A Force Direction Control Method for Robotic Bipedal Walking based on a Reduced Order Model

In this paper, we present a control method for bipedal robotic walking based on insights we obtain from simple models. Inspired by the virtual pendulum (VP) concept and the spring-mass walking models, we propose a force direction control method to redirect the axial force of a compliant leg in order for walking with upright trunk. We first consider a dynamic simulation of a simple planar walking model to validate the proposed method with proper foot placement rule, under the presence of force disturbance. Finally, we design a controller to implement the proposed force direction control scheme onto a more realistic model, a planar five link biped, which involves individual leg controller and walking state machine. The simulation results indicate that the robot model equipped with the proposed controller can overcome terrains with moderate roughness.