Virtual prototyping and digital twin

Concurrent Engineering methodology and process analysis and modeling showed the importance of tools that allow the designers to evaluate, from the beginning, different aspects of product definition. 3D CAD systems, simulation tools and virtual prototyping technologies can support the designer during her/his decision-making activity but, in order to provide an effective support, they must be tailored to the needs of the design process of each specific product. During last years, different types of tools appeared on the market to support this tailoring activity and to promote the development of product-dependent applications. In this paper, we have focused the attention on software tools named KAE (Knowledge Aided Engineering) development shells. Applications implemented by using this type of tools can support experts during the decision making process to evaluate alternative solutions. They provide a kernel for the integration of different technologies, and represent a basic step for the development of the product design. In this paper we present a brief overview of the architecture of a typical KAE application and we provide a survey of the most significant systems that we have developed, within different application domain, taking advantage of the KAE technology. © 2003 by Springer Science+Business Media New York.

Keywords: Feature technology , Knowledge aided engineering

Styling design, as every creature of the modern world, is born from various and multiple parents: taste's, evolution, marketing requirements, technical design constraints, costs and qualitative standards of the project. Furthermore, the multiplying of material and technological resources, extends the creative potential of designers, yet requires the acquisition of new knowledge: this leads to the need, from the very preliminary stages, of concurrent engineering approaches to manage the product development process and the different product views depending on the specialists involved. Time Compression Techniques (Rapid Prototyping, Reverse Engineering, conceptual modelling, process simulation) are suitable tools in implementing Concurrent Engineering principles, especially if based on Internet applications. However, today, the research effort has to be oriented towards the definition of an effective and well-structured model of the design process to successfully integrate such technologies. In this context the goal of the present work is the study of a styling product development methodology to minimize the process iterations maintaining an aesthetically coherent product model representation. We focus on the product model definition (using functional-aesthetic features) and on the 3D digitizing phase, that is the most critical aspect for the shape preservation. A practical example, developed in the office furniture domain, is reported.

In the racecar design process the definition of suspension type and geometry is an important stage. A good design of the main parameters, in terms of static and dynamic angles in bump and steer, is the basis of a successful racecar quite often. This paper aims at introducing the development of a new software tool, called MLKrace, that can analyse the suspensions kinematics for a wide range of different layouts. There are today a lot of commercial tools that analyse or simulate suspension behaviour. In general their application is restricted to the classic double wishbone suspension and in this case the calculation of the kinematics is not so difficult. This layout is used on both ends of the majority of formula and sports race cars but it isn't the only possible one. The MLKrace software is instead more suitable to analyse innovative suspension geometries, the mathematics being based on the resolution of the so-called Stewart platform, a method originally devised for parallel robot kinematics. Therefore full multilink or hybrid systems can be designed as easily as a double wishbone. In addition push rod, pull rod or outboard spring systems can be added and the driveshaft required float is computed. Multilink-McPherson hybrid suspensions can be designed as well. The flexibility is the great advantage of this new software. Apart from the mathematic model, a massive effort was devoted to the design of the Windows interface with the aim of making the designer's job particularly easy and effective compared to outdated MS-Dos interfaces of most of the existing software. The output is shown in the form of 2D and 3D animations, a large number of predefined diagrams, numeric tables and regression functions. Copyright © 2002 SAE International.

Despite massive research efforts carried out by racing car manufacturers aerodynamics is probably the most unexplored field in the design of high performance vehicles. Scale wind tunnel testing is still the most effective way for the development of a new car, CFD codes being at the experimental stage. Wind tunnel engineers produce what is called an "aero map": a simple graph expressing aerodynamic forces versus ride height. That means, drag, downforce, and relative distribution are measured on an array of front and rear different ride heights. The same concept can be applied to track testing with the use of proper sensors on the real vehicle, such as ground height laser sensors and suspension force transducers. Reading such a map and relating it to static and dynamic suspension characteristics is a vital task for performance optimisation. In the perfect world the centre of pressure would always be in the ideal position anywhere on the track, thus enabling the driver to make the most out of the car. As a matter of fact any unwanted, back and forth movement of the centre of pressure due to pitch and/or heave (e.g. under power, in braking, or on road bumps) affects cornering behaviour: the car can be perceived as difficult and tricky for the driver thus jeopardising performance. A module dedicated to non-linear aerodynamics (called "Aerolap") has been added to the RCS software for lap time simulation, working in close co-operation with the Minardi Formula 1 and BMS Scuderia Italia teams. The vehicle model can now take into account the effects of ride height variations on aerodynamic forces, as well as non-linear suspension and tire ground stiffness. The user can therefore simulate the impact of set-up modifications on aerodynamic balance along the track as well as on overall performance. The RCS project (presented at the 2000 SAE Motorsports Engineering Conference in Detroit) was conceived as a pit lane support tool for the race engineer, who usually works under pressure in a noisy, stressing environment were things happen -and decisions are taken- all very quickly. Therefore a particular effort was devoted to interface and graphics. Regarding the Aerolap an innovative method was devised for map visualisation as an alternative to the usual contour plot. This seems to enable a far more intuitive correlation with performance results. On the math side two different methods were used to approximate the aero map surface: a Gaussian array and the so-called Akima's triangles, the former giving more reliable results where extrapolation is required. Copyright © 2002 SAE International.

This paper outlines new trends in geometric modelling, showing how systems are moving from a geometry-based approach to a physically-based approach. The possibility to simulate the actual behaviour of a product is at the basis of Virtual Prototypes that are becoming a common practice in today's product development process. As a consequence, also interaction modalities and techniques have to be improved in order to satisfy new system requirements and functionalities. The research work described in this paper shows how haptic interaction techniques represent an evolution of current interaction technologies providing intuitive and realistic modalities for interacting with virtual applications. In particular, the paper describes a research work we have carried out integrating haptic technologies together with physically-based modelling and simulation techniques. © 2001 Springer Science+Business Media New York.

Keywords: Haptic interaction , Human-computer interaction , Non-rigid material modelling , Physically-based modelling , Virtual prototyping

The paper aims at introducing the developments of a performance simulation method for predicting the potential lap time of a given racing car on a given circuit. It is based on a previous work published in [1]. This first attempt produced fairly reliable results but it was not totally satisfactory since computation was very slow. It was then decided to restart from scratch with the following approach. Reference is made to the renowned «Milliken» [2]. The vehicle maximum G-G envelope is estimated. Then the model follows the «real» raceline -acquired with on-board instrumentation- performing within the G-G envelope. Accurate comparison with real-world data is used to identify and calibrate some of the model parameters. After calibration the model can be used to study the effect of different set-ups, aerodynamic balance, gear ratios etc. Where the circuit is new to the team a trajectory can be designed on a circuit map by using a built-in, parametric CAD-like interface. G-G envelope estimation prior to actual simulation has largely improved the computational speed. Also, the graphic interface aims at pit-lane use by the race engineer. The software is the product of a joint research between the University of Brescia and the team BMS Scuderia Italia therefore it is not available on the market. Copyright © 2000 Society of Automotive Engineers, Inc.

Kinematic modelling of robots and flexible material simulation have been an important aspect in robotic research issues over the last years. In this article a new approach for the design of arbitrary gripper and robot architectures will be presented. It will be shown how these robot systems can be simulated based on the presented design structure. Further the integration of flexible material simulation will be displayed. A particle based object models will be shown and the mathematical basics will be described. Finally, the integration of the flexible material simulation into the robot simulation software will be displayed and evaluated.

A modular environment for modeling, simulation, and 3-D animation of mechanical and robotic system is described. The key word of the whole project is modularity, accomplished first of all in the dynamic modeling approach, through the adoption of a declarative definition of models, and a strict standardization of the interfaces among submodels. The issue of efficiency is also pursued through the adoption of an object-oriented database to manage the system model data and through a symbolic manipulation process. This allows one to derive an efficient procedural form of an numerical solution of the system model.

This modeling and simulation environment allows the system engineer to design and simulate automated systems handling non-rigid materials taking into account their physical properties. The system's three main components include one which geometrically models both the workspace and the handling machinery, one which physically models and simulates the behavior of flat elastic and visco-plastics bulk types of non-rigid materials, and a robot off-line programming system. The second module, SoftLand, is based on the particle-based model and constitutes the innovative component.

In this paper are calculated stress concentration factors in collar and shouldered shafts subjected to axial or bending load, using both the boundary element (BEM) and finite element (FEM) methods. The values obtained by the two methods are in good agreement; for shouldered shafts in bending they are also very close to the available data in the literature obtained by the photoelastic technique. For shouldered shafts in traction, the values obtained are close to some experimental data of the literature and higher than others. Additionally, BEM and FEM values are interpolated in order to give useful plots and formulae. © 1998 Elsevier Science Ltd.

Keywords: Boundary element , Finite element , Stress concentration factor

The paper describes a method to optimise the thickness balance within a composite laminate with layers oriented according to a limited set of angles. The laminate must be symmetric, balanced and loaded in-plane. The optimisation process is particularly suited to be used in conjunction with a finite element program. It provides the designer with the optimal overall engineering characteristics and a list of all the possible orientation combinations ranked with respect to their safety factor. The optimisation method is based on the first order gradient optimum search method and operates iteratively in the engineering elastic characteristics field. The cost function implemented up to now is the structure stiffness but no conceptual limitations exist for different functions. Some simple applications are listed at the end of the paper in order to verify the capabilities of the method. © 1997 Elsevier Science Limited.

Several industrial sectors are concerned with the design and manufacturing of flexible products. However traditional CAD and simulation systems cannot be used to study and simulate process that involve such kinds of products. Our objective has been to develop a modelling and simulation environment able to deal with different classes of non-rigid material, from flat to bulk, in a unified way. This has been done at two different levels: object modelling and interactions modelling. For what concerns the former a particle-based model has been adopted where an object is described by a set of particles with their mass, radius and other physical properties. Regarding the latter we decided to define a unified approach to manage object interactions with the environment. To verify the potential of the developed prototype some application case studies have been selected: the automated folding of a cotton sleeve, the draping of a skirt over a human body and the opening and closure of a convertible car soft top.

The paper presents a software environment to model and simulate non-rigid materials behaviour during handling operations according to their physical properties (e.g. stiffness), and to detect undesirable deformations (e.g., material breakage). The system provides a graphical and integrated environment for modelling and graphically simulating rigid objects (e.g. robot arm, gripper) combined with flexible products (e.g. garment, meat). It consists of three main modules: a module to geometrically model the workspace and the robot composing the automated handling system, a module to physically model and simulate the behaviour of flexible materials and finally a module for robot off-line programming. An approximated and descretised model has been adopted to describe non-rigid materials in order to incorporate both its geometric and physical properties. To show the functionality of the system, the simulation of an industrial operation (automated folding of a cotton sleeve) is illustrated.

The top Formula 1 and Indycar teams make large use of computer simulation to improve the performance of their cars and make the set-up process quicker on the circuit. The paper aims to present a lap time simulation software dedicated to racing cars. It is based on the background of vehicle dynamics research developed at the University of Brescia, Italy (see [1]). It should be stated that racecar dynamics is strongly non-linear due to the fact that tyres are always very near the limit of adhesion. Moreover this makes the effect of lateral load transfer fundamental for the general balance of the car. Therefore Pacejka's Magic Formula has been used for lateral force/slip while longitudinal force computation is based on the assumption of a maximum longitudinal coefficient of friction μ. This is not only for simplicity but it is also due to lack of available data. The combined case is then based on the so-called "traction circle". Lateral and longitudinal load transfer and downforce as well as their effects on tyre load are taken into account. The vehicle model is capable of following a trajectory acquired with the on-board instrumentation. Also, the use of genetic algorithms enables the program to find the optimum cornering line for any given track. Some results are shown and compared with real world data. © Copyright 1996 Society of Automotive Engineers, Inc.

In a previous work the stress intensity factors of shouldered and collar shafts are determined by a boundary element method (BEM) analysing the influence of the ratios between shaft and collar diameters, between the rounded fillet radius and shaft diameter, between length and height of the collar. In general the values obtained are lower than experimental values of the literature, hence it seems advisable to compare results with those obtained by another numerical method. In addition to studying other configurations by BEM, stress concentration factors are hence calculated by a finite element method (FEM) and compared with the BEM and literature results. BEM and FEM values are interpolated in order to give useful plots and a formula. © 1995.

Keywords: boundary element method , collar shaft in torsion , shouldered shaft in torsion , Stress concentration factor

The time of the "magic touch" approach to race car design is nearly over, and modern engineering techniques are more and more employed in high-level racing. Finite Element Analysis, Computational Fluid Dynamics, Vehicle Dynamics are some of the computer-aided methods which are being successfully applied to improve engine performance, aerodynamics, structural effectiveness and driveability. People at the Department of Mechanical Engineering of the University of Brescia have been working on chassis and suspension modeling in co-operation with racing and sports car makers and leading-edge teams since 1989. Current research partners are the FIAT Research Centre (CRF), Dallara Racing Cars, the Scuderia Italia Touring Car Team, and others.

In the present paper a methodology is described whereby the subdivision of a multiply connected planar domain into mappable regions is automatically performed. The technique proposed, which was developed to be applied within an interface between a geometric modeler (b-rep type) and a 3-D BEM code for elastic stress analysis, can be as well applied to 2-D finite element discretization problems. At the present stage of development, the technique operates over planar domains which are externally and internally bounded by polygonal contours and may contain any number of circular holes.

The paper describes a method to optimize composite structures which is particularly useful in conjunction with the finite element technique. The main features of the method consist in a two level approach: first an overall optimization of an equivalent orthotropic laminate is performed, then an optimum lay-up sequence search is carried-on. The optimization techniques are based on the gradient method and the Lagrangian multipliers technique. In the present implementation some limitation must be fulfilled: the laminates must be balanced and symmetric. Up to now only stiffness related cost functions have been considered; some applications are displayed at the end of the paper.

Stress intensity factors (SIFs) are computed by the boundary element method for standard compact tension specimens. Traction singular elements are employed along the crack front which enable SIFs not only to be extrapolated from crack opening displacements but also to be directly obtained as problem unknowns. Both straight and curved crack fronts are analyzed: the latter are taken to be in the form of circular arcs with curvature radii ranging from 3.145 to 0.707 the specimen thickness. The influence of Poisson's ratio on the stress intensity factor distribution is also investigated. © 1987 Martinus Nijhoff Publishers.

In this paper 8‐node traction singular boundary elements are employed to represent displacement and traction variations in the vicinity of the crack front in three‐dimensional geometries. The numerical procedure suggested for evaluating the singular integrals extending over these special elements is described. The efficiency and accuracy of the special elements and integration procedure are demonstrated by the results obtained in a simple test problem whose analytical solution is known. The interaction of two circular coplanar cracks embedded in an infinite medium under uniform tension loading is also analysed. Finally, the stress intensity factor variation computed for a semi‐circular inner surface crack in a pressurized cylinder is presented. Copyright © 1987 John Wiley & Sons, Ltd