H.: ZMP Compensation by On-Line Trajectory Generation for Biped Robots

This paper proposes an adaptive trajectory genera-tion strategy of using on-line ZMP information with an impedance control method. During walking, since the robot experiences various disturbances like pulling or pushing forces, the walking mechanism should have the robustness against those disturbances, and it re-quires an on-line adaptation ability. If sensed ZMP goes out of the preset ZMP boundary, the on-line tra-jectory planner generates the trajectory of the base link in the vertical direction to compensate the required mo-ment for recovering stability. The ZMP equation and sensed ZMP information are used in this trajectory generation strategy. In this paper, an impedance con-troller with impedance modulation is used to control biped robots for stable walking. Computer simulation with a 3-dof environment model for which a combina-tion of a nonlinear and linear compliant contact mod-els is used, shows that the proposed controller performs well. Moreover, the biped robot with the proposed tra-jectory generator can walk even when it is pushed with a certain amount of force.