The Improvement of the Hydraulic Quadruped Robot Response Rapidity and Impedance Control

Hydraulic quadruped robots are favored by scientific research institutions in various countries because of their high load and adaptability to unstructured environments. However, research on improving the response rapidity and compliance control of hydraulic robots is still lacking. The improvement of the response rapidity and dynamic compliance are researched. Firstly, the single-leg position control model of hydraulic quadruped robot is established, and based on this, force closed loop is added to realize position-based impedance control. The phenomenon that when the load is large, the hydraulic system responds slowly, so impedance control is difficult to achieve the desired effect, and it is found to be caused by the hysteresis of the position control system. Secondly, by analyzing the natural frequency of the quadruped robot and based on the variation law of the natural frequency of the motion process, the segmented PID control strategy and feedforward control strategy are proposed. Finally, the quadruped robot single-leg experimental platform was built, and the proposed control strategy was tested and verified. The experimental results show that the strategy of segmented PID control and feedforward control can fully improve the response rapidity of the system. On this basis, the position-based impedance control method can be used to reduce the force on the hydraulic cylinder after the robot is impacted.