A visualization framework for the analysis ofneuromuscularsimulations

We present a visualization framework for exploring and analyzing data sets from biomechanical and neuromuscular simulations. These data sets describe versatile information related to the different stages of a motion analysis. In studying these data using a 3D visualization approach, interactive exploring is important, especially for supporting spatial analysis. Moreover, as these data contain many various but related elements, numerical analysis of neuromuscular simulations is complicated. Visualization techniques enhance the analysis process, thus improving the effectiveness of the experiments. Our approach allows convenient definitions of relationships between numerical data sets and 3D objects. Scientific simulation data sets appropriate for this style of analysis are present everywhere motion analysis is performed and are predominant in many clinical works. In this paper, we outline the functionalities of the framework as well as applications embedded within the OpenSim simulation platform. These functionalities form an effective approach specifically designed for the investigation of neuromuscular simulations. This claim is supported by evaluation experiments where the framework was used to analyze gaits and crouch motion

Physics-based control of virtual characters in low frequency simulations

International audienceUsing a lower simulation frequency for physics-based control of virtual characters frees computation time that can be used for more complex environment. However, using low simulation frequency may introduce instabilities inside the simulation. In this paper, we demonstrate that even a simple control strategy can be used at a low simulation frequency by adapting the control parameters. Indeed we show that lower frequencies hold a more restrictive space of possible control parameters than higher ones. We propose a method to find optimized control parameters for frequencies as low as 200Hz. As using such low frequencies may introduce foot-ground contact instabilities, we also introduce an additional control feedback on the stance leg. Our controller shows similar robustness as high frequency controller while using 0.8ms per simulation step

A subject-specific software solution for the modeling and thevisualization of muscles deformations

Today, to create and to simulate a virtual anatomical version of a subject is useful in the decision process of surgical treatments. The muscular activity is one of the factors which can contribute to abnormal movements such as in spasticity or static contracture. In this paper, we propose a numerical solution, based on the Finite Element (FE) method, able to estimate muscles deformations during contraction. Organized around a finite element solver and a volumetric environment, this solution is made of all the modeling and simulation processes from the discretization of the studied domain to the visualization of the results. The choices of materials and properties of the FE model are also presented such as the hyperelasticity, the contention model based on inter-meshes neighboring nodes pairing, and the estimation of nodal forces based on the subject-specific muscular forces and action line

A visualization framework for the analysis of neuromuscular simulations

We present a visualization framework for exploring and analyzing data sets from biomechanical and neuromuscular simulations. These data sets describe versatile information related to the different stages of a motion analysis. In studying these data using a 3D visualization approach, interactive exploring is important, especially for supporting spatial analysis. Moreover, as these data contain many various but related elements, numerical analysis of neuromuscular simulations is complicated. Visualization techniques enhance the analysis process, thus improving the effectiveness of the experiments. Our approach allows convenient definitions of relationships between numerical data sets and 3D objects. Scientific simulation data sets appropriate for this style of analysis are present everywhere motion analysis is performed and are predominant in many clinical works. In this paper, we outline the functionalities of the framework as well as applications embedded within the OpenSim simulation platform. These functionalities form an effective approach specifically designed for the investigation of neuromuscular simulations. This claim is supported by evaluation experiments where the framework was used to analyze gaits and crouch motions

Evaluation of a geometry-based knee joint compared toaplanarknee joint

Today neuromuscular simulations are used in several fields, such as diagnostics and planing of surgery, to get a deeper understanding of the musculoskeletal system. During the last year, new models and datasets have been presented which can provide us with more in-depth simulations and results. The same kind of development has occurred in the field of studying the human knee joint using complex three dimensional finite element models and simulations. In the field of musculoskeletal simulations, no such knee joints can be used. Instead the most common knee joint description is an idealized knee joint with limited accuracy or a planar knee joint which only describes the knee motion in a plane. In this paper, a new knee joint based on both equations and geometry is introduced and compared to a common clinical planar knee joint. The two kinematical models are analyzed using a gait motion, and are evaluated using the muscle activation and joint reaction forces which are compared to in-vivo measured forces. We show that we are able to predict the lateral, anterior and longitudinal moments, and that we are able to predict better knee and hip joint reaction force

Novel event classification based on spectral analysis of scintillation waveforms in Double Chooz

Liquid scintillators are a common choice for neutrino physics experiments, but their capabilities to perform background rejection by scintillation pulse shape discrimination is generally limited in large detectors. This paper describes a novel approach for a pulse shape based event classification developed in the context of the Double Chooz reactor antineutrino experiment. Unlike previous implementations, this method uses the Fourier power spectra of the scintillation pulse shapes to obtain event-wise information. A classification variable built from spectral information was able to achieve an unprecedented performance, despite the lack of optimization at the detector design level. Several examples of event classification are provided, ranging from differentiation between the detector volumes and an efficient rejection of instrumental light noise, to some sensitivity to the particle type, such as stopping muons, ortho-positronium formation, alpha particles as well as electrons and positrons. In combination with other techniques the method is expected to allow for a versatile and more efficient background rejection in the future, especially if detector optimization is taken into account at the design level

Contrôle de mouvement pour la simulation d'humains virtuels anatomiques

This report presents my research activity which is centered around the areas of virtual human modeling, processing and visualization of motion simulation data, and control for animation and predictive simulation. Some of this work makes it possible to precisely model the joints of the human biomechanical system thanks in particular to correlative constraints but also to patient-specific geometric models constructed by medical imaging. Others are interested in muscle modeling and more specifically in a three-dimensional and adaptive version of the principle of musculotendinous units. I have also contributed to the field of simulation in deformable bodies of muscle models, starting from the generation of finite element models from segmented MRI data to the simulation of the contraction of a set of muscles, applied to muscles of the leg and muscles of the neck.Other works have focused on methods for processing captured data to prepare for neuromuscular simulations. These slightly more technical aspects have been supplemented by studies on the visualization of the results of these simulations thanks to the proposal of several software solutions according to the objectives of the simulations.The main focus of my research activities is on motion control and in particular in the context of physics-based animation. I have worked on the design of controllers capable of robustly following a reference motion in real time and without preprocessing. I also worked on a genetic algorithm control approach by proposing a hierarchical vision of the design. Part of my research also concerned the real-time, low-frequency, interactive animation of a virtual character in constant interaction with a liquid-formed environment.The most recent works tackle the issue of motion control and predictive motion simulation, in particular for direct control and prediction by optimal control or by reinforcement learning on patients with pathologies.Ce mémoire présente mon activité de recherche qui se centralise autour des domaines de la modélisation de l’humain virtuel, le traitement et la visualisation de données de simulations de mouvement, et le contrôle pour l’animation et la simulation prédictive. Certains de ces travaux permettent de modéliser précisément les articulations du système biomécanique humain grâce notamment à des contraintes corrélatives mais aussi des modèles géométriques patients-spécifiques construits par de l’imagerie médicale. D’autres s’intéressent à la modélisation des muscles et plus précisément d’une version tridimensionnelle et adaptative du principe d’unités musculo-tendineuses. J’ai également contribué au domaine de la simulation en corps déformables de modèles musculaires, en partant de la génération de modèles éléments finis à partir de données d’IRM segmentées jusqu’à la simulation de la contraction d’un ensemble de muscles, et ce pour des muscles de la jambe ou bien du cou.D’autres travaux se sont intéressés à des méthodes de traitement de données capturées en vue de la préparation à des simulations neuromusculaires. Ces aspects un peu plus techniques ont été complétés par des études sur la visualisation des résultats de ces simulations grâce à la proposition de plusieurs solutions logicielles en fonction des objectifs des simulations.L’axe principal de mes activités de recherche est mis sur le contrôle de mouvement et en particulier dans le cadre de l’animation basée physique. J’ai réalisé des travaux sur la conception de contrôleurs capable de suivre de manière robuste un mouvement de référence en temps-réel et sans prétraitement. J’ai également travaillé sur une approche de contrôle par algorithme génétique en proposant une vision hiérarchique de la conception. Une partie du travail a aussi concerné l’animation temps-réel, basse fréquence, interactive d’un personnage en interaction constante avec son environnement formé de liquide.Les travaux les plus récents s’attaquent à la problématique du contrôle de mouvement et de la simulation prédictive de mouvement, notamment pour le contrôle direct et la prédiction par contrôle optimal ou par apprentissage par renforcement sur des patients atteints de pathologies

Définition et réalisation d'outils de modélisation et de calcul de mouvement pour des humanoides virtuels

Understanding and animating human motions are closely related to approaches of analysis ans synthesis. These approaches raise crucial problems in many scientific fields such as biomechanics, anthropology and animation. Obtaining realistic animated motions is a highly delicate and complex issue when evaluated by the trained human eye. We study and realize in this thesis a complete and coherent chain of analysis and synthesis of human locomotions which certifies the respect of motion realism criteria. This chain is made up of a method of kinematical adaptation, of a dynamics process of validation of this method and of a method of forward dynamics synthesis. We propose for each of these three parts, methods of human modeling, methods of motion modeling and methods of motion computation. We focus our work on methods of normalisation and manipulation of a database of motions.Comprendre et animer des mouvements humains sont intimement liés aux approches d'analyse et de synthèse. Ces approches soulèvent des problèmes fondamentaux dans de nombreux domaines scientifiques tels que la biomécanique, l'anthropologie et l'animation. Obtenir des mouvements animés réalistes est un point hautement délicat et complexe face à la perception exercée d'un observateur. Nous étudions et réalisons donc une chaîne complète et cohérente d'analyse et de synthèses de locomotions humaines qui certifie le respect de critères de réalisme du mouvement. Cette chaîne est composée d'une méthode d'adaptation cinématique, d'un procédé de validation dynamique de cette méthode et d'une méthode de synthèse en dynamique directe. Nous proposons dans chacune de ces trois parties, des méthodes de modélisation de l'humain, des méthodes de modélisation du mouvement et des méthodes de calculs du mouvement. Nous orientons ces travaux sur des méthodes d'adimensionnement et de manipulation d'une base de données de mouvements

Définition et réalisation d'outils de modélisation et de calcul de mouvement pour des humanoides virtuels

Understanding and animating human motions are closely related to approaches of analysis ans synthesis. These approaches raise crucial problems in many scientific fields such as biomechanics, anthropology and animation. Obtaining realistic animated motions is a highly delicate and complex issue when evaluated by the trained human eye. We study and realize in this thesis a complete and coherent chain of analysis and synthesis of human locomotions which certifies the respect of motion realism criteria. This chain is made up of a method of kinematical adaptation, of a dynamics process of validation of this method and of a method of forward dynamics synthesis. We propose for each of these three parts, methods of human modeling, methods of motion modeling and methods of motion computation. We focus our work on methods of normalisation and manipulation of a database of motions.Comprendre et animer des mouvements humains sont intimement liés aux approches d'analyse et de synthèse. Ces approches soulèvent des problèmes fondamentaux dans de nombreux domaines scientifiques tels que la biomécanique, l'anthropologie et l'animation. Obtenir des mouvements animés réalistes est un point hautement délicat et complexe face à la perception exercée d'un observateur. Nous étudions et réalisons donc une chaîne complète et cohérente d'analyse et de synthèses de locomotions humaines qui certifie le respect de critères de réalisme du mouvement. Cette chaîne est composée d'une méthode d'adaptation cinématique, d'un procédé de validation dynamique de cette méthode et d'une méthode de synthèse en dynamique directe. Nous proposons dans chacune de ces trois parties, des méthodes de modélisation de l'humain, des méthodes de modélisation du mouvement et des méthodes de calculs du mouvement. Nous orientons ces travaux sur des méthodes d'adimensionnement et de manipulation d'une base de données de mouvements

Motion control and prediction of virtual characters

International audienc