Estimation of external contact loads using an inverse dynamics and optimization approach: general method and application to sit-to-stand maneuvers.

ROBERT ; CAUSSE ; MONNIER

Type de document
ARTICLE A COMITE DE LECTURE REPERTORIE DANS BDI (ACL)
Langue
anglais
Auteur
ROBERT ; CAUSSE ; MONNIER
Résumé / Abstract
This paper presents a general method to estimate unmeasured external contact loads (ECL) acting on a system whose kinematics and inertial properties are known. This method is dedicated to under-determinate problems, e.g. when the system has two or more unmeasured external contact wrenches. It is based on inverse dynamics and a quadratic optimization, and is therefore relatively simple, computationally cost ective and robust. Net joint loads (NJL) are included as variables of the problem, and thus could be estimated in the same procedure as the ECL and be used within the cost function. The proposed method is tested on human sit-to-stand maneuvers performed holding an handle with one hand, i.e. asymmetrical movements with multiples external contacts. Three sets of measured and unmeasured contact load components and three cost functions are considered and simulated results are compared to experimental data. For the population and movement studied, better results are obtained for a least square sharing between actuated degrees of freedom of the relative motor torques (motor torques normalized by the maximal torque production capacity). Moreover, the number of unknown ECL components does not signicantly inuence the results. In particular, measuring only the vertical force under the seat lead to a relatively correct estimation of the ECL and NJT (RMS dirences about 10 % and 20 % of the amplitude for the ECL and the NJT respectively), and to observe the inuence of an experimental parameter (the Seat Height).
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