Walking motion generation of humanoid robots: Connection of orbital energy trajectories via minimal energy control

Specifying a ZMP trajectory is not a natural characteristic in human walking. The relationship between the CoM and the ZMP is not trivial due to the inverted pendulum characteristics of biped locomotion. Because of this reason, it is difficult to design the trajectory and in most of the cases it is selected as a constant in the phase of single support. It is more important to consider the walking motion generation as a CoM state transfer. Even if in the system the ZMP can be considered as the input, it is desirable to have state feedback ensuring more robust locomotion. In this paper we propose to realize this transfer using minimal energy control. Using a linear mass concentrated model the analytic solution is obtained and used for arbitrary footstep planning.