Performance Limitation on ZMP Feedback Control of Humanoid Robot

摘要

This paper presents balance control analysis of humanoid robot based on Zero Moment Point (ZMP) feedback control. The ZMP is often used as a standard evaluation of the stability of humanoid robot. Balance control is performed by controlling ZMP position so that it is always located in convex hull of the foot-support area. To simplify the design of controller, one-mass model which represents lower body part of the humanoid robot model has been commonly applied. However, the one-mass model causes the system becomes non-minimum phase, so that performance limitation is occurred. These disadvantages are attributed to the Waterbed effect in frequency domain and unavoidable undershoot in time domain. Therefore, this paper proposes the ZMP feedback control based on two-mass model, representing lower and upper body part of the humanoid robot. The proposed model results in minimum phase system. Finally, a design of controller based on the proposed model using Linear Quadratic Optimal Control by evaluating output of the system is described and confirmed using simulation.