Co-contraction of antagonist bi-articular muscles for tracking control of human limb

This paper considers muscle contraction dynamics during co-contraction of antagonist bi-articular muscles for tracking control of a human limb. Co-contraction of antagonist muscles play an important role for joint stiffness and stability and experimental results show the existence of co-contraction during volitional movements. This paper shows the role of co-contraction by using three pairs of bi-articular antagonistic muscles. It is indicated that the co-contraction is useful not only to compensate the stability of the joint, but also to control the output force direction. The main contribution is to model the co-contraction control of human limb by using three pairs of bi-articular antagonistic muscles. A robust integral of the sign of the error (RISE) controller is shown to yield semi-global asymptotic tracking. The tracking control performance and stability are verified in the simulation.