Virtual prototyping and digital twin

Recent trends in industrial manufacturing impose the adoption of changeable systems, based on reconfigurable and flexible equipment. In this scenario, industrial robotics platforms are central to design highly reconfigurable systems. A Robotic Reconfigurable Machining Platform (RRMP), as defined, is a modular architecture for robotic workcells, designed in order to exploit the flexibility features of robots and extend their field of application to high precision machining. RRMP calibration is a key task, which involves calibration of tools, workpieces and peripherals. However, state-of-the-art calibration methods and tools lead to hardly predictable system downtime, which impacts the reconfiguration phase. A novel method to perform the workpiece calibration is proposed for the reduction of the reconfiguration efforts in RRMPs. The method is addressed through a full integration with a virtual environment for robot simulation and programming. The method is finally applied to an industrial case study and compared to the most widely diffused online approach.

Keywords: Robot offline programming , Robotic machining , Workpiece calibration

Contract furniture design is the process of creating finished commodities for hospitality, retail, store, office, restaurants, etc. According to the process stage, numerous stakeholders with different skills, abilities, background and interests are involved in the development of products and services. The management of these temporary networks is complex and requires proper computer-supported cooperative work platforms able to achieve coherent design solutions. The paper explores contract furniture design challenges and requirements to define a technological platform to support companies in market analysis and penetration, product configuration and team working. System architecture and its main software modules are described in detail and preliminary implementation results shown. © 2014 CAD Solutions, LLC.

Keywords: collaborative product development , virtual engineering , web enabled design

The large volume vacuum systems are used in many industrial operations and research laboratories. Accidents in these systems should have a relevant economical and safety impact. A loss of vacuum accident (LOVA) due to a failure of the main vacuum vessel can result in a fast pressurization of the vessel and consequent mobilization dispersion of hazardous internal material through the braches. It is clear that the influence of flow fields, consequence of accidents like LOVA, on dust resuspension is a key safety issue. In order to develop this analysis an experimental facility is been developed: STARDUST. This last facility has been used to improve the knowledge about LOVA to replicate a condition more similar to appropriate operative condition like to kamaks. By the experimental data the boundary conditions have been extrapolated to give the proper input for the 2D thermofluid-dynamics numerical simulations, developed by the commercial CFD numerical code. The benchmark of numerical simulation results with the experimental ones has been used to validate and tune the 2D thermofluid-dynamics numerical model that has been developed by the authors to replicate the LOVA conditions inside STARDUST. In present work, the facility, materials, numerical model, and relevant results will be presented. © 2014 A. Malizia et al.

This article presents a methodology for the treatment of uncertainty in nonlinear, interference-fit, stress analysis problems arising from manufacturing tolerances. Image decomposition is applied to the uncertain stress field to produce a small number of shape descriptors that allow for variability in the location of high-stress points when geometric parameters (dimensions) are changed within tolerance ranges. A meta-model, in this case based on the polynomial chaos expansion, is trained using a full finite element model to provide a mapping from input geometric parameters to output shape descriptors. Global sensitivity analysis using Sobol's indices provides a design tool that enables the influence of each input parameter on the observed variances of the outputs to be quantified. The methodology is illustrated by a simplified practical design problem in the manufacture of automotive wheels.

Keywords: Dimensional tolerances , Global sensitivity analysis , Interference fit , Polynomial chaos expansion , Shape descriptor

A strong integration between different design tools is desirable to improve the work of engineers, reducing the number of errors and speeding up the design process. In this article, the authors present a strong integration between three-dimensional computer-aided design models and multidomain simulation applied to the design of a magnetomechanical energy harvester. A MATLAB framework controls a block-oriented Simulink model, drives the Finite Element Method Magnetic simulation and manages the updating of the Solid Works computer-aided design models of the device. The parameters involved in the different simulations and in the computer-aided design models are stored in a unique data file. Moreover, constructive drawings are automatically updated and are immediately suitable for tolerance and design constraint checks and also for the effective prototyping of the device. Constructed prototypes are immediately suitable to validate the performance predicted by the model.

Keywords: Computer-aided design-computer-aided engineering integration , Energy Scavenging , Multidomain simulation , Virtual prototyping

The dynamic properties of crossing and veering in coupled structures have been studied both numerically and analytically, but they are difficult to investigate using Finite Element Analysis because of the change in the topological arrangement due to the different configuration. Isogeometric Analysis, recently developed method for numerical simulation, could overcome some of the drawbacks of the change in the configuration such as remeshing, coupling between the nodes of the different models, need of a fine mesh to allow small change in the configuration to be comparable to the mesh size. The key of this method is to avoid meshing and using the same basis functions used by the geometry, namely Non-Uniform Rational B-Splines (NURBS), to define the discretization of a Finite Element model. Other advantages are the possibility of increasing the order of the functions to obtain smooth stress field across the element interfaces. An experimental test-rig composed by beams and masses, which allow different configuration and dynamic coupling as well, is used as test case to validate the accuracy of the results with respect to both experimental data and classical Finite Element Analysis.

Keywords: Crossing and veering phenomena , Isogeometric analysis , Modal analysis of coupled structure , Nitsche's method

The present paper proposes an experimental and a numerical analysis of the frictional effect on the mode II delamination. Frictional stresses between the crack edges can absorb and dissipate significant energy contributions in the delamination zones, especially under cyclic loading conditions. The experimental tests are performed for a set of unidirectional End-Notched Flexure (ENF) composite specimens, which are subjected to fatigue loading law with increasing mean value. The numerical analyses are performed considering a cohesive-frictional constitutive model, which is able to reproduce the transition of the interface behavior from the sound elastic condition to the fully cracked one, with only frictional strength. Finally, the numerical results are compared with the experimental ones in order to evaluate the frictional constitutive parameters. © 2013 Elsevier Ltd.

Keywords: Delamination , Fracture , Friction , Interface model , Mode II

A drilled plate of ferromagnetic material suitably coupled by coils of enameled copper wire fed by a DC power supply to 30 V is considered in this paper. It is analyzed with finite element and later experiments are performed to validate the obtained results. After polishing the plate, two strain gauges for measuring the deformation along the x axis and along the z axis are installed. The values of strain are 5 μm/m in z direction and -2 μm/m in x direction. The experimental-numerical comparison shows that the laboratory results are lower than numerical, while signs and orders of magnitude are the same. It is concluded that the results of the FEM analysis can be considered acceptable because the orthogonality of the plane of the coils relative to the plane of the plate and because of the packing coefficient of copper. The position of the two coils is changed in order to found the optimal configuration which allows the maximum compressive stresses in the area around the hole; it is obtained using two coils joined (positioned above the hole) or using a single coil. Moreover numerical simulations are executed to verify the improvement of the fatigue life calculating the stress at the crack tip. © 2013 Elsevier Ltd. All rights reserved.

Keywords: Drilled plates , Induced strain , Induced stress , Magnetic induction , Magnetoelastic behavior

The paper presents a concept design of a remote handling (RH) system oriented to maintenance operations on the divertor second cassette in FAST, a satellite of ITER tokamak. Starting from ITER configuration, a suitably scaled system, composed by a cassette multifunctional mover (CMM) connected to a second cassette end-effector (SCEE), can represent a very efficient solution for FAST machine. The presence of a further system able to open the divertor port, used for RH aims, and remove the first cassette, already aligned with the radial direction of the port, is presumed. Although an ITER-like system maintains essentially shape and proportions of its reference configuration, an appropriate arrangement with FAST environment is needed, taking into account new requirements due to different dimensions, weights and geometries. The use of virtual prototyping and the possibility to involve a great number of persons, not only mechanical designers but also physicist, plasma experts and personnel assigned to remote handling operations, made them to share the multiphysics design experience, according to a concurrent engineering approach. Nevertheless, according to the main objective of any satellite tokamak, such an approach benefits the study of enhancements to ITER RH system and the exploration of alternative solutions. © 2013 Elsevier B.V.

Keywords: Divertor , FAST , Fusion engineering , ITER , Remote handling , Virtual prototyping

In this paper, two optimization approaches to improve the product design process have been analysed. Through the analysis of a case study, concerning the designing of a new High Energy Absorption Rear Underrun Protective Device (HEARUPD), two different optimization approaches (simplex and simulated annealing) have been compared. In the implemented optimization processes, the crash between an economy car and the rear part of a truck has been simulated by dynamic numerical (FEM) analyses. Moreover, authors have proposed the use of a suitable linear function of four variables with the purpose of reducing the multi-objective optimization processes to mono-objective ones. That has been made to simplify the analysis procedures without affecting the quality and the completeness of the optimization processes. The obtained results, as well as showing the high effectiveness of the integrated use of numerical crash analyses and optimization methods, demonstrate that simplex method is more effective than simulated annealing one for optimization problems where the single analysis loop requires much time. Even if the solutions are quite similar in terms of calculated values of the objective function, design and state variables, simplex method needs shorter computational time than simulated annealing to obtain an optimized solution. © 2012 Springer-Verlag London Limited.

Keywords: Numerical crash analysis , Optimization , Simplex , Simulated annealing

In this work a new distal interlocking system has been developed which is easy to use, allows a reduction of the operating time and consequently the exposure to radiations both for surgeon and patient. The main goal of this study has been the design of a new intramedullary nail for tibial fractures able to simplify and speed up the distal locking operation phases. After a preliminary stage during which several candidate concepts have been proposed and analysed, the best solution has been developed and deeply investigated. The new system, called "expansion nail", has been firstly modelled by setting up a full parametric CAD model and, then, tested by running non linear FEM analyses to evaluate stresses and stability of the joining during normal working conditions. The new design has shown very high mechanical stability in the axial compression and torsional load cases. Since its very simple self-locking system, the new expansion intramedullary nail would reduce the operating time and the exposure to radiations for the surgeons as well as the patients. © 2012 Springer-Verlag France.

Keywords: Intramedullary nail , Non linear FEM analyses , Parametric CAD model , Redesign , Virtual prototyping

This article concerns the design of lower limb prosthesis, both belowand above knee. It describes a newcomputer-based design framework and a digital model of the patient around which the prosthesis is designed and tested in a completely virtual environment. The virtual model of the patient is the backbone of the whole system, and it is based on a biomechanical generalpurpose model customized with the patient's characteristics (e.g. anthropometric measures). The software platform adopts computer-aided and knowledge-guided approaches with the goal of replacing the current development process, mainly hand made, with a virtual one. It provides the prosthetics with a set of tools to design, configure and test the prosthesis and comprehends two main environments: the prosthesis modelling laboratory and the virtual testing laboratory. The first permits the three-dimensional model of the prosthesis to be configured and generated, while the second allows the prosthetics to virtually set up the artificial leg and simulate the patient's postures and movements, validating its functionality and configuration. General architecture and modelling/simulation tools for the platform are described as well as main aspects and results of the experimentation. © 2013 The Author(s) Published by the Royal Society. All rights reserved.

Keywords: Digital patient , Human modelling , Lower limb prosthesis , Virtual prototyping

This paper presents an environment, named Virtual Testing Lab-VTL, where the orthopedic technicians can test the prosthesis replicating the traditional procedures. It is part of an innovative design framework centered on digital models of the whole patient or of his/her anatomical districts, which constitute the backbone of the whole prosthesis design process. The virtual lab permits to realize a complete amputee's digital model, an avatar, by which it is possible to execute prosthesis set up and evaluate its functionality simulating postures and movements. First, we describe the state of art of techniques used, i.e., virtual humans and motion capture systems. Then, the application of virtual humans for the prosthesis design and simulation is presented as well as preliminary results. © 2013 CAD Solutions, LLC.

Keywords: Prosthesis design , Virtual human , Virtual testing

Lower limb prostheses for above or below knee amputees are still designed and produced almost completely in a manual way, deeply relying on the experience and manual skills of orthopaedic technicians. This paper presents the main features characterising the prototype of a virtual environment developed to assist the technicians designing and testing the prosthesis. To reach the ambitious goal of replacing the manual process with a complete virtual one several issues have been considered and addressed: the capture and formalisation of process knowledge of orthopaedic technicians, the acquisition of patient's information and digital data, the development of an integrated solution to design and test standard and custom-fit components and the simulation of the gait of a virtual human wearing the virtual prosthesis. The architecture of the prosthesis design platform as well as the modelling and simulation tools are described. Finally, the experimentation phase and related results are presented and discussed. © 2013 Copyright Taylor and Francis Group, LLC.

Keywords: design environment , digital human modelling , lower limb , prosthesis

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 design framework is described, detailing features of the main design steps. Then, the paper discusses the acquisition and formalisation of the knowledge related both to the prosthesis manufacturing process and to the considered component. Finally, we present the computer-aided module, named socket modelling assistant-SMA, we specifically developed 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 modelling steps and available interactive tools that emulate orthopaedic technician's operations are described. Results of the experimentation phase are described. At current state of the prototype development, they are encouraging and have permitted to preliminarily validate the proposed approach and envisage future improvements. Copyright © 2013 Inderscience Enterprises Ltd.

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

This paper focuses on a structured methodology that uses virtual reality (VR) and digital human modeling (DHM) to study maintenance procedures of industrial products. VR technologies help to highlight the most critical aspects of maintenance operations, while DHM tools allow detailing working sequences. Data coming from these analyses are then used to draw up a multimedia maintenance manual based on digital video animations, audio comments, explanatory images and written recommendations. Information is available to maintenance personnel directly on the working site through portable electronic devices. Further, web-based multimedia manuals can be updated on-line and help to shorten learning time and maintenance downtimes. © 2013 Springer-Verlag France.

Keywords: Design for maintainability , Digital human modelling , Multimedia maintenance manuals , Virtual design review

Servo-actuated mechanisms are increasingly sub-stituting fully mechanical drives in order to increase flexibility and reconfigurability of modern automatic machines. The overall servomechanism performance, especially in the case of high-dynamic motions, is the direct consequence of several interacting factors, namely electric motor and linkage dynamics, controller efficacy, and requested motion law. In particular, Point-To-Point (PTP) trajectories are usually designed in order to comply with technological constraints, imposed by the required interaction with the handled product, and to maximize some optimality criterion such as, for instance, energy efficiency or limited actuation torques. In this context, the present paper proposes a novel method for generating either energy-optimal or torque-optimal PTP motions described by piecewise fifth-order polynomials. The optimization cost functions are based on a virtual prototype of the system, which comprises behavioral models of power converter, controller and electric motor coupled with the mechanical system. Results are then compared with experimental data obtained on a physical prototype. The comparison quantitatively shows that better-behaved PTP trajectories can be designed by including the dynamic contribution of each sub-system component. © 2013 IEEE.

Keywords: Servo-Actuated Mechanism , Trajectory Generation , Virtual Prototyping

Constant-force actuators based on dielectric elastomers can be obtained by coupling a dielectric elastomer 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 dielectric elastomer's electromechanical response. Within this scenario, a hyperviscoelastic 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 that are expected to work under given nominal conditions. Simulations and experimental results are provided, which predict the system response to fast changes in activation voltage and actuator position as imposed by an external user. © The Author(s) 2012.

Keywords: bond graph modeling , Dielectric elastomer actuator , quasi-linear viscoelasticity

This paper reports about the design and modeling process of high performance servo-actuated mechanisms for automatic machines.Besides being a delicate and time consuming process, coupled simulations based on virtual prototyping finally offer the chance to integrate engineering methods proper of control system engineering and mechanical design. In particular, the main target of this work isto investigate how different virtual prototyping approaches, each havingincreasing level of detail, can contribute to the appropriate prediction of the expected machine performance.These results are then compared with experimental data obtained on a real servomechanism prototype. The comparison quantitatively demonstrate the improvement on torque prediction and position error reduction when detailed models of the controller and the electric motor dynamics are coupled with the mechanical system model. © (2013) Trans Tech Publications, Switzerland.

Keywords: Co-simulation , Digital product design , Integrated mechatronic design , Virtual prototyping

A continuum model is described for the study of the electro-elastic finite deformations of dielectric elastomers. The model: i) derives directly from a global energy balance; ii) does not require the postulation of any force or stresstensor of electrical origin; iii) only requires the knowledge of permittivity and shear moduli of the considered material; and iv) is presented in Lagrangian form which is suited for the implementation in multi-physic finite element simulation environments.