Pattern Generation for Humanoid Robot with Natural ZMP Trajectory

Walking pattern generation is one of the key problems in control of humanoid robots. Zero Moment Point (ZMP)-based approaches such as Linear Inverted Pendulum Mode (LIPM) and Gravity Compensated Inverted Pendulum Mode (GCIPM) were proposed to generate the walking pattern. In proposed methods, the ZMP is considered fixed in the middle of supporting foot sole during stepping. But, in the natural human walking, ZMP is not fixed and moves forward under the supporting foot during stepping. This paper proposes a pattern generation method using GCIPM with considering moving ZMP under the robot supporting foot. It is supposed that the ZMP follows a first-order function and moves forward from the heel in the direction of toe. Simulation results show that the reference trajectories which are generated considering the moving ZMP cause the smooth movement for COM.