Stabilization of Unstable Limit Cycles in a Push-off Based Dynamic Walker by Reversible Switching Surfaces

By employing the concept of “Reversible Switching Surfaces” (RSS), we demonstrate that it is possible to stabilize unstable periodic orbits of a push-off based dynamic walker. The concept is implemented by a simple event-based control which kinematically controls the foot during the swing phase to adjust the heel-strike. The feedback controller is designed based on the theory of Virtual Holonomic Constraints (VHC). Simulation results demonstrate, there exists a broad range of VHC which satisfies stable dynamic walking.

I. Introduction

Due to human locomotion complexity, bipedal robots have not precisely presented human walking behavior. For instance, the robots based on “Zero Moment Point” (ZMP) are stable, but not sufficiently efficient [1], [2]. On the other hand, limit cycle walkers show efficient and human-like behavior; though, they do not have enough stability and robustness [3]–[6].