Moving single support ZMP trajectories for humanoid robot walking reference generation

Humanoid walking robots are expected to assist us in the future. This will require stable and reliable bipedal walk. The control of the hard-to-stabilize bipedal structure requires suitable walking references. The Zero Moment Point (ZMP) criterion is commonly used as a measure of stability of the walk. A stable walking reference can be generated in such a way that the Zero Moment Point stays always within the supporting polygon defined by the robot feet. In many approaches the ZMP reference is kept fixed under the supporting foot. However, it is found experimentally that during natural human walk, the Zero Moment Point moves forward under the feet. This paper presents a reference generation method based on ZMP criterion and natural walking. A stabilizing controller is developed. The walking performance with the fixed and forward moving ZMP references are compared with the model of a 12 DOF biped robot.