A method for dynamically balancing a point foot robot

In this paper we apply a general control framework, Whole-Body Operational Space Control (WBOSC), to an under-actuated point-foot biped. We use WBOSC to reproduce the behavior of the Prismatic Inverted Pendulum (PIP) as the center of mass dynamics for our point foot biped. We present and analyze a new algorithm that dynamically balances the PIP model by choosing footstep placements. Our algorithm uses the shooting method and numerical integration to find a footstep location even when the robot´s constraints do not permit an analytic solution to the model dynamics. This approach stabilizes the robot in simulation, and keeps the physical robot upright for as many as 15 steps. The primary limitation appears to be inaccurate foot positioning.