A master–slave control method with gravity compensation for a hydraulic teleoperation construction robot

Lingtao Huang,Tao Ni,Hironao Yamada,Yanan Li

doi:10.1177/1687814017709701

Lingtao Huang, Tao Ni + Show 2 more

Open Access

https://doi.org/10.1177/1687814017709701

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Abstract

This research develops a gravity compensation method that determines the mass of a task object easily and compensates for the external force caused by the task object when it is conveyed by a hydraulic teleoperation construction robot. Moreover, this study establishes a master–slave system for this robot; two joysticks act as the master, and an excavator with four links (fork glove, swing, boom, and arm) represents the slave. To compensate for the influence of gravity, a previous gravity compensation method is proposed and applied to the boom and arm. However, it is ineffective during the conveyance process especially when the task object is heavy because the driving force is influenced by gravity of the task object. Therefore, this research presents a gravity compensation method that can effectively determine the mass of a grasped object and compensate for the external force induced by its gravity, as verified through pressing, grasping, and conveying experiments.

Highlights

In a master–slave system, a human operator manipulates joysticks to govern the remote robot’s positions, velocities, and contact forces with the environment
To compensate for the external force caused by the gravities of links and the gravity of the grasped object in the hydraulic construction robot, a gravity compensation method is proposed in this research
An operator must perceive a reasonable sense of force from the construction robot

Summary

Introduction

In a master–slave system, a human operator manipulates joysticks to govern the remote robot’s positions, velocities, and contact forces with the environment. Mechanical solutions are not sufficient when joint angles are changed, especially when robots are grasping objects In this condition, operators need to overcome more reaction torques to manipulate the joysticks. To compensate for the external force caused by the gravities of links (boom and arm) and the gravity of the grasped object in the hydraulic construction robot, a gravity compensation method is proposed in this research. Each joystick is composed of two direct current motors that enable an operator to sense the grasping of an object by the fork glove and to feel the work reaction force induced by the construction robot. The construction robot is small and works slowly; the influence of the inertia item and Coriolis, as well as of the centripetal item, should be omitted relative to that of gravity in the calculation of the dynamic equation of the boom and arm in this research. External force fs0b induced by the gravity of the boom fsgb and driving force fsb can be obtained using equation (4). fsga can be obtained by substituting a for the subscript b in the correlation equations

Experiments and analysis

Conclusion