Reactive biped walking control for a collision of a swinging foot on uneven terrain

This paper describes a biped walking control method for a collision of a swinging foot on uneven terrain. Because a swing leg moves to a desired landing position, an unexpected collision on a terrain may be happened by a distance error between a foot and a terrain. A swing foot has to not only absorb a impact force, but also changes a trajectory as long as a swing foot contacts on a terrain. Furthermore it is required to keep a balance against a contact force. To prevent a trip over and a losing balance by contact on a terrain, two reactive key components are installed: 1) Set appropriate impedance gains of the feet according to a walking phase, 2) Update the desired landing position to the COG (Center of Gravity) pattern generation immediately as a detecting/releasing contact. In this paper, focused on a swing motion, a robust biped walking with a collision of a swinging foot on a uneven terrain is realized. The proposed method is validated through simulation results with the HRP-2 humanoid robot.