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International audience; A specific half squat motion is analyzed as a planar movement. Experimental data about this motion are recorded with a motion capture device and two force plates. Joint torques are estimated with-a 3D Opensim model and a sagittal Matlab model. Torque variations from the two models are consistent even if the magnitudes of the corresponding variables differ. These results are attributable to the different anthropometric tables which the two models are based on. Another strategy developed here consists in estimating joint torques without the measured ground reaction forces. In that case, global vertical reaction force is well estimated. The use of the sagittal Matlab model is an efficient way to preliminarily analyze squat trajectories. The next step in this work is the study of the influence of the load represented by the weight of a knee prosthesis.

International audience; This study is devoted to investigate the influence of a knee orthosis for human walking by using a mathematical model for a 7-links planar biped-composed with two identical legs, two feet and one trunk-with an orthosis attached to both thigh and calf, during walking. In the first part, we design a cyclic walking gait in the sagittal plane for human without the orthosis. The second part we consider that the human looses his muscular possibilities in one of his knees. To overcome his handicap the human is equipped of a knee orthosis. We analyse the positive effect of the orthosis over the assisted knee to track the previous designed reference trajectory. By using at each time an optimisation algorithm, we minimise the torques provided by the human. The numerical tests confirm the possibility to reduce the torque produced in the disabled knee. The next step is to take into account explicitly an information from EMG signal during a walking to modulate the power of the orthosis.

International audience; This paper proposes a mathematical model for a 7-links an-thropomorphic biped-composed with two identical legs, two feet and one trunk-with an orthosis attached to both thigh and calf, during walking. We consider a cyclic walking gait in the sagittal plane. In the first part, we obtain trajectories of the motion for different walking speeds. It confirmed the fact that much more torque is recquired in the stance leg than in the swing leg. The second part analyses the impact of an ortho-sis, which fully assists the knee over the walking. Simulations point out the fact that valid joints have to compensate the weight of the orthotic system and show the interest to assist the knee of the stance leg.