Virtual prototyping and digital twin

In a scenario of a small and customized production of Electric Vehicles, it is important to have methodologies and tools able to guarantee high flexibility, good quality, and reduced time to market. The optimisation of electric motors and battery design stages is a key factor to achieve the expected results. Specific activities such as design automation, virtual prototyping and simulation are fundamental to obtain highperformance customised solutions. In this context the study of cooling systems for Li-Ion battery packs is one of the most important problems regarding EV and PHEV powertrain design. The proposed research presents a Knowledge Based methodology to support the cooling design of a battery pack and an analytical tool to evaluate the temperature and heat generation due to electrochemical reactions. All the research project is finalized to a definition of a Knowledge Based System to define a battery layout including engineering knowledge. The current strategies of battery pack design depend on the market size. In particular, the research activity is focalized on customized production of a SME (Small Medium Enterprise). The main question concerns the estimation of heat generated from electrochemical reactions in a single battery cell. In order to achieve these objectives, a preliminary phase for knowledge acquisition is necessary and a process of formalization has been carried out using the Knowledge Management methods. A first prototype of the Knowledge Based Engineering tool has been developed to determine the optimal cooling condition of a battery pack. The main module is based on an analytical approach which has been formulated to evaluate the average thermal flow generated by a standard LiFePO4 polymeric cell at different values of current and state of charge (SOC). This method can be used for different types of geometry and different chemical compositions. Finally, the proposed approach has been validated by experimental measures and numerical simulations in collaboration with a medium enterprise of electric energy storage systems and light ecological vehicles. Copyright © 2012 by ASME.

Developing green propulsion concepts for aviation requires some changes in standard procedures for the preliminary aircraft design. Standard design procedures are not readily applicable to aircraft/rotorcraft that use multiple energy sources; innovative concepts like hybrid propulsion systems require new approaches in weight and performance prediction. In this paper the application of new methods is explored to account for the changes in the governing equations when using hybrid propulsion: a design code allows predicting the performances once the hybrid propulsion architecture is chosen. Focus is on hybrid propulsion systems based on a diesel heavy fuel ICE (Internal Combustion Engine) combined with an electric motor in a parallel configuration. This study relies on simple structure and material performance indexes, neglects stability and control analysis, and uses very simple aerodynamic models.

Keywords: Aircraft sizing , Diesel , Hybrid propulsion

The KAD (Knowledge Aided Design) tool is developed to predict the performance of an F1 car in different driving conditions and with different configurations. The regulations to put in trimming a car, also in the exasperated technology of the competitions, still demand a remarkable dose of luck and an elevated number of tests. It is then important to know a set of regulations close to the optimal trim before testing the car on the track. The difficult phase of this process is to evaluate the lap time. As a matter of fact driving style, track conditions and car behavior should be simulated. The optimisation of the fuzzy controller that simulates the pilot for an F1 racing car is difficult due to handling problems and velocity of response. For this purpose a specific Genetic Algorithm (GA) was conceived and tuned to work with a lumped mass model of an F1 racing car for the optimization of the fuzzy controller that simulates the pilot. A new mutation and a new crossover operator were defined to complement the standard crossover and mutation operators of the basic Holland's GA. This was necessary in order to increase the overall performance of the fuzzy pilot. This approach was tested on an F1 car due to the huge amount of data available (Donnarumma, 1998; Moelenbein, 1989; Lee and Takagi, 1993).

Keywords: Control , Fuzzy logic , KAD , Performance

The research goal is material texture simulation by means of electro-tactile stimuli. This paper presents a novel tactile display, the procedure adopted to generate the stimulating signals, and the experimental testing. The tactile system elaborates data from scans of real material samples and generates electrical stimuli to reproduce roughness and texture coarseness sensations. It also adds a coherent sound feedback to improve the realism of the simulation. The research defines an experimental protocol to carry out system calibration and tests with users in order to validate the proposed tactile system as a new tool for material simulation. Experimentations have been carried out to measure the users' response to different material classes (wood, paper, rubber, textile fabric). Experimental results concern how good the adopted simulation approach is and the tactile stimuli simulated by the system are. Main findings relate to the system performance and the users' response in terms of signal recognition and material class discrimination. © 2012 IEEE.

Keywords: Advanced tactile display , Material simulation , Multimodal and multisensory interaction , Perception & Psychophysics

Nowadays, Virtual Reality technologies have spread in numerous industrial and research contexts for their ability to provide the perception of virtual spaces and objects by an appropriate combination of sensory channels stimuli. Haptic feedback enhances the user's perceptual immersion during the interaction with virtual prototypes. Commercial haptic force feedback devices are affected by some functional limitations, such as the size of workspace and the type of contact they can provide. The present work aims at developing an innovative device starting from the customization of an anthropomorphic arm. This allows to increase the workspace, to provide a surface contact and to improve the whole ergonomics of the system. The system multi-layer architecture is designed to have a lower level of robot control and a higher level of highly usable graphic user interface, which displays both the virtual prototype and the manipulating virtual probe. © 2012 IEEE.

Keywords: Anthropomorphic arm , FFD , Virtual Prototyping

The paper presents a novel tactile display to simulate material properties such as roughness and texturewhile exploringVirtual Prototypes surfaces inVirtual Reality environments.The final aim of the system is to immerse users into an involving and enhanced product experience stimulating emotional and affective reaction. The developed display adopts a selective stimulation technique to differently activate skin mechanoreceptors and hence to generate surface texture sensations. The stimulation is realized by both an electric component made of a pin matrix through which the current flows and by a mechanical one obtained by a shaker keeping the tactile pad vibrating. Main development stages are described and experimental results discussed. They show that almost 65% of users are able to discriminate different signals. When acoustic cues are added, this percentage increases. © 2012 Taylor & Francis Group, London.

This paper presents a novel study on the simulation of material texture by means of electro-tactile stimuli and details the effects on the users' ability to recognize and discriminate different material classes. The research exploits a novel tactile display to simulate material texture and validates the adopted simulation strategy by experimental testing. The tactile system elaborates data from real material samples and combines electrical stimuli and mechanical vibration to reproduce both roughness and texture coarseness sensations. Then, an experimental protocol based on the theory of Psychophysics is defined to carry out system calibration and tests with users. The research aims at validating the proposed simulation strategy and checking the user response on virtual tactile stimuli. Experimentations were carried out to reproduce virtual material texture and measure the users' ability to distinguish different virtual materials and to recognize the material class. Experimental results provide interesting details about tactile perception mechanisms and validate the adopted approach for tactile signals' recognition and material class discrimination. Copyright © 2012 by ASME.

Background: It is common practice to prescribe customised footwear to people with diabetes to reduce the risk of foot ulceration. Although shoe customising systems have been proposed, effective tools for designing shoe lasts for diabetic patients are lacking. The shape of the lasts must meet certain biomechanical objectives, while maintaining the style of the shoe.Method: The main contributions of this work are as follows: the creation of an artificial-neural-network-based framework to correlate foot measurements and medical data to required footwear features; the definition of repeatable geometrical procedures to measure foot and last scans; and the definition of geometrical operators to modify the last shape according to its original aesthetic and specific footwear parameters. These parameters are computed by a knowledge-based system on the basis of the patient's pathology and best practices of experienced technicians.Results: Dedicated software systems integrated in a common platform are implemented to support the last design process. Test case studies and a survey show the advantages provided by the proposed approach in terms of achieved quality and shoe developing time (72% time savings).Conclusions: A design framework with dedicated tools is proposed for the customisation of shoe lasts for diabetic patients. Further research should be focused on tools to design the insole, outsole and other shoe components. © 2012 Copyright Taylor and Francis Group, LLC.

Keywords: diabetic foot , foot-last fitting , last design , last measurement

The Generalized Differential Quadrature (GDQ) method is applied to study the dynamic behavior of anisotropic doubly-curved shells and panels of revolution with a free-form meridian. The First-order Shear Deformation Theory (FSDT) is used to analyze the above mentioned moderately thick structural elements. In order to include the effect of the initial curvature in the evaluation of the stress resultants three different approaches, specifically Qatu approach, Toorani-Lakis approach and Reissner-Mindlin approach, are considered and compared. An improvement of the Classical Reissner-Mindlin Theory (CRMT) using a different kinematical model is considered. By so doing a generalization of the theory of anisotropic doubly-curved shells and panels of revolution is proposed. Four different anisotropic shell theories, namely General First-order Shear Deformation Theory by Qatu (GFSDTQ), General First-order Shear Deformation Theory by Toorani-Lakis (GFSDTTL), General First-order Shear Deformation Theory by Reissner-Mindlin (GFSDTRM) and Classical Reissner-Mindlin Theory (CRMT), are compared in order to show the differences and the accuracy of these theories. The solution is given in terms of generalized displacement components of points lying on the middle surface of the shell. Simple Rational Bézier curves are used to define the meridian curve of the revolution structures. Results are obtained taking the meridian and circumferential coordinates into account, without using the Fourier modal expansion methodology. Furthermore, GDQ results are compared with those obtained by using commercial programs such as Abaqus, Ansys, Nastran, Straus and Pro/Mechanica. Very good agreement is observed.

The Generalized Differential Quadrature (GDQ) Method is applied to study laminated composite shells and panels of revolution. The mechanical model is based on the so called First-order Shear Deformation Theory (FSDT) deduced from the three-dimensional theory, in order to analyze the above moderately thick structural elements. In order to include the effect of the initial curvature from the beginning of the theory formulation a generalization of the kinematical model is adopted for the Reissner-Mindlin theory. The solution is given in terms of generalized displacement components of points lying on the middle surface of the shell. The results are obtained taking the two co-ordinates into account, without using the Fourier expansion methodology, as done in semi-analytical methods. After the solution of the fundamental system of equations in terms of displacements and rotations, the generalized strains and stress resultants can be evaluated by applying the Differential Quadrature rule to the generalized displacements themselves. The transverse shear and normal stress profiles through the laminate thickness are reconstructed a posteriori by simply using local three-dimensional equilibrium equations. No preliminary recovery or regularization procedure on the extensional and flexural strain fields is needed when the Differential Quadrature technique is used. By using GDQ procedure through the thickness, the reconstruction procedure needs only to be corrected to properly account for the boundary equilibrium conditions. In order to verify the accuracy of the present method, GDQ results are compared with the ones obtained with 3D finite element methods. Stresses of several composite shell panels are evaluated. Very good agreement is observed without using mixed formulations and higher order kinematical models. Various examples of stress profiles for different shell elements are presented to illustrate the validity and the accuracy of GDQ method. © 2012 Elsevier Ltd. All rights reserved.

Keywords: First-Order Shear Deformation Theory , Generalized Differential Quadrature method , Laminated composite shells , Shear and normal stress recovery

The Generalized Differential Quadrature (GDQ) Method is applied to study laminated composite degenerate shell panels such as rectangular and annular plates. The theoretical treatment is maintained general in order to expose in a unique way the procedure adopted to obtain the stress profiles through the thickness of plates without specifying the equations for rectangular and annular plates. By simply imposing some geometrical relations the equations governing the problem of plates under consideration, that are degenerate shells, are inferred from the theory of shells of revolution. The mechanical model is based on the so called First-order Shear Deformation Theory (FSDT) deduced from the three-dimensional theory in order to analyse the above moderately thick structural elements. The solution is given in terms of generalized displacement components of points lying on the middle surface of the plate. After the solution of the fundamental system of equations in terms of displacements and rotations, the generalized strains and stress resultants are evaluated by applying the Differential Quadrature rule to the generalized displacements. The transverse shear and normal stress profiles through the laminate thickness are reconstructed a posteriori by using local three-dimensional elasticity equilibrium equations. No preliminary recovery or regularization procedure on the extensional and flexural strain fields is needed when the Differential Quadrature technique is used. By using GDQ procedure through the thickness, the reconstruction procedure needs only to be corrected to properly account for the boundary equilibrium conditions. In order to verify the accuracy of the present method, GDQ results are compared with the ones obtained with semi-analytical formulations and with 3D finite element methods. Stresses of several composite plates are evaluated. Very good agreement is observed without using mixed formulations and higher order kinematical models. Various examples of stress profiles for rectangular and annular plate elements are presented to illustrate the validity and the accuracy of GDQ method. © 2012 Elsevier Ltd. All rights reserved.

Keywords: Laminates , Numerical analysis , Plates , Shear and normal stress recovery

High quality electromechanical products require sophisticated and costly diagnostic tools to ensure the absence of defects in the final artefacts. The main requirements for reliability tests are flexibility, sensor sharing and early defect detection. The aim is the substitution of the current practice based on manual checking of few samples with standardized and repeatable quality control carried out by autonomous mobile platforms. Virtual planning of the inspection tasks, the simulation of the navigation in a poorly structured environment as well as the interaction with the product, are crucial aspects which have been faced through a dedicated system framework. The paper proposes a solution composed of a software for the virtual planning and simulation of inspection tasks, hardware setup composed of an autonomous platform with sensors and actuators, and a service oriented software infrastructure for navigation and perception. Consistent paths to be followed by the robot are elaborated in a graphical environment on the basis of inspected product locations and measuring tasks. The system has been implemented for household appliance inspection in reliability laboratories where life tests are carried out under real operation conditions. The results in terms of inspection mission planning capabilities and localization performances are presented. © 2012 Springer-Verlag.

Keywords: Autonomous diagnostic testing , Reliability test system , Virtual planning and simulation

The present work sets the basis for the development of a systematic eco-sustainable computer aided design procedure. During years modules for the specific design of all phases of a product life-cycle have been developed: manufacturing, assembly, reliability, maintainability, resilience, disassembly, end-of-use, etc. This work instead places itself in a broader context of "Design for ecology". It means to overcome the limits of a classic design process such as "Design for X", through an approach that makes the designer aware of the consequences that each design modification (to the geometry, the material or the manufacturing process) determines on the environmental impact of the product entire life-cycle. This work proposes a method of integrated management of (1)virtual prototyping software (such as structural optimization, FEM and CAD), (2) function modelling methodology and (3) LCA tools. It is mainly based on the configuration of structural optimization strategies especially conceived to obtain lighter and more compact products, therefore, more eco-sustainable. The method, due to the nature of the instruments it employs, can be applied only to products that can be modelled in a CAD environment. The article, in particular, shows how to articulate the workflow between virtual prototyping and LCA tools. A case study regarding a moped rim is used to explain the procedure while software implementation is still underway. Copyright © 2012 by ASME.

This article presents a very compact electromechanical wideband energy harvester optimized for tire applications. The device exploits an asymmetric magnetic spring to be adaptive and effective at almost any vehicle speed. The device has been simulated through an experimentally validated SIMULINK block-oriented model. The simulation takes into account nonlinear dynamic and adaptive resonant behavior of the seismic mass, electromagnetic, and magnetostatic coupling between floating magnetic mass and coils, and the transfer of the generated power to an external load by means of a nonlinear circuit interface. A particular focus on the pneumatic effect on the floating magnet has been made. 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 nonlinear equivalent spring dashpot model of the pneumatic effect and a method to estimate its parameters from geometry have been proposed. An analysis of different nonlinearities of the system at different vehicle speed and a study on the combined effect of softening and hardening behavior of the device have been performed and discussed. © SAGE Publications 2011.

Keywords: adaptive resonance , electromechanical device , energy scavenger , nonlinear dynamic

Objective: In restored teeth, stresses at the tooth-restoration interface during masticatory processes may fracture the teeth or the restoration and cracks may grow and propagate. The aim was to apply numerical methodologies to simulate the behavior of a restored tooth and to evaluate fatigue lifetimes before crack failure. Materials and methods: Using a CAD-FEM procedure and fatigue mechanic laws, the fatigue damage of a restored molar was numerically estimated. Tessellated surfaces of enamel and dentin were extracted by applying segmentation and classification algorithms, to sets of 2D image data. A user-friendly GUI, which enables selection and visualization of 3D tessellated surfaces, was developed in a MatLab® environment. The tooth-boundary surfaces of enamel and dentin were then created by sweeping operations through cross-sections. A class II MOD cavity preparation was then added into the 3D model and tetrahedral mesh elements were generated. Fatigue simulation was performed by combining a preliminary static FEA simulation with classical fatigue mechanical laws. Results: Regions with the shortest fatigue-life were located around the fillets of the class II MOD cavity, where the static stress was highest. Significance: The described method can be successfully adopted to generate detailed 3D-FE models of molar teeth, with different cavities and restorative materials. This method could be quickly implemented for other dental or biomechanical applications. © 2010 Academy of Dental Materials.

Keywords: 3D fatigue simulation , 3D image acquisition , CAD-FEM modeling , Class II MOD restoration , Micro-CT

This paper concerns the usage of virtual humans to validate lower limb prosthesis design. In particular, we are developing an innovative design framework centered on digital models of the whole patient or of his/her anatomical districts, which constitute the backbone of the design process. The framework integrates a set of virtual "assistants" to guide the technicians during each design task providing specific knowledge and design rules. In this paper, we focus the attention on the last step of the prosthesis deign process, i.e., the final set-up with the patient using a biomechanical model of the amputee. First, we describe the state of art on virtual humans and main features of the new design framework. Then, the application of virtual humans for the prosthesis set-up is presented as well as preliminary results. Copyright © 2011 by ASME.

Keywords: Lower limb prosthesis , Product development , Virtual humans , Virtual prototyping

This paper introduces a virtual laboratory to design prosthetic socket, which integrates a 3D CAD module, named Socket Modelling Assistant (SMA), specifically developed to create the socket digital model, and a CAE system to analyze the stumpsocket interaction. Software tool, named Virtual Socket Lab (VSL), is part of a knowledge-based framework to design lower limb prosthesis centered on digital models of the patient or of his/her anatomical districts. The focus of this paper is on the definition of an automatic simulation procedure to study the stump-socket interaction and validate socket design. We first introduce the new design framework and main features of VSL. Then, we present a state of art on FE models adopted for residual lower-limb and prosthetic socket during last two decades highlighting key issues. Finally, the identified procedure and the integration strategy within SMA are described as well as preliminary results of the experimentation. © 2011 CAD Solutions, LLC.

Keywords: Physics-based modelling and simulation , Socket , Socket-stump interaction

Viscoelastic contact interfaces can be found in various robotic components that are covered with a compliant surface (pad) such as anthropomorphic hands, biomimetic haptic/tactile sensors, prostheses, and orthoses. In all these cases, it is desirable to obtain thin and resistant pads with predetermined compliance and damping properties (e.g., mimicking the human skin and pulpy tissues). In order to overcome the limits of homogeneous layers of a soft viscoelastic material, which is commonly used in the aforementioned devices, this paper suggests the adoption of soft pads that are composed of a continuous external layer (skin) coupled with an internal layer having fluid-filled voids. The process to design the pad starts with the selection of a hyperelastic medium with proper tribological features, whose constitutive parameters are determined by numerically fitting nonlinear stress-strain curves under pure homogenous deformations. The optimization of the internal layer morphology is then achieved through nonlinear finite element analysis (FEA) that provides an estimate of hardness and friction influence on the pad static compliance. Finally, the pad is filled with a viscous fluid that is chosen to modify time-dependent phenomena and to increase damping effects. The effectiveness of the procedure is proven by designing and modeling better-behaved artificial pads that mimic human-finger dynamic properties. © 2011 IEEE.

Keywords: Finite deformations , finite element analysis (FEA) , hyperelasticity , quasi-linear model , viscoelastic contact

Constant-Force actuators based on Dielectric Elastomers (DE) can be obtained by coupling a DE film with particular compliant frames whose structural properties must be carefully designed. In any case, the practical achievement of a desired force profile can be quite a challenging task owing to the time-dependent phenomena which affect the DE electromechanical response. Within this scenario, a hyper-viscoelastic model of a rectangular Constant-Force actuator is reported. The model, based on the Bond Graph formalism, can be used as an engineering tool when designing and/or controlling actuators which are expected to work under given nominal conditions. Numerical simulations are provided which predicts the system response to fast changes in activation voltage and actuator position as imposed by an external user. © 2011 by ASME.

The haptic feedback perceived during the interaction with consumer products is an important aspect since it concurs in creating, together with the aesthetic features and sonic feedback, the emotional response during the first contacts with a product. And this may be decisive for the user's decision of purchasing a product instead of another one. So the design of the haptic behavior of interaction elements of products can be both a successful strategy for capturing consumers' attention but even a need for avoiding problems during the use. The paper describes the process of virtualization of the interaction with an industrial consumer product by means of haptic, sound and visualization technologies in order to obtain a prototype (interactive Virtual Prototypes) useful to design and test the haptic feedback of interaction elements directly with end users. Copyright © 2011 by ASME.