Stable landing method for biped robot by using switching control

Abstract

This paper proposes the switching control method to realize stable landing for a biped robot. If the landing of the biped robot is unstable, the robot may fall down. Therefore, it is necessary for the biped robot to realize stable landing. In order to achieve the stable landing, force controller should be implemented at the moment of landing. Since force control enables the sole to softly contact the ground. If the landing state becomes stable, control method needs to change position control for the biped robot moving. In other words, the controller should be switched according to the contact condition between the sole and the ground. Therefore, switching control method which consists of position control and force control is proposed. Zero Moment Point (ZMP) is used as index to switch the controller. Position control is applied when ZMP exists in the area around the center of the foot. Force control is used when ZMP exists around the edge of the foot. The validity of the proposed method is confirmed from the simulation results by using the model of inverted pendulum with a sole.