Dynamic Compliance Analysis for LHDS of Legged Robot, Part B: Force-Based Impedance Control

In this paper, the dynamic compliance analysis for force-based impedance control is studied. First, the mathematical model of legged robot joint hydraulic driver, called hydraulic drive unit (HDU), is built. Then the force-based impedance control model of the leg hydraulic drive system (LHDS) is built based on the robot system kinematics, statics and dynamics. Next the dynamic compliance of the control model is studied and found to be composed in a serial-parallel structure. Further, the two main factors which influence the impedance control accuracy are found. Finally, the composition theory of dynamic compliance is proved by experiments. The theory proposed in this paper provide theoretical foundation for the compensation of force-based impedance control.