Dynamic Compliance Analysis for LHDS of Legged Robot, Part A: Position-Based Impedance Control

In this paper, the dynamic compliance analysis for position-based impedance control is studied. First, the leg hydraulic drive system (LHDS) of legged robots is studied and the mathematical model of hydraulic drive unit (HDU) position control system is built. Then, combined with kinematics, statics and dynamics of the leg mechanical structure, the position-based impedance control method is applied to LHDS. Moreover, the serial–parallel composition of the dynamic compliance of position-based impedance control is analyzed and the three key factors influencing the impedance control accuracy are found, which is the main contribution of this paper. Finally, the key factors proposed in this paper are verified experimentally by using both LHDS and HDU performance test platform. The theories and experiments proposed in this paper provide a theoretical foundation for the compensation of position-based impedance control.