Simulation of human gait using computed torque control.

This paper presents a method for the mathematical modeling of both the single and double support phases of the human gait. The governing equations are obtained by considering the linkage model to be in a floating state and the foot-ground interaction is imposed in the form of geometric constraints. Two stages for the single support phase and one stage for the double support phase are considered, each described by a different foot-ground constraint. Feedback controller functioning according to the computed torque control method is used to achieve the normal gait described by the hip and ankle trajectories. Weighted least square optimization is used to solve the redundancy of control torques during the double support phase. The geometric simulation indicates that the imposed trajectories can be realized by the proposed model with some deviations in joint motions. The control strategy is tested by artificially perturbing the trajectories. The corrective actions are able to resume the desired pattern within half cycle, but with control torque magnitudes considerably away from reasonable limits. This is attributed to the insufficiency of the planar kinematic model and the assumption that the joint torques are unbounded.