Impact Force Suppression for Redundant Legged Biped Robot Based on Unified Decoupling Control Method

Abstract

A swinging leg of a biped robot landing, impact force usually occurs between the sole and the ground, and then it causes instability of the gait. The paper describes the advantages of adopting redundant legs to the robot in order to conquer the difficulty, and proposes a novel way of the motion control for the redundant legged biped robot.In general, each leg of a conventional biped robot consists of 3 joints, namely, hip, knee and ankle in the sagittal plane. On the other hand, the proposed robot has been added extra joints, and thereby has redundancy in terms of degrees-of-freedom. Since the redundant leg can select its arbitrary posture, regardless of the tip position, the structure enables to move the position of the center of mass (COM) of the leg independently. The impact force is suppressed by controlling the COM acceleration of the landing leg. In order to achieve the decoupled motions between the tip and the COM, the unified decoupling controller is introduced. The controller includes three types of the disturbance observers together, and both desired motions are realized consequently. The validity of the proposed approach is confirmed in physical experimental results.