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

Abstract

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.