Analysis and Verification on Energy Consumption of the Quadruped Robot with Passive Compliant Hydraulic Servo Actuator

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

doi:10.3390/app10010340

Abstract

The hydraulic servo actuator with passive compliance (HPCA) is designed for hydraulically-driven quadruped robots. It is characterized by an accumulator that connects to the piston chamber of the hydraulic cylinder to buffer impact forces between a robot’s feet and the ground. This paper studies the energy efficiency of this actuator in the dynamic locomotion of a quadruped robot. Different from the traditional methods of storing potentially recyclable energy using accumulators, the energy-saving principle of HPCA is to utilize the pressure-transition characteristics of the asymmetric hydraulic cylinder with control of the symmetrical valve. The accumulator can store and release oil during the switching of the transition point in each gait cycle of the robot, thereby improving the energy efficiency of the actuator. The influence of the initial inflation pressure and working volume of the accumulator on the energy efficiency of the HPCA is studied by simulation and physical experiments. The results show that the HPCA has a higher energy efficiency that is independent of the physical parameters of the accumulator.

Highlights

Legged robots are receiving increased attention as the most prominent mobile robot technology for almost all terrain adaptations [1,2]
The desired trajectories (x p in legend) of the actuators magnified by a corresponding multiple are used as a reference in some pictures. It can be seen from the results that, for the hip actuator at the left-front leg, the first abrupt point of the piston chamber pressure (Ppis ) always occurs in 0.15 s during the swing phase, and the second appears at the transition from the swing phase to the supporting phase, while for the actuator at the right-rear leg, the first abrupt point of the piston chamber pressure (Ppis ) always occurs in 0.35 s during the swing phase, and the second abrupt point appears at the transition from the supporting phase to the swing phase of the cycle
The reversing of the piston causes the pressure in the piston chamber to increase, and part of the oil that should be expelled from of the actuators flows into the accumulator, so the values are negative

Summary

Introduction

Legged robots are receiving increased attention as the most prominent mobile robot technology for almost all terrain adaptations [1,2]. The more general methods for improving the energy efficiency of legged robots can be divided into three classes: employment of structures or actuators with elastic or flexible components, passive locomotion, and motion optimization. Elastic components can be connected in series between the output of the actuator and the load to form a series elastic actuator [9,10] or a variable stiffness actuator [11,12]. These kinds of actuators can obtain the precise output force by

Methods

Results

Conclusion