Effectiveness of Disturbance Rejection of Imaginary Impedance Based Posture Control against Angular Errors in Thigh Links of Six-Legged Robot

Abstract

This paper deals with the disturbance rejection performance of a posture control method based on imaginary impedance for a six-legged robot. In the mechanism proposed by Hirose et al., the thigh links are important for controlling the body posture. Angular errors occur in these thigh links, when the robot walks over a step obstacle, angular sensors generate error signals, or zero point errors of angular sensors exist. In this study, we consider the errors as a step disturbance. We first derive a mathematical model for posture control in the presence of a disturbance. Next, a LQI controller based on imaginary impedance is designed to suppress the effect of the disturbance. The disturbance rejection performance of the proposed posture control method is verified by 3D simulations and experiments.