Jean-Claude Léon

• Grenoble Institute of Technology

Computational simulation is critical in the modern engineering design process. Currently, the use of simulation is limited by the time-consuming process of converting CAD assemblies into FEA models which are efficient to run and yet sufficiently accurate. In addition to the geometric representation of components, analysts require additional knowled...

The simulation of grasping operations in virtual reality (VR) is required for many applications, especially in the domain of industrial product design, but it is very difficult to achieve without any haptic feedback. Force feedback on the fingers can be provided by a hand exoskeleton, but such a device is very complex, invasive, and costly. In this...

Background: Embryology is a complex morphologic discipline involving a set of entangled mechanisms, sometime difficult to understand and to visualize. Recent computer based techniques ranging from geometrical to physically based modeling are used to assist the visualization and the simulation of virtual humans for numerous domains such as surgical...

Achieving grasping tasks in real time with haptic feedback may require the control of a large number of degrees of freedom (DOFs) to model hand and finger movements. This is mandatory to grasp objects with dexterity. Here, a new device called HaptiHand is proposed that can be added to a haptic feedback arm and provide the user with enough DOFs so t...

Shape idealization transformations are very common when adapting a CAD component to FEA requirements. Here, an idealization approach is proposed that is based on generative shape processes used to decompose an initial B-Rep object, i.e. extrusion processes. The corresponding primitives form the basis of candidate sub domains for idealization and th...

The invention relates to a computer-assisted design method for a second three-dimensional object, from a first three-dimensional object known only by its boundary surfaces (through a surface model of the B-Rep type) of the planar, cylindrical, cone, sphere, or toroid type, excluding free-forms in defining the boundary of the object, the comprising...

Purpose – Preparing digital mock-ups (DMUs) for finite element analyses (FEAs) is currently a long and tedious task requiring many interactive CAD model transformations. Functional information about components appears to be very useful to speed this preparation process. The purpose of this paper is to shows how DMU components can be automatically e...

An interaction peripheral device capable of controlling an element for touching and grasping multidimensional virtual objects, including at least two interaction modules, each interaction module being intended to be actuated by a finger of an operator and including a control sensor allowing control of displacement, according to a predetermined numb...

Products and virtual humans are commonly described using 3D models of their components and anatomical entities, respectively. Functions stand for symbolic information bringing a high level description of product subsets and apply also to human body anatomical entities. Ontology-based approaches bring new means to improve the efficiency of these dig...

Axisymmetry and planar reflective symmetry properties of mechanical components can be used throughout a product development process to restructure the modeling process of a component, simplify the computation of tool path trajectories, assembly trajectories, etc. To this end, the restructured geometric model of such components must be at least as a...

Multiple models of anatomy have been developed independently and for different purposes. In particular, 3D graphical models are specially useful for visualizing the different organs composing the human body, while ontologies such as FMA (Foundational Model of Anatomy) are symbolic models that provide a unified formal description of anatomy. Despite...

Pre-processing of CAD models derived from Digital Mock-Ups (DMUs) into finite element (FE) models is usually completed after many tedious tasks of model preparation and shape transformations. It is highly valuable for simulation engineers to automate time-consuming sequences of assembly preparation processes. Here, it is proposed to use an enriched...

Digital Mock-ups (DMUs) are widespread and form a common basis for product description. However, DMUs produced by industrial CAD systems essentially contain geometric models and their exploitation often requires new input data to derive various simulation models. In this work, analysis and reasoning approaches are developed to automatically enrich...

The complete product definition can be seen as the result of a process where all the various requirements (functional, aesthetic, economical, feasibility, and so on) are satisfied at the best. For this reason the Product Design Process (PDP) involves many actors, tasks, and activities, currently supported by dedicated IT tools such as: computer-aid...

Being able to automatically mesh composite geometry is an important issue in the context of CAD-FEA integration. In some specific contexts of this integration, such as using virtual topology or meshing constraints topology (MCT), it is even a key requirement. In this paper, we present a new approach to automatic mesh generation over composite geome...

La méthode et l'algorithme associé permettent d'effectuer une analyse morphologique d'un objet 3D pour déterminer ses décompositions possibles en primitives élémentaires. La méthode élaborée concerne des objets 3D volumiques décrits par leur frontière (modèles B-Rep). Les primitives volumiques sont de type extrusion et les surfaces frontières sont...

A digital mock-up (DMU), with its B-Rep model of product components, is a standard industrial representation that lacks geometric information about interfaces between components. Component shapes reflect common engineering practices that influence component interfaces with interferences and not only contacts.The proposed approach builds upon relati...

The approach proposed here is based on coupling a mechanical model to the input surface geometry provided by the designer. The mechanical model is based on a set of bar networks subjected to tension forces only. Constraints are specified by the designer to express the deformation behaviour of the surface in the area of interest and define functiona...

We present a prototype of a hands-on immersive peripheral device for controlling a virtual hand with high dexterity. This prototype is as easy as a mouse to use and allows the control of a high number of degrees of freedom (dofs) with tactile feedback. The goals corresponding to design issues, physiological behaviors, include the choice of sensors'...

This paper presents a prototype of a hands-on immersive peripheral device for controlling a virtual hand with high dexterity. Based on the results of users' tests on previous versions of our device and on the analysis of a manipulation task, this prototype is as easy as a mouse to use and allows the control of a high number of degrees of freedom (d...

ISSN 1759-3433 - Paper 30

Mechanical components are often related to technological meaning: it is a screw, a ball bearing, . . . Technological meaning relates to the notion of function which, in turn, refers to the environment of a component. Here, it is shown how a digital mock-up contextualizing a set of components is used to annotate its components with technological inf...

Digital Mock-ups (DMUs) are widespread and form a common basis for product description. However, DMUs produced by industrial CAD systems essentially contain geometric models and their exploitation often requires new input data to derive various simulation models. In this work, analysis and reasoning approaches are developed to automatically enrich...

In order to set up a framework dedicated to the transformation of digital mock-ups (DMUs) into simulation models, this paper exposes the problem of simulation assembly model preparation. It analyses the differences between standalone component and assembly preparations to justify the reasons for the time consuming tasks specific to assemblies. To t...

Computer-Aided Geometric Design modelers are now based on powerful mathematical curve and surface models, but efficient tools to handle, analyze and modify these objects are actually expected. Designing product shapes using geometric operations on free-form curves and surfaces is still a tedious task. Moreover, designers would prefer to use meaning...

We propose a new iterative algorithm for computing the homology of arbitrary shapes discretized through simplicial complexes. We demonstrate how the simplicial homology of a shape can be effectively expressed in terms of the homology of its sub-components. The proposed algorithm retrieves the complete homological information of an input shape inclu...

In addition to being a very expressive media, 2D sketches representing the contour of a shape are commonly used as a basis for 3D sketch-based modeling. This paper investigates an alternative to the standard way of creating such sketches: instead of carefully following the contour with a pen and erasing or over-sketching, the user progressively sha...

Assembly/Disassembly (A/D) simulations are important to improve designs and efficiency of product development processes. In order to get efficient simulation processes it is important to simulate all the possible relative movements between the components in a mechanical system (assembly). This is important both in the context of interactive simulat...

With the increasing interest to automatically simplify products' 3D models to cope with varying engineering demands, the identification of functional designation of compo-nents has become an insistent need. In this work, we suggest a method to classify elementary components of a product into a taxonomy of functional designations. This is done based...

A Digital Mock-Up contains a set of component. What are the possible treatments that can be derived from this model? An analysis of the DMU content is performed to answer this question and show the lack of consistency in a DMU explaining the difficulties in performing automated treatments to derive technological and functional information about com...

In two-photon lithography a high repetition rate laser scans through calculated trajectories in order to induce polymerization in the resin which give rise to complex microstructures. When there are sharp angles within trajectories, the polymerized resin at angles receives more energy from the laser. The polymerized structure becomes larger, and th...

Nous présentons un prototype d'un périphérique immersif pour contrôler une main virtuelle avec une grande dextérité. Ce prototype est basé sur des résultats de tests utilisateurs réalisés sur des versions précédentes de notre périphérique, ainsi que sur l'analyse d'une tâche de saisie. Aussi simple à utiliser qu'une souris, il permet le contrôle si...

In this research report, we present an efficient method for computing the homology of a large simplicial complex from the homologies of its sub-complexes. The method uses a constructive version of the Mayer-Vietoris exact sequence which is an algebraic tool relating the homology of a topological space to the homologies of its sub-spaces and their i...

Computer Aided Design (CAD) and Computer Aided Engineering (CAE) are two significantly different disciplines, and hence they require different shape models representations. As a result, models generated by CAD systems are often unsuitable for Finite Element Analysis (FEA) needs. In this paper, a new approach is proposed to reduce the gaps between C...

Symmetry properties of components have many applications during a product development process, including shape transformations for modification purposes, Finite Element Analysis (FEA), model retrieval, etc. This paper presents an algorithm to generate 3D model symmetry planes using the B-Rep model of CAD volumes. In the framework of CAD software, 3...

During product development processes, simulations involving user's grasping operations are of increasing interest to incorporate more quantitative information in DFA (Design For Assembly) or immersive simulations. We present several prototypes of an immersive peripheral device for controlling a virtual hand with fine dexterity. These prototypes are...

Computer Aided Design (CAD) and Computer Aided Engineering (CAE) are two significantly different disciplines, and hence they require different shape models representations. As a result, models generated by CAD systems often need to be submitted to shape transformations for Finite Element Analysis (FEA). In this paper, a new approach is proposed to...

Computer Aided Design (CAD) and Computer Aided Engineering (CAE) are two significantly different disciplines requiring different shape model representations. As a result, models generated by CAD systems often need to be submitted to shape transformations for Finite Element Analysis (FEA). In this paper, a new approach is proposed to ease integratio...

We analyse and compare several prototypes of the HandNavigator, a peripheral device allowing a user to interact with a virtual environment by controlling a virtual hand with fine dexterity. Our prototypes, as easy to manipulate as a computer mouse, integrate a large panel of small sensors enabling the simultaneous control of a large number of degre...

Nous présentons plusieurs prototypes du Hand Navigator, un pé- riphérique qui permet à un utilisateur d'interagir à travers une main avec un environnement virtuel avec une grande dextérité. Nos pro- totypes, qui sont aussi simples à tenir et à lâcher qu'une souris d'ordinateur, intègrent une grande variété de capteurs miniatures qui permettent le c...

This demonstration provides experimentation on several versions of the Hand Navigator, a peripheral device allowing to control a virtual hand with fine dexterity. Our devices, as easy to hold and to release as a mouse, integrate various small sensors enabling the simultaneous control of a large number of degrees of freedom. Our demonstration invite...

The concept of product view and the corresponding required models is a basic constituent of a product development process where shape transformations are repeatedly encountered. Here, topological and geometric issues are identified and major shape modeling principles are studied. As a result, some core concepts of a framework for product view integ...

L'étude de comportement mécanique de structures et/ou d'écoulements s'appuie fréquemment sur des modèles géométriques perçus comme des assemblages de volumes, surfaces, lignes, connectés entre eux et comportant des singularités non-variétés. Une classification d'objets comportant des singularités nonvariétés et des propriétés topologiques globales...

Non-manifold models are frequently encountered in engineering simulations and design as well as in computer graphics. However, these models lack shape characterization for modelling and searching purposes. Topological properties act as a kernel for deriving key features of objects. Here we propose a classification for the non-manifold singularities...

Even if today's CAD systems can easily represent free-form shapes by means of NURBS surfaces, their definition and modification still require a deep knowledge and a great skill in the manipulation of the underlying mathematical models. This paper presents an attempt to bring the feature concepts, well-known in the classical mechanical domain, to th...

To perform a mechanical simulation of a component, its geometrical model usually needs to be simplified in accordance with the hypotheses on its mechanical behaviour. Here, the preparation and the simplification of the model for the structural analysis act upon an intermediate polyhedral representation and take into account the mechanical hypothese...

Micro-manufacturing with a Two-Photon Polymerization (TPP) technique is an emerging manufacturing technique to produce small objects of tens of μm size. Combined with three axes numerically controlled equipment, it becomes possible to produce a wide diversity of product shapes. As a result, controlling this equipment while taking into account the m...

This paper addresses the way models mixing various types of geometric representations (e.g. NURBS curves and patches, polylines, meshes), potentially immersed in spaces of different dimensions (e.g. NURBS patch and its 2D trimming lines), can be deformed simultaneously. The application domains range from the simple deformation of a set of NURBS cur...

Non-manifold models have classically been used in Finite Element (FE) simulations to describe the shape of a mechanical part. Sketching the shape of an object is also important in a design stage, where non-manifold models could be of help for the designer. The purpose of the taxonomy proposed here is to be able either to accept or reject them based...

Assembly/Disassembly (A/D) simulations using haptic devices are facing difficulties while simulating insertion/extraction operations such as removing cylinders from holes. In order to address this configuration as well as others, an approach based on contact identification between components is presented in this paper. This approach can efficiently...

The use of free-form shapes has become mainstream to design complex products that have to fulfil engineering requirements as well as aesthetic criteria. Even if today’s CAD systems can easily represent free-form shapes by means of NURBS surfaces, their definition and modification still require a deep knowledge and a great skill in the manipulation...

Preparing a CAD model for Finite Element (FE) analysis can be a time-consuming task, where shape and mesh simplifications play an important role. It is important that the simplified model has the same mechanical properties as the original one, and that the deviation from the original stays within a given tolerance. Most FE mesh simplification algor...

Currently, the product development process being collaborative and distributed, it relies on multiple skills and representations of the product. Obtaining the digital representation of the product model required for each product view is time consuming because component shapes and their associated data need to be adapted. In this part 1 paper, an an...

The preparation of a Finite Element Analysis (FEA) model from a Computer Aided Design (CAD) model is still a difficult task since its Boundary Representation (B-Rep) is often composed of a large number of faces, some of which may be narrow or feature short edges that are smaller than the desired FE size (for mesh generation). Consequently, these fa...

This paper presents a first step in the elaboration of a knowledge-based modelling environment supporting the conceptual design phase of an industrial product; more precisely, car styling is the considered application field. To capture and structure the semantics embedded in the first sketches representing the product, an ontology has been created...

Starting from the modelling requirements of the early design phase of the product development, the paper will show a possible strategy to overcome some limitations of current CAS/CAD systems. In fact, the styling stage involves both technical knowledge and fuzzy and dynamic aspects, which have to be taken into account for a proper management. The p...

The concept of product view and the corresponding required models is a basic constituent of a product development process. Integration across product views is addressed through an analysis of the key characteristics of current geometric modellers. Here, topological and geometric issues are identified and major shape modelling principles are studied...

Computer-Aided Geometric Design modelers are now based on powerful mathematical curve and surface models, but there is still a considerable need for efficient tools to handle, analyze and modify these objects. Designing product shapes using geometric operations on free-form curves and surfaces is still a tedious task. Moreover, designers would pref...

This paper introduces a new approach to automatic mesh generation over composite geometry. This approach is based on an adaptation of advancing front mesh generation techniques over curved surfaces, and its main features are: elements are generated directly over multiple parametric surfaces: advancing front propagation is adapted through the extens...

This paper presents a first step in the elaboration of a semantic-based modelling environment addressed to the conceptual design phase of an industrial product. Up to now, shape generation and manipulation in aesthetic design are still based on low-level geometric tools that come from the classical computer-aided design paradigm. On the other hand,...

Simulations of Assembly/Disassembly (A/D) processes covers a large range of objectives, i.e. A/D sequencing, path finding, ergonomic analysis …, where the 3D shape description of the component plays a key role. In addition, the A/D simulations can be performed either from an automated or interactive point of view using standard computer equipment o...

The evaluation of the mechanical behaviour of a product through a FE simulation requires an adaptation of the shape represented in its CAD model. During this shape modification process, several shape sub-domains are removed to simplify the subsequent mesh generation and FE solving tasks. The removal of a shape sub-domain is always driven by a speci...

La modélisation des opérations de désassemblage fait intervenir de multiples données (géométriques, cinématiques, technologiques, ...) et nécessite de passer par une étape d'analyse des liaisons cinématiques entre composants au cours des différentes étapes de montage/démontage. Dans ce contexte, le but principal abordé ici est le développement d'un...

En utilisant un critère mécanique a posteriori caractérisant l'influence des variations de forme d'un objet sur la solution mécanique associée, il est possible de quantifier la cohérence des différentes formes produites d'un point de vue mécanique. Cette cohérence indique dans quelle mesure des objets de formes différentes ont un comportement mécan...

Generally, a layer-by-layer method along one specific direction (two-and-half-dimensional method) is used to fabricate three-dimensional (3D) microstructures. Ultrathin layers and long processing times are necessary to obtain smooth surfaces in near flat regions of microstructures. In their approach, the authors slice these nearly flat areas along...

Generally, a layer-by-layer method along one specific direction two-and-half-dimensional method is used to fabricate three-dimensional 3D microstructures. Ultrathin layers and long processing times are necessary to obtain smooth surfaces in near flat regions of microstructures. In their approach, the authors slice these nearly flat areas along anot...

Obtaining the digital representation of the product model required for each product view is time consuming because component shapes and their associated data need to be adapted. This shape adaptation is considered as performed in the product view interface where a mixed shape representation reduces the prescriptive effects of the component models t...

La préparation des modèles CAO pour l'analyse par éléments finis reste une tâche difficile : la représentation par les frontière (B-Rep) de la pièce contient souvent un grand nombre de faces trop étroites et d'arêtes de trop petite taille pour générer un maillage de qualité satisfaisante. Par conséquent, ces faces, arêtes et sommets sont considérée...

The preparation of Finite Element analysis models (FE models) from Computer Aided Design (CAD) models is still a difficult task since its Boundary Representation (B-Rep) is often composed of a large number of thin faces, small edges, which are much smaller than the desired element size, and are not relevant for the meshing process. Such inconsisten...

A mechanical behavioural analysis can be useful at different stages of the product development process, and there are different scenarios where a FE (Finite Element) analysis can support the design phase. Unfortunately, preparing a model suitable for the FE analysis and solving a FE problem are time expensive and need a considerable involvement of...

To perform a mechanical simulation of a part, a geometrical model needs to be very often simplified. This simplification is performed based on hypotheses about its mechanical behaviour. Here, a new process of adaptive shape simplification is presented. The preparation of the model for the structural analysis acts upon an intermediate polyhedral rep...