Simultaneous planning of CoM and ZMP based on the preview control method for online walking control

The present paper describes a newly proposed method of planning the CoM trajectory that realizes the desired ZMP. We introduce the permissible ZMP region as well as the desired ZMP trajectory. When the robot suffers from disturbances, the ZMP trajectory desired in the future is adjusted and the future permissible region is used evenly in order to suppress the change of the ZMP at the moment of disturbance. The proposed method is based on the CoM trajectory generation method that uses preview control theory. Simulation results reveal the feasibility of the proposed method. The proposed method is then implemented as a part of walking control system of HRP-2, which generates a walking pattern that starts from the estimated actual robot motion at 40 [Hz]. Walking experiments on unknown terrain are conducted in order to demonstrate the performance of the proposed method.