Papers by Xavier Merlhiot
An algorithmic contribution to interactive mechanical simulation tools for industrial digital mock-ups
PARIS-BIUSJ-Physique recherche (751052113) / SudocSudocFranceF
Contact determination methods for nonsmooth time-stepping schemes
Quasi-Dynamic Splines
Copyright © 2007 by the Association for Computing Machinery, Inc.
Une contribution algorithmique aux outils de simulation mécanique interactive pour la maquette numérique industrielle
New Results - Utilisation d'approximations par Machines à Vecteur Support et algorithmes évolutionnaires
Fast computation of contact points for robotic simulations based on CAD models without tessellation
2016 IEEE/RSJ International Conference on Intelligent Robots and Systems (IROS), 2016
Computing multiple contact points between geometric models evolved in a virtual 3D environment is... more Computing multiple contact points between geometric models evolved in a virtual 3D environment is central to many robotic simulation applications. While this task can be performed efficiently and robustly between complex polyhedra, using the exact analytic geometric models issued by CAD modelers still suffers from efficiency limitations. Yet models composed of smooth surfaces are required to ensure smooth contact constraints, thus avoiding possible numerical artifacts which may dramatically affect the behavior of the system in the case of functional contacts. This paper builds on the observation that industrial CAD models are mostly composed of simple surfaces to perform an off-line identification of similar features and build a bounding volume hierarchy in order to locate potential contacts. Those are then computed by dedicated analytic methods, or an iterative root-finder, depending on the actual geometric representations of the features. In the context of dynamic simulation of ro...
Journal of Biomechanics, 2018
Short communication MRI-based experimentations of fingertip flat compression: geometrical measure... more Short communication MRI-based experimentations of fingertip flat compression: geometrical measurements and finite element inverse simulations to investigate material property parameters
Journal of Mechanics in Medicine and Biology, 2018
Finite element fingertip models are useful tools to assess product ergonomics. While “real geomet... more Finite element fingertip models are useful tools to assess product ergonomics. While “real geometry” approaches provide accurate results, developing models requires medical images. “Simpified geometry” approaches have to date not been tested to see whether they can provide equally accurate results in terms of mechanical response, i.e. force-displacement response and dimensions of fingertip contact area. Four fingertip models were built either from medical images (Visible Human project) or from simplified geometries. Simulations of fingertip flat contact compression at 20[Formula: see text] were performed. A 2nd order hyperelastic material property was used to effectively reproduce the mechanical behavior of the fingertip. Models based on simplified geometries such as conics proved as accurate as models reconstructed from medical images. However, accurate positioning of the bony phalanx is paramount if a biofidelic mechanical response is to be reproduced.
Computer-Aided Design and Applications, 2018
With the restriction of the diameter and feed direction of the cutting tool in milling process, e... more With the restriction of the diameter and feed direction of the cutting tool in milling process, electric discharge machining (EDM) is the only effective machining technology for the uncut regions with internal sharp corner. Automatic design of the electrode is of great significance for the CAD/CAM integration of EDM technology. In current CAD/CAM system the electrode design is done manually by technologists based on experience and knowledge. The procedure is tedious and timeconsuming. In this paper, a novel approach is proposed to automatically generate the electrode CAD model taking the topological vertices of uncut region as the hint. The hint feature points are innovatively defined and classified into three types: internal-sharp points, cutting-into points and interacting points. Based on this, our approach firstly determines the faces and the type of uncut region. Secondly, the interacting region is decomposed into the isolated region by reconstructing the topological structure, patching the split face and partitioning the shared face. Thirdly, the modeling parameters are extracted from the isolated region. Finally, the electrode CAD model is created by executing a set of generic modeling operations. The electrode CAD model can be directly used in the process planning, so as to promote the integration of CAD and CAM.
Fast and Accurate Local Minimal Distance Computation between Industrial CAD Models for Interactive Dynamics Simulations
CAD'17, 2017
Meccanica, 2017
Models with impact or dry friction, yielding discontinuous velocities or accelerations, have moti... more Models with impact or dry friction, yielding discontinuous velocities or accelerations, have motivated research for appropriate numerical methods in the community of non-smooth dynamics. In this work, we apply such methods on the grand piano action. This multibody system has two properties of interest in terms of modelling and simulation: it is extremely sensitive to small misadjustements, and its functioning strongly relies on dry friction and stick-slip transitions-known to be crucial for the touch of the pianist. Using numerical methods of non-smooth contact dynamics, the non-smooth character of dry friction was conserved, in contrast to classical approaches based on regularization which additionally impose the somewhat arbitrary choice of a regularizing parameter. The use of such numerical method resulted in computations about a few hundred times faster than those reported in recent literature. For the first time, the presented predictions of the piano action's simulations are forces (in particular, the reaction force of the key on the pianist's finger), instead of displacements which filter out most of the dynamical subtleties of the mechanism. The comparisons between measured and simulated forces in response to a given motion are successful, which constitutes an excellent validation of the model, from the dynamical and the haptic points of view. Altogether, numerical methods for non-smooth contact dynamics applied to a non-smooth model of the piano action proved to be both accurate and efficient, opening doors to industrial and haptic applications of sensitive multibody systems for which dry friction is essential.
HAL is a multidisciplinary open access archive for the deposit and dissemination of scientific re... more HAL is a multidisciplinary open access archive for the deposit and dissemination of scientific research documents, whether they are published or not. The documents may come from teaching and research institutions in France or abroad, or from public or private research centers. L'archive ouverte pluridisciplinaire HAL, est destinée au dépôt et à la diffusion de documents scientifiques de niveau recherche, publiés ou non, émanant des établissements d'enseignement et de recherche français ou étrangers, des laboratoires publics ou privés.
Human Fingertip Finite Element Models: Towards a Set of Parameters for a Hyperelastic Law
22nd Congress of the European Society of Biomechanics (ESB), LYON, FRANCE, 10-/07/2016 - 13/07/20... more 22nd Congress of the European Society of Biomechanics (ESB), LYON, FRANCE, 10-/07/2016 - 13/07/2016It is now well established that a hyperelastic law is needed for developing fingertip finite element models. However, quite often in the literature, the material law parameters are not well known or rest on experimentations performed with very small sample of subjects. Thus finding a hyperelastic law as well as its parameters from experimentations performed on several subjects would facilitate the fingertip modeling task. In this abstract, a nearly-incompressible 2nd order hyperelastic law will be proposed and its two parameters will be defined using an inverse simulation approach
Method and device for detecting collision between two numerically simulated objects
Arxiv preprint arXiv: …, 2007
the work presented here is aimed at introducing a virtual human controller in a virtual prototypi... more the work presented here is aimed at introducing a virtual human controller in a virtual prototyping framework. After a brief introduction describing the problem solved in the paper, we describe the interest as for digital humans in the context of concurrent engineering. This leads us to draw a control architecture enabling to drive virtual humans in a realtime immersed way, and to interact with the product, through motion capture. Unfortunately, we show this control scheme can lead to unfeasible movements because of the lack of balance control. Introducing such a controller is a problem that was never addressed in the context of real-time. We propose an implementation of a balance controller, that we insert into the previously described control scheme. Next section is dedicated to show the results we obtained. Finally, we propose a virtual reality platform into which the digital character controller is integrated.
Arxiv preprint arXiv: …, 2007
Une contribution algorithmique aux outils de simulation mécanique interactive pour la maquette numérique industrielle
Http Www Theses Fr, 2009
This paper presents an extension of an existing contact determination method based on the notion ... more This paper presents an extension of an existing contact determination method based on the notion of quasi-LMDs that was first aimed at multi-rigid body simulations which use nonsmooth time stepping methods to the more general case of mechanical systems featuring both rigid and deformable bodies, including self-contact and conforming contact situations. This method uses body shapes represented by dilated simplicial complexes, which covers in a generic manner the cases of solid bodies as well as the ones of thin shells and circular cross-section 3D beams. The extended method remains compatible with time-stepping schemes, and we illustrate it with interactive virtual prototyping cases from the automotive industry where such deformable bodies are frequently encountered in the form of electrical cables and harnesses. Xavier Merlhiot Figure 1: Left: local open cover of ∂C by {Ω 1 , Ω 2 } at a corner of the admissible configuration set C. Center: gaps between dilated simplicial complexes. Right: a LMD and a quasi-LMD (in green).
Through the presentation of application cases of a family of time-stepping schemes, we will give ... more Through the presentation of application cases of a family of time-stepping schemes, we will give emphasis on numerical issues triggered by specific simulation objectives, outline how some of these issues have been overcome and what are the remaining open ones. The first application is industrial virtual prototyping, which actually generates a family of typical scenarios where interactivity is demanded. The second application is a specific assembly case study, featuring many 3D beams in contact, which demonstrates how the same time-stepping scheme and associated solver can apply to problems of very different scales in terms of configuration space dimension and number of contacts.
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Papers by Xavier Merlhiot