GAIT TRANSITION CONTROL OF FLEXIBLE BIPED ROBOT WITH VARIABLE LEG LENGTH AND SWING LEG DYNAMICS

The spring-loaded inverted pendulum (SLIP) model is a typical biped walking model, which has been the basis for the study of human-like walking robots. In this paper, we extend the SLIP model to include a rigid torso, foot mass and to adopt telescopic legs of variable length. The influence of the dynamics of the torso and swing leg on the gait of the robot is fully considered. Firstly, the dynamic equations are derived using the Euler– Lagrange method. Secondly, the feedback linearization controller is designed to track the desired trajectory and regulate the swing leg orientation and the attitude of the torso. Thirdly, the gait switching strategy is presented to realize walking gait transition by controlling the legs length and the hip torques, thus the average walking speed can be changed. Finally, computer simulations are carried out to verify the effectiveness of the presented method. Simulation results show that the controller is effective for tracking the desired trajectory of the system and realize the transition between two natural gaits. Furthermore, a stable limit cycle is formed and the robot can walk stably.