Biological Principles of Control Selection for a Humanoid Robot's Dynamic Balance Preservation

This paper presents a contribution to the study of control law structures and to the selection of relevant sensory information for humanoid robots in situations where dynamic balance is jeopardized. In the example considered, the system first experiences a large disturbance, then by an appropriate control action, resumes a “normal” posture of standing on one leg. In order to examine the control laws used by humans, an experiment was performed in which a human subject was subjected to perturbations and the ensuing reactions were recorded to obtain complete information about the subject’s motion and ground reaction force. Then, a humanoid model was advanced with characteristics matching those of the experimental human subject. The whole experiment was simulated so as to achieve a simulated motion that was similar to that of the human test subject. The analysis of the control laws applied, and the behavior of selected ground reference points (ZMP, CMP and CM projection on the ground surface), provided valuable insight into balance strategies that humanoid robots might employ to better mimic the kinetics and kinematics of humans compensating from balance disturbances.