Control of the heel-off to toe-off motion of a dynamic biped gait

A mechanism for the control of the heel-off to toe-off motion of a dynamic biped gait is presented. It is argued that the reaction force between the ground and the biped foot is an important factor in a satisfactory implementation of dynamic gait. This force must be properly controlled while the foot is in the heel-off to toe-off phase. Since the foot rolls over the ground surface in this phase and the global description of the surface is unknown, the foot has to execute a nonholonomic constraint motion. The formulations of nonholonomic constraints and system dynamics under the constraints are derived for the roll-over motion. A feedback control mechanism is designed based on the formulations. The formulation and the feedback control mechanism are applied to a four-link biped model. Successful simulation results of the heel-off to toe-off motion prove that the formulation and control mechanism are valid for the nonholonomically constrained motion of the biped