Walking control by chattering-free VS servo using passive walking trajectory

Chattering-free variable structure (VS) servo control is proposed and applied to walking control. In this paper, a passive walking model is utilized as a reference trajectory generator for an active walking machine. The developed walker on the level ground generates the ankle torque by pushing levers to the ground to eliminate loss of the kinematics energy. The proposed VS-servo control law includes an integration of the sign function, so the input is not a bang-bang signal. Adequate ankle torque can be obtained because undesirable release of the levers from the ground can be avoided. The walking on level ground is realized by combining the artificial gravity compensation and the VS-servo. The simulation results show that the VS-servo control has good performance and that the proposed walking strategy is effective. Experimental result demonstrates the effectiveness in practice.