L'apport de l'analyse biomécanique 3-D dans les stratégies préventives à partir de 2 exemples

in Julia, M; Croisier, Jean-Louis; Perrey, S (Eds.) et al Prévention des troubles musculo-squelettiques chez le sportif (2013)

De nouveaux outils de mesure permettent de quantifier la cinématique et la dynamique articulaire fonctionnelle des athlètes (systèmes optoélectroniques 3D, plateforme de forces, électromyographie, …). Ces ... [more ▼]

De nouveaux outils de mesure permettent de quantifier la cinématique et la dynamique articulaire fonctionnelle des athlètes (systèmes optoélectroniques 3D, plateforme de forces, électromyographie, …). Ces données sont importantes dans le sens où elles donnent à l’équipe médicale et sportive des informations objectives sur le geste du sportif dans sa pratique réelle. Elles favorisent la compréhension et l’amélioration de la performance ainsi que la prévention lésionnelle et la détection de situations à risque. Dans le cadre d’un suivi longitudinal des sportifs, ces mesures sont intéressantes pour mettre en place des critères objectifs et spécifiques à l’athlète de retour sur le terrain après une blessure. Ce document a pour objectif de présenter les principaux outils disponibles dans les laboratoires de biomécanique et d’illustrer leurs utilisations à travers 2 exemples : l’influence de la raideur de l’épaule sur la mobilité de l’épaule et l’analyse cinématique du service au tennis. [less ▲]

Sensitivity analysis for multibody systems formulated on a Lie group

in Multibody System Dynamics (2013)

A direct differentiation method and an adjoint variable method are proposed for the efficient semi-analytical evaluation of the sensitivities of multibody systems formulated in a matrix Lie group ... [more ▼]

A direct differentiation method and an adjoint variable method are proposed for the efficient semi-analytical evaluation of the sensitivities of multibody systems formulated in a matrix Lie group framework. These methods rely on the linearization of the equations of motion and/or of the time integration procedure. The simpler structure of the equations of motion in the Lie group formalism appears as an advantage for that purpose. Lie bracket contributions and the non-linearity of the exponential map need to be taken into account in the sensitivity algorithms. Nevertheless, essential characteristics of formulations of the direct differentiation method and the adjoint variable method on linear spaces are recovered. Some implementation issues are discussed and two relevant examples illustrate the properties of these methods. [less ▲]

Shoulder injury prevention in sports using 3D motion capture

Poster (2012, December 07)

In sports, where regular and intensive training could progressively lead to traumatic situations, accurate measurement of kinematic parameters can help to predict and anticipate injuries. Overhead ... [more ▼]

In sports, where regular and intensive training could progressively lead to traumatic situations, accurate measurement of kinematic parameters can help to predict and anticipate injuries. Overhead throwing athletes may develop an increased stiffness of the shoulder capsule. The resulting diminution of the gleno-humeral range of motion is usually associated with decreased performance and injury risks. This study illustrates the detection of these situations that put the athlete at risk. [less ▲]

Toward Optimization of Flexible Multibody Systems: How to Open the Simulation Black Box?

Conference (2012, September)

Investigations on a Level Set based approach for the optimization of flexible components in multibody systems with a fixed mesh grid

in Proceedings of The 6th Asian Conference on Multibody Dynamics: Shanghai (China), 26-30 aout 2012 (2012, August)

This paper considers the optimization of flexible components in mechanical systems thanks to a "fully integrated" optimization method which includes a flexible multibody system simulation based on ... [more ▼]

This paper considers the optimization of flexible components in mechanical systems thanks to a "fully integrated" optimization method which includes a flexible multibody system simulation based on nonlinear finite elements. This approach permits to better capture the effects of dynamic loading under service conditions. This process is challenging because most state-of-the-art studies in structural optimization have been conducted under (quasi-)static loading conditions or vibration design criteria and also because this ``fully integrated" optimization method is not a simple extension of static optimization techniques. The present paper proposes an approach based on a Level Set description of the geometry. This method leads to an intermediate level between shape and topology optimizations. Gradient-based optimization methods are adopted for their convergence speed. Numerical applications are conducted on the optimization of a connecting rod of a reciprocating engine with cyclic dynamic loading to show the feasibility and the promising results of this approach. [less ▲]

A Newmark-type integrator for flexible systems considering nonsmooth unilateral constraints

in Proceedings of the First Joint International Conference on Multibody System Dynamics (2012, June)

Mechanical systems are usually subjected not only to bilateral constraints but also to unilateral constraints. Inspired by the HHT time integration method for smooth flexible multibody dynamics, this ... [more ▼]

Mechanical systems are usually subjected not only to bilateral constraints but also to unilateral constraints. Inspired by the HHT time integration method for smooth flexible multibody dynamics, this paper presents a Newmark-type integrator, denoted by nonsmooth HHT method, to include the nonsmooth property of unilateral constraints. Through numerical examples accounting for both rigid and flexible body models, a bunch of methods are compared with the unilateral constraints on both velocity level and position level. Results show that the presented nonsmooth HHT method benefits from the accuracy and stability property of the classical HHT method with controllable numerical damping. In particular, when it comes to the analysis of flexible systems, the nonsmooth HHT method shows much better accuracy property than that of the other methods, including the Moreau–Jean time-stepping method and the fully implicit Newmark methods. [less ▲]

Formulation of Kinematic Joints and Rigidity Constraints in Multibody Dynamics using a Lie Group Approach

in Proceedings of the 2nd Joint International Conference on Multibody System Dynamics (IMSD) (2012, May)

The matrix Lie group approach allows to formulate and solve the equations of motion of a multibody system in a parametrization-free framework. The kinematic joints and the rigidity constraints should also ... [more ▼]

The matrix Lie group approach allows to formulate and solve the equations of motion of a multibody system in a parametrization-free framework. The kinematic joints and the rigidity constraints should also be formulated as constraint equations on the Lie group. Working on the Special Euclidean group SE(3), we introduce a method to obtain appropriate vectorial constraint equations in terms of mixed coordinates. Moreover, we present an absolute coordinates formulation, based on an relative coordinates elimination method, so that the minimum number of constraint equations necessary to describe the joints is used. [less ▲]

Trends and challenges in flexible multibody dynamics: From simulation to control and design

Conference (2012, May)

From direct to inverse analysis in flexible multibody dynamics

Conference (2012, March)

Today, state-of-the-art simulation packages in flexible multibody dynamics allow the high-fidelity analysis of industrial mechanisms and machines in many application fields including robotics, automotive ... [more ▼]

Today, state-of-the-art simulation packages in flexible multibody dynamics allow the high-fidelity analysis of industrial mechanisms and machines in many application fields including robotics, automotive systems, aeronautics, deployable structures or wind turbines. The dynamic response of a given system can thus be evaluated in the time-domain for given load cases and given initial values. However, in many practical cases, the engineer does not have a precise knowledge of the mechanical design, the loading conditions and the initial state. This situation occurs for example in structural optimization, optimal control, experimental identification and health monitoring problems. The complexity of simulation codes and the computational cost of high-fidelity models are still important obstacles for the development of efficient resolution methods for these inverse problems. A current challenge is thus to elaborate simplified and more efficient modelling strategies in flexible multibody dynamics in order to enable the development of inverse analysis methods. The talk is divided into three parts. The first part provides an overview of available simulation techniques for flexible mechanisms with a particular emphasis on finite element-based approaches and time integration methods. Some illustrations are presented in the fields of deployable structures, vehicle dynamics and wind turbines. In the second part, optimization problems in flexible multibody dynamics are addressed and solved using gradient-based methods. Efficient methods for sensitivity analysis are discussed and special problems are treated such as the structural optimization of mechanical components or the numerical solution of inverse dynamics problems. The third part discusses a recently-developed Lie group approach which allows the formulation of the equations of motion of a multibody system in a parameterization-free setting. Based on this general formalism, which is characterized by an increased modularity and a reduced complexity, a large variety of Lie group solvers are foreseen not only for time integration but also for model reduction, sensitivity analysis and optimization. [less ▲]

A level set approach for the optimal design of flexible components in multibody systems

Conference (2012, February 29)