Virtual prototyping and digital twin

First aim of this paper is to describe a methodology developed to create virtual fragments of archeological archetypes in CAD (Computer Aided Design) environment. A simple Reverse Engineering (RE) technique was adopted to reconstruct the shape of vases allowing the archeologists, and so the CAD inexpert personnel, to use it. Moreover, another relevant aspect is the definition of a procedure to simulate shape errors on the virtual prototypes to make more realistic the results. The characteristics of the fragments to be reproduced were selected by means of Design of Experiment (DOE) techniques. So, an algorithm was implemented to simulate the shape error, related to the working operations, that represents the typical noise for the feature recognition of archeological findings. Furthermore, this algorithm can make more complex the hypotheses related to the Gaussian model of simulation of the error and can adapt the value of the shape error (i.e. increasing it) according to the data gathered in archaeological excavation. The case study was based on the definition of a catalogue of archetypes of the black Campanian vases studied and classified by the archeologist J.P. Morel. The procedure conceived was applied to five (among one hundred) vases of the virtual catalogue obtaining forty instances of fragments affected by errors and so creating virtual mock-ups of typical pieces which may be found in the archeological site considered for the case study.

Keywords: Archetype , Design of experiments , Geometric modeling , Profile reconstruction , Simulation of the shape and recognition errors

A critical point for manufacturing companies has always been the optimization of their production processes to increase the productivity and minimize the related costs, chasing an efficiency principle. Thanks to advent of Industry 4.0 (I4.0) era, some technologies, perceived as far away few years ago, now can be reached by everyone. The use of these technologies allows factories to acquire and evaluate their production data (and much more) and carry out complex analyses in short time making possible the improvement of the production processes. Aim of this paper is to propose a methodological framework in which, starting from an existing process, where workers and machines have already been assigned to each station of a production line, the use of Industrial Internet of Things (IIoT) devices, such as wearable ones, allows to carry out analyses of the performance parameters of the production lines by means of an event-based simulation. In this way it is possible to evaluate if improvements are possible by re-balancing or re-scheduling the line. A case study, regarding a manual task of a real manufacturing production line, is presented to demonstrate the applicability and the effectiveness of the described framework.

Keywords: Internet of Things , Line balancing , Methodological framework , Wearable devices

The International Fusion Materials Irradiation Facility-DEMO Oriented Neutron Source (IFMIF-DONES) consists of complex systems and massive components that need to be on site assembled and maintained. For several of them it is required to perform maintenance, inspection and monitoring tasks over many years in a hostile environment and in efficient, safe and reliable manner. The maintenance of IFMIF-DONES' systems and components, located mainly in the Test Systems (TS), in the Lithium Systems (LS) and in the Accelerator Systems (AS), is classified as a Remote Handling (RH) Class 1st activity and as such is considered a crucial and essential activity whose success will strictly depend on the IFMIF-DONES RH capability. According to this, a Remote Handling System (RHS) for IFMIF-DONES, which comprises the whole set of Remote Handling Equipment and tooling for the execution of maintenance tasks, has been designed. A wide range of technologies is involved: special cranes, manipulator arms, lift interface frames, special cameras, control systems and virtual reality. In this paper an overview on status of the design of the main robotic systems and tooling of the RHS of IFMIF-DONES, including design requirements, functions and maintenance tasks to be performed, is given.

Keywords: IFMIF-DONES , Maintenance , Remote handling maintenance

Soft continuum robots provide high dexterity in constrained spaces, while guaranteeing a compliant interaction with the surrounding environment. Over the last years, they have been used to improve many manipulation tasks, going from maintenance, inspection and repair in industrial-related environments to minimally invasive surgery in the medical field. This paper investigates the use of soft continuum robots for remote measurement tasks, and focuses on the following application scenarios where they have already demonstrated their benefits: space, aerospace, nuclear, marine and medical fields. The limitations of existing applications and perspectives of future directions are also discussed.

In this paper, a novel concept of robotic manipulator is developed for direct additive manufacturing on non-planar surfaces. The application scenario is the metal coating of the internal surface of radome systems, using frequency selective surface patterns. The manipulator is presented from the design, modeling, and control point of view. It is developed following an application-driven approach, meaning that the requirements from the application and the additive manufacturing technology are translated into the design specifications of the robotic system. Simulation results demonstrate that the proposed control strategy based on a decentralized architecture is satisfactory to accurately control the motion of the robotic mechanisms along the trajectory foresees by the direct additive manufacturing task.

Keywords: Additive manufacturing , Aerosol jet printing , Design method , Robot control , Virtual prototyping

Remote handling of heavy in-vessel components inside nuclear fusion reactors requires the use of large robotic mechanisms, whose numerical analysis is highly complex. As a matter of fact, these robots are subject to large deformations, either induced by the geometric configuration of their mechanical structure or by the heavy payloads they usually transport. This work was motivated by the need of deriving physical-based predictive models able to simulate the mechanical behavior of such large robotic mechanisms, while performing dynamic tasks. The method formulates the dynamics of robotic manipulators on a Lie group, and uses a finite element procedure to discretize the flexible bodies. The method is applied to a complex mechanism, the serial/parallel flexible manipulator which has been recently selected for DEMO blanket remote handling. The case studies investigated in this paper involve the simulations of this manipulator while handling the inboard and outboard blanket segments according to the sequence of maneuvers planned for their removal processes from the vessel. The results show that such dynamic simulations could give useful information for design, analysis and control of remote handling equipment. The generality of the method makes this approach prone to be easily used in simulating the dynamics of other flexible manipulators for remote handling of large in-vessel components inside nuclear fusion reactors.

Keywords: DEMO , Flexible manipulators , Remote maintenance , Robot dynamics , Tokamak

Nowadays, more than in the past, marine industries are paying increasing attention to the environmental impact of ships and vessels. Several solutions have been studied and adopted with the final aim of reducing the exhaust gas emissions, mainly acting on the fuel consumption reduction. Within this scenario, the aim of this article is to investigate the energy performance and the fuel saving potential when employing a magnetic continuously variable transmission in a marine propulsion system. Such magnetic continuously variable transmission, considered among other possible continuously variable transmission designs since its torque capabilities are perfectly suitable for the application at hand, is employed in order to optimize the overall propulsion efficiency through an appropriate optimal variation of the reduction ratio as a function of the propeller loads. A secondary benefit, although not less important, is that the magnetic continuously variable transmission is an oil-free transmission that consequently offers a lower environmental impact as compared to traditional lubricated gearboxes. Owing to these considerations, in the article, the magnetic continuously variable transmission size is first selected on the basis of a simplified static model of the vessel. Subsequently, a dynamic mathematical model representing the overall drivetrain dynamic of the propulsion plant is developed, with the purpose of simulating the transmission behaviour during fast ship manoeuvres. Then, in order to test the effectiveness of the proposed design, a trawler is selected as a case study. This particular ship type has been chosen as it provides a variegated operative profile in terms of speed and required thrust, thus being a representative case of those ships in which a continuously variable transmission installation could effectively provide practical benefits. A quantitative analysis of the plant efficiency is finally provided and critically discussed.

Keywords: continuously variable transmission , fuel consumption , Marine propulsion plant , ship energy efficiency , time domain simulation

At present, energy consumption strongly affects the financial payback period of industrial robots, as well as the related manufacturing process sustainability. Henceforth, during both design and manufacturing management stages, it becomes crucial to assess and optimize the overall energy efficiency of a robotic cell by means of digital manufacturing tools. In practice, robotic plant designers and managers should be able to provide accurate decisions also aimed at the energy optimization of the robotic processes. The strong scientific and industrial relevance of the topic has led to the development of many solutions but, unfortunately, state of the art industrial manipulators are equipped with closed controllers, which heavily limit the feasibility and performance of most of the proposed approaches. In light of the aforementioned considerations, the present paper presents a novel simulation tool, seamlessly interfaced with current robot offline programming tools used in industrial practices, which allows to automatically compute energy-optimal motion parameters, thus reducing the robot energy consumption, while also keeping the same productivity and manufacturing quality. The main advantage of this method, as compared to other optimization routines that are not conceived for direct integration with commercial industrial manipulators, is that the computed parameters are the same ones settable in the robot control codes, so that the results can automatically generate ready-to-use energy-optimal robot code. Experimental tests, performed on a KUKA Quantec KR210 R2700 prime industrial robot, have confirmed the effectiveness of the method and engineering tool.

Keywords: Automatic code generation , Energy optimization , Industrial robotics , Industry 4.0 , Robot offline programming , Sustainable manufacturing , Virtual prototyping

Elloboat is a tracked vehicle for launching and beaching of small boats and watercrafts, capable of operating in a wide range of operative conditions, here including rescue applications. This paper presents the vehicle architecture and discusses the main design issues. The effects of track dimensions on terrain compaction, bulldozing resistances and, consequently, on track sinkage are analyzed by means of the Bekker model. Obviously, track dimensions also influence the vehicle mass and size, leading to a complex engineering problem. Since vehicle speed and acceleration are limited, stability during locomotion can be assessed using a quasi-static approach, computing the longitudinal and lateral tipping angles for a given vehicle configuration and payload position, and imposing a proper limit to their minimum. Stability analysis can be exploited not only in the design phase, but also for the real-time evaluation of the actual margin of stability, so as to help the operator in the vehicle path/speed planning.

Keywords: Beaching , Bekker Theory , Launch , Small Boat , Tracked Vehicle , Watercraft

Robotic deburring (RD) still requires long and delicate physical tests to tune the process-parameters, thus drastically reducing the robotic cell productivity. Henceforth, engineering methods and tools are needed to optimise the RD application within a virtual environment, replicating the real behaviour of the robot tooling under different process conditions, namely unpredictable variety of burr size/shape and limited accuracy of the robot motions. To this purpose, the spindle compliance, which plays a fundamental role, is unfortunately not evaluated by state-of-the-art simulation tools. The present paper proposes a virtual prototype (VP) of a radially-compliant spindle, suitable to assess and optimise the deburring efficiency in different case scenarios. A multi-body model of the spindle, integrated with the process behavioural model, predicts process forces and optimal deburring parameters, delivering the contour maps of the envisaged deburring error as function of feed rate and tool compliance. An industrial case-study is provided.

Keywords: parameter design , passively compliant spindle , robotic deburring , virtual prototyping

Aim. To evaluate the biomechanical effects of four different auxiliary-aligner combinations for the extrusion of a maxillary central incisor and to define the most effective design through finite element analysis (FEA). Materials and Methods. A full maxillary arch (14 teeth) was modelled by combining two different imaging techniques: cone beam computed tomography and surface-structured light scan. The appliance and auxiliary element geometries were created by exploiting computer-aided design (CAD) procedures. The reconstructed digital models were imported within the finite element solver (Ansys® 17). For the extrusion movement, the authors compared the aligner without an attachment with three auxiliary-aligner designs: a rectangular palatal attachment, a rectangular buccal attachment, and an ellipsoid buccal attachment. The resulting force-moment (MF) system delivered by the aligner to the target tooth and the tooth displacement were calculated for each scenario. Results. The maximum tooth displacement along the z-axis (0.07 mm) was obtained with the rectangular palatal attachment, while the minimum (0.02 mm) was obtained without any attachments. With the ellipsoid attachment, the highest undesired moments Mx and My were found. The rectangular palatal attachment showed the highest Fz (2.0 N) with the lowest undesired forces (Fx = 0.4 N; Fy = -0.2 N). Conclusions. FEA demonstrated that the rectangular palatal attachment can improve the effectiveness of the appliance for the extrusion of an upper central incisor.

Although the so-called Industry 4.0 trend is promoting the increasing automation of processes in the factories of the future, manual activities still play an extremely important role within the factory and human factors greatly affect the process performance. However, the analysis of human-machine interaction and the prediction of human performance in industry are difficult but crucial to have an optimized design of workspaces and interfaces, reducing time and cost of implementation, and avoiding late design changes. This research adopts a multimodal human-centered approach for the analysis of human-machine interaction, and proposes a multimodal experimental set-up for the evaluation of the workers' experience to support the design of industrial workstations. The set-up combines virtual mockups, interaction with both physical and virtual objects, and monitoring sensors to track users and analyze their actions and reactions. It allows creating a multimodal environment able to deepen the interaction between humans and systems or interfaces, to support design activities. Indeed, it has been demonstrated that the analysis of the reactions of the users involved, allows to evaluate the quality of the interaction, identify the critical issues, define corrective actions, and propose guidelines for system design or redesign [1]. The paper describes the application of the proposed set-up on two industrial case studies and reports the main results. © 2019 Publicaciones Dyna Sl.

Keywords: Digital Manufacturing , Human Factors , Human-Centered Design , Industry 4.0 , Virtual Reality

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.

Keywords: 3D-reconstruction , Bronze statue restoration , Cultural heritage , Feature recognition , Virtual prototyping

Virtual, Augmented and Mixed Reality technologies are more and more getting attention from tourism researchers and professionals, because of their recognized potential to support marketing activities. The paper describes the development of a multisensory environment thought for a travel agency, which combines visual, auditory, tactile and olfactory stimuli. The idea is to develop an experience able to provide a virtual preview of the desired holiday destination, resulting in both an attractive experience for the customer and an effective way to increase sales. A case study about the multisensory experience of a walk on Italian Alps has been developed. The multisensory experience is based on a video streaming, recorded in the real environment, synchronously matched with a haptic interface. The haptic interface is made up of a pair of slippers provided with actuators, and also an actuator positioned on the customer trunk, used to reproduce the feeling of a snowball hit. Moreover, an olfactory display is also used to provide pine smell during the walk. During the experience, the user is sitting on a yoga ball, whose inclination allows him/her to start and stop the multisensory virtual experience.

Keywords: Multisensory simulation , User experience , Virtual prototyping , Virtual tourism

This paper describes the application of a novel virtual prototyping methodology to wind turbine blade design. Numeric modelling data and experimental data about turbine blade geometry and structural/dynamical behaviour are combined to obtain an affordable digital twin model useful in reducing the undesirable uncertainties during the entire turbine lifecycle. Moreover, this model can be used to track and predict blade structural changes, due for example to structural damage, and to assess its remaining life. A new interactive and recursive process is proposed. It includes CAD geometry generation and finite element analyses, combined with experimental data gathered from the structural testing of a new generation wind turbine blade. The goal of the research is to show how the unique features of a complex wind turbine blade are considered in the virtual model updating process, fully exploiting the computational capabilities available to the designer in modern engineering. A composite Sandia National Laboratories Blade System Design Study (BSDS) turbine blade is used to exemplify the proposed process. Static, modal and fatigue experimental testing are conducted at Clarkson University Blade Test Facility. A digital model was created and updated to conform to all the information available from experimental testing. When an updated virtual digital model is available the performance of the blade during operation can be assessed with higher confidence.

Keywords: Composite materials , Design , Digital twin , Finite element method , Modelling and simulation , Wind turbine

The pillars of Industry 4.0 require a modern smart factory to be integrated, store data into the Cloud, access the Cloud for data analytics and share information at software level for simulation and Hardware-In-the-Loop capabilities. The resulting Cyber-Physical System is often called Cyber-Physical Manufacturing System, and it becomes fundamental to cope with the increased system complexity and the desired performances. However, since a lot of old production systems are based on monolitic architectures, with limited external communication ports and reduced local computational capabilities, it is very difficult to make such production lines compliant to Industry 4.0 pillars. Wireless Sensor Network is a solution for the smart connection of a production line to a Cyber-Physical System architecture, data processing through Cloud Computing. The scope of this research work is to propose an intermediate layer within the architecture that allows each device, production line and machine to be independently connected despite the adopted protocol. The solution is based on OSGi Framework, which is able to seamlessly integrate both hardware and software wireless sensors, send data into the Cloud for further data analysis, and grant both Hardware-In-the-Loop and Cloud Computing capabilities. A general description of the architecture is here proposed, together with preliminary results on a real manufacturing line for data collection and analysis over a period of two months.

Keywords: Cyber-Physical Manifacturing System , Industry 4.0 , OSGi Framework , Wireless Sensor Network

Molding is one of the most widely used processing technologies in manufacturing. Among typical molding parameters, the mold temperature is a critical one for the quality of the molding process. A solution to this issue can be the employment of induction heating which, through a high-frequency electromagnetic field, produces eddy currents and a consequent rapid heating of the material into the cavity of the mold. The necessity to maintain the mold walls at the operative temperature makes the induction heating to be one of the most efficient non-contact means of heating. In fact, induction heating is characterized by quickness, efficiency, and energy saving; however, the design and the sizing of an induction heating system is complex due to different parameters involved in the electromagnetic and thermal phenomena. In this context, the paper aims to define a methodology to support engineers in the design and sizing of an induction heating system for molds, taking as case study a mold for composite parts. A model-based approach is proposed to analyze and simulate the mold heating, considering three different levels of modelling: Analytical (0D), Finite-Difference Methods (2D) and Finite Element Methods (3D). The Analytical approach investigates the solution of the physical equations applied to the volume of the material involved. Instead, the Finite-Difference approach (2D) solves the heat transfer problem by discretizing the domain and by solving for temperature at discrete points. Finally, the Finite Element method (3D) solves partial differential equations on a 3D discretized domain.

Keywords: Epoxy-Based carbon fiber prepregs , Induction heating , Model-Based simulations , Mold heating , Resin curing , Virtual prototyping

This paper presents a preliminary investigation on the workflow that allows to replicate object by using 3D laser scanner and a desktop fused filament fabrication 3D printer. Pitfalls and limitations of those technologies will be pointed out in order to find the bottleneck of the workflow, paying specific attention to what concerns the digital workflow from the acquisition to the generation of the g-code. The findings and conclusions are drawn from a case study that has been carried out using the minimum amount of human intervention, especially during the digital post-processing of the data. The objects under investigation is a broken car door handle. Firstly, it has been digitalized using a 3D laser scanner properly calibrated and set. The accuracy, precision and resolution of the measurement tool have been recorded and the as-is acquired data has been checked against topological errors. The as-is acquired model has been compared with the original geometry. The 3d polygonal mesh has been prepared for being printed: the material, machine and process parameters have been chosen. A simulation of the deposition process to estimate warps and deviation from the nominal geometry was carried out. Finally, the object has been additively manufactured using a desktop Fused Filament Fabrication machine: the printed object has been again compared with the original geometry.

The final subject position is often the only evidence in the case of the fall of a human being from a given height. Foreseeing the body trajectory and the respective driving force may not be trivial due to the possibility of rotations and to an unknown initial position and momentum of the subject. This article illustrates how multibody models can be used for this aim, with specific reference to an actual case, where a worker fell into a stair well, prior to stair mounting, and he was found in an unexpected posture. The aim of the analysis was establishing if this worker was dead in that same place, if he had been pushed, and which was his initial position. A multibody model of the subject has been built (“numerical android”), given his stature and his known mass. Multiple simulations have been performed, following a design of experiments where various initial positions and velocity as well as pushing forces have been considered, while the objective function to be minimized was the deviation of the numerical android position from the actual worker position. At the end of the analysis, it was possible to point how a very limited set of conditions, all including the application of an external pushing force (or initial speed), could produce the given final posture with an error on the distance function equal to 0.39 m. The full analysis gives a demonstration of the potentiality of multibody models as a tool for the analysis of falls in forensic inquiries.

Keywords: accident , android , biomechanics , crime , doe , fall , forensic , multibody

This work is focused on the analysis of the fall of a human being from a given height. With reference to forensic disputes, the final subject position is often the only evidence and foreseeing the body trajectory and the respective driving force may not be trivial. This article illustrates how multibody models can be used for this aim. A multibody model of a human subject has been built, given his stature and his known mass. This model was made of 15 segments, whose inertial properties, joint centres and volumes were deduced from anthropometric databases. This model was validated against experimental tests performed on a Hybrid III dummy: it was able to reproduce the peak impact head force with an error lower than about 10%. Some examples are produced to illustrate the usefulness of this validated model as a tool for the analysis of falls, and how it can be easily parametrized to make multiple simulations with different initial conditions/environment configurations. As such it is a valuable tool for forensic analyses.

Keywords: Anthropometric data , Fall from height , Forensic biomechancis , Multibody model