Simulating reactive/passive postures by means of a human active torque hybrid minimization

In this paper we propose a hybrid approach minimizing the active torque produced by muscles groups at the joint level. The proposed approach is hybrid in the sense that it combines the local knowledge of the external torque induced by external forces such as gravity and exerted force, and the full knowledge of the passive-resistive torque characteristics due to ligaments and connective tissues. The algorithm is exploited within a context of posture adjustment when a muscle group reaches a critical fatigue level. It proposes a target joint state that can be characterized as active or passive. The active solution, if it exists, can be further characterized by a desired degree of active torque amplitude reduction (between 0 and 100%). In any cases at least one passive solution exists; it relies on the passive/resistive torque appearing in the neighbourhood of the joint limits.