Impedance control and modulation for stable footing in locomotion of biped robots

This paper proposes an impedance control method with impedance modulation strategy for biped robot locomotion. Both the constrained leg and the free leg are controlled by impedance control. The impedance parameters changes depending on the gait phase of the biped robot. To reduce the magnitude of an impact and guarantee a stable footing when a foot contacts with the ground, the damping coefficient of the free leg is increased drastically and the reference trajectory of the leg is modified. Computer simulations with a 3DOF environment model for which a combination of a nonlinear and linear compliant contact models is used, show that the proposed control method works well and is superior to the computed-torque method in impact regulation.