A non-smooth simulation of the dynamics of the grand piano action

International audienceTwo models of the grand piano key mechanism are presented: a single-degree-of-freedom model and a model based on 6 rotating bodies, 13 contact zones with nonlinear springs, 3 of them (hammer-jack, jack-escapement button, hammer-check) being also subject to Coulomb friction. The latter model introduces discontinuities on the velocities. The problems raised by the usual regular-dynamics formulation are discussed and a non-smooth dynamics approach is proposed. Based on the comparison between experimental and simulation results, it is discussed whether the simulation should be driven by the force exerted by the pianist or by the displacement of the key

Non-smooth simulation of a 6-DOF dynamical model of the grand piano action

International audienceTwo models of the grand piano key mechanism are presented: single-degree-of-freedom and 6 rigid rotating bodies coupled by 13 contact zones with nonlinear springs. Coulomb friction is considered in pivots and at several contact zones, introducing discontinuities in the velocities. Therefore, some problems are raised by the usual regular-dynamics formulation. The results given by the single-degree-of-freedom show that these problems must be addressed. A non-smooth dynamics approach is proposed using the XDE (eXtended Dynamic Engine) software developed at CEA LIST. Simulation results are compared to experiments for several playing nuances. Sensitivity analysis and model simplification will be discussed

Simulation of a non-smooth dynamical model of the piano key

International audienceFollowing the literature, two kinds of models for the grand piano action are presented here: one single-degree-of-freedom model and one model based on 6 rotating bodies, 13 contact zones with nonlinear springs, 3 of them (hammer-jack, jack-escapement button, hammer-check) being also subject to Coulomb friction. The latter is simulated by a non-smooth dynamics approach. It appears that force-driven simulations of the key position compare equally well for both models. This is not true for position-driven simulations of the reaction force exerted by the piano key on the pianist's finger

Passive Control Architecture for Virtual Humans

International audienceIn the present paper, we introduce a new control architecture aimed at driving virtual humans in interaction with virtual environments, by motion capture. It brings decoupling of functionalities, and also of stability thanks to passivity. We show projections can break passivity, and thus must be used carefully. Our control scheme enables task space and internal control, contact, and joint limits management. Thanks to passivity, it can be easily extended. Besides, we introduce a new tool as for manikin's control, which makes it able to build passive projections, so as to guide the virtual manikin when sharp movements are needed

Integration of a Balanced Virtual Manikin in a Virtual Reality Platform aimed at Virtual Prototyping

International audienceThe 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 real-time 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

A robust, efficient and time-stepping compatible collision detection method for non-smooth contact between rigid bodies of arbitrary shape

International audienceThis paper proposes an efficient collision detection method which is compatiblewith time-stepping methods in the sense that it enables the robust simulation non-smooth contact between rigid bodies with complex shapes, including industrial CAD models of various topology and in presence of conforming contact situations. It introduces a discrete representation of rigid body shapes based on dilated simplicial complexes, which generalizes the notion of triangulation to domains of arbitrary topological dimension. It also defines finite collections of point contacts between those shapes thanks to quasi-LMDs, which are defined as an extension of local minimum distances with respect to small relative rotations, between the base complexes. Smooth gap functions associated to these point contacts are defined, as well as complete and smooth generalized contact kinematics, enabling the use of non-smooth contact laws like Signorini or Coulomb. Quasi-LMDs also lead to the stable treatment of conforming contact cases. An efficient method based on 5D+1 bounding volume hierarchies for computing quasi-LMDs is presented. Finally, robustness and performance benchmarks show that our method combined with a fast time-stepping-based solver allows interactive-time simulations of complex and possibly conforming contact situations

An algorithmic contribution to interactive mechanical simulation tools for industrial digital mock-ups

PARIS-BIUSJ-Physique recherche (751052113) / SudocSudocFranceF