Identification of Transitioning Controller in Step-and-Brake Motion

Abstract

The goal of this work is to identify a controller of a human who steps and brakes. The loci of the center of mass (COM) of the motion of interest were measured and plotted in the state space. It was seen in them that the motion gradually converged to a regulatory behavior after the landing, which was supported by overlaying the loci of regulatory motions on them. Two hypotheses were made to model the behavior: (1) the delay in ground force manipulation (or the center of pressure (ZMP)) causes the smooth transition, or (2) a control which can produce both a stepping motion and a regulatory motion by adjusting the references of COM and ZMP works. (1) was rejected since a negative feedback gain was identified together with the delay. In order to verify (2), a stepping controller developed for biped robots was employed as a model of the human's control scheme. The identified controller showed qualitative similarity to the measured behavior, though it still has some points of discussion.