Impedance control for biped robot locomotion

This paper proposes a control method for biped robot locomotion based on impedance control and impedance modulation. Both legs are controlled by the impedance control, where the desired impedance at the hip and the swing foot are specified. The impedance parameters are changed depending on the gait phase of the biped robot. To reduce the magnitude of impact and to guarantee a stable footing at foot landings on the ground, the damping coefficient of the impedance of the landing foot is increased drastically and the reference trajectory of the landing foot is reset at its initial contact with the ground. A series of computer simulations of a 12-degree-of-freedom (DOF) biped robot with a 6-DOF environment model which consists of nonlinear and linear compliant spring-and-dampers, shows that the proposed control method works well and is superior to position-oriented control methods such as the computed-torque control method in impact regulation during foot landings and adaptation to some ground irregularity.