Virtual prototyping and digital twin

Although the 3D shape recovery of a real object have been greatly improved in the last few years, modeling a complex virtual object by starting from the real prototype is still a very time-consuming activity. In this paper an originally conceived method and testing software to recover a CAD model from a real object is presented. The developed software tool joins a professional Computer-Aided Design (CAD) and a Mixed Reality (MR) tool in the same interface, enabling the operator to use standard CAD tools and features together with a camera, which provides external image streaming displayed in the workspace background. Moreover, a special programmed library performs a real-time calculation of camera position and other parameters with respect to standard markers in order to drive the CAD 3D virtual camera and align it to external world. In that way rendered virtual models may be superimposed to external images of reality grabbed by the video camera. Thus with MR-CAD tool the operator may easily recover a complex shape directly from the external views of a real object or may start the object re-design from the previous reconstructed geometry. Furthermore the interface is totally integrated in a CAD environment, both avoiding to work with unfamiliar new software and exploiting CAD geometry database and tools. Finally, MR-CAD can be considered a significant step ahead in the bi-directional interaction of virtual and real models, reducing also the gap between real prototypes and CAD data.

Keywords: Augmented reality , Mixed-reality , Reverse engineering , Virtual prototyping

Researchers in astrophysics and earth observation are still interested in balloon campaigns for making measurements outside the atmosphere. It is possible to trim a bit more from the ballooning costs by increasing the number of parts that can be reused, and by the careful design, the integration and the consolidation of a standard gondola apparatus (something like the mass production of cars). This paper will focus on one of the aspects capable of reducing costs, namely reusable power sources such as solar panels (SP) and fuel cells (FC) and how to protect them during the most difficult phases of the flight (take-off, landing). We will describe two possible ways of deploying and stowing a SP, and report the results of a thermal simulation aimed at ascertaining whether FC may be used in a stratospheric balloon environment.

This paper presents a plug-in, named Cloth Assembler, implemented in the framework of the Italian PRIN Project (Research Project of National Interest) VI-CLOTH (Virtual CLOTHing). The base idea is to allow the designer to interactively define/the necessary information to assemble 2D panels on a virtual mannequin and to generate the 3D physical model in its initial configuration, initial step for the garment simulation process. Starting from 2D single pieces, ClothAssembler allows a user, as a virtual tailor, to specify assembly rules among cloth panels (e.g., cut lines, dart, and buttons), insert accessories, such as zips and hooks, and, finally specify finishings on single pieces and the presence of different textile multilayer, pockets, reinforcement lines, etc. The plug-in can be easily integrated with any commercial 2D CAD system and represents the connection element between 2D cloth world and 3D physics-based modelling and simulation systems. It has been validated with three real test-cases, a T-shirt, a denim skirt, and a pair of trousers.

Keywords: Apparel design , Assembly process , CAD , Cloth models , Virtual prototyping

Cloth modelling is a research field of increasing interest both for computer animation and computer-aided design purposes. Aiming at being closer to cloth manufacturers needs, this work proposes an integration of a particle-based modelling approach within a CAD oriented system for real design of apparel and complex-shaped cloth. The particle-based model, originally defined on single textile layers, is extended to take into account the physical effects of seams and darts, construction constraints, layered parts, and other manufacturing processes that contribute to the final shape of the garments. Starting from an initial 3D configuration of the particle grid consistent with mannequin and support geometries, the physical simulation process is then computed, based on constrained Newtonian dynamics laws. Stable and efficient algorithms for the time discretization of the Newtonian ODE problem are proposed, based on implicit and semi-implicit BDF(2) or hybrid Euler-BDF(2) techniques. As applications, several test models are considered, simulated on rigid supports or mannequins, for both numerical comparisons and global shape analysis, from simple cloth geometries up to complex-shaped models for real apparel manufacturing. © 2006 Elsevier Ltd. All rights reserved.

Keywords: Apparel design , Cloth modelling , ODE solution , Particle-based modelling , Virtual simulation

The paper presents the results of a research project aimed at developing an innovative system for modeling industrial 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 six degrees of freedom (DOF) haptic tools for modeling digital shapes, with sweep operators applied to class-A surfaces and force computation models based on chip formation models. The system aims at exploiting designers' existing skills in modeling products, improving the products design process by reducing the necessity of building several physical models for evaluating and testing the product designs. The system requirements have been defined observing designers during their daily work and translating the way they model shapes using hands and craft tools into specifications for the modeling system and the haptic tool. The system prototype has been tested by designers who have found it intuitive and effective to use. © Springer-Verlag London Limited 2005.

Keywords: Haptic modeling , Haptics , Product design , Virtual prototyping

The paper presents two applications of haptic technologies to demonstrate how they can increase human computer interaction during different steps of design process. The first application aims at developing a system to generate digital shapes by manipulating haptic tools that resemble the physical ones that the modelers use in everyday work. The second is focused on the use of haptic interfaces to evaluate ergonomics of virtual products control boards. We designed and developed the mentioned haptic devices; the first uses two FCS HapticMaster equipped with a innovative strong and stiff 6 DOF device carrying simulated clay modeling tools. The second is an "ad hoc" mechatronic device able to simulate some controls with rotary motions (knobs). The described haptic devices are integrated in more complex virtual reality applications; the paper describes their architecture and the methodologies proposed to simulate material shaping and ergonomic validation. The main aspects of haptic modeling and rendering are also discussed. © 2006 Elsevier Ltd. All rights reserved.

Keywords: Haptic modeling , Haptics , Product design , Virtual prototyping

In the productive process of moulds for ophthalmic lenses, the availability of a specialized tool for the analysis of the optical property of 3D virtual models of ophthalmic lenses and relevant injection moulds, may reduce the tests on physical prototypes during the design phase. The optical properties of interest are usually power and astigmatism of the lens surface. Both of them are proportional to the geometric curvature of the lens surfaces. Therefore the identification of the optical properties of a surface can be brought back to the computation of the minimum and maximum curvature maps on lens surface. Some commercial software tools able to perform curvature analysis on both physical and virtual models exist, but they show some limitations: methods and algorithms used to compute the desired parameters are not declared, the size of the area used to compute the desired parameter cannot be set by the operator and no estimate on the accuracy of the computed results is given. These last two issues are crucial: the area considered in the analysis should be related to the area actually used; the accuracy of the adopted algorithm should be verified and compared with the eye sensitivity to geometric errors of the lens surface. Aim of the present work is to describe the functioning principles of a software tool for curvature analysis and optical properties computation of either virtual models expressed as high resolution meshes or physical prototypes of lenses sampled using a Coordinate Measuring Machines (CMMs), that overcomes the cited limitations. Such tool will be included into an integrated tool for design, analysis, manufacturing and verification of ophthalmic lenses.

A Design of Experiment (DoE) based methodology is proposed for use in optimising sailing mast structures. The method uses Finite Element Analysis to simulate mast behaviour when subject to typical design loadings. Due to the large number of possible combinations of design variables the use of a fractional factorial selection is used to determine their values for the limited number of simulations required. The analysis is based around a mast for use with the Mini Transat 6.50 class of yacht and provides a suitable challenge when compared to the typically conservative approach used in mast design. The mast structure is considered with respect to standing rigging working loads and spreaders geometry on the deformed shape of a pretensioned mast. Responses in terms of maximum value of mast camber, position of mast camber and generalized distance from optimal curves are provided, response surfaces over design variables domains are built and the most influential parameters are selected. Moreover, the present approach allowed us to provide combinations of parameters leading to optimal matching between a given target curve and the shape of a pretensioned mast. © 2006 Roval Institution of Naval Architects.

The results of the braking numerical simulations on a pegs-wing ventilated disk brake rotor, obtained by performing a fading braking procedure, are compared with the experimental ones obtained in the same brake, mounted on a work bench, in the same fading braking procedure. The numerical simulations are performed on the entire disk, besides some structural parameters, thermal conductivity, specific heat and elastic modulus, are considered as a function of the temperature; the other parameters are considered as constant. The results of the numerical simulations are in a good agreement with the experimental ones. It is also shown that numerical calculations can be considered conservative, since the numerical thermal field is a little bit higher than the experimental one. Furthermore the pegs-wing ventilated disk brake rotor is able to dissipate a great amount of thermal flux showing a great dimensional stability.

Keywords: Caliper , Disk brake rotor , Fading testing procedure , Finite elements , Pads , Thermal stress

The integration of physics-based models within CAD systems for garment design leads to highly accurate cloth shape results for virtual prototyping and quality evaluation tasks. To this aim, we present a physics-based system for virtual cloth design and simulation expressly conceived for design purposes. This environment should allow the designer to validate her/his style and design option through the analysis of garment virtual prototypes and simulation results in order to reduce the number and role of physical prototypes. Garment shapes are accurately predicted by including material properties and external interactions through a particle-based cloth model embedded in constrained Newtonian dynamics with collision management, extended to complex-shaped assembled and finished garments. Our model is incorporated within a 3D graphical environment, and includes operators monitoring the whole design process of apparel, e.g. panel sewing, button/dart insertion, multi-layered fabric composition, garment finishings, etc. Applications and case studies are considered, with analysis of CAD modelling phases and simulation results concerning several male and female garments. © 2004 Elsevier Ltd. All rights reserved.

Keywords: Cloth design , Newtonian dynamics , Physics-based modelling , Virtual simulation

Current tools aimed at supporting the conceptual phase of product design are not intuitive to use, and do not exploit designers' skill and creativity. This paper presents the results of a research work aiming at integrating user-friendly and effective ways of interaction based on ad-hoc haptic interfaces into free-form shape modeling systems. Copyright © 2005 by the Association for Computing Machinery, Inc.

Keywords: Concept product design , Free-form shape modeling , Haptic modeling , Haptics , Virtual prototyping

Gestures, besides speech, represent the mostly used means of expression by humans. For what regards the product design field, designers have multiple ways for communicating their ideas and concepts. One of them concerns the model making activity, where designers make explicit their concepts by using some appropriate tools and specific hand movements on plastic material with the intent of obtaining a shape. Some studies have demonstrated that visual, tactile and kinesthetic feedbacks are equally important in the shape creation and evaluation process [1]. The European project "Touch and Design" (T'nD) (www.kaemart.it/touch-and-design) proposes the implementation of an innovative virtual clay modeling system based on novel haptic interaction modality oriented to industrial designers. In order to develop an intuitive and easy-to-use system, a study of designers' hand modeling activities has been carried out by the project industrial partners supported by cognitive psychologists. The users' manual operators and tools have been translated into corresponding haptic tools and multimodal interaction modalities in the virtual free-form shape modeling system. The paper presents the project research activities and the results achieved so far. Copyright 2005 ACM.

Keywords: Haptic interaction , Haptic modeling , Virtual prototyping

Purpose - To set-up the study of an unmanned system for refuelling of vehicles, with attention to VOCs recovery. Design/methodology/approach - Presents the architecture of a robotic arm for refuelling. Special attention was allocated to the safety characteristics of the automatic refuelling station assuring the highest protection of people and their safeguard against accidents, preventing any dangerous response of the robotic arm in all the predictable conditions. A concurrent engineering methodology jointly with the life-cycle approach was adopted for the study and evaluation of the equipment. Findings - Finds that a six DoF arm with a tubular architecture with relocated actuation equipped with a specifically designed filler satisfying stage II rules is suitable to perform the task of safe refuelling of vehicles. Research limitations/implications - Provides hints to design refuelling stations, also for fluids of the future (e.g. hydrogen). Practical implications - This robot is a low cost and efficient solution for replacing humans in petrol pump stations, while preserving environmental health. Refuelling will be comfortable and safe even in adverse climate conditions or for dangerous fuels (e.g. hydrogen). Originality/value - Introduces a robotic arm made with tubes so that cables, pipes and VOCs run inside it and a filler granting easy mating with the cap and VOCs collection. © Emerald Group Publishing Limited.

Keywords: Equipment safety , Organic compounds , Petroleum , Pumps , Robotics

In this paper the authors will describe the work which the University of Florence and IFAC-CNR (Florence) have performed in order to design an innovative platform for High-latitude LDB flights based on multi-experiments and versatility concepts. In order to satisfy the functional requirements and difficult structural constraints in terms of stiffness, strength and weight, the authors will describe an innovative approach to designing the gondola using problem-solving techniques, virtual prototyping and topology optimization in a systematic way. By means of these tools, a set of optimized geometries has been tested, starting from the first implementation of the BarSPOrt experiment's platform. Some of these solutions will be described.

In addition to stepping through the typical hardware parts of an Attitude Control System borne for stratospheric platform, the paper describes some fast position sensors. The use of two axis magnetometers at high latitude, even though with a lower accuracy, is analyzed. A high-accuracy motorized sun tracker based on a Position Sensitive Detector photodiode capable of driving the gondola in pointing or scanning mode in any given arbitrary anti-sun direction is also presented. Lastly, as an important part of the entire sensor development project, the paper describes a simulation of the thermal behavior of a pressurized cylinder in which electronic photosensitive devices and a CPU system are housed. To employ electronic device built within a commercial temperature range and intended to stay on the ground, it is extremely important to have a pressurized and conditioned environment in order to avoid a reduction in the performances of some ACS components.

This work deals with the definition of a virtual approach to the ergonomic analysis of the installation of a bulky technical product. Both the weight and the size could create difficulties to the users managing it during the transport, unpacking, and installation phases. This study is developed over two steps: the first step regards the execution of laboratory tests to carry out a physical description of the movement required to manage the product. Based on the results of the first step, in the second phase a virtual simulation of the movement required for the product installation is realized. Once terminated both the physical and the virtual tests, the results from the two models are compared to verify the correspondence of the virtual model with the real one through the comparison of a typical ergonomic parameter for lifting task that is the measure of the forces on the L4 and L5 inter-vertebral disk of the subject executing the test. The objectives of the work are the validation of the results of the physical test and the virtual analysis, to demonstrate the feasibility of pre-prototype tests by using a simulacrum (made of polystyrene) of an industrial product instead of a real prototype, and, finally, the use of human manikin software for the study of ergonomics of the mounting and maintenance operations. Copyright © 2005 SAE International.

A CAD-oriented system is proposed for the design of complex-shaped functional cloth, provided with a physics-based modelling core for simulation and virtual prototyping tasks. Textiles are physically modelled as particle grids in 3D space subjected to Newtonian dynamics, with internal spring, bending and shear forces derived from KES-F data measuring material behaviour. Interactions with the environment are expressed as external forces, collisions against obstacles, self-collisions and constraints. Differently from physics-based animation systems, the proposed system is conceived for real design purposes, and includes functionalities emulating the construction process of actual clothing and structural textiles, e.g., mesh sewing/assembly, insertion of small components, multi-layered fabric composition, mechanical shape deformation, and 2D-to-3D mapping methods. As applications, several cases of textile configurations are considered, with geometric models directly provided by industrial companies and presenting different levels of design complexities, such as garment models (e.g., men's jackets) for the clothing sector, or functional textiles used in the automotive industry (e.g., soft car tops). © The Eurographics Association 2004.

Virtual prototyping of cloth has recently become a topic of increasing interest both in computer graphics and computer-aided design for industrial fabric or apparel production. Aiming at an accurate simulation of garment shapes, this paper presents a physics-based system for virtual cloth modelling, specifically conceived for design purposes and targeted to the clothing industry. This environment should allow the designer/modellist to validate her/his style and design options through the analysis of garment virtual prototypes and simulation results in order to reduce the number and role of physical prototypes. To this end, a complete physics-based model has been defined, oriented to actual complex-shaped apparel, incorporating aspects related to garment's shape and structure (e.g., 2D profiles of basic patterns and multi-layered parts), mechanical/structural properties of fabric materials and multi-layered parts, and design/manufacturing processes (e.g., ironing, starching). The physical garment's model has been developed upon a particle-based model embedded in constrained Newtonian dynamics with collision management. The system has been validated within European and national projects, simulating several female and male garments with different levels of design complexities and directly provided from involved clothing companies. © 2004 by CAD Solutions Company Limited.

Keywords: Garment design and manufacturing , Garment simulation , Physics based-models

Reverse engineering techniques are broadly used in the development process of products with meaningful aesthetic properties. Many stylists prefer to evaluate the product shape on the basis of a full-scale hand made physical mock-up. Such model has then to be converted into a 3D CAD model, to begin the product engineering and production processes. A critical aspect of the RE process is that the physical mock-up, made by the stylist, usually does not take into account the engineering production constraints. The surface reconstruction activity must then be followed by a modelling phase, where the engineering designer modifies the reconstructed model shape in order to make it suitable for production. At the end of this process, no matter how accurate and precise the surface reconstruction phase has been, the product model will be different from the original mock-up, and then it needs to be submitted to the stylist for the validation of its shape. For the stylist, getting used to working with physical models, the shape validation on a virtual model is not a trivial task. The objective of this research is to develop a software tool to support the identification of aesthetic and functional regions of the product model shape, that have been modified with respect to the original mock-up. The proposed approach is based on the decomposition of a 3D surface analysis problem into a simpler 2D curves analysis problem. This approach simulates the traditional method used by stylists to evaluate the quality of shapes. The implementation of the developed algorithms has been performed using a commercial software package (I-deas FreeForm by EDS/Unigraphics) and it has been successfully applied on real test cases. © 2003 Elsevier Ltd. All rights reserved.

Keywords: Physical mock-up , Product engineering , Style , Virtual mock-up