Force/Torque-based Compliance Control for Humanoid Robot to Compensate the Landing Impact Force

Biped robot may become unstable during dynamic walking because of the huge impact/contact forces produced by foot instant landing. In this paper, force/torque-based compliance control is applied to absorb the impact forces generated between the contacting foot and the ground to keep stable dynamic walking. By imitating human's muscles to absorb the landing force, this method models the ground and the foot of robot as a spring-damping system. Because of the difference between the single support phase and double support phase in the robot walking cycle, different modes are applied in the two phases. In the double support phase, the damping coefficient of the landing foot is set suitable to absorb grounding force. In the single support, position control is adopted to recover the motion gait using polynomial. We have implemented the method in our real robot, KONG-I, which has 12 d.o.f in two legs. The dynamic walking experiments verified the validity of the compliance control.