Pushing manipulation by humanoid considering two-kinds of ZMPs

This paper discusses the pushing manipulation of an object by a humanoid robot. For such a pushing task, we show that there are two kinds of ZMPs, i.e., the conventional "Zero Moment Point (ZMP)" considering all sources of the force/moment acting in the foot supporting area, and the "Generalized Zero Moment Point (GZMP)" which is an generalization of ZMP for a humanoid robot whose hands do not contact with an object. We first obtain the stable region of the GZMP on the floor. Moreover, since the difference between these two ZMPs corresponds to the magnitude of contact force applied by the hands, we propose the pushing manipulation by a humanoid robot by modifying the desired ZMP trajectory for a humanoid. The effectiveness of the proposed method is confirmed by simulation results.