Evaluation of decentralized reactive swing-leg control on a powered robotic leg

Animals and robots balance dynamically by placing their feet into proper ground targets. While foot placement controls exist for both fully robotic systems and powered prostheses, none enable the dynamism and reactiveness of able-bodied humans. A control approach was recently developed for an ideal double pendulum dynamical system that places feet into ground targets for a wide range of initial conditions and in the presence of significant locomotion disturbances. While its performance in simulation make it an attractive candidate to control legged robotic systems, it is unclear if the approach can be used on real-world systems. In this paper we transfer and evaluate the approach on robotic hardware. Our results show that the controller can be transferred to robotic systems and allow them to achieve comparable foot placement accuracies to an ideal double pendulum simulation, both when motion is undisturbed, as well as when obstacles are encountered in early, mid, and late swing. These results suggest that the proposed approach is a potential alternative control method for legged robots and powered prostheses, enabling recovery from sudden swing-leg disturbances such as trips and unexpected obstacle encounters. The results also point out the need for additional considerations when tuning the controller in order to generate human-like swing trajectories and durations.