Abstract EN:

The human body is considered as rigid body segments connected by hinge joints and controlled by the central nervous system. Its inputs are the joint torques and outputs are the segment positions. Postural strategies employed in standing lead to a double inverted pendulum model. Its parameters can be estimated by anthropometric tables. In order to adjust the model for an individual, a simulated annealing is chosen. Joint torques are classically estimated by inverse dynamics. An alternative approach, based on the use of a nonlinear unknown inputs observer, is then proposed. A class of fuzzy observers based on a descriptor form is then studied. The convergence conditions of the prediction error can be conservative. Four approaches are then proposed to relax these conditions. The results obtained with the use of an unknown input observer are compared with the ones obtained with the use of inverse dynamics. It seems that observer based results are more accurate for human standing studies.