Reactive stepping strategies for bipedal walking based on neutral point and boundary condition optimization

Generating a physically feasible pair of motion pattern and force pattern for walking motions of a humanoid robot can be analyzed as a two point boundary value problem. The final boundary condition plays a critical role as the state trajectory depends on it and the remaining time to the goal. In this paper, the effect of the boundary condition is exploited to compensate disturbances during the walking motion and two strategies to modify it are proposed. The first one is based on the neutral point condition and it prioritizes stabilization in one step. The second one is based on an optimal formulation which can include future steps in the cost function. The unilateral constraint on the reaction force and the kinematic workspace are taken into account to compare both reactive control methods.