation. Conclusions: Despite a number of AM-based methodologies have been proposed for designing cranial implants or to correct orbital hypertelorism, to the best of the authors’ knowledge, the present work is the first to simultaneously treat osteotomy and titanium cranium plaque.
Abstract: Background: Current approaches to quantifying the severity of pectus excavatum require internal measurements based on cross-sectional imaging. The aim of this study is to exploit a novel index evaluated on the external surface of the chest with a three-dimensional (3D) optical scanner. Methods: Fifty-one children (41 male, 10 female) between 2 and 17 years of age were evaluated with a 3D optical scanner. Pectus excavatum severity was calculated by using an ad hoc instant 3D scanner and defining an automatic procedure to generate an optical 3D correction index (CI3D). For the latter, an ideal threshold was derived from a statistical analysis, and five blind surveys were collected from pediatric specialists on chest wall deformities. The CI3D was then correlated with blind clinical assessments of PE severity. Results: The cutoff thresholds were determined to optimally discriminate between six degrees of severity of PE patients by a correlation analysis. The correlation coefficient obtained by matching the CI3D with the average subjective severity shows that the proposed method outperforms traditional approaches. Conclusions: The optical 3D index has a good match with the average subjective assessment in distinguishing patients with mild to severe PE. This innovative approach offers several advantages over existing indices, as it is repeatable and does not require cross-sectional imaging. The index might be particularly suitable for monitoring the efficacy of nonoperative treatment and, in the future, for designing an optimal personalized usage of therapeutic devices.
Abstract: Reverse Engineering (RE) is a long-term goal of engineering and computer science; it aims at the reconstruction of CAD models from measured data by means of 3D mathematical surfaces and geometrical features representing the geometry of a physical part. In the last two decades, reviews and surveys have occasionally covered this topic, but a systematic dissertation of modeling methods from a mechanical engineering point of view is still missing. The purpose of this paper is to fill this gap; starting from a general description of the overall RE framework (acquisition, segmentation, classification, fitting), both an up-to-date survey and a categorization of available modeling techniques and tools working on 3D data are provided. The main aspects of various strategies are discussed as well, in order to highlight strengths and weaknesses characterizing different approaches. Moreover, an overview of commercial software for RE is presented, considering both dedicated solutions and packages supplied as add-on with ‘traditional’ CAD systems. Finally, possible improvements to be addressed by the research in the RE field are discussed, outlining potential future trends that are still to be investigated.
Abstract: The percutaneous interventions in the treatment of structural heart diseases represent nowadays a viable option for patients at high risk for surgery. However, unlike during the traditional open heart surgery, the heart structures to be corrected are not directly visualized by the physician during the interventions. The interpretation of the available medical images is often a demanding task and needs specific skills i.e. clinical experience and complex radiological and echocardiographic analysis. The new trend for cardiovascular diagnosis, surgical planning and intervention is, today, mutually connected with most recent developments in the field of 3D acquisition, interactive modelling and rapid prototyping techniques. This is particularly true when dealing with complex heart diseases since 3D-based techniques can really help in providing an accurate planning of the intervention and to support surgical intervention. To help the research community in confronting with this new trend in medical science, the present work provides an overview on most recent approaches and methodologies for creating physical prototypes of patient-specific cardiac structures, with particular reference to most critical phases such as: 3D image acquisition, interactive image segmentation and restoration, interactive 3D model reconstruction, physical prototyping through additive manufacturing. To this purpose, first, recent techniques for image enhancement to highlight anatomical structures of interest are presented together with the current state of the art of interactive image segmentation. Finally, most suitable techniques for prototyping the retrieved 3D model are investigated so as to derive a number of criteria for manufacturing prototypes useful for planning the medical intervention.
Keywords: 3D modelling | Cardiovascular diseases | Heart | Medical imagery | Rapid prototyping | Surgical planning
Abstract: Template-Based reverse engineering approaches represent a relatively poorly explored strategy in the field of CAD reconstruction from polygonal models. Inspired by recent works suggesting the possibility/opportunity of exploiting a parametric description (i.e. CAD template) of the object to be reconstructed in order to retrieve a meaningful digital representation, a novel reverse engineering approach for the reconstruction of CAD models starting from 3D mesh data is proposed. The reconstruction process is performed relying on a CAD template, whose feature tree and geometric constraints are defined according to the a priori information on the physical object. The CAD template is fitted upon the mesh data, optimizing its dimensional parameters and positioning/orientation by means of a particle swarm optimization algorithm. As a result, a parametric CAD model that perfectly fulfils the imposed geometric relations is produced and a feature tree, defining an associative modelling history, is available to the reverse engineer. The proposed implementation exploits a cooperation between a CAD software package (Siemens NX) and a numerical software environment (MATLAB). Five reconstruction tests, covering both synthetic and real-scanned mesh data, are presented and discussed in the manuscript; the results are finally compared with models generated by state of the art reverse engineering software and key aspects to be addressed in future work are hinted at.
Abstract: Pectus Excavatum, one of the most frequent chest wall deformities, is characterized by a depression of the sternum and costal cartilages. Patients with mild deformities are generally treated conservatively by using the so called Vacuum Bell (VB) i.e. a suction cup to be placed on the patient's sternal region. Three different sizes, as well as a model fitted for young women, of VB are available on the market. Unfortunately, the variability of the surface to be treated, the possible asymmetry of the caved-in area and the prolonged use, can make the device uncomfortable and, in some cases, ineffective for the patient. In order to cope with these issues, the present paper proposes a computer-aided method for customized vacuum bell design to be used by non-expert user, e.g. by medical staff. In particular, the present work entails the development of a system comprising: 1) a dedicated software capable of acquiring the 3D chest geometry - by using a low-cost range sensor, i.e. Kinect v2 - and of processing the point cloud so to generate NURBS surfaces of the chest; 2) a procedural CAD modeling of a personalized VB implemented within Siemens NX 11 CAD environment. Using the devised method, the medical staff is required only to use the 3D scanning system for acquiring the patient chest and to sketch, in a CAD-based interface, the boundary of the area to be treated. Once these tasks are performed, the system automatically builds the personalized VB model, ready to be manufactured.
Abstract: With the aim of retrieving 3D surfaces starting from single shaded images, i.e. for solving the widely known shape from shading problem, an important class of methods is based on minimisation techniques where the expected surface to be retrieved is supposed to be coincident with the one that minimise a properly developed functional, consisting of several contributions. Despite several different contributes that can be explored to define a functional, the so called 'smoothness constraint' is a cornerstone since it is the most relevant contribute to guide the convergence of the minimisation process towards a more accurate solution. Unfortunately, in case input shaded image is characterised by areas where actual brightness changes rapidly, such a constraint introduces an undesired over-smoothing effect for the retrieved surface. The present work proposes an original strategy for avoiding such a typical over-smoothing effect, with regard to the image regions in which this is particularly undesired such as, for instance, zones where surface details are to be preserved in the reconstruction. The proposed strategy is tested against a set of case studies and compared with other traditional SFS-based methods to prove its effectiveness.
Keywords: 3D model | Minimisation | SFS | shape from shading | Smoothing | Smoothness constraint | variational approach
Abstract: Underwater exploration, in the last years, has evolved toward a wide adoption of increasingly smaller ROVs (Remotely Operated Vehicle). As a consequence, the need to equip these underwater vehicles with robotic arms is currently rising as well. According to this demand, the paper presents three innovative solutions achieved in the UVMS (Underwater Vehicle-Manipulator System) field. Firstly, the paper proposes a modular architecture for a lightweight underwater robotic arm, which can be mounted on small-sized ROVs. The modular concept of the arm enables several different configurations, each one characterized by the related DOFs, deployed according to the type of application to be performed. Secondly, the arm has been equipped with an adaptive gripper that, taking advantage of the additive manufacturing techniques, is able to easily grip differently shaped objects. Lastly, the underwater arm is controlled through a Master–Slave approach, designed for commercial off-the-shelf electronics, that on the one hand, entailed a significant reduction of the bill of materials, but, on the other hand, required a greater effort in the software development. Experimental tests have been carried out to measure and evaluate the gripping and manipulation capability of the robotic arm and the performance of the proposed control system.
Keywords: Flexible gripper | Master-slave control | Modular robotic arm | Underwater manipulation | Underwater vehicle-manipulator systems (UVMS)
Abstract: Within the T-VedO project, financed by Tuscany Region, the Reverse Engineering and Virtual Prototyping Lab team of the Department of Industrial Engineering of Florence (Italy) developed a number of methods for the semiautomatic generation of digital 2.5D models starting from paintings. Once such models are prototyped, they can be used to enhance visually impaired people tactile experience of artworks. Such methods, combined into a systematic procedure, allow to solve most of the typical problems arising when dealing with artistic representation of a painted scene. The present paper presents both an overview of the proposed procedure, including most recent updates, and the results obtained for a selected number of artworks of the Florentine Renaissance.
Abstract: Wrist injuries are one of the most common fractures, specifically around 25% of fractures among the pediatric population and up to 18% in the elderly age group are distal radius fractures. To date, the standard treatment entails the use of a tailor-made plaster of Paris cast. Although it is a simple and reliable treatment, it presents several disadvantages: its weight generally causes discomfort, it cannot be taken off without breaking it, it can cause skin rashes and prevents ventilation of the treated area. To overcome the limitations of the above mentioned treatment, 3D printed orthopaedic casts based on reverse engineering (RE) and additive manufacturing (AM) techniques have been proposed in literature. Despite these solutions prove to be a valid alternative to the standard treatment, the clinical use of AM-based devices is not trivial due to the need of expert CAD modelers to design the 3D model of the orthosis starting from the patient’s anatomy 3D acquisition. In this work, the authors identify a systematic procedure to create an orthosis model, compliant with medical guidelines, using common CAD tools. The systematic procedure, even still manually performed, envisages a set of tasks, grouped into five main blocks, that will be easy to be automatized in the future, thus eliminating the necessity of designing expertise to model the orthosis. The proposed procedure allows to design a device composed of two halves, to ease the application, locked through a zip tie-based mechanism. A preliminary ventilation pattern is proposed and tested with a FEM analysis to ensure structural resistance. The procedure has been tested on six case studies: all the orthoses models were correctly generated without major complications and positive user feedbacks were generally obtained throughout the tests.
Abstract: The surgical process adopted to repair cranial defects using an implant, typically called Cranioplasty, has seen an abrupt increase in recent years due to the introduction of Reverse Engineering (RE) and Additive Manufacturing (AM) techniques. By adopting these techniques, CT/MRI data can be used to reconstruct, in a pre-operative stage, the 3D anatomy of the defective skull in order to design a patient-specific digital model of the prosthesis. The so-designed cranial plate can be then fabricated via AM, in a suitable metal alloy, and implanted. This allows for a perfect fit of the implant during the actual surgery, reducing the risks for the patient and increasing the efficacy of the treatment. This paper reviews existing approaches for the virtual reconstruction of defective skulls, and a basic classification, proposing four different classes of strategies (Mirroring, Surface Interpolation, Template-Based and Slice-based techniques) is provided. The findings of the study suggest that the reconstruction of skull defects is still an open problem, due to the complexities imposed by surface that needs to be retrieved (i.e. the human anatomy). All the presented approaches share weaknesses and limits, which are discussed in the article. Finally, possible directions to improve the existing techniques are briefly presented.
Abstract: This paper presents a knowledge based engineering environment methodology to support the designer in the correct setting of geometrical and dimensional tolerances in assemblies of mechanical components. The procedure is based on the definition of the functional requirements needed to allow the proper working of the assembly; in the further, a software tool is used to do a statistical analysis of the assembly relations, providing an estimation of the components waste due to poor compliance to the tolerances. A case study given by the design of a marine power transmission is presented: the methodology leads to the change of some tolerances to improve the design by reducing the number of waste components. The strength of the methodology is represented by the fact it can help unskilled designers in the correct setting of tolerances in drawings.
Abstract: Sintering shrinkage of prior cold compacted iron rings with different geometry (height to wall thickness ratio) and green density in the 6.5–7.3 g/cm3 range was investigated. It displays a minimum at an intermediate green density. Axial, tangential and radial shrinkages are different, due to the gradients of green density along the axial and the radial directions. Therefore, the effect of height on shrinkage and its anisotropy is the result of their effect on the stress distribution in the green parts during cold compaction, and the resulting green density and deformation experienced by the powder. Anisotropy decreases on increasing shrinkage.
Keywords: geometry | green density | Shrinkage anisotropy
Abstract: A densification equation derived from deformation occurring in the powder mix during cold compaction was applied to investigate densification of a commercial water atomized AISI 316 stainless steel powder with different particle size distribution, mixed with 1% organic binder, in the production of rings with different H/(Dext-Dint). Knowing the constitutive model of the powder mixes, the mean compaction pressure was determined and correlated to the deformation of the powder column. From these correlations it is possible to derive a densification equation having a physical meaning, also individuating the parameters describing the densification behavior, and in turn the compressibility, of the different powders investigated.
Abstract: In previous work the anisotropic dimensional change on sintering has been investigated in depth. An anisotropy parameter has been identified, depending both on geometry and on sintering conditions, and it has been used to define a model for the anisotropic behaviour. A design procedure accounting for anisotropic dimensional changes has been proposed. This work summarizes the main results obtained within the Design for Sintering Club Project, aimed at validating and enlarging the aforementioned design procedure by the application on real industrial parts. Project partners provided axi-symmetric parts, which were measured both in the green state and after sintering in standard industrial conditions. The real dimensional changes were compared to the dimensional changes predicted by means of the design procedure based on the anisotropy model. The results, also compared to the attainable dimensional tolerances, allowed validating the design procedure, and showing directions to further improvement.
Keywords: Anisotropy | Design for sintering | Dimensional change
Abstract: This work aims at determining the constitutive model of four commercial water atomised low alloyed steel powders during cold compaction. Single-action experiments were performed, obtaining cylindrical specimens with different H/D ratios. The distribution of axial and radial stresses was investigated, and the relationships describing both the radial stress transmission coefficient and the flow stress as functions of the relative density were determined. The radial stress transmission coefficient also confirmed the hypothesised value of Poisson’s coefficient. The friction coefficient between the powder column and the die wall was determined, also highlighting the influence of the H/D ratio. Measuring the axial and radial strains due to spring-back, the axial and radial elastic moduli were determined, as functions of the relative density. The results obtained for the four materials were compared, also highlighting both differences and similarities.
Abstract: The use of composite structures is increasing constantly in the last years, pushed by advantages of reduced weight and high strength. Moreover, the recent scenario points out a great attention on thermoplastic matrix composites due to their intrinsic recyclability as well for their possibility to re-use and re-manufacturing. However, the adoption of these materials can be further appreciated considering the secondary material workability as far as by demonstrating the possibility to re-manufacture the thermoplastic composite. The proposed work presents an experimental analysis carried out to investigate the downstream workability of a thermoplastic composite by one of the most versatile and flexible process. Glass fiber reinforced Polyamide 6 is the investigated material and the Single Point Incremental Forming is the implemented manufacturing approach. Since the composite matrix is characterized by a glass transition temperature higher than 50 °C, an external heating source has been necessary to perform the process in “hot” conditions. The process feasibility was fully demonstrated as well as the same was optimized in order to derive proper guidelines that can drive the process designer in the method star-up.
Keywords: Downstream process | Short glass-fibers | SPIF | Thermoplastic composite
Abstract: In the present work, sheet-forming processes, i.e. super plastic forming and single-point incremental forming, have been adopted for the manufacturing of custom prostheses, instead of subtractive and additive techniques that are time- and cost-consuming for a single-piece production. Regarding concerns of the material, three different titanium alloys were used: pure titanium and two grades of the alloy Ti-6Al-4V (the standard one and the extra low interstitial one). Since no standard protocol exists to assess the mechanical performance of cranial implants, an experimental procedure has been designed and used in this work for producing polymethylmethacrylate supports, on which the cranial prostheses were firmly connected and subjected to impact puncture tests (drop tests). An experimental campaign could thus be conducted to investigate the effect on the mechanical response of (a) the titanium alloy, (b) the initial blank thickness and (c) the manufacturing process. Drop tests, carried out according to the proposed procedure, have shown no failure of the prostheses, neither in the area of the impact nor in the anchoring region and have revealed that, irrespective of the adopted manufacturing process, which does not alter the material, the amount of energy absorbed by the implants is always larger than 70%.
Keywords: Drop test | Pure titanium | SPF | SPIF | Ti-6Al-4V | Ti-6Al-4V-ELI
Abstract: Considering the progressively expansive trade world, "time to market" of productions and goods has turned into a key element for business accomplishment. There are diverse practices that antedate design faults and unveil products on the market in minus time. Among the most used methods in the design and explanation of the necessities, quality function deployment (QFD) and design for Six Sigma (DFSS) can be used. In the prototyping stage, it is probable to address the emergent technology of additive manufacturing. Today, 3D printing is employed as a quick prototyping technique. Nevertheless, the tangible task which industry is fronting is the adoption of these machines for large-scale production of components, which is now possible with new HP multi fusion. The goal of this paper is to illustrate the entire product development process taking advantage of the most modern models and technologies for the final realization of a case study that involves the design and prototyping of an innovative multifunctional fan (lamp, aroma diffuser, and fan) through the multi jet fusion of HP. To begin with, issues related to the DFSS, the QFD and their application to identify the fan requirements are explored. Once the requirements have been defined, the modern CAD design systems and the CAE systems for the validation of the case study will be analyzed and applied. Finally, HP's multi jet fusion methodology and design rules for additive manufacturing will be analyzed in detail, trying to exploit all the positive aspects it offers.
Keywords: CAD | CAE | Design for additive manufacturing | Design for Six Sigma | FEA | Multi jet fusion | Product development | QFD | Rapid prototyping
Abstract: Over the last years, good strategies for efficient manufacturing were considered increasing the volume of production and reducing the time and costs. Emerging design strategies as the Design for Environment and life cycle assessment, the Design for Sustainability, the Design for Disassembly moved the focus to conceive a product by taking care of all the effect that its use can cause to the economy, to the society and to the environment, also at its disposal. In this context, design strategies have to be enhanced in order to integrate innovation with sustainability and social care. Thus, the horizon for strategic manufacturing has to pay particular attention to the effects that it could produce to the surrounding environment. This way, some manufacturing techniques that could be considered obsolete in terms of sustainability awareness, but that are not yet ready to be replaced by advanced available technologies, need a requalification in order to be collocated in the current scenario. In this paper, the open moulding technique has been discussed in order to update the current manufacturing technique to meet the emerging sustainable strategies. Through the integration of QFD and TRIZ an innovative design method have been assessed to enhance the manufacturing process by means of computer aided engineering devices. PrinterCAD is a project that aims to manage additive and subtractive techniques, applied to complex and large-scale products, by means of an open source software with an integrated module, in order to enhance the CAD, CAM and slicing for the 3D printer’s languages intercommunication.
Abstract: Feature-based modeling and feature recognition algorithm are state of the art technologies, mainly used to favor the integration and exchange of data between design and manufacturing phases. This paper aims to investigate the possibility to extend the use of the feature recognition as a means for the prevention of ergonomics issues during the manual assembly phase, such as Work-related Musculo-Skeletal Disorders (WMSDs). Starting from the features analysis of a 3D product model, the proposed five steps method allows preventively identifying potential ergonomics issues. The main novelty of this study is related to the correlation between design tools, product virtual representations (e.g. 3D models), assembly and ergonomics aspects. Results obtained with two case studies, a cooker hood and a tool-holder carousel, confirm the usefulness of the proposed method in helping designers to prevent potential ergonomics issues for operators involved in the assembly phase.
Abstract: Versatile, cheap and non-invasive 3D acquisition techniques have received attention and interest in the field of biomedicine in recent years as the accuracy of developed devices permits the acquisition of human body shapes in detail. Interest in these technologies derives from the fact that they have the potential to overcome some limitations of invasive techniques (CT, X-rays, etc.) and those based on 2D photographs for the acquisition of 3D geometry. However, the data acquired from the 3D scanner cannot be directly used but need to be processed as they consist of 3D coordinates of the acquired points. Therefore, many researchers have proposed different algorithms which recognise the shape of human body and/or its features when starting from a 3D point cloud. Among all possible human body features to be evaluated, symmetry results the most relevant one. Accordingly, this survey systematically investigates the methods proposed in the literature to recognise 2D symmetry by the symmetry line and bilateral symmetry by the symmetry plane. The paper also analyses qualitative comparisons among the proposed methods to provide a guide for both practitioners and researchers.
Keywords: 3D scan | Digital human model | Symmetry line | Symmetry plane
Abstract: The design of gas turbine ventilation systems (VSs) is a lengthy and tedious process, often requiring weeks to refine a single design concept and by additional time to manufacture it. This is particularly true when dealing with structural design since the typical approach followed by main worldwide manufacturing companies is to outsource finite elements analysis and, often, the 3d modelling phase itself. Moreover, the structural design process is iterative: the modeling and finite elements analysis steps are repeated several times whenever a new VS has to be produced. Accordingly, speeding-up the structural design phase is today a crucial issue for gas turbine sector. Keeping the above objective in mind, the present paper proposes a CAD-based tool, implemented in a commercial 3D CAD software package (SolidWorks), supporting and partly automating the complex structural VS design process. The solution suggested in this work consists of the design and implementation of a SolidWorks add-in, called DuctWorks, developed by using C# programming language. Differently from commercially available solutions, the proposed tool is specifically thought keeping in mind the necessity of performing a final structural assessment, which is of utmost importance given the considerable dimensions and stresses this kind of VS are subject to in the specific field of GT and energy production industry. Tested against a set of case studies, DuctWorks proved to be effective in allowing designers to accelerate the ventilation systems design process with excellent results when compared with the traditional design process.
Abstract: The standard treatment for bones fractures entails the use of a tailor-made plaster cast which has several disadvantages: its weight generally causes discomfort, it cannot be taken off without breaking it, it can cause skin rashes and prevents ventilation of the treated area. Therefore, the application of traditional casts to orthopaedics patients does not represent, to date, the best option. To overcome the above-mentioned drawbacks, many strategies based on reverse engineering and additive manufacturing techniques have been proposed and proved to be a valid alternative for producing custom orthoses. Encouraged by the aforementioned results, the authors have developed a low-cost system (called Oplà), specifically dedicated to the hand-wrist-arm district of paediatric patients and capable of creating a 3D CAD model of the orthosis ready to be printed by using additive manufacturing techniques. Such a system comprises a 3D scanner, a control software and a semi-automatic CAD procedure to easily model the orthopaedic device on each patient, without the need of CAD modelling professionals. To evaluate if Oplà can be effectively used by the medical staff to design patient specific 3D printable orthoses in the clinical practice, a preliminary usability assessment has been performed. Five professional nurses from the Meyer Children’s Hospital of Florence (Italy) have been selected and trained in the use of the system. Subsequently, each of them has been asked to perform the whole process for the same patient. Effectiveness, efficiency and satisfaction have been measured in accordance to ISO 9241-11. Results proved that the Oplà system is characterized by a good usability allowing the user to easily and intuitively perform all the tasks in a reasonable time.
Abstract: Given a to-be-watermarked 3D model, a transformed domain analysis is needed to guarantee a robust embedding without compromising the visual quality of the result. A multiresolution remeshing of the model allows to represent the 3D surface in a transformed domain suitable for embedding a robust and imperceptible watermark signal. Simplification of polygonal meshes is the basic step for a multiresolution remeshing of a 3D model; this step is needed to obtain the model approximation (coarse version) from which a refinement framework (i.e. 3D wavelet analysis, spectral analysis, …) able to represent the model at multiple resolution levels, can be performed. The simplification algorithm should satisfy some requirements to be used in a watermarking system: the repeatability of the simplification, and the robustness of it to noise or, more generally, to slight modifications of the full resolution mesh. The performance of a number of software packages for mesh simplification, including both commercial and academic offerings, are compared in this survey. We defined a benchmark for testing the different software in the watermarking scenario and reported a comprehensive analysis of the software performances based on the geometric distortions measurement of the simplified versions.
Keywords: 3D watermarking | Mesh comparison | Mesh simplification | Wavelets 3D
Abstract: The visualization and analysis of mosaics and pavements are often compromised by their large sizes, which do not enable the observer to perceive their whole arrangement or to focus on details placed in farthest areas from its boundaries. Moreover, the usual precarious state of conservation of these artefacts, often with damaged or missing areas, makes it difficult to perceive their original aesthetic value. To overcome these limitations, we propose an application of augmented reality able to support the observer in two ways: first, the application completes the missing surface of the mosaic or pavement by integrating the existent surface with a virtual reconstruction; second, it enables the analysis of the geometric pattern of the mosaic/pavement by overlaying virtual lines and geometric figures in order to explicit its geometric arrangements. The result is achieved via a custom Android application able to recognize and track the mosaic figure pattern and extra marker board, obtaining in that way a coordinate system used to render in real-time the reconstruction of the mosaic. Such rendering is overlaid to the video stream of the real scene. The application runs on a standard smartphone embedded in a Google Cardboard-compatible viewer and therefore is extremely affordable. As a case study, in order to reconstruct its aspects and to analyse its geometric pattern, we chose the roman mosaic re-found in Savignano sul Panaro (near Modena, Italy) in 2011, after 115 years from its first discovery, which is preserved less than half of its original 4.5 x 6.9 m surface.
Keywords: Augmented Reality | Cultural heritage | Geometric pattern | Photogrammetry | Real-time visualization | Roman mosaic
Abstract: This paper proposes the integration of photogrammetric reconstruction, 3D modelling and augmented reality application in order to achieve the complete visualization of a stone sculpture even if highly damaged or fragmentary. The first part of the research aims to the reconstruction of the original aspect of an incomplete sculpture, by using photogrammetry techniques based on standard resolution photos and free software in order to obtain a first model; then, we integrate this model with other 3D digital data (from other sculptures of the same period) or with 3D modelling based on historical sources and views from historians, aiming to achieve the original aspect of the sculpture. The second part of the research consists of the embedding of the obtained model in a custom application able to render in real-time the 3D reconstruction of the lion. Then, the rendering is overlaid to the video stream of the real scene and, as a result, a complete 3D digital model of the sculpture is achieved and could be visualized through a VR viewer. As a case study, we focus on a Roman stone sculpture of a male lion conserved in the Museo Estense of Modena (Italy), which lacks of its head and its four legs. The original aspect of the lion may be achieved by integrating the damaged sculpture with other photogrammetric reconstructions of lions sculptures of the same period and with 3D model based on historical sources. Finally, the lion is visualized through an augmented reality application which digitally overlays the reconstructed models on the original one.
Abstract: This paper deals with a numerical investigation, based on the Finite Element (FE) theory, of a Structural Health Monitoring (SHM) system for a large radio-telescope, aimed to damage detection and location. The investigated SHM system is based on the comparison of the Frequency Response Functions (FRFs) achieved under both pristine and damaged configurations, respectively. A preliminary study has been carried out in order to achieve information on the optimal sensors locations. As a result, the structural response of the radio-telescope under the in-service loading conditions has been numerically investigated. All FE analyses have been carried out by means of MD Nastran® code.
Abstract: Manual Material Handling (MMH), by pushing or pulling carts, is a common task that characterizes any manufacturing or service operation, and there is always a significant human input to those operations in terms of physical load. The physical load represents the effect of input forces during MMH operations that depend on the interaction between material handling equipment and the working environment. Many times MMH represents a critical issue related to human-machine interaction due to the carts can work in environment with parameters different from those used in designing, subjecting workers to risk of musculoskeletal disorders. The aim of this work, developed in collaboration with Fiat Chrysler Automobiles (FCA), is to develop a new procedure that allows estimating the initial and the maintenance forces necessary to push or pull carts, knowing the characteristics of the cart and the environment in which it works, in order to preventively assess the ergonomic indexes according to ISO 11228-2. The procedure is based on multibody simulations. The cart is modeled by Computer Aided Design (CAD) code and, then, imported in a multibody code where numerical simulations are performed in order to calculate the forces. In the multibody code static and dynamic friction coefficients of bearing of wheels are assigned, together with parameters of contact between wheels and floor. Changing the pivot angle of two floating wheels, several simulations have been carried out. Moreover, considering a cart used at the assembly line of the FCA plant of Pomigliano d'Arco (Naples), experimental tests have been performed in order to validate the procedure by comparing numerical results with the experimental ones.
Abstract: In this paper, a new methodology supporting the design of landing gears is proposed. Generally, a preliminary step is performed with simplified FE model, usually one-dimensional, to achieve the reaction forces involving each component during all aforementioned aircraft operations. Though this approach gives a valid support to the designer, it is characterized by several problems, such as the related approximations. So, it is important, by a numerical point of view, to develop an isostatic FE model equivalent to the real one. In fact, if the landing gear is modelled as hyperstatic, the static equilibrium equations are insufficient for determining the internal forces and reactions on each sub-component; so, the modelled material properties and geometries assume an increasing importance, which gets the model too approximating. The proposed methodology consists of achieving the reaction forces by means of multibody simulations, by overcoming such problems, since each component is modelled as rigid. In this paper, also a FE model for the investigation of the structural response is proposed. Aimed to Certification by Analysis purposes, the developed multibody and the FE models have been assessed against an experimental landing gear drop test carried out by Magnaghi Aeronautica S.p.A., according to the EASA CS 25 regulations.
Keywords: Drop test | Dynamic behaviour | FE analysis | Landing gear | Multibody
Abstract: This study proposes a novel automatic method for facial landmark localization relying on geometrical properties of 3D facial surface working both on complete faces displaying different emotions and in presence of occlusions. In particular, 12 descriptors coming from Differential Geometry including the coefficients of the fundamental forms, Gaussian, mean, principal curvatures, shape index and curvedness are extracted as facial features and their local geometric properties are exploited to localize 13 soft-tissue landmarks from eye and nose areas. The method is deterministic and is backboned by a thresholding technique designed by studying the behaviour of each geometrical descriptor in correspondence to the locus of each landmark. Occlusions are managed by a detection algorithm based on geometrical properties which allows to proceed with the landmark localization avoiding the covered areas. Experimentations were carried out on 3132 faces of the Bosphorus database and of a 230-sized internal database, including expressive and occluded ones (mouth, eye, and eyeglasses occlusions), obtaining 4.75 mm mean localization error.
Keywords: 3D face | Differential geometry | Face analysis | Feature extraction | Landmark localization
Abstract: In the present work a novel rear suspension for motorcycles, able to achieve the required progressiveness in terms of rigidity by using a constant-stiffness spring and an innovative compact mechanism, is studied. The key component is an eccentric system inserted in the shock absorber head. As reference, the rear suspension of the Ducati Multistrada MY 2010, characterized by the use of a variable-stiffness spring, is analyzed. The aim of the paper is to prove that the novel proposed solution can obtain a response, in terms of wheel load, similar to that of the reference system. At first, a mathematical model to simulate the kinematics of the novel suspension is presented. This model is able to evaluate the influence of geometric dimensions of the components, checking successfully the ability to reproduce the behavior of the original suspension. After the preliminary design, the kinetostatic model is included within an optimization algorithm ad-hoc created to obtain the optimum dimensions of each component. In order to obtain the inertial parameters, two 3D models of both the suspensions are created. Finally, two multibody models of the two suspensions are implemented in Adams environment in order to evaluate their dynamic behaviour. Results confirm the goodness of the novel solution being comparable to the reference one in terms of dynamic response during the simulation of a typical experimental test performed in Ducati.
Abstract: Collaborative robots must operate safely and efficiently in ever-changing unstructured environments, grasping and manipulating many different objects. Artificial vision has proved to be collaborative robots’ ideal sensing technology and it is widely used for identifying the objects to manipulate and for detecting their optimal grasping. One of the main drawbacks of state of the art robotic vision systems is the long training needed for teaching the identification and optimal grasps of each object, which leads to a strong reduction of the robot productivity and overall operating flexibility. To overcome such limit, we propose an engineering method, based on deep learning techniques, for the detection of the robotic grasps of unknown objects in an unstructured environment, which should enable collaborative robots to autonomously generate grasping strategies without the need of training and programming. A novel loss function for the training of the grasp prediction network has been developed and proved to work well also with low resolution 2-D images, then allowing the use of a single, smaller and low cost camera, that can be better integrated in robotic end-effectors. Despite the availability of less information (resolution and depth) a 75% of accuracy has been achieved on the Cornell data set and it is shown that our implementation of the loss function does not suffer of the common problems reported in literature. The system has been implemented using the ROS framework and tested on a Baxter collaborative robot.
Abstract: In several application contexts, virtual solid models require to integrate portions of polygonal meshes with synthetic models, designed by traditional parametric/analytical multipatches systems. The paper reports the research aiming at covering the theoretical and numerical aspects connected with an extended geometric solid modeling system, focusing on the B-Rep models and introducing the new paradigm of Extended B-Rep (EB-Rep), which is able to integrate mesh-faces as part of a B-rep model. This paradigm introduces a notion of continuity between parametric and discrete representations, regularized Boolean Operations, a join operator and an approach to represent a valence semi-regular mesh as an EB-Rep structure. A prototype of the geometric solid modeling kernel has been realized and tested in the OpenCascade library environment.
Abstract: 3D recording, digital surveying and mapping are efficient and manageable tools for reconnaissance, documentation and monitoring in underwater archaeology. Lab4Dive project, co-funded by the European Union's EMFF Programme, through the EASME and DG MARE call on 'Blue Labs', aims to design, develop and validate an innovative, marketable and competitive technology, which will assist underwater archaeologists in the field and will contribute significantly to the successful outcome of the survey process, documentation and preservation of submerged archaeological sites. In this article, the Lab4Dive system and its preliminary testing results, will be presented. The system is based on an underwater tablet coupled with an intelligent underwater case embedded with environmental sensors, a high-resolution camera and compatible with different commercial acoustic positioning systems, which will be integrated with a cloud data gathering system. During the dive, the tablet provides the diver with an augmented navigation interface, which guides him towards the selected targets. The cloud data gathering system allows the archaeologists to produce a 3D reconstruction of the site, which encompasses all the acquired information, enabling them to further study and analyze the data before the next mission.
Keywords: 3D documentation | 3D Reconstruction | IoT | Marine Robotics | Underwater Archaeology
Abstract: Images obtained in an underwater environment are often affected by colour casting and suffer from poor visibility and lack of contrast. In the literature, there are many enhancement algorithms that improve different aspects of the underwater imagery. Each paper, when presenting a new algorithm or method, usually compares the proposed technique with some alternatives present in the current state of the art. There are no studies on the reliability of benchmarking methods, as the comparisons are based on various subjective and objective metrics. This paper would pave the way towards the definition of an effective methodology for the performance evaluation of the underwater image enhancement techniques. Moreover, this work could orientate the underwater community towards choosing which method can lead to the best results for a given task in different underwater conditions. In particular, we selected five well-known methods from the state of the art and used them to enhance a dataset of images produced in various underwater sites with different conditions of depth, turbidity, and lighting. These enhanced images were evaluated by means of three different approaches: objective metrics often adopted in the related literature, a panel of experts in the underwater field, and an evaluation based on the results of 3D reconstructions.
Abstract: Objectives To investigate the influence of specific resin-composite, glass ceramic and glass ionomer cement (GIC) material combinations in a “multi-layer” technique to replace enamel and dentin in class II mesio-occlusal-distal (MOD) dental restorations using 3D-Finite Element Analysis (FEA). Methods Four 3D-FE models (A–D) of teeth, adhesively restored with different filling materials, were created and analyzed in comparison with a 3D model (E) of a sound lower molar. Models A, B & C had “multilayer” constructions, consisting of three layers: adhesive, dentin replacement and enamel replacement. Model A: had a low modulus (8 GPa) composite replacing dentin and a higher modulus (12 GPa) composite replacing enamel. Model B: had a GI cement replacing dentin and a higher modulus (12 GPa) composite replacing enamel. Model C: had a low modulus (8 GPa) composite replacing dentin and a very high modulus (70 GPa) inlay replacing enamel. Model D: had a lithium disilicate inlay replacing both dentin and enamel with a luting cement base-layer. Polymerization shrinkage effects were simulated and a load of 600 N was applied. All the materials were assumed to behave elastically throughout the entire deformation. Results Model A showed the highest stress distribution along all the adhesive interfaces of the shrinking resin-based materials with a critical condition and failure risk marginally and internally. Model D, by contrast, showed a more favorable performance than either of the multilayer groups (A–C). Stress and displacement plots showed an elastic response similar to that obtained for the sound tooth model. Model B and Model C performed according to their bilayer material properties. The use of a non-shrink dentin component simulating a GIC clearly affected the shrinkage stress at the basis of the Model B; while the bulk resin composite having a 12 GPa Young's modulus and linear polymerization shrinkage of 1% strongly influenced the biomechanical response in the bucco-lingual direction. Significance Direct resin-based composite materials applied in multilayer techniques to large class II cavities, with or without shrinking dentin layers, produced adverse FEA stress distributions and displacements. An indirect lithium disilicate inlay used to replace lost dentin and enamel in posterior restored teeth generated lower stress levels, within the limits of the elastic FEA model.
Keywords: CAD | Class II restorations | Finite element analysis | Image analysis | Materials properties
Abstract: Objective To assess the effect of a ferrule design with specific post material-shape combinations on the mechanical behavior of post-restored canine teeth. Methods Micro-CT scan images of an intact canine were used to create a 3-D tessellated CAD model, from which the shapes of dentin, pulp and enamel were obtained and geometric models of post-endodontically restored teeth were created. Two types of 15 mm post were evaluated: a quartz fiber post with conical–tapered shape, and a carbon (C) fiber post with conical–cylindrical shape. The abutment was created around the coronal portion of the posts and 0.1 mm cement was added between prepared crown and abutment. Cement was also added between the post and root canal and a 0.25 mm periodontal ligament was modeled around the root. Four models were analysed by Finite Element (FE) Analysis: with/without a ferrule for both types of post material and shape. A load of 50 N was applied at 45° to the longitudinal axis of the tooth, acting on the palatal surface of the crown. The maximum normal stress criterion was adopted as a measure of potential damage. Results Models without a ferrule showed greater stresses (16.3 MPa) than those for models with a ferrule (9.2 MPa). With a ferrule, stress was uniformly distributed along the abutment and the root, with no critical stress concentration. In all models, the highest stresses were in the palatal wall of the root. Models with the C-fiber post had higher stress than models with the quartz fiber posts. The most uniform stress distribution was with the combination of ferrule and quartz fiber post. Significance The FE analysis confirmed a beneficial ferrule effect with the combination of ferrule and quartz fiber post, with tapered shape, affording no critical stress concentrations within the restored system.
Abstract: Objectives To study the influence of resin based and lithium disilicate materials on the stress and strain distributions in adhesive class II mesio-occlusal-distal (MOD) restorations using numerical finite element analysis (FEA). To investigate the materials combinations in the restored teeth during mastication and their ability to relieve stresses. Methods One 3D model of a sound lower molar and three 3D class II MOD cavity models with 95° cavity-margin-angle shapes were modelled. Different material combinations were simulated: model A, with a 10 μm thick resin bonding layer and a resin composite bulk filling material; model B, with a 70 μm resin cement with an indirect CAD-CAM resin composite inlay; model C, with a 70 μm thick resin cement with an indirect lithium disilicate machinable inlay. To simulate polymerization shrinkage effects in the adhesive layers and bulk fill composite, the thermal expansion approach was used. Shell elements were employed for representing the adhesive layers. 3D solid CTETRA elements with four grid points were employed for modelling the food bolus and tooth. Slide-type contact elements were used between the tooth surface and food. A vertical occlusal load of 600 N was applied, and nodal displacements on the bottom cutting surfaces were constrained in all directions. All the materials were assumed to be isotropic and elastic and a static linear analysis was performed. Results Displacements were different in models A, B and C. Polymerization shrinkage hardly affected model A and mastication only partially affected mechanical behavior. Shrinkage stress peaks were mainly located marginally along the enamel-restoration interface at occlusal and mesio-distal sites. However, at the internal dentinal walls, stress distributions were critical with the highest maximum stresses concentrated in the proximal boxes. In models B and C, shrinkage stress was only produced by the 70 μm thick resin layer, but the magnitudes depended on the Young's modulus (E) of the inlay materials. Model B mastication behavior (with E = 20 GPa) was similar to the sound tooth stress relief pattern. Model B internally showed differences from the sound tooth model but reduced maximum stresses than model A and partially than model C. Model C (with E = 70 GPa) behaved similarly to model B with well redistributed stresses at the occlusal margins and the lateral sides with higher stress concentrations in the proximal boxes. Models B and C showed a more favorable performance than model A with elastic biomechanics similar to the sound tooth model. Significance Bulk filling resin composite with 1% linear polymerization shrinkage negatively affected the mechanical behavior of class II MOD restored teeth. Class II MOD direct resin composite showed greater potential for damage because of higher internal and marginal stress evolution during resin polymerization shrinkage. With a large class II MOD cavity an indirect composite or a lithium disilicate inlay restoration may provide a mechanical response close to that of a sound tooth.
Abstract: Objective To study the influence of the different class II mesio-occlusal-distal (MOD) cavity shape on the stress and strain distributions in adhesive indirect restorations, using numerical finite element analysis (FEA). To investigate the relationship between restored teeth failure and stiffness of food, three values of Young's modulus were used for the food. Methods A 3D model of a sound lower molar and three class II MOD cavities with different shape were created. Slide-type contact elements were used between tooth surface and food. An adhesive resin-based cement, modeled with fixed-type contact elements, and a single restorative filling materials were considered. To simulate polymerization shrinkage effect, which is basically restricted to the thin composite cement layer, shell elements were employed and the thermal expansion approach was used. A vertical occlusal load of 600 N was applied, while assigning fixed zero-displacements on the cutting surfaces below the crevices. All the materials were assumed to be isotropic and elastic. A static linear analysis was carried out. Results In the lingual cusp, the displacements increased as the values of the stiffness food increased. In the restored teeth, the stress near the restoration-tooth interface was strongly dependent on the MOD cavity shape. The stress peaks were mainly located along the enamel–dentin interface at the lingual side; wedge-shaped MOD cavity with a low angle, in combination with the lowest food stiffness provided the best results. Significance A more complex load application on the occlusal surfaces was introduced. Food stiffness slightly affected the stress distribution of the restored and sound teeth. Teeth with adhesive class II MOD indirect resin composite restorations were potentially more susceptible to damage if the class II MOD cavity-margin-angle was higher than 95°. Restored teeth with a higher cavity-margin-angle led to considerable stress concentration in the lingual cusp along the enamel–dentin interface. These models were more susceptible to fracture in the lingual cusps when compared to the buccal ones.
Abstract: A new method for secondary features segmentation, performed in highdensity acquired geometric models, is proposed. Four types of secondary features are considered: fillets, rounds, grooves and sharp edges. The method is based on an algorithm that analyzes the principal curvatures. The nodes, potentially attributable to a fillet of given geometry, are those with a certain value for maximum principal curvature. Since the deterministic application of this simple wor king principle shows several problems due to the uncertainties in the curvature estimation, a fuzzy approach is proposed. In order to segment the nodes of a tessellated model that pertain to the same secondary features, proper membership functions are evaluated as function of some parameters, which affect the quality of the curvature estimation. A region growing algorithm connects the nodes pertaining to the same secondary feature. The method is applied and verified for some test cases.
Keywords: Computational geometry | Features extractions | Fuzzy logic | Mechanical engineering computing | Region growing algorithm
Abstract: The present paper deals with methods for product development aimed to support designing activities and to re-use company know-how. The work is addressed to complex products i.e. products characterized by several components and dependencies among them. Then, the paper presents both the methodological approach and the application to the 3D CAD modelling of an automotive car door assembly. The work uses directed graphs and a series of algorithms to provide a Graphical User Interface (GUI) able to support a designer by reducing the development time of new car door assemblies and increasing the accuracy of the design activities. According to a digital pattern approach, the GUI is used to determine the set of changes to 3D CAD models that typically occur in the automotive field, during the development of new car door assemblies.
Keywords: Automotive car door design and development | CAD modelling | Digital pattern for product development | Directed graphs
Abstract: Aim of this work is to investigate the behaviour of a new reverse shoulder prosthesis, characterized by a humeral metaphysis with a variable offset, designed to increase the range of movements and to reduce the impingement. In particular, by means of virtual prototypes of the prosthesis, different offset values of the humeral metaphysis have been analysed in order to find the best positioning able to maximize the range of movements of the shoulder joint. The abduction force of the deltoid, at different offset values, has been also estimated. The study has been organized as follows. In the first step, the point clouds of the surfaces of the different components of the prosthesis have been acquired by a 3D scanner. This kind of scanner allows to convert camera images into three-dimensional models by analysing the moiré fringes. In the second step, the acquired point clouds have been post-processed and converted into CAD models. In the third step, all the 3D reconstructed models have been imported and assembled through a CAD system. After, a collision analysis has been performed to detect the maximum angular positions of the arm at different metaphysis offset values. In the last step, FEM models of shoulder joint with the new prosthesis have been created. Different analyses have been performed to estimate how the deltoid abduction force varies depending on the offset of the humeral tray. The study allowed to understand how the offset of the metaphysis affects the performances of the shoulder. The obtained results can be effectively used to give surgeons useful guidelines for the installation of these kinds of implants.
Keywords: CAD | Range of movements | Reverse engineering | Reverse shoulder prosthesis
Abstract: This paper presents a nonlinear finite element formalism for modelling the dynamics of flexible manipulators using the special Euclidean group SE(3) framework. The method is based on a local description of the motion variables, and results in a singularity-free formulation which exhibits important advantages regarding numerical implementation. The motivation behind this work is the development of a new class of model-based control systems which may predict and thus avoid the deformations of a real flexible mechanism. Finite element methods based on the geometrically exact beam theory have been proven to be the most accurate to account for flexibility: in this paper we highlight the key aspects of this formulation deriving the equations of motion of a flexible constrained manipulator and we illustrate its potential in robotics through a simple case study, the dynamic analysis of a two-link manipulator, simulating different model assumptions in order to emphasize its real physical behavior as flexible mechanism.
Abstract: The current trend in manufacturing is to obtain a flexible work cell in which human and robot can safely interact and collaborate. Virtual Reality (VR) represents an effective tool capable of simulating such complex systems with a high level of immersion. In order to take advantage of VR technologies to study Human-Robot Cooperation (HRC), a digital model of a redundant manipulator (KUKA LBR iiwa) has been developed starting with kinematic modeling and then coupled with the real robot. This approach allows simulating HRC in several scenarios, to reproduce the safe behavior on the real robot, as well as to train operators.
Abstract: Transparent and removable aligners represent an effective solution to correct various orthodontic malocclusions through minimally invasive procedures. An aligner-based treatment requires patients to sequentially wear dentition-mating shells obtained by thermoforming polymeric disks on reference dental models. An aligner is shaped introducing a geometrical mismatch with respect to the actual tooth positions to induce a loading system, which moves the target teeth toward the correct positions. The common practice is based on selecting the aligner features (material, thickness, and auxiliary elements) by only considering clinician's subjective assessments. In this article, a computational design and engineering methodology has been developed to reconstruct anatomical tissues, to model parametric aligner shapes, to simulate orthodontic movements, and to enhance the aligner design. The proposed approach integrates computer-aided technologies, from tomographic imaging to optical scanning, from parametric modeling to finite element analyses, within a 3-dimensional digital framework. The anatomical modeling provides anatomies, including teeth (roots and crowns), jaw bones, and periodontal ligaments, which are the references for the down streaming parametric aligner shaping. The biomechanical interactions between anatomical models and aligner geometries are virtually reproduced using a finite element analysis software. The methodology allows numerical simulations of patient-specific conditions and the comparative analyses of different aligner configurations. In this article, the digital framework has been used to study the influence of various auxiliary elements on the loading system delivered to a maxillary and a mandibular central incisor during an orthodontic tipping movement. Numerical simulations have shown a high dependency of the orthodontic tooth movement on the auxiliary element configuration, which should then be accurately selected to maximize the aligner's effectiveness.
Abstract: The demand of new tools devoted to integrate aesthetic design into classic parametric CAD suites has undergone a raising interest from the user community. Industrial tools for reconstructing the 3D geometry of an object starting from 2D representations and for surfacing wireframe models according to designers intent, assumed a high relevance and have experienced a steady evolution. The problem of surfacing wireframe models with consistent closing surface patches is still a hot topic in the computer graphics as well as in the industrial field, as demonstrated by a number of recent works. In this paper, authors propose a procedure for enhancing the surfacing process by using shading information, together with the wireframe model. In particular, this work allows to use shading, represented either in a rendered 3D model or sketched by a designer, for retrieving consistent geometrical information related to the 3D object. The procedure is accompanied by some selected case studies, to highlight its strengths and weaknesses.
Keywords: 3D reconstruction | CAD | Hand-drawn sketches | Surfacing | Wireframe model
Abstract: 3D body scanners are nowadays used in a range of applications spanning from health, fashion and fitness to reverse engineering applications for robotics and computer vision. Nowadays very good performances are achievable when using commercial 3D body scanners; however, focusing on relative complex shape of some body details, the results still lack precision and acceptable accuracy. Such critical issue remains unsolved also when dealing with the instantaneous acquisition of the hand-wrist-arm (HWA) anatomy. In this paper, we present a new approach that leverages the emerging 3D depth cameras technologies to design a compact low cost 3D dedicated HWA scanner system capable of delivering almost instantaneous full 3D measurement.
Keywords: 3D body scanner | 3D surface | calibration | depth sensors | hand-wrist-arm anatomy
Abstract: Cardiovascular diagnosis, surgical planning and intervention are among the most interested in recent developments in the field of 3D acquisition, modelling and rapid prototyping techniques. In case of complex heart disease, to provide an accurate planning of the intervention and to support surgical planning and intervention, an increasing number of Hospitals make use of physical 3D models of the cardiac structure, including heart, obtained using additive manufacturing starting from the 3D model retrieved with medical imagery. The present work aims in providing an overview on most recent approaches and methodologies for creating physical prototypes of patient-specific heart and cardiac structures, with particular reference to most critical phases such as segmentation and aspects concerning converting digital models into physical replicas through rapid prototyping techniques. First, recent techniques for image enhancement to highlight anatomical structures of interest are presented together with the current state of the art of semi-automatic image segmentation. Then, most suitable techniques for prototyping the retrieved 3D model are investigated so as to draft some hints for creating prototypes useful for planning the medical intervention.
Keywords: 3D modelling | 3D printing | Cardiovascular diseases | Heart | Medical imagery | Rapid prototyping | Surgical planning
Abstract: This work presents Reverse Engineering and Computer Aided technologies to improve the inspection of injection moulded electro-mechanical parts. Through a strong integration and automation of these methods, tolerance analysis, acquisition tool-path optimization and data management are performed. The core of the procedure concerns the automation of the data measure originally developed through voxel-based segmentation. This paper discusses the overall framework and its integration made according to Smart Manufacturing requirements. The experimental set-up, now in operative conditions at ABB SACE, is composed of a laser scanner installed on a CMM machine able to measure components with lengths in the range of 5÷250 mm, (b) a tool path optimization procedure and (c) a data management both developed as CAD-based applications.
Abstract: Nowadays, the most updated CAE systems include structural optimization toolbox. This demonstrates that topological optimization is a mature technique, although it is not a well-established design practice. It can be applied to increase performance in lightweight design, but also to explore new topological arrangements. It is done through a proper definition of the problem domain, which means defining functional surfaces (interface surfaces with specific contact conditions), preliminary external lengths and geometrical conditions related to possible manufacturing constraints. In this sense, its applicability is possible for all kind of manufacturing, although, in Additive Manufacturing, its extreme solutions can be obtained. In this paper, we aim to present the general applicability of topological optimization in the design workflow together with a case study, exploited according to two design intents: the lightweight criterion and the conceptual definition of an enhanced topology. It demonstrates that this method may help to decrease the design efforts, which, especially in the case of additive manufacturing, can be reallocated for other kind of product optimization.
Abstract: This work describes an integrated method of 3D modelling algorithms with a modal approach in a multibody environment which provides a slimmer and more efficient simulation of flexible component contacts realistically reproducing system impacts and vibrations. A non-linear numerical model of the impulse contact forces based on the continuity approach of Lankarani and Nikravesh is developed. The model developed can evaluate deformation energy taking into account the material's characteristics, surface geometries and the velocity variations of the bodies in contact. ADAMS®-type modelling is applied to the sliding contacts of the links of a chain and its mechanical tensioner (“blade”) in the timing of an internal combustion engine. The blade was discretized by subdividing it into smaller components inter-connected with corresponding centres of gravity through 3D General Forces. Static and dynamic tests were performed to evaluate the stiffness, damping and friction parameters for the multibody model and to validate the methodology.
Abstract: This work describes a simple, fast, and robust method for identifying, checking and managing the overlapping image keypoints for 3D reconstruction of large objects with numerous geometric singularities and multiple features at different lighting levels. In particular a precision 3D reconstruction of an extensive architecture captured by aerial digital photogrammetry using Unmanned Aerial Vehicles (UAV) is developed. The method was experimentally applied to survey and reconstruct the 'Saraceni' Bridge' at Adrano (Sicily), a valuable example of Roman architecture in brick of historical/cultural interest. The variety of features and different lighting levels required robust self-correlation techniques which would recognise features sometimes even smaller than a pixel in the digital images so as to automatically identify the keypoints necessary for image overlapping and 3D reconstruction. Feature Based Matching (FBM) was used for the low lighting areas like the intrados and the inner arch surfaces, and Area Based Matching (ABM) was used in conjunction to capture the sides and upper surfaces of the bridge. Applying SIFT (Scale Invariant Feature Transform) algorithm during capture helped find distinct features invariant to position, scale and rotation as well as robust for the affinity transformations (changes in scale, rotation, size and position) and lighting variations which are particularly effective in image overlapping. Errors were compared with surveys by total station theodolites, GPS and laser systems. The method can facilitate reconstruction of the most difficult to access parts like the arch intrados and the bridge cavities with high correlation indices.
Keywords: Architectural reconstruction | Area Based Matching | Feature Based Matching | Photogrammetry | SIFT algorithm
Abstract: The participation of blind people (BP) in cultural life can be improved by enhancing methodologies and tools for facilitating the 3D reproduction of artworks and, at the same time, to facilitate their exploration. The creation of integrated systems including not only tactile media such as, for instance, sculptures or bas-reliefs but even a set of tools capable of providing the users with an experience cognitively comparable to the one originally envisioned by the artist, may undoubtedly enhance artworks exploration. The present work aims to design a conceptual system to aid BP in the tactile exploration of bas-reliefs. This conceptual system comprises both a hand-tracking system and an audio device, together with a number of methodologies, algorithms and information related to physical design. The designed layout, preliminarily tested to understand its potential and limits, proved to be a promising first attempt in enhancing the BP exploration experience.
Keywords: 3D reconstruction | Blind people | Hand-tracking system | Tactile bas-relief | Tactile exploration
Abstract: This paper describes the features of AMCOMP, a CAD environment conceived to manage the computation of the Added Masses of bodies moving in an infinite fluid. A methodology already published in literature has been implemented in a CAD environment and its features are exploited to perform the evaluation of the Added Masses. These include the importing of the model in STL file format and the computation of the complete Added Mass matrix and non-dimensional terms. The CAD has been validated by computing the Added Masses values of bodies whose exact formulation was found in literature. The validated tool has been applied to more complex case studies where the Added Masses values were guessed using empirical laws or the equivalent ellipsoid approximation. Significant differences have been found between approximated methods and computations on real shapes. It is shown that the precision in the Added Masses computation and the computational time depend on the meshing quality of the model and power of the PC on which the software runs. Several tools have been merged to obtain a model useful for the Added Masses computation and to assess the errors arising from using approximated formulas instead of the real shape of the body.
Abstract: The mounting attention to environmental issues requires adopting better disassembly procedures at the product's End of Life. Planning and reckoning different disassembly strategies in the early stage of the design process can improve the development of sustainable products with an easy dismissing and recycling oriented approach. Nowadays many Computer Aided Process Planning software packages provide optimized assembly or disassembly sequences, but they are mainly based on a time and cost compression approach, neglecting the human factor. The environment we developed is based upon the integration of a CAD, an Augmented Reality tool, a Leap Motion Controller device, see-through glasses and an algorithm for disassembly strategies evaluation: this approach guarantees a more effective interaction with the 3D real and virtual assembly than an approach relying only on a CAD based disassembly sequence planning. In such a way, the operator may not test in a more natural and intuitive way automatic disassembly sequences, but he/she can also propose different strategies to improve the ergonomics. The methodology has been tested in a real case study to evaluate the strength points and criticalities of this approach.
Abstract: This paper presents the development of a CAD conceived to support the modelling of lightweight and lattice structures just from the initial stages of the design process. A new environment, called LWSM (acronym of LightWeight Structures Modelling), has been implemented in Python programming language in an open-source CAD software to allow the fast modelling of several sandwich structures or the filling of solid parts with cubic and tetrahedral lattice structures which can be produced by Additive Manufacturing (AM) techniques. Several tests have been carried out to validate the tool, one of which is included in the paper. The design of a bracket component inside LWSM using a traditional dense geometry and a lattice structure is described. The use of Design for Additive Manufacturing (DfAM) functions helps the user in the design of innovative structures which can produced only with AM technologies. A significant change in the shape of the part respect to traditional solutions is noticed after the use of DfAM functions by experimenters: FEM analysis confirms a strong weight reduction.
Abstract: PMI annotations are widely used to support the Model Based Design within modern companies. In particular, the introduction of digital annotations marks the transition from the 2D drawings to the 3D representation in many manufacturing and design companies. However, today the implementation of the PMI technology presents some limits, such as the lack of functions to generate structure templates to be applied to similar CAD models. The proposed approach aims to overcome the limits of traditional tools which are not able to add a PMI annotation’s structure from one model to another one. The paper describes a method to reuse digital PMI annotations in a new model during the design phase, where the annotations are inherited from similar CAD documents. The proposed approach is based on two levels of geometric analysis: the searching of similar template models from an XML database, and the identification of the related geometric entities, which are used as associated objects for the definition of 3D annotations. The test case is focused on the automatic generation of PMI annotations for exhaust duct items used in oil & gas applications. The proposed tool has been developed within a software program called Duct Designer, which is used for the CAD automation of duct items. Particularly, the test case enhances the retrieval and reuse of sizing schemes from previous 3D models in order to obtain an automatic rebuilding of the geometric annotations.
Keywords: Digital annotations | Model-based definition (MBD) | Oil & gas | Product manufacturing information (PMI)
Abstract: Sintering shrinkage of uniaxially cold compacted axi-symmetrical parts is anisotropic. Not only is the shrinkage of height (parallel to the compaction direction) different from that of the diameters (in the compaction plane), but even the dimensional changes of the inner and of the outer diameters differ significantly. This behaviour has been investigated on iron rings with different geometry and green density. In the compaction plane radial and tangential shrinkages are different, and tangential shrinkage significantly changes along the wall thickness. This is due to the distribution of radial and tangential stresses during cold compaction that in turn depends on the axial stress. The stress field and its dependence on both green density and geometry were hypothesized to propose a working direction to interpret the anisotropy of sintering shrinkage in real parts.
Keywords: Geometry | Green density | Sintering shrinkage
Abstract: A feasibility study was performed in order to demonstrate the benefits of designing and manufacturing a customized foot orthosis by means of digital technologies, such as Reverse Engineering (RE), Generative Design (GD) and Additive Manufacturing (AM). The aim of this work was to define the complete design-manufacturing process, starting from the 3D scanning of the human foot anatomy to the direct fabricating of the customized foot orthosis. Moreover, this first methodological study tries to combine a user-friendly semi-automatic modelling approach with the use of low-cost devices for the 3D laser scanning and the 3D printing processes. Finally, the result of this approach, based on digital technologies, was also compared with that achieved by means of conventional manual techniques.
Abstract: The paper presents a description of a methodology to accurately estimate the natural frequencies of a hybrid metal-composite gear, where the web is made of a polymer matrix reinforced with two-dimensional (2D) triaxial braided fabrics. The proposed approach is based on a multi-scale composite modeling starting from evaluation of homogenized material properties of the gear web at the meso-scale for a subsequent FE-based modal analysis. For this purpose, the mechanical behavior of a single Repetitive Unit Cell (RUC) at the meso-scale is analyzed with a FE procedure which takes into account the interweaving and cross-section geometry of the yarns, volume fraction and local fiber orientation. It is shown that the described modeling strategy allows to predict gear's natural frequencies that are close to the experimental results. Significant accuracy enhancement is achieved with respect to the model in which the web material is considered as perfectly isotropic.
Abstract: Titanium and its alloys are widely used in cranioplasty because they are biocompatible with excellent mechanical properties and favor the osseointegration with the bone. However, when Titanium alloys have to be worked several problems occurred from a manufacturing point of view: the standard procedure for obtaining Titanium prostheses is represented by the machining processes, which result time and cost consuming. The aim of this research consist to introduce alternative flexible sheet forming processes, i.e. Super Plastic Forming (SPF) and Single Point Incremental Forming (SPIF), for the manufacturing of patient-oriented titanium prostheses. The research activities have already highlighted the potentiality of the investigated forming processes that can be alternatively used taking into account both the damage morphology and the need of urgency operation. In the present work, the way of manufacturing the Ti prostheses by SPF and SPIF is described. A comparative analysis has been performed, thus highlighting the peculiarities of the investigated processes and the prostheses feasibility.
Keywords: Single Point Incremental Forming | Super Plastic Forming | Titanium alloy
Abstract: We present the stress analysis of a pouring concrete device. In order to test the prototype of a pouring concrete equipment composed of fivearms with hollow rectangular cross sections, an extensive study about equipment for pouring concrete has been undertaken. An upgrade of a four-arms device already existing and actually working would be developed. Tests have been performed both on the prototype of the equipment and on a virtual model of the device, performed by a 3D CAD modeler and analyzed through FEM numerical programs. During experimental tests, a laser device has measured deflections at the end of the fifth arm, corresponding to applied loads. For measuring strains in the critical points highlighted by the numerical simulation strain rosette have been employed. In both the static and the dynamic conditions, Mohr's circles have been drawn from the 3D strain state and the 2D plane stress experimental records and they have been compared with those predicted through the finite element analysis. From the comparison between numerical and experimental results, a very good correlation has been obtained for static loading to assess the soundness of the virtual model.
Keywords: Articulated device | CAD | FEM | Mohr's circle | Strain analysis
Abstract: Hybrid Manufacturing (HM) is oriented to combine the advantages of additive manufacturing, such as few limits in shape reproduction, good customization of parts, distributive production, minimization of production costs and minimization of waste materials, with the advantages of subtractive manufacturing, in terms of finishing properties and accuracy of dimensional tolerances. In this context, our research group presents a design technique that aims to data processing that switches between additive and subtractive procedures, to the costs and time of product-manufacturing optimization. The component prototyping may be performed combining different stages (addiction, gross milling, fine milling, deposition…) with different parameters and head/nozzles and is able to work with different materials either in addictive, either in milling. The present paper is dedicated to introduce different strategies, or in other terms, different combinations of machining features (addictive or deductive) and different materials to complete a prototype model or mold. The optimization/analys ispiece of software is fully integrated in classic CAD/CAM environment for better supporting the design and engineering processes.
Abstract: During manufacturing, porcelain whiteware changes its shape due to the sintering process. For this reason, leader companies in the field of ceramics apply strict controls on final products in order to reach high quality standards. Typically, three quality parameters are considered: drop of the bottom, bending of the rim and roundness. To date, the assessment of such parameters is still based on visual inspections and manual measurements. In the present paper, authors propose a new quality assessment procedure based on reverse engineering (RE), able to measure the most relevant quality parameters in an effective, reliable and repeatable way.
Keywords: 3D model | 3D reconstruction | 3D scanning | measurement | porcelain | porcelain tableware | quality control | quality parameters | reverse engineering | whiteware
Abstract: Body scanning presents unique value in delivering the first digital asset of a human body thus resulting a fundamental device for a range of applications dealing with health, fashion and fitness. Despite several body scanners are in the market, recently depth cameras such as Microsoft Kinect® have attracted the 3D community; compared with conventional 3D scanning systems, these sensors are able to capture depth and RGB data at video rate and even if quality and depth resolution are not optimal for this kind of applications, the major benefit comes from the overall acquisition speed and from the IR pattern that allows poor lighting conditions optimal acquisition. When dealing with non-rigid bodies, unfortunately, the use of a single depth camera may lead to inconsistent results mainly caused by wrong surfaces registration. With the aim of improving existing systems based on low-resolution depth cameras, the present paper describes a novel scanning system for capturing 3D full human body models by using multiple Kinect® devices in a compact setup. The system consists of an instantaneous scanning system using eight depth cameras, appropriately arranged in a compact wireframe. To validate the effectiveness of the proposed architecture, a comparison of the obtained 3D body model with the one obtained using a professional Konica Minolta Range Seven 3D scanner is also presented and possible drawbacks are hinted at.
Keywords: 3D modelling | Body scanning | Custom Avatar | Depth Camera | Model Fitting
Abstract: Modular product design is an efficient strategy to let manufacturing companies meet the customers' requirements by offering a wide variety and customization of products and significantly saving time and cost during engineering and production (Fei et al., 2011). Despite numerous approaches for function modeling and modular product design (Srinivasan et al., 2012; Eckert, 2013; Vermaas, 2013) that have been developed in the last decades, carrying out an efficient product variants' design process is still an open issue for many manufacturing companies. The proposed approaches offer numerous ways to model information about product functionality, but each approach is useful and particularly well suited for different applications and domains (Summers et al., 2013). The present research compares the existing approaches for product variants design and defines a function-based model to support product design and redesign according to a modular framework, merging qualitative technical issues with business-oriented evaluation. Such a framework has been used to develop a multiuser IT platform, composed of a knowledge-based engine and four different tools to support designers and engineers in product variants creation, management, and configuration, from product functional modeling to cost estimation and life cycle assessment. The proposed model has been tested on industrial cases in the context of household appliances. Experimental results demonstrates that, after a preliminary context analysis and a proper knowledge base creation, such a model supports a more conscious decision-making and promote collaboration within an interdisciplinary design team. Finally, the case study shows the necessity, but in the meanwhile the insufficiency, of a functional decomposition as the only representation viewpoint.
Keywords: Computer-Aided Design | Design Methods | Function Modeling | Product Family and Platform | Product Modeling
Abstract: Cost estimation is a critical issue for many companies concerning both offers generation and company strategic evaluations. In this paper, a framework for early cost estimation has been proposed to some firms for an assessment of its main features. The aim of the industrial survey is to promote a discussion on the needs and the expectations regarding cost estimation in order to obtain feedbacks to be addresses in the implementation of a software tool. Gather data has led to a ranking of the main characteristics the tool should have.
Keywords: CAD | Design to Cost | Early cost estimation | Knowledge-based engineering | PLM | Product configuration
Abstract: In this research activity, a new methodology for the synthesis of hand exoskeleton mechanisms has been developed and validated through real prototypes. The innovative methodology is based on a new parallel mechanism and has been tested by building a robotic assistive device for hand opening disabilities applied to real cases. The studied robotic orthosis is designed to be a low-cost, adaptable and portable hand exoskeletons to assist people with hand opening disabilities in their activities of daily livings. As regards the methodology for the synthesis of hand exoskeleton mechanism, the authors propose to use a motion capture system to acquire the real hand phalanx trajectories and the geometrical characteristics of the patient’s hand, and to use optimization algorithms to properly defines the novel kinematic mechanism that better fits the finger trajectories. The preliminary testing phase of the prototype on a single patient is concluded; currently, through the collaboration with an Italian rehabilitation center, a group of patients are testing the proposed HES methodology.
Keywords: Hand exoskeleton | Hand opening disabilities | Kinematic synthesis | Portable and wearable robotics
Abstract: Shape from shading (SFS) denotes the problem of reconstructing a 3D surface, starting from a single shaded image which represents the surface itself. Minimization techniques are commonly used for solving the SFS problem, where the objective function is a weighted combination of the brightness error, plus one or more terms aiming to obtain a valid solution. We present a regularized quadratic penalty method where quadratic penalization is used to adaptively adjust the smoothing weights, and regularization improves the robustness and reliability of the procedure. A nonmonotone Barzilai–Borwein method is employed to efficiently solve the arising subproblems. Numerical results are provided showing the reliability of the proposed approach.
Abstract: The design of an aid for the hand function based on exoskeleton technologies for patients who have lost or injured hand skills, e.g. because of neuromuscular or aging diseases, is one of the most influential challenge in modern robotics to assure them an independent and healthy life. This research activity is focused on the design and development of a low-cost Hand Exoskeleton System (HES) for supporting patients affected by hand opening disabilities during the Activities of Daily Living (ADLs). In addition, the device, able to exert suitable forces on the hand, can be used during the rehabilitative sessions to implement specific tasks useful to restore the dexterity of the user’s hand. The validating and testing phase, conducted in collaboration with the Don Carlo Gnocchi Foundation, showed satisfying results both in terms of portability and wearability which are fundamental requirements for assistance during the Activities of Daily Living (ADLs) and for rehabilitation of people with hand impairments.
Abstract: An engineering design process consists of a sequence of creative, innovative and routine design tasks. Routine tasks address well-known procedures and add limited value to the technical improvement of a product, even if they may require a lot of work. In order to focus designers work on added value tasks, the present work aims at supporting a routine task with a Design Archetype (DA). A DA captures, stores and reuses the design knowledge with a tool embedded in a CAD software. The DA algorithms drive the designer in selecting the most effective design concept to deliver the project requirements and then embody the concept through configuring a CAD model. Finally, a case study on the definition of a DA tool for gear design demonstrates the effectiveness of the DA tool.
Abstract: Sustainability is becoming one of the main drivers of the modern product and system design. However, sustainability assessments are usually carried out at the end of the design process to check the validity of the decisions already taken. As a consequence, when targets are not achieved, numerous time-consuming iteration loops are necessary to optimize the initial solution. The paper merges functional-based and design-to-cost approaches to propose a CAD-based platform able to assess product lifecycle costs and impacts from the earliest design stages by configuring and assessing feasible design solutions. It considers both economic expenses and environmental impacts during all phases of product lifecycle on the basis of the company knowledge.
Abstract: 3D face was recently investigated for various applications, including biometrics and diagnosis. Describing facial surface, i.e. how it bends and which kinds of patches is composed by, is the aim of studies of Face Analysis, whose ultimate goal is to identify which features could be extracted from three-dimensional faces depending on the application. In this study, we propose 105 novel geometrical descriptors for Face Analysis. They are generated by composing primary geometrical descriptors such as mean, Gaussian, principal curvatures, shape index, curvedness, and the coefficients of the fundamental forms, and by applying standard functions such as sine, cosine, and logarithm to them. The new descriptors were mapped on 217 facial depth maps and analysed in terms of descriptiveness of facial shape and exploitability for localizing landmark points. Automatic landmark extraction stands as the final aim of this analysis. Results showed that some newly generated descriptors were sounder than the primary ones, meaning that their local behaviours in correspondence to a landmark position is thoroughly specific and can be registered with high similarity on every face of our dataset.
Keywords: 3D face | Face analysis | Face expression recognition | Face recognition | Geometry | Landmarks
Abstract: 3D face was recently investigated for various applications, including biometrics and diagnosis. Describing facial surface, i.e. how it bends and which kinds of patches is composed by, is the aim of studies in Face Analysis, whose ultimate goal is to identify which features could be extracted from three-dimensional faces depending on the application. In this study, we propose 54 novel geometrical descriptors for Face Analysis. They are generated by composing primary geometrical descriptors such as mean, Gaussian, principal curvatures, shape index, curvedness, and the coefficients of the fundamental forms. The new descriptors were mapped on 217 facial depth maps and analysed in terms of descriptiveness of facial shape and exploitability for localizing landmark points. Automatic landmark extraction stands as the final aim of this analysis. Results showed that the newly generated descriptors are suitable to 3D face description and to support landmark localization procedures.
Keywords: 3D Face | Face Analysis | Face Recognition | Geometry | Landmarks
Abstract: This article focused on the study of the influence of morphological parameters on the mechanical performance (Young's modulus) of Cellulose Acetate-Graphene Oxide nanocomposites produced by Supercritical CO2 assisted phase inversion, by means of an algorithm managing two parametric variational 3D finite element (FE) models simulating micro- and nano-level of the nanocomposite. Micro-level showed interconnected spherical pores, while nano-level showed a dispersion of not fully exfoliated graphene sheets. 3D FE model exploited the periodic representative volume element (PRVE) concept and accounted for the nanocomposite morphology as determined from Field Emission Scanning Electron Microscopy (FESEM) experiments. Model predictions were compared with experimental results obtained by compression tests at different weight percentages of graphene oxide with respect to the polymer. Once validated, such a FE simulation procedure allows to know in advance which and how to vary the geometrical parameters during the nanocomposite production to improve its final mechanical performance.
Abstract: In the present work, by means of an integrated approach, a new rear suspension for motorcycles, able to achieve the required progressiveness in terms of rigidity by using a constant-stiffness spring and a compact mechanism, has been studied. The key component is an eccentric system inserted in the shock absorber head. As reference, we analyzed the rear suspension of the Ducati Multistrada MY 2010, characterized by the use of a variable-stiffness spring. The aim of the paper is to prove that the new proposed solution can obtain a response, in terms of load to the wheel, similar to that of the actual system. At first, a mathematical model to simulate the kinematics of the new suspension is presented. This model is able to evaluate the influence of geometric dimensions of the components, checking successfully the ability to reproduce the behavior of the original suspension. After the preliminary design, the kinematic and static models are included within an optimization algorithm ad-hoc created to calculate the exact dimensions of each component. Two Matlab/Simulink® lumped mass models, respectively referred to the novel and reference suspension, are used to compare the dynamic responses during the travelling of a particular road profile used in Ducati’s experimental tests. Finally, an accurate modeling of the components, considering also the production processes to be used for their creation, is provided.
Abstract: Material behavior depends on average peak temperature, stress magnitude and stress gradient. This assumption is valid since temperatures varies slowly when compared to pressure (stress). In this paper, a RR Merlin head is simulated with a few mathematical models used in Formula 1 racing. These extremely simplified models make it possible to evaluate temperatures and pressures starting from very few data. The method is described in detail, along with the many experimental coefficients available from several years of design activity. A step by step approach is used to allow the comprehension of this method that was developed by the Authors. The choice of the RR Merlin was dictated by the public availability of experimental data on temperatures. In fact, in the case of the RR Merlin XX, very reliable experimental results are available in NACA TN 2069. A reverse engineering process was applied on a rescued RR Merlin XX head. An accurate redesign was performed to obtain a 3D model. Assembly instructions and tolerances were found on original Rolls Royce overhaul manuals. In this way assembly and working loads were calculated and simulated. Nonlinear FEA analysis was performed on this CAD model with extremely satisfactory results for the thermal loads. Well known criticalities of the original design were found. The results were compared with NACA results both for heat rejection and temperatures. However, the mechanical stresses proved to be more critical for simulation and evaluation. Therefore, they will be discussed in another, dedicated paper.
Abstract: An innovative method of tool wear assessment, based on the digitization of the cutting tool performed by a piezoelectric 3D scanner and on the analysis of the surfaces of a 3D model generated using the Reverse Engineering technique, has been developed. To this purpose, face milling experiments were carried out under dry cutting condition on AISI 420 B stainless steel using inserts in cemented carbide, with a two-layers coating (TiN and TiAlN). The time dependence of the insert wear was analysed by interrupting milling at predetermined time values. The proposed approach has been validated by comparing the output provided by the reverse engineering method to that measured experimentally by analysing the worn insert images obtained using a stereo microscope. An excellent agreement between the results given by the two different methodologies has been found. The worn tools have also been analysed using the scanning electron microscopy technique in order to understand the wear mechanisms operating during dry milling.
Abstract: Aim of this paper is to analyse and compare the characteristics of Feature Based and Direct Modeling techniques to determine their pros and cons for typical design processes. The first is one of the most common approach to create CAD models to be used for the machining phase of mechanical parts and assemblies. The second is a new method, alternative to the first one, based on a user-friendly approach, without rigid rules and constraints, that could represent the future of the CAD methodologies. Moreover, the Surface Modeling approach is analyzed and compared to the others, due to its common use in automotive and aeronautics fields. Considering the Feature Based Modeling as benchmark, three case studies were analysed to examine the peculiarities of these techniques, and to determine and highlight their advantages and their drawbacks. Several aspects were contemplated to perform the tests: the execution time for the realization of each operation, the easiness to create features and geometries, the possibility to adequately modify and upgrade the models and the number of operations needed to get the complete virtual prototype. In the end, the results were analysed and discussed focusing the attention on the possibility to adopt the Direct Modeling as substitute of the Feature Based and/or Surface Modeling and of the current CAD techniques.
Keywords: CAD | Direct modeling | Feature based modeling | Fuselage | Main landing fear | Surface modeling | Top-down approach | Virtual prototyping | Wing
Abstract: 3D inspection process is getting more and more interest for manufacturing industries as it helps to carefully check the expected quality of the released products. Much more attention is oriented to optical devices able to quickly capture the whole shape of the product providing many useful information on the process variability and the deliverability of the key characteristics linked to the quality of the product/process. Although the optical control of 3D scanners is mature enough, many factors may influence the quality of the scanned data. These factors may be strictly related to internal elements to the acquisition device, such as scanner resolution and accuracy, and external to it, such as proper selection of scanning parameters, ambient lighting and characteristics of the object surface being scanned (e.g. surface colour, glossiness, roughness, shape), as well as the sensor-to-surface relative position. For the 3D laser-based scanners, the most common on the market, it would be of great industrial interest to study some scanning factors mainly affecting the quality of the 3D surface acquisitions and provide users with guidelines in order to correctly set them so to increase the massive usage of these systems in the product inspection activities. In this context, by using a commercial triangulation 3D laser scanner, the effects of some scanning factors that may affect the measurement process were analysed in the present paper. Working on a sheet metal test part, more complex than the ones commonly used in laboratory and documented in the literature, the scanner-to-object relative orientation and the ambient lighting, as well as an internal scanner parameter, were tested. Through a Design of Experiments (DoE) approach, and setting root mean square error (RMSE) as response function, the outcomes of the tests mainly pointed out that the scanner-to-object relative orientation as well as its position within the field of view of the measurement device are the key factors mostly influencing the accuracy of the measurement process.
Keywords: 3D inspection process | 3D laser scanner | Design of Experiments | Surface acquisition
Abstract: In this work we present a preliminary study on a system able to design automatically sockets for lower-limb prosthesis. The socket is the most important part of the whole prosthesis and requires a custom design specific for the patient’s characteristics and her/his residuum morphology. The system takes in input the weight and the lifestyle of the patient, the tonicity level and the geometry file of the residuum, and creates a new model applying the correct geometric deformations needed to create a functional socket. In fact, in order to provide the right fit and prevent pain, we need to create on the socket load and off-load zones in correspondence of the critical anatomical areas. To identify the position of such critical areas, several neural networks have been trained using a dataset generated from real residuum models.
Abstract: This paper introduces the novel concept of fixture capability measure to determine fixture layout for the best assembly process yield by optimizing position of locators and reference clamps to compensate stochastic product variations and part deformation. This allows reducing the risk of product failures caused by product and process variation. The method is based on three main steps: (i) physics-based modelling of parts and fixtures, (ii) stochastic polynomial chaos expansion to calculate fixture capability, and (iii) fixture capability optimisation using surrogate modelling. The methodology is demonstrated and validated using the results of an aerospace wing sub-assembly joined by riveting technique.
Abstract: Nowadays, the creation of methodologies and tools for facilitating the 3D reproduction of artworks and, contextually, to make their exploration possible and more meaningful for blind users is becoming increasingly relevant in society. Accordingly, the creation of integrated systems including both tactile media (e.g., bas-reliefs) and interfaces capable of providing the users with an experience cognitively comparable to the one originally envisioned by the artist, may be considered the next step for enhancing artworks exploration. In light of this, the present work provides a description of a first-attempt system designed to aid blind people (BP) in the tactile exploration of bas-reliefs. In detail, consistent hardware layout, comprising a hand-tracking system based on Kinect® sensor and an audio device, together with a number of methodologies, algorithms and information related to physical design are proposed. Moreover, according to experimental test on the developed system related to the device position, some design alternatives are suggested so as to discuss pros and cons.
Keywords: 3D reconstruction | Blind people | Hand-tracking system | Kinect sensor
Abstract: In this paper a novel approach, enabling rapid time to market and making shoe collaborative design effectively possible, will be presented. The solution suggested in this work consists of two elements: first, the implementation of a SolidWorks add-on called SYS (SYstem Shoe) whose main goal is to provide a widespread CAD software packages with specific features for shoe design; secondarily the development of a web platform, capable to communicate with and control the SYS add-on. This platform provides the unique opportunity of making the entire system (installed on a server PC) available to external users (small factories concurring to the shoe production chain), without the need of a CAD software own installation. The scenario in which the described system is supposed to work consists of a inter-company network with a main node equipped with the web-CAD platform. This main node acts as a server towards the peripheral nodes (clients: shoe assembly and component-making companies).
Abstract: Reverse Engineering (RE), also known as "CAD reconstruction", aims at the reconstruction of 3D geometric models of objects/mechanical parts, starting from 3D measured data (points/mesh). In recent years, considerable developments in RE were achieved thanks to both academic and industrial research (e.g. RE software packages). The aim of this work is to provide an overview of state of the art techniques and approaches presented in recent years (considering at the same time tools and methods provided by commercial CAD software and RE systems). In particular, this article focuses on the "constrained fitting" approach, which considers geometrical constraints between the generated surfaces, improving the reconstruction result. On the basis of the overview, possible theoretical principles are drafted with the aim of suggest new strategies to make the CAD reconstruction process more effective in order to obtain more ready/usable CAD models. Finally, a new RE framework is briefly outlined: the proposed approach hypothesizes a tool built within the environment of an existing CAD system and considers the fitting of a custom-built archetypal model, defined with all the a-priori known dimensions and constraints, to the scanned data.
Abstract: The stylistic design of new industrial products often starts from shaded handmade sketches which, usually, need to be converted into 3D digital models by using CAD software packages for the subsequent design phases. This conversion often represents the bottleneck of the whole development process. Shape from Shading (SFS), which attempts to recover the 3D geometry of an object starting from a single shaded representation, is potentially capable of speeding-up the 3D conversion. However, existing approaches prove to be extremely unstable and error prone mainly due to the under-determination of the SFS problem. In order to increase the performance of shading based reconstruction authors propose a step-by-step variational-based approach. In particular, the problem is solved into multiple steps, each one providing the initialization for the following, so that the solution gradually converges towards the final surface. Tested against a set of case studies, the method proved its effectiveness.
Keywords: 3D design | Computer aided design | Numerical optimization | Shape from shading | Stylistic content | Variational approach
Abstract: Minimization techniques are widely used for retrieving a 3D surface starting from a single shaded image i.e., for solving the shape from shading problem. Such techniques are based on the assumption that expected surface to be retrieved coincides with the one that minimize a properly developed functional, consisting of several contributions. Among the possible contributes defining the functional, the so called "smoothness constraint" is always used since it guides the convergence of the minimization process towards a more accurate solution. Unfortunately, in areas where actually brightness changes rapidly, it also introduces an undesired over-smoothing effect. The present work proposes two simple yet effective strategies for avoiding the typical over-smoothing effect, with regards to the image regions in which this effect is particularly undesired (e.g., areas where surface details are to be preserved in the reconstruction). Tested against a set of case studies the strategies prove to outperform traditional SFS-based methods.
Keywords: 3D model | Minimization | Shape from shading | Smoothing | Smoothness constraint | Variational approach
Abstract: The work described in the paper is motivated by the lack of computer-aided tools to support Product Planning and, more specifically ideation processes of New Product Development (NPD) initiatives. The domain is populated by software applications aimed at managing and organizing Product Planning activities, which thus poorly contribute to the definition of new product characteristics, and models to stimulate novel ideas. The latter face limitations in terms of overlooked implementation with CAD tools supporting the following NPD phases and poor exploration of the design space. The authors propose an original method and software prototype capable to provide a wide range of stimuli, whose testing demonstrated much better results than traditional approaches in terms of quantity and variety of generated ideas.
Keywords: CAD | idea generation | New Product Development | product attributes | Product Planning | Value Dimensions
Abstract: A methodology for integrating the CAD-CAE design of a chain drive system is presented by evaluating meshing angles. The methodology correlates the angles of engagement with transverse vibrations and the tensile force of the chain links, showing that the dynamic behaviour of a chain drive can be significantly improved by fine tuning the meshing angles. An objective parameter was introduced to evaluate divergence from correct meshing. Here the methodology is applied to optimize the timing chain system of a high power V12 quadruple overhead camshaft engine. The reliability of the method relies on multibody modelling all the components and accurate experimental tests. Correlating the experimental measurements provided exact modelling of the contact forces, exact evaluation of stiffness and damping values and precise dynamic modelling of the tensioners and guides. Finally, the dynamic performance of the two different primary stage chain drive layouts were compared.
Keywords: Chain stiffness | Contact force model | Meshing impact | Multibody dynamics | Tensioner | Transverse vibration
Abstract: Despite of the widespread of annotated 3D virtual models, it is still important to produce engineering drawings for a correct communication among the people of the design and manufacturing chain. Automatic drafting through meta drawing definitions, called Drafting Schemes, is proposed in this paper to save time when drawing becomes a repetitive task. The approach produces drafts with a predetermined content in terms of views arrangement and dimensioning strategy, and guarantees robust results to the variations of the input geometry. In fact, the geometrical entities referenced by the generated dimensions are retrieved through dedicated search algorithms based on recognition of geometric features of the input model. The approach has been implemented and tested on a family of gear motors showing feasibility and good results in terms of drafting time savings.
Keywords: Design Automation | Drafting | Feature Recognition | Knowledge Based Systems
Abstract: Technical knowledge and experience are intangible assets crucial for competitiveness. Knowledge is particularly important when it comes to complex design activities such as the configuration of manufacturing systems. The preliminary design of manufacturing systems is subject to a huge variability of inputs and outputs and involves decisions which must satisfy many competing requirements. This early engineering phase relies mostly on experience of designers and engineers and is associated with long lead times and high probability of mistakes. Knowledge-Based Engineering (KBE) and knowledge representation techniques are considered to be a successful way to tackle this design problem at an industrial level. This paper presents a methodology to support the configuration of powertrain assembly lines, reducing design times by introducing a best practice for production systems provider companies. The methodology is developed in a real industrial environment, introducing the role of a knowledge engineer. The approach includes extraction of existing technical knowledge and implementation in a knowledge-based software framework. The framework is then integrated with other software tools allowing the first phase design of the line including the line technical description and a 2D and 3D CAD line layout. The KBE application is developed and tested on a specific powertrain assembly case study for which existing knowledge is collected, formalised, implemented in the application and integrated with existing tools. Finally, the paper presents a first validation among design engineers, comparing traditional and new approaches and estimating a cost-benefit analysis useful for future possible KBE implementations.
Abstract: The present work collects some results of the three-years Research Program "BioForming", funded by the Italian Ministry of Education (MIUR) and aimed to investigate the possibility of using flexible sheet forming processes, i.e. Super Plastic Forming (SPF) and Single Point Incremental Forming (SPIF), for the manufacturing of patient-oriented titanium prostheses. The prosthetic implants used as case studies were from the skull; in particular, two different Ti alloys and geometries were considered: one to be produced in Ti-Gr23 by SPF and one to be produced in Ti-Gr2 by SPIF. Numerical simulations implementing material behaviours evaluated by characterization tests were conducted in order to design both the manufacturing processes. Subsequently, experimental tests were carried out implementing numerical results in terms of: (i) gas pressure profile able to determine a constant (and optimal) strain rate during the SPF process; (ii) tool path able to avoid rupture during the SPIF process. Post forming characteristics of the prostheses in terms of thickness distributions were measured and compared to data from simulations for validation purposes. A good correlation between numerical and experimental thickness distributions has been obtained; in addition, the possibility of successfully adopting both the SPF and the SPIF processes for the manufacturing of prostheses has been demonstrated.
Abstract: Cranioplasty is a surgery in which a prosthesis must be anchored on skull bone to repair a defect. One of the most used materials is the titanium. However, titanium prostheses could be made using the incremental sheet forming (ISF). Since titanium and bone are characterized by different Young modules, a detailed design of anchoring system is required to avoid cranial rupture. Aim of this study was to present a design procedure in order to identify the optimal anchoring system in case of craniofacial prostheses made with ISF. In detail, an optimization process and a predictive model for bone stress were used, choosing the numerical outputs of different FEM analyses as input data. The results indicate that our predictive and optimization models are accurate and, so, that this procedure could be very helpful for the prosthesis design, as demonstrated by the application of the procedure to a real case study.
Abstract: Persian architecture is characterised by shapes and patterns, which can be analysed through mathematical models. Beside 2D patterns, many of the traditional geometric ornaments are realised on 3D surfaces such as domes or vaults. Literature mainly addresses the 3D problem by means of a 2D scheme, which is an important and synthetic representation but is not exhaustive and lacks of clarity. This paper proposes a framework based on the integration of 2D drawings, as in the traditional approach, and a photogrammetric 3D model based on a sample of standard resolution images (tourist pictures). The framework is tested on a muqarnas, a characteristic Persian ornament, in order to study and analyse its modular design and hierarchy of elements. As a case study, the entrance iwan of the Shah Mosque in Isfahan, Iran, is considered. The result is a link between the 3D patterns and the geometry of architectural elements, which completes and overcomes their schematic 2D representation.
Keywords: CAD modelling | Geometric analysis | Iwan | Modules | Muqarnas | Persian ornament | Representation of architecture
Abstract: A 3D automatic facial expression recognition procedure is presented in this work. The method is based on point-by-point mapping of seventeen Differential Geometry descriptors onto the probe facial depth map, which is then partitioned into seventy-nine regions. Then, features such as mean, median, mode, volumes, histograms are computed for each region and for each descriptor, to reach a varied large set of parameters representing the query face. Each set of parameters, given by a geometrical descriptor, a region, and a feature, form a trio, whose featuring numerical values are compared with appropriate thresholds, set via experimentation in a previous phase by processing a limited portion of the public facial Bosphorus database. This allows the identification of the emotion-based expression of the query 3D face among the six basic ones (anger, disgust, fear, joy, sadness, surprise). The algorithm was tested on the Bosphorus database and is suitable for applications in security, marketing, medical. The three-dimensional context has been preferred due to its invariance to different lightening/make-up/camouflage conditions.
Keywords: 3D face | Differential geometry | Emotions | Face expression recognition (FER) | Facial expression recognition | Shape index
Abstract: This study proposes a novel approach to automatically localise 11 landmarks from facial RGB images. The novelty of this method relies on the application, i.e., point-by-point mapping, of 11 differential geometry descriptors such as curvatures to the three individual RGB image components. Thus, three-dimensional features are applied to bidimensional facial image representations and used, via thresholding techniques, to extract the landmark positions. The method was tested on the Bosphorus database and showed global average errors lower than five millimetres. The idea behind this approach is to embed this methodology in state-of-the-art 3D landmark detection methods to accomplish a full automatic landmarking by exploiting the advantages of both 2D and 3D data. Some landmarks such as pupils are arduous to be automatically extracted only via three-dimensional techniques. Thus, this method is intended as a bridging-the-gap preliminary technique that takes advantages of 2D imaging only for integrating advanced landmark localisation methodologies.
Abstract: Digital documentation and high-quality 3D representation are always more requested in many disciplines and areas due to the large amount of technologies and data available for fast, detailed and quick documentation. This work aims to investigate the area of medium and small sized artefacts and presents a fast and low cost acquisition system that guarantees the creation of 3D models with an high level of detail, making the digitalization of cultural heritage a simply and fast procedure. The 3D models of the artefacts are created with the photogrammetric technique Structure From Motion that makes it possible to obtain, in addition to three-dimensional models, high-definition images for a deepened study and understanding of the artefacts. For the survey of small objects (only few centimetres) it is used a macro lens and the focus stacking, a photographic technique that consists in capturing a stack of images at different focus planes for each camera pose so that is possible to obtain a final image with a higher depth of field. The acquisition with focus stacking technique has been finally validated with an acquisition with laser triangulation scanner Minolta that demonstrates the validity compatible with the allowable error in relation to the expected precision.
Keywords: Cultural heritage | Focus stacking | Photogrammetry | Small artefacts | Structure from motion
Abstract: The present work aims at the development of an advanced control system implemented through Adams/View-Matlab/ Simulink co-simulation for a high-performance motorcycle dynamics study. In particular, the purpose of this study is to create a model able to consider several aspects of the rider-motorbike dynamic simulation and its control system, generally treated separately in the literature, making also use of an original and accurate modelling of the rider. From a previous multi-body model of motorcycle/virtual rider, developed by the authors, a flexible tool is created to simulate system dynamics to follow any trajectory at a prescribed velocity profile. Considering high-performance motorcycle dynamics are greatly influenced by the rider's weight, his movements have been accurately replicated to obtain the most realistic results. To simulate the passive impedance of rider's arms, a torque was applied to the steering as per the literature. The aerodynamic force was modelled as a function of kinematics variables and rider's posture. The control system is very flexible and adaptable to different manoeuvres realistically reproducing engine and braking performance, steering torque and rider movements. Numerical results show that the control system can accurately direct the motorcycle/ rider system along an entire lap of the Monza circuit, following a desired path at a given velocity profile. The model developed allows a complete view of the motorbike-rider dynamic behaviour thus being useful during both design phase and set-up, with a considerable saving in terms of both cost and time; it can also evaluate the influence on the system dynamics of riders with different anatomical characteristics and driving styles.
Abstract: The geometric segmentation of a discrete geometric model obtained by the scanning of real objects is affected by various problems that make the segmentation difficult to perform without uncertainties. Certain factors, such as point location noise (coming from the acquisition process) and the coarse representation of continuous surfaces due to triangular approximations, introduce ambiguity into the recognition process of the geometric shape. To overcome these problems, a new method for geometric point identification and surface segmentation is proposed. The point classification is based on a fuzzy parameterization using three shape indexes: the smoothness indicator, shape index and flatness index. A total of 11 fuzzy domain intervals have been identified and comprise sharp edges, defective zones and 10 different types of regular points. For each point of the discrete surface, the related membership functions are dynamically evaluated to be adapted to consider, point by point, those properties of the geometric model that affects uncertainty in point type attribution. The methodology has been verified in many test cases designed to represent critical conditions for any method in geometric recognition and has been compared with one of the most robust methods described in the related literature.
Abstract: The present paper proposes a new method for axis identification in discrete axially symmetrical geometric models. This method is based on-a-never-used-before property of the axially symmetrical surfaces for which the symmetry line of any section curve of the surface (or of a portion of it in the case of an incomplete axially symmetrical surface) always intersects the axis of symmetry of the surface. Thus the working principle of the method makes it very robust to local defectiveness, measurement noise and outliers. In order to compare it with the most cited methods presented in literature, several types of tests have been designed and performed. The robustness of those methods, on the one hand, has been evaluated by defining the Statistical Confidence Boundary at 1σ confidence level. The trueness of the method, on the other hand, has been evaluated on geometric models obtained by measuring real objects. The high robustness, which characterizes the proposed method, makes it particularly suitable for product geometric inspection where high accuracy is required.
Abstract: The paper deals with the relationship between geometrical or topological entities of complex systems and the physics in which the systems are involved. In particular, the paper deepens the integration of thermal physics with geometrical constraints. Therefore, the results of the work could be used within the development of a 3D-multiphysical sketcher viz., a tool for the preliminary design of complex systems, characterized by the presence of one or more overlapping physics. Firstly, the model of Topologically & Technologically Related Surfaces (TTRS) is used and related Minimal Reference Geometrical Elements (MRGEs) and constraint conditions are implemented by means of Modelica language. Then, the implementation of new objects for MRGEs and constraint conditions are applied to a mechanical assembly. Finally, the integration of TTRS model within thermal physics is applied to the case of the layout designing for electronic boards.
Keywords: Modelica language | Multiphysics | preliminary design | TTRS