Biped locomotion by reduced ankle power

Power reduction in the ankle joints of a biped robot is considered in this paper. The ankle of human being has small torque and is very flexible within a certain range (very stiff near and beyond this range). This characteristic makes foot landing soft and gives a good contact between its sole and the ground. This feature can be implemented in a biped robot by using a small actuator for the ankle joints. A small actuator consumes less energy and makes the robot leg light. With less power in the ankle joints, walking becomes more difficult to control for the robot. This problem can be solved by providing the feedback control presented in this paper. The authors demonstrate two locomotion examples, standing and walking respectively, to show the validity of the proposed control scheme. In standing, the control input is the displacement of the ankle joint of the supporting leg. The control mechanism decides the bending angle of the body and the position of the swinging leg. For walking, only the bending angle of the body is used to avoid the discontinuity of the control input. Experimental results are presented to show the effectiveness of the new mechanism.