Active Compliance Control on the Hydraulic Quadruped Robot With Passive Compliant Servo Actuator

Zisen Hua,Shuaishuai Zhang,Yibin Li,Xuewen Rong,Hui Chai

doi:10.1109/access.2019.2951830

Abstract

A hydraulic servo actuator with passive compliance (HPCA) is designed for hydraulic actuated quadruped robots, aiming to solve the response discrepancy of the low-bandwidth servo valve to impact forces between robot's feet and the ground. This paper focuses on the performance of this passive compliance method combined with an active compliance control strategy when used on quadruped robots. First, the frequency-response characteristics of the HPCA are further discussed. Then, combined with the requirements of the quadruped robot, a compliant method characterized by incorporating dynamic feedforward control and joint angle feedback control items into the virtual model is proposed. Finally, both the new algorithm and the performance of the HPCA are verified by simulation and experiment. The results demonstrate that, compared with the original actuator, the frequency-response characteristics of the HPCA have better adaptability for the quadruped robot, while the efficiency of the active compliance control is also improved by this novel passive compliance strategy.

Highlights

In the wild or complex indoor environment, quadruped robots have demonstrated advantages that wheeled or tracked locomotion robots do not possess [1], [2]
The main purpose of this paper is to study the performance of the hydraulic servo actuator with passive compliance (HPCA) used on a hydraulic quadruped robot that is controlled by compliant strategy
The HPCA is designed to improve the output performance of the original actuator used on legged robots and to reduce the impact force between the robot’s feet and the ground

Summary

INTRODUCTION

In the wild or complex indoor environment, quadruped robots have demonstrated advantages that wheeled or tracked locomotion robots do not possess [1], [2]. The piston displacement xp is magnified 57 times for reference It can be seen from the flow curves that the addition of the accumulator does not significantly change the flow supplied by the servo valve (Qpis and Qpis (HPCA)) when the given signal frequency is low, and the flow supply capability is obviously enhanced with increasing frequency. The reason for such phenomena is that the addition of the accumulator effectively reduces the chamber pressure of the HPCA required by the piston motion. This is consistent with the frequency response of the actuators analyzed above.

LEG DYNAMICS

SIMULATION SETUP

Findings

CONCLUSION