Trajectory-free reactive stepping of humanoid robots using momentum control

Momentum control approaches have been successfully applied to balance controllers for humanoid robots due to their integrated controllability of ground reaction force and the center of pressure. In this paper, we introduce a trajectory-free reactive stepping controller using momentum control. The controller is characterized by moving passively in the direction of external pushes without attempting to follow some prescribed trajectory, thereby achieving a natural reactive stepping behavior adaptive to various perturbations. Constructed on top of momentum control, our stepping controller is realized straightforwardly by setting a set of suitable inputs such as the desired momentum rate change and the target swing foot position to the momentum controller for each phase of stepping. We demonstrate the effectiveness of our approach through various simulation experiments on a humanoid robot model.