Stability enhancement of 3-D biped walking based on Passive Dynamic Autonomous Control

Previously, we have realized an efficient 3-D biped walking based on the Passive Dynamic Autonomous Control (PDAC), which is one of the point-contact methods. Since the dynamics based method such as the point-contact method utilizes the inherent dynamics of the robot, an efficient walking can be realized compared with the model based method. However, the stable range of the point-contact method is small and the robustness of the walking is not large enough for practical use. In order to increase robustness of the point-contact method, this paper proposes a swing leg retraction and a double support phase for the point-contact method. The swing leg retraction enhances the convergence range of the walking system; also, by use of the double support phase, the robot dynamics converges to a stable orbit even if a disturbance happens at a foot-contact. Finally, the proposed biped walking algorithm is verified by experiments.