Identification of a Step-and-Brake Controller of a Human Based on COM-ZMP Model and Terminal Capturability Condition

The goal of this work is to find a plausible mathematical model of a human's step-and-brake control scheme as the minimum motion unit of skillful locomotive behaviors. A controller designed for biped robots based on the reduced dynamics and minimal conditions to stabilize robots, namely, the terminal capturability was picked up as the primary candidate of the model. Motion loci of the center of mass (COM) and the zero-moment point (ZMP) of a human subject were measured, and control parameters were identified from them. The identification result showed that the model well suited the human's behavior in spite of its minimal property only with a slight modification taking an asymmetry of the natural falling speed depending on the direction and the inertial torque about COM into account. A contribution of this work over the previous researches which focused on the capturability is that a model of the feedback controller that reproduces the overall dynamic stepping motion process was identified in a mathematically explicit form in it.