Locomotion control of biped robots on irregularly protruded uneven surface

Abstract

This paper proposes the control method for walking of biped robots on geometrically realistic uneven surface with irregular protrusions. The focus is to maintain the robot's stability performing foot motions successively in order to adapt the foot to uneven terrain. A foot has 15 force sensors at regular intervals which fit into the 5 by 3 terrain matrix. The control strategy of landing phase (LP) is to form a 1) larger and 2) appropriately located contact polygon (convex hull) between foot and ground considering current ZMP (Zero Moment Point) position during the transition from LP to stable double support phase (SDSP). Therefore, the desired ZMP needed for the next step is determined at the center of the contact area at the end of LP. The GCIPM (Gravity Compensated Inverted Pendulum Mode) is modified for the base trajectory based on newly located ZMP position, regulated and interpolated to ensure the balance and smooth transition between phases. To evaluate the stability of the biped locomotion on the uneven terrain, ZMP is computed in world coordinate. Computer simulations of 28-DOF biped robot with 6-DOF environment model using SimMechanics.