Virtual prototyping and digital twin

This paper presents a very compact electro-mechanical wideband energy harvester optimized for tire applications. The energy conversion process of the device takes into account the simulation of different phenomena like: non linear dynamic and adaptive resonant behavior of the seismic mass, electromagnetic and magneto-static coupling between floating magnetic mass and coils, transfer of the generated power to an external load by means of a nonlinear circuit interface. The paper is focused on the pneumatic effects of the floating magnet sliding into a calibrated guide. A convenient choice of clearance between moving and fixed parts can be used to create an effective air brake preventing or softening shocks with end stops and to modify system dynamic. A block-oriented Simulink®, experimentally validated, model has been realized to predict scavenger device performance and to optimize design parameters. Equivalent linearized stiffness and damping factors due to pneumatic effects have been modeled in the lumped parameters system to get a simplified model and to formalize relations with the geometrical characteristics. Analysis of the effect of several nonlinearities at different vehicle speed have been performed.

Keywords: Adaptive resonance , Electro-mechanical device , Energy scavenger

Activated dust mobilization during a Loss of Vacuum Accident (LOVA) is one of the safety concerns for the International Thermonuclear Experimental Reactor (ITER). Intense thermal loads in fusion devices occur during plasma disruptions, edge localized modes and vertical displacement events. They will result in macroscopic erosion of the plasma facing materials and consequent accumulation of activated dust into the ITER vacuum vessel (VV). These kinds of events can cause dust leakage outside the VV that represents a high radiological risk for the workers and the population. A small facility, Small Tank for Aerosol Removal and Dust (STARDUST), was set up at the ENEA Frascati laboratories to perform experiments concerning the dust mobilization in a volume with the initial conditions similar to those existing in ITER VV. The aim of this work was to reproduce a low pressurization rate (300 Pa s-1) LOVA event in a VV due to a small air leakage for two different positions of the leak, at the equatorial port level and at the divertor port level, in order to evaluate the influence of obstacles and walls temperature on dust resuspension during both maintenance (MC) and accident conditions (AC) (Twalls = 25 °C MC, 110 °C AC). The dusts used were tungsten (W), stainless steel 316 (SS316) and carbon (C), similar to those produced inside the vacuum chamber in a fusion reactor when the plasma facing materials vaporize due to the high energy deposition. The experimental campaign has been carried out by introducing inside STARDUST facility an obstacle to simulate the presence of objects, such as divertor. In the obstacle a slit was cut to simulate the limiter-divertor gap inside ITER VV. In this paper experimental campaign results are shown in order to investigate how the divertor and limiter-divertor gap influence dust mobilization into a VV. A two-dimensional (2D) modelling of STARDUST was made using the CFD commercial code FLUENT, in order to get a preliminary overview of the fluid dynamics behaviour during a LOVA event and to justify the mobilization data. In addition, a numerical model was developed to compare numerical results with experimental ones. © 2011 IAEA, Vienna.

In the present paper, starting from a first attempt design of engine components, a CAD/CAE integrated approach for designing engine is proposed. As first step, some typological quantities are setting in order to define the designed engine, for example the number of cylinders, displacements, thermodynamic cycle and geometrical constraints. Using literature approach and tailored design methodologies, the developed software provides the geometric parameters of the main engine components: crankshaft, piston, wrist pin, connecting rod, bedplate, engine block, cylinder head, bearings, valvetrain. Form the geometrical parameters, the developed software, using 3D CAD parametric models, defines a first functional model of each component and of their mutual interactions. Then a numerical analysis can be evaluated and it provides important feedback result for design targets. In the paper the particular case of a crank mechanism model is presented. The assembly of crankshaft, pistons, wrist pins, connecting rods are modeled by means of a full parametric approach and driven by the first geometrical design. Then a numerical validation of the solution is done and a feedback procedure is taken into account. In that case, a structural modification on the crankshaft is used for a dynamic torsional requirement. The proposed software proves to be a useful and quick instrument for a conception of a new engine. As a consequence, it is an interesting method to reduce the design time and costs, allowing automatic optimization techniques. © 2011 SAE International.

In the present paper, starting from a first attempt design of engine components, a CAD/CAE integrated approach for designing engine is proposed. As first step, some typological quantities are setting in order to define the designed engine, for example the number of cylinders, displacements, thermodynamic cycle and geometrical constraints. Using literature approach and tailored design methodologies, the developed software provides the geometric parameters of the main engine components: crankshaft, piston, wrist pin, connecting rod, bedplate, engine block, cylinder head, bearings, valvetrain. Form the geometrical parameters, the developed software, using 3D CAD parametric models, defines a first functional model of each component and of their mutual interactions. Then a numerical analysis can be evaluated and it provides important feedback result for design targets. In the paper the particular case of a crank mechanism model is presented. The assembly of crankshaft, pistons, wrist pins, connecting rods are modeled by means of a full parametric approach and driven by the first geometrical design. Then a numerical validation of the solution is done and a feedback procedure is taken into account. In that case, a structural modification on the crankshaft is used for a dynamic torsional requirement. The proposed software proves to be a useful and quick instrument for a conception of a new engine. As a consequence, it is an interesting method to reduce the design time and costs, allowing automatic optimization techniques. Copyright © 2011 SAE International.

The hazelnut production for food-farming field industry is made up of several processes and some of those could be suitable for performing virtual simulations. An aim for using simulations is to check the strong and weak features of the machineries and then apply suitable modifications. Both machineries and hazelnuts 3D models are then requested but, while machinery model is unique or the technical solution is represented through a deterministic sketch, hazelnut model must represent as good as possible its real statistical distribution of its characteristics. Then a parametric model of the hazelnut is useful for being a reference model whose parameters can be edited to generate a defined number of hazelnuts consistent with real distributions.

Keywords: 3D parametric model , Hazelnut , Stochastic simulation

This work concerns the usability assessment of two control devices for a wheelchair-mounted robot manipulator aimed at assisting physical disabled people. The assessment of the usability is a crucial issue for the design of such products, since they communicate with their users not only through their shape, but especially through their control interfaces. In a first phase, the study focuses on defining a synthetic usability index on the basis of the methodologies currently in use. In a second phase, some experiments in Virtual Reality (VR) have been carried out. The use of VR technologies for the collection of the experimental data has been fundamental in terms of safety, costs and repeatability of the tests. Another important result has been the reduction of the sources of noise, thanks to preliminary simulations in VR and non-invasive questionnaires and interviews for capturing the subjective perceptions of users. Finally, it is worth noticing that the developed model may show its validity also in evaluating the usability of other products. Indeed, it provides a basis for a more extensive use of VR experiments for evaluating different design solutions in terms of global usability requirements. © Organizing Committee of TMCE 2010 Symposium.

Keywords: Analytic Hierarchy Process (AHP) , Assistive robotics , Participatory design , Usability index , Virtual reality experiments

Site-specific wind potential assessment shows difficulties mainly because it needs very long on-site anemometric monitoring. This paper proposes to reduce the long-term monitoring by exploiting other initial information about parameters to be estimated via MCMC (Markov chain Monte Carlo). The proposed Bayesian approach allows the integration of prior information (e.g. obtained from atlases, databases and/or fluid-dynamic assessment) with sampling data, and furnishes effective and timely posterior information about Weibull parameters of the wind speed distribution. Real sampling data, collected from a southern Italian site, are analysed in order to illustrate the main features of the methodology. Moreover, the effectiveness of both the filtering strategy adopted to deal with the high correlation that usually characterizes the anemometric data, and the seasonal adjustment proposed to obtain a sample unbiased by seasonal effect is highlighted. The results of the application show that the proposed methodology fits the applicative needs very well. A bootstrap simulation remarks that the attained precision of the Bayesian estimates carried out from a one-month sample is comparable to the maximum likelihood estimates obtained from an actual one-year sample. © 2010 John Wiley & Sons, Ltd.

Keywords: Bayesian estimators , Markov chain Monte Carlo , Weibull distribution , Wind speed distribution

In this paper the optimization process of a new High Energy Absorption Rear Underrun Protective Device called HEARUPD is discussed. The main objectives of the HEARUPD design optimization process have been related to the reduction in car decelerations (high crashworthiness) and avoiding the car underrun (high structure stability). In the implemented optimization process, the crash between an economy car (GEO Metro) and the rear part of a truck has been simulated by numerical models. A linear function of the decelerations measured on the car has been used as objective to minimize, the main dimensional values of the rear underrun protective device, instead, have been chosen as design variables. The Simplex Method has been used as optimization technique. At the end, a detailed analysis of the optimized model has been also performed. The obtained results have shown the HEARUPD, in comparison with a reference device, is able to dissipate a higher quantity of energy, reducing both the deceleration peaks and the frontal car crushing. © Organizing Committee of TMCE 2010 Symposium.

Keywords: Crash test , Finite element method analyses , Optimization , Rear underrun protective device , Simplex method , Truck

This paper presents a new design framework to configure lower limb prostheses, both transfemoral and transtibial, where the key elements are the patient digital avatar and the domain knowledge. The technician is supported during the design process by the knowledge acquired from analysis of the traditional process and represented in the framework. The last one integrates virtual prototyping tools and knowledge management techniques. A specific software tool, named Socket Modelling Assistant, has been developed to design the socket, the custom-fit component of the prosthesis. A commercial CAD system is used to model the standard components (e.g., knee, foot and tubes) and to create the final assembly. Patient avatar and his/her data (e.g., anthropometric and physiological parameters) are the backbone of the whole product design process. They guide both the selection of standard components and the modelling of the socket digital model. Copyright © 2010 by ASME.

In this paper, we propose a knowledge-based approach to design lower limb prostheses; in particular, we focus on the 3D modelling of the socket, the most critical component. First, the architecture of a dedicated knowledge based engineering framework is described, detailing features of the main design steps. Then, the paper discusses the acquisition and formalization of the knowledge related both to the prosthesis manufacturing process and to the considered component. Finally, we present a computer-aided module, named Socket Modelling Assistant-SMA, to design the socket; it is a virtual laboratory where the socket virtual prototype is generated directly on the digital model of patient's residual limb. It guides and supports the designer during each step in an automatic and/or semi-automatic way applying design rules and procedures. The guided modelling steps and available tools are described. Work in progress and future developments conclude the paper. © Organizing Committee of TMCE 2010 Symposium.

Keywords: 3d socket modelling , Knowledge-based design , Lower limb prosthesis , Virtual prototyping

This paper presents a new 3D design paradigmfor the development of specific custom-fit products, such as the soft socket of prostheses for lower limb amputees. It is centered on the digitalmodel of the human body and, contrarily to the traditional process almost manually based, it considers the integration of methods and tools coming from different research and application fields: Reverse Engineering, Medical Imaging, Virtual Prototyping, Physics-based Simulation, and Rapid Prototyping. The paper describes the techniques adopted to acquire and create the digital model of the residual limb, the procedure to generate the socket model, the strategy developed for the functional simulation of the socket-stump interaction and, finally, the realization of the physical prototype. Each design step is described with the related problems and the obtained results. Both trans-tibial and trans-femoral amputees have been considered; however, for now the complete process has been validated for trans-tibial prostheses. Major outcomes of the proposed approach stand in a better quality of the final product, in a shorter involvement of the amputee implying a lower psychological impact, in a limited use of physical prototypes, and in a shorter development time. Moreover, the resulting paradigm answers to the Collaborative Engineering guidelines by optimizing the interaction between different domains and enhancing their contributions in a homogeneous development framework. © 2010 Elsevier B.V. All rights reserved.

Keywords: Custom-fit products , Human-centric soft product design , Physics-based modeling for soft products , Prosthesis development process

In order to overcome the limits due to the fact that homogeneous layers of soft material placed over robotic limbs behave differently with respect to biological models, this paper suggests the adoption of soft covers (pads) with differentiated structure. In particular, it is proposed to divide the allowable pad thickness into two layers: a continuous external layer (skin) and a discontinuous internal layer, so that the overall stiffness can be adjusted by properly shaping the discontinuous layer. The methodology adopted for designing the internal layer is composed of two steps. Firstly, the cover surface is conceptually split into finite elementary triangular sub-regions. Secondly, the internal layer of each triangular element is designed in order to replicate the shape of the non-linear compression law which is typical of endoskeletal structures covered by pulpy tissues. A series of symmetrically-disposed inclined micro-beams is used for the purpose. Once the compression law of each triangular element is known, the overall pad compliance can be modulated by correctly choosing the number and size of the elements composing the pad. Equipment and results of a combined experimental and numerical analysis (FEM) are presented. The results confirm that the proposed concept can be an effective solution when designing soft covers whose behavior need to match the compliance of the biological counterpart. As an example, artificial pads which mimic the human finger behavior are presented. © 2010 by ASME.

A fully mechanical, infinitely variable transmission (IVT) based on the use of an oscillating inertia is described. The system includes a four-bar linkage mechanism, an epicyclic gear train, and a pair of one-way clutches. The IVT can be used in place of both gearbox and clutch in self-propelled vehicles. A mathematical model is presented. Numerical simulations compare the behavior of a car fitted with a manual gearbox and the same car fitted with the IVT.

A novel mathematical procedure is presented, which makes it possible to optimize lozenge-shaped dielectric-elastomer-based linear actuators for known materials and desired force/stroke requirements. Simulation and experimental results are provided which both demonstrate the efficacy of the proposed optimization procedure with respect to traditional design approaches and show that simpler, cheaper, lighter, and better-behaved lozenge-shaped actuators can be conceived, which do not require any integration of compliant frame elements.

Keywords: Dielectric elastomers , Optimal design. , Smart actuators

This paper addresses issues related to the assessment of product designs that today successfully uses virtual prototyping methods and techniques. Design assessment is usually performed by engineers and designers. Current trend is involving customers in the products design assessment in order to check the level of acceptability and satisfaction before proceeding with the production. In this view, methods for design review may be used in participatory design sessions where customers can intervene for customizing products. The paper presents a tool that has been originally developed for designers for the validation and modification of aesthetic properties of digital shapes, and that has also been used by customers, in participatory design sessions, for customizing their products. Copyright © 2010 by ASME.

In this paper the set up and the carrying out of experimental ballistic tests on a tail rotor transmission shafts for helicopter, which are impacted by a 7.62 NATO projectile, are presented. After the tests, a 3D acquisition of the impacted area on each shaft has been performed in order to acquire exactly the shape of the damage. The acquisition has been carried out with a 3D range camera. The experimental activities have been compared with the results of a numerical simulation of the impact, which has been computed with an explicit finite element code. The direct comparison has been done by superimposing the two meshes (from FE analysis and from 3D acquisition). This method has proved to be effective for identifying analogies and differences and for giving the possibility to promote a "quantitative" discussion with the aim of improving the accuracy of the numerical models and simulation conditions. The adoption of the Reverse Engineering practice has proved to be a powerful method for integrating and comparing the simulation data with real data, and give suggestions to further analysis. Copyright © 2010 by ASME.

Most of the activities concerning the design review of new products based on Virtual Reality are conducted from a visual point of view, thus limiting the realism of the reviewing activities. Adding the sense of touch and the sense of hearing to traditional virtual prototypes, may help in making the interaction with the prototype more natural, realistic and similar to the interaction with real prototypes. Consequently, this would also contribute in making design review phases more effective, accurate and reliable. In this paper we describe an application for product design review where haptic, sound and vision channels have been used to simulate the interaction with a household appliance. © 2010 Springer-Verlag.

Keywords: Interaction Design , Multimodal Interaction , Product Design Review , Virtual Prototyping

The paper describes a haptic device whose aim is to permit the assessment of digital prototypes of industrial products with aesthetic value. The device haptically renders curves belonging to digital surfaces. The device is a haptic strip consisting of a modular servo-controlled mechanism able to deform itself, allowing the user to feel the resulting shape with his free hands. The haptic strip is also equipped with two force sensitive handles placed at the extremities, and a capacitive touch sensor along its length, which are used for applying deformations to the digital shape. © 2010 Springer-Verlag Berlin Heidelberg.

Keywords: Haptic linear strip , Multimodal application , Virtual Prototyping

The paper presents a system we have studied and developed to aid the stereoscopic visualisation of virtual models of products whose shape can be explored and modified using a haptic interface. The haptic system has a wide working space that allows users to stand in front of the system and to operate as they are used to do in real life for making physical prototypes. The paper also shows several visualisation solutions that have been studied before obtaining the best performing one in which the stereoscopic glasses worn by the user as well as his point of view are tracked in order to enhance the realistic perception of the 3D mixed image. Some initial tests have been performed with end-users, both CAS designers and model makers, with the support of human factors experts in order to correctly assess the usability of the system and to understand how potentially effective it is in aiding product designers in their work. © 2010 Inderscience Enterprises Ltd.

Keywords: haptic interfaces , projection based visualisation systems , stereoscopic visualisation , virtual prototyping , visuo-haptic display

The paper presents the results of a research project aiming to develop an innovative framework for the conceptual design of products based on haptic technology. The system consists of a Computer-Aided Design (CAD) system enhanced with intuitive designer-oriented interaction tools and modalities. The system integrates innovative haptic tools with 6 Degrees of Freedom (DOF) for modelling digital shapes, with sweep operators applied to class-A surfaces and force computation models based on chip formation models. The system aims to exploit designers' skills in modelling products, improving the products' design process by reducing the necessity to build several physical models for the evaluation and testing of product designs. The system requirements have been defined after observing designers during their daily work and translating the way they model shapes using their hands and craft tools into specifications for the system. The system has been tested by designers, who have found it intuitive and effective to use. Copyright © 2010 Inderscience Enterprises Ltd.

Keywords: Conceptual design , Haptic modeling , Product design , Product development , Virtual prototyping