PERIODIC WALKING CONTROL OF BIPED ROBOTS WITH TORSO USING VARIABLE STIFFNESS ACTUATION

A spring-mass model with a torso represented by a rigid rod was proposed, whose stable walking control on level ground was analyzed. By controlling the torque of the hip joint and changing the stiffness of the spring legs, the system converged to the desired gait. According to the nonlinear and strong coupling characteristics of the system, the dynamic model was transformed into a linear system by the feedback linearization method. The PD control and P control were used to control the torso inclination and the hip joint trajectory of the robot. The numeric simulation results showed that the feedback linearization and variable stiffness control methods used in this study can realize the stable walking of the biped robot. It presented satisfactory anti-disturbance performance to external forces and the variation of inclination angle of torso with robustness.