Stability Analysis of a Biped Walking Robot with Foot Rotation Inducator

초록

This paper presents the stability analysis of a biped walking robot. Stability analysis of a biped walking robot is compounded of statically stable walk and dynamically stable walk. In statically stable walk, Center Of Gravity of a biped walking robot’s mass is located inside of the convex polygon of a bottom of the foot. Also Zero Moment Point should be located inside of the convex polygon to dynamically stable walk. But ZMP equation requires an assumption that the supporting foot is fixed firmly to the ground during the walking, therefore Foot Rotation Indicator concept is more suitable in the case of biped robot falling to the ground. In order to simplify the stability analysis, first we modeled the biped robot as a simplified inverted pendulum, which consists of a triangular foot, an ankle joint, and a massive link. The static and dynamic stability equation for this model is derived and the COG, ZMP, and FRI are then investigated. Finally, we expand it to the real biped walking robot IWR-III, also the control method of FRI is suggested when the robot is falling down. The simulation results show that the FRI concept is valid as an indicator of stability.