ZMP trajectory generation for reduced trunk motions of biped robots

Trunk motions are typically used to stabilize the locomotion of biped robots, which can be very large in some leg trajectories. This paper proposes a method to reduce the motion range of the trunk by generating a desired trajectory of the zero-moment point (ZMP). The trajectory is determined by a fuzzy logic based upon the leg trajectories that are arbitrary selected. The resulting ZMP trajectory is similar to human's one and the ZMP continuously moves forward. The proposed scheme is simulated on a 7-degree-of-freedom biped robot. Its results indicate that the proposed ZMP trajectory increases the stability of the locomotion and thus resulting in reduction of motion range of the trunk.