Dynamic Posture Stabilization of a Biped Robot SUBO-1 on Slope-Changing Grounds

This paper describes a model-based dynamic posture stabilization of a biped robot on slope changing grounds. The ground slope generally is changing when a biped robot is walking outdoors on uneven grounds. Hence, if biped robots are used outside, their robustness against slope-changing grounds is necessary for stable walking. In this paper, a Zero Moment Point (ZMP) controller on level ground was designed as a basic posture stabilizer, and a disturbance observer (DOB) was additionally designed to reject a disturbance due to the ground slope. A simple single inverted pendulum model with a flexible joint is used for the ZMP controller and DOB designs. Finally, the performance of the proposed ZMP-DOB controller was verified through MATLAB simulations and walking in place experiments using a biped robot, SUBO-1 on a slope-changing treadmill.