Control of Biped Robot with Stable Walking

Abstract

This paper presents the development results of the 10 DOF biped robot with stable and human-like walking using the simple hardware configuration. Kinematics model of the 10 DOF biped robot and its dynamic model based on the 3D inverted pendulum are presented. Under assumption that the COM of the biped robot moves on the horizontal constraint plane, ZMP equations of the biped robot depending on the coordinate of the center of the pelvis link obtained from the dynamic model of the biped robot are given based on the D'Alembert's principle. A ZMP servo control system is constructed to track the ZMP of the biped robot to ZMP reference input which is decided by the footprint of the biped robot. A discrete time optimal controller is designed to control ZMP of the biped robot to track trajectories reference inputs based on discrete time systems. When ZMP of biped robot is controlled to track trajectory reference input decided inside stable region, a trajectory of COM is generated as stable walking pattern of the biped robot. Based on the stable walking pattern of the biped robot, a stable walking control method of the biped robot is proposed. From the trajectory of COM of the biped robot and trajectory reference input of the swinging leg, inverse kinematics solved by solid geometry method is used to compute the angle of joints of the biped robot. Because joint's angles reference of the biped robot are computed from the stable walking pattern of the biped robot, the walking of the biped robot is stable if the joint's angles of the biped robot are controlled to track those references. The stable walking control method of the biped robot is implemented by simple hardware using PIC18F4431 and dsPIC30F6014. The simulation and experimental results show the effectiveness of this control method.