Virtual prototyping and digital twin

A novel design for a Dielectric Elastomer (DE) actuator is presented. The actuator is obtained by coupling a cylindrical DE film with a series of slender beams axially loaded beyond their buckling limit. Similarly to previous published solutions, where different actuator geometries were coupled with compliant mechanisms of various topologies, the elastic beams are designed so as to provide a suitable compensating force that allows obtaining a quasi-constant available thrust along the entire actuator stroke. The overall system performance are subsequently evaluated by means finite element analysis, accounting for the large deflection of the buckled-beam springs and for the DE material hyperelasticity. Final results confirm that compact and better behaved constant force cylindrical actuators can be obtained, which potentially outperform similar devices in terms of achievable stroke. Copyright © 2013 by ASME.

Artificial Muscles based on Dielectric Elastomers (DE) can potentially enable the realization of bio-inspired actuation systems whose intrinsic compliance and damping can be varied according to the task requirements. Nonetheless, the control of DE-based Variable Impedance Actuators (VIA) is not trivial owing to the non-linear viscoelastic response which characterizes the acrylic dielectrics commonly employed in practical devices. In this context, the purpose of the present paper is to outline a novel strategy for the control of DE-based VIA. Although the proposed methodology is applicable to generic DE morphologies, the considered system is composed of a couple of conically-shaped DE films in agonistic-antagonistic configuration. Following previously published results, the system dynamic model is firstly recalled. Then, a DE viscoelasticity compensation technique is outlined together with a control law able to shape the DE actuator impedance as desired. The operative limits of the system are explicitly considered and managed in the controller by increasing the operating DE actuator stiffness if required. In addition, the problem of model uncertainties compensation is also addressed. Finally, as a preliminary step towards the realization of a practical DE-based VIA, the proposed control approach is validated by means of simulations. Copyright © 2013 by ASME.

Industrial robotics provides high flexibility and reconfigurability, cost effectiveness and user friendly programming for many applications but still lacks in accuracy. An effective workcell calibration reduces the errors in robotic manufacturing and contributes to extend the use of industrial robots to perform high quality finishing of complex parts in the aerospace industry. A novel workcell calibration method is embedded in an integrated design framework for an in-depth exploitation of CAD-based simulation and offline programming. The method is composed of two steps: a first offline calibration of the workpiece-independent elements in the workcell layout and a final automated online calibration of workpiece-dependent elements. The method is finally applied to a robotic workcell for finishing aluminum housings of aerospace gear transmissions, characterized by complex and non-repetitive shapes, and by severe dimensional and geometrical accuracy demands. Experimental results demonstrate enhanced performances of the robotic workcell and improved final quality of the housings. © Springer-Verlag Berlin Heidelberg 2013.

Keywords: Aerospace industry , Industrial robotics , Integrated design , Workcell calibration

Deburring of aerospace components is a complex task in case of large single pieces designed and optimized to deliver many mechanical functions. A constant high quality requires accurate 3D surface contouring operations with engineered tool compliance and cutting power. Moreover, aeronautic cast part production is characterized by small lot sizes with high variability of geometries and defects. Despite robots are conceived to provide the necessary flexibility, reconfigurability and efficiency, most robotic workcells are very limited by too long programming and setup times, especially at changeover. The paper reports a design method dealing with the integrated development of process and production system, and analyzes and compares a CAD-based and a digitizer-based offline programming strategy. The deburring of gear transmission housings for aerospace applications serves as a severe test field. The strategies are compared by the involved costs and times, learning easiness, production downtimes and machining accuracy. The results show how the reconfigurability of the system together with the exploitation of offline programming tools improves the robotic deburring process. © Springer-Verlag Berlin Heidelberg 2013.

Keywords: CAD-based tools , Digitizers , Industrial robotics , Integrated design , Offline programming

The interest in novel methods and tools for opt imizing the energy consumption in robotic systems is cur- rently increasing. From an industrial point of view,it is desirable to develop energy saving strategies also applicable to established manufacturing systems with no need for either hardware substitu tion or further investme nts. Within this scenario,the present paper reports amethod for reducing the total energy con- sumption of pick-and-place manipulators for given TCP position profiles.Firstly,electromechanical mod- els of both serial and parallel manipulators are derive d.Then,the energy-optimal trajectories are calculated, by means of constant time scaling,starting from pre-scheduled trajectories comp atible with the actuation limits. In this manner,the robot work cycle can be energetically optimized also when the TCP position profiles have been already definedon the basis of technological constraints and/or design choices aimed at guarante eing manufacturing process efficacy/robustness.The effectiveness of the pro- posed procedure is finallyevaluated on two simulation case studies. Copyright © 2013 Published by Elsevier Ltd. All rights reserved.

Keywords: Electromechanical modeling , Energy efficiency , Robotic manufacturing , Virtual prototyping

In the field of dental health care, plaster models combined with 2D radiographs are widely used in clinical practice for orthodontic diagnoses. However, complex malocclusions can be better analyzed by exploiting 3D digital dental models, which allow virtual simulations and treatment planning processes. In this paper, dental data captured by independent imaging sensors are fused to create multi-body orthodontic models composed of teeth, oral soft tissues and alveolar bone structures. The methodology is based on integrating Cone-Beam Computed Tomography (CBCT) and surface structured light scanning. The optical scanner is used to reconstruct tooth crowns and soft tissues (visible surfaces) through the digitalization of both patients' mouth impressions and plaster casts. These data are also used to guide the segmentation of internal dental tissues by processing CBCT data sets. The 3D individual dental tissues obtained by the optical scanner and the CBCT sensor are fused within multi-body orthodontic models without human supervisions to identify target anatomical structures. The final multi-body models represent valuable virtual platforms to clinical diagnostic and treatment planning. © 2013 by the authors; licensee MDPI, Basel, Switzerland.

Keywords: Dental CBCT images , Optical scanning , Orthodontic model , Sensor fusion , Tooth segmentation

Mixed prototyping (MP) is an emerging approach for usability testing, thanks to its multimodal environment, which is able to involve sight, hearing and touch thus improving the ability to analyze the inter-relationships between the physical form and the behavior of the industrial products. This paper presents a method to perform usability tests in a mixed reality (MR) environment for analyzing human performance in target acquisition tasks while interacting with household appliances. The proposed method is based on the use of different kinds of digital and physical prototypes and, moreover, it introduces an experimental physical archetype for mixed prototyping that contributes to increase the efficiency of the usability evaluation process. Through this archetype the design of a user interface can be easily changed by the adoption of plug-and-play moving components (knobs and buttons) that allow to model in a few seconds any kind of control panel for washing machines, thus reducing the prototyping costs and enlarging the variety of MR interfaces that can be evaluated. The paper proposes also a validation of the use of the physical archetype through a case study in which three different control panel alternatives have been evaluated in a competitive usability study. The competitive testing allows to gather user behaviors with a broad range of design options before the development of a new control panel refined through iterative design. Experimental results show that the proposed method based on the physical archetype can be an effective support to improve the usability of the product interface. © 2012 Elsevier B.V.

Keywords: Design review , Interaction design , Mixed prototyping , Usability test

The term User Experience (UX) is commonly associated with interactive computer-based systems. Companies operating in the consumer market are recently discovering the importance of designing UX, and in particular multisensory UX, of any kind of system, and not necessarily high-tech products. One of the most effective ways to design UX is to enable users interacting with the prototype of the system during the design process, and in particular already during its initial stages. These prototypes should provide the same experience occurring while interacting with the corresponding real product. To this aim Virtual Prototypes (VPs) may be effectively used, especially in the early design stages when the activities are still in progress and changes are frequent. Multisensory UX can be effectively designed through VPs only if all the senses involved in the real interaction are recreated into the virtual simulation. To date, despite a growing interest of research and industry in the development and use of VPs, many applications are still limited to visual and sound simulations. This paper focuses on the use of VPs to design multisensory UX, concentrating on the introduction of the sense of touch in the simulation. The methodological approach as well as the development of a case study are described in the paper. © 2013 IEEE.

Keywords: Haptics , User experience design , Virtual prototyping

In recent years, the production of consumer goods has exceeded that of industrial products. This has led to changes in the areas of design and production. The target users of industrial products (in the Business to Business-B2B market) are industries that decide to purchase a product on the basis of its technical features, functions and performance. Differently, the target users of consumer products (in the Business to Consumer-B2C market) are the consumers who choose a product driven by other aspects, besides features and functions, such as the perceived value, the expected benefits, the emotions elicited, as well as features and functions. This has brought a paradigm shift in the design process. And in fact, the design of consumer products is increasingly focusing on the so-called user experience. The designer must not design only the product, but also the user experience in relation to its use. The resulting product should have a high perceived value and generate positive emotions in the consumer. These factors make a successful product on the market. Therefore, the role of the designer is designing the products and the perceptual aspects of their use, that is, designing the user experience and deriving from that the products' specifications. Consequently to that, the design process has changed in the last years. In fact, the user is now at the center of the design process, named user-centered design. Being the new focus the target users, the evaluation of their interaction with the new designed products is expected to be rigorous and systematic. An efficient approach has proved to be one in which the validation is made up by involving users in the early stages of the product design. Since typically at the level of the concept the product, or a prototype that is comparable with it at the perceptual level, is not available, it is not possible to make a thorough validation of its use with users. However, new methodologies of Virtual Prototyping allow us to simulate multisensory user interaction with product concepts early in the design process. This chapter introduces the use of interactive Virtual Prototyping (iVP) methodology for the design of the user experience with the concept of a new product. Interactive components of new products and their behavior are simulated through functional models, and users can experience them through multisensory Virtual Reality (VR) technologies.

The need for companies to improve their competitiveness may lead to innovation and the reconceptualization of traditional products and processes, with companies making an effort to enhance product elements related to functionality, attractiveness, technology and sustainability, and implementing mass-customisation concepts. Mass-customised products are developed to satisfy specific customer needs, in line with increasing demand for product variety and customisation. The analysis of what customers really want, capturing the Voice of the Customer (VOC), is one of the strategies used to establish effective product development processes. Using a VOC survey, it is possible to transform customer needs into the functional and psychological requirements of the product. This paper presents a methodology based on Virtual Reality (VR) technologies to support the capturing of the VOC in regard to the visual, haptic and auditory characteristics of products. This method can be applied to the beginning of the product development process, to allow companies to deduce from the data the requirements of new industrial customised products. A flexible and interactive Virtual Prototype (VP) of a product category is then developed as a product platform in a draft version by designers and configured according to customer needs, using an immersive VR environment. This method, based on the use of VP, reduces the number of physical prototypes that need to be manufactured during the product development process, thus reducing overall costs. In addition, the VP based method supports the mass-customisation process of products through the real-time integration and collection of data for product configuration preferences, involving as many users as possible representative of the target users of the new products. To demonstrate this process a case study concerning the development of the VP for a washing machine, a summary of test sessions with users and results are presented. Specifically, the results presented in this paper are related to improvements in capturing the VOC and reductions in Virtual Prototyping cost and time. © 2012 Springer Science+Business Media, LLC.

Keywords: Product customisation , Virtual Prototyping , Voice of the Customer

This paper describes a desktop-mechatronic interface that has been conceived to support designers in the evaluation of aesthetic virtual shapes. This device allows a continuous and smooth free hand contact interaction on a real and developable plastic tape actuated by a servo-controlled mechanism. The objective in designing this device is to reproduce a virtual surface with a consistent physical rendering well adapted to designers' needs. The desktop-mechatronic interface consists in a servo-actuated plastic strip that has been devised and implemented using seven interpolation points. In fact, by using the MEC (Minimal Energy Curve) Spline approach, a developable real surface is rendered taking into account the CAD geometry of the virtual shapes. In this paper, we describe the working principles of the interface by using both absolute and relative approaches to control the position on each single control point on the MEC spline. Then, we describe the methodology that has been implemented, passing from the CAD geometry, linked to VisualNastran in order to maintain the parametric properties of the virtual shape. Then, we present the cosimulation between VisualNastran and MATLAB/Simulink used for achieving this goal and controlling the system and finally, we present the results of the subsequent testing session specifically carried out to evaluate the accuracy and the effectiveness of the mechatronic device. © 2013 Covarrubias et al.

Keywords: Desktop haptic strip , Mec (minimal energy curve) spline approach , Surface rendering

The paper describes the results of an on-going research activity whose aim is to allow companies, operating in the consumer goods market, to design the multisensory experience of their products. In case of the household appliances market, which is the research context of this study, the user experience derives from the interaction with specific product features such as the door, buttons, and drawers. Designing a good multisensory experience is complex since it means taking into account a combination of visual, hearing and haptic feedbacks a user perceives when interacting with the product. Virtual Reality offers the technologies to design and test that experience thought virtual prototypes, even if to date there is a lack of methodological approaches to practically guide and support this design activity. Relying on the results of previous authors' researches, the paper describes further methodological advances focused on making usable the proposed approach in the current design practice. The case study chosen to demonstrate the effectiveness of the method is a dishwasher door and the paper describes how to re-engineer the haptic feedback of a commercial model in order to make it more perceptually appealing at the moment of purchase. © 2013 CAD Solutions, LLC.

Keywords: Haptic interaction , Reverse engineering , User experience design , Virtual prototyping

The paper describes an application based on Virtual and Augmented Reality technologies specifically developed to support maintenance operations of industrial products. Two scenarios have been proposed. In the first an operator learns how to perform a maintenance operation in a multimodal Virtual Reality environment that mixes a traditional instruction manual with the simulation, based on visual and haptic technologies, of the maintenance training task. In the second scenario, a skilled user operating in a multimodal Virtual Reality environment can remotely train another operator who sees the instructions about how the operations should be correctly performed, which are superimposed onto the real product. The paper presents the development of the application as well as its testing with users. Furthermore limits and potentialities of the use of Virtual and Augmented Reality technologies for training operators for product maintenance are discussed. © 2013 Copyright Taylor and Francis Group, LLC.

Keywords: assembly , haptics , virtual prototyping

In the domain of industrial product development, products have been traditionally communicated to final users by means of technical drawings, sketches and physical prototypes. Recently, companies have tended to develop digital versions of products, which can be used with the purpose of communicating a new product to users, and also with the aim of allowing users to evaluate the product and its variants before its physical construction. Virtual prototyping is a relatively recent practice used in various industrial domains, which aims at anticipating a product that does not exist in reality yet. This practice can be used for evaluating the aesthetic quality of a product, its functional features and also its ergonomic and usability aspects. Current virtual reality technology well supports the implementation of effective virtual prototypes. In fact, one can touch, move, manipulate, and operate the virtual prototypes of products, such as household appliances, electronic devices, etc., with a good degree of realism. In order to do this, the interaction with virtual prototypes is multimodal and multisensory, and is often based on the combination of visual, haptic and auditory modalities. This paper shows how virtual prototypes can be used instead of physical artefacts or mock-ups for the communication of a new product or of variants of an existing product, and for the preliminary evaluation of its usage. The effectiveness of this practice is proved by tests performed by users. © 2013 Copyright Taylor and Francis Group, LLC.

Keywords: haptic interaction design , virtual environments , virtual prototyping

Today, the tests of a new product in its conceptual and design stage can be performed by using digital models owning various levels of complexity. The level of complexity depends on the nature and on the accuracy of the tests that have to be performed. Besides, the tests can involve or not the interaction with humans. Particularly, this second aspect must be taken into account when developing the simulation model. In fact, this introduces a different kind of complexity with respect to simulations where humans are not involved. Simulation models used for numerical analyses of the behavior of the product (such as Finite Element Analysis, multi- body analysis, etc.) are typically named Digital Mock- Ups. Instead, simulations that are interactive in their nature, requiring humans- in- the- loop, are named interactive Virtual Prototypes. They cannot be intended as a simple upgrade of a CAD model of a product, but they are instead a combination of functional models, mapped into sensorial terms and then accessed through multisensory and multimodal interfaces. In this paper, the validity of this concept is demonstrated through some case studies where interactive Virtual Prototypes are used to substitute the corresponding physical ones during activities concerning the product conceptualization and design. © 2013 CAD Solutions, LLC.

Keywords: CAD modeling , Mixed prototyping , Simulations , Virtual prototyping

The paper describes an application based on low cost Virtual Reality technologies whose aim is to help designers in testing some functional aspects of their product concepts without the need of building physical mockups. In particular the application allows the designers to test aspects related to the usage of products. A case study that enables designer to verify the ergonomics aspects of the interactive Virtual Prototype (iVP) of a commercial refrigerator has been implemented. The iVP is based on a three-dimensional scale representation of the product and the use of a low cost user interface as input/output device. The paper describes the implementation of the iVP and the results of some preliminary user study that has been performed in order to validate the visuo/haptic interaction approach. © Springer-Verlag London 2013.

The paper describes a novel application of real-time finite element analysis controlled by a haptic device. The user can impose displacement constraints to a virtual structure using a probe and sense in real-time the response in terms of forces on her/his hand. In addition, conventional color map results are visualized on a desktop monitor. The application has been developed with the aim of simplifying the teaching of the mechanical behavior of materials in engineering schools by transforming the learning phase into an enactive process. A set of examples commonly used in the mechanical engineering courses have been implemented and tested. The paper describes and discusses the system implementation, the potentialities and the issues of such approach. Copyright © 2013 by ASME.

The paper describes a desktop-haptic interface (DHI) that has been conceived to support designers in the evaluation and modification of aesthetic virtual shapes. The objective in designing this device is to reproduce a 2D cross-section of virtual objects with a consistent physical rendering well adapted to designers needs allowing a continuous and smoothly free hand contact interaction on a real and developable metallic strip. The desktop-haptic interface consists in a servo-actuated metallic strip that has been devised and implemented by using the Minimal Energy Curve (MEC) spline approach in which the equidistant interpolation points scheme has been adopted for modeling the structure chain consisting of several rigid struts and pivots. Then, we present the co-simulation between the multi-body environment and MATLAB/Simulink used for achieving this goal and control the system and finally, we present the results of the experimental validation session specifically carried out to evaluate the accuracy and the effectiveness of the interface. Copyright © 2013 by ASME.

The aim of present work is the containment of the inertia forces, the stiffness components optimization and the fit tolerances of valve train in internal combustion engines (I.C.E.) 4T. The proposed methodology allows, through the development of a test machine, the evaluation of axial stiffness of tappet depending on eccentricity of the cam tappet contact, performing a functional analysis that simulate the behaviour of the system in operational condition, even if, some adjustment of tolerances of the fit between tappet and his guide, occurred. The dynamic study of the valve train, through modern computer codes, is performed by connecting lumped masses, springs and dampers that characterize each element. In numerical models the tappet is represented as constituted by the tappet and by the hydraulic element. Each of these elements is characterized by stiffness and mass. The structural rigidity of the tappet has, in fact, important effects on the dynamic behaviour of the entire valve train. The test machine makes possible the choice of the dimensional and geometrical tolerances of the fit between tappet and his guide; allows furthermore the evaluation of errors occurred during construction and integration phase. In addition, the test machine is also suitable for reverse engineering applications, makes it possible to automatically draw the cam profile in polar coordinates. © 2012 Springer Science+Business Media Dordrecht.

Keywords: Cam , Dynamics , Fit tolerance , I.C.E , Tappet , Timing system

This paper describes the Multi Disciplinary Optimization of an airship with unconventional configuration. The shape of the airship is based upon two semi-ellipsoids, whose axis ratios can be altered for optimization purpose. The parameters to optimize are: volume, ratio between longitudinal and lateral semi-axis, ratio between vertical and lateral semi-axis, percentage of the top surface covered by photovoltaic films, dimension of the tail. The goals of the optimization are: equilibrium between buoyancy and weight, reaching of the design speed, static longitudinal stability of the vehicle. The mathematical model developed to evaluate airship features includes the computation of the ballonet volume, a weight breakdown, the energy storage for night operations, the power system evaluation and stability considerations. Six heuristic optimization strategies have been applied in order to achieve the best solution; some case studies have been developed and the final optimal configurations found by algorithms have been analyzed in order to validate the optimization framework. The approach demonstrate that the heuristic optimization strategies used are good tool for the conceptual design of unconventional airship since this problem requires a multi-disciplinary approach and several parameters including aerodynamics, propulsion, mass breakdown, aerostatics and stability, which are strongly dependent each other, must be jointly considered and addressed at the same time to obtain an optimum and balanced design. © 2013 by the American Institute of Aeronautics and Astronautics, Inc. All rights reserved.