Disturbance Elimination for the Modular Joint Torque Sensor of a Collaborative Robot

Zhigang Chen,Wenlei Qin,Jie Zhao,Carlos Llopis-Albert,Yongsheng Gao,He Zhang,Qiang Li

doi:10.1155/2020/2405134

Abstract

The ability to obtain accurate torque information and detect collision information is the key demand for collaborative robots. Given the highly integrated modular joint, the joint torque-sensing system is disturbed by other elements during online measurement, affecting the accuracy of measurement. For example, the torque ripple caused by the periodic deformation of the flexspline of the harmonic driver and the temperature drift due to the heating of motor are the two main factors affecting the measurement of the torque sensor. In this study, a torque sensor suitable for a modular joint is developed. Moreover, a strain gauge configuration based on a specified phase difference for torque ripple cancelation and a temperature compensation method based on the combination of the Wheatstone bridge and a nonlinear model are proposed. Finally, the performance of the developed sensor is experimentally evaluated.

Highlights

Collaborative robots can be remarkably applied in various industries, for example, medical treatment, 3C electronics, and public service [1, 2]
0.5022 strain gauge configuration as shown in Figure 13, while the other sensor adopts the strain gauge configuration as shown in Figure 8. e former is the type without torque ripple cancelation, and the latter has torque ripple cancelation. e modular joint is equipped with these two sensors. en, the modular joint is rotated at a velocity of 35.16°/s without load
The developed sensor is lighter than M2210C1 and can be calibrated online with the modular joint to improve sensing accuracy

Summary

Introduction

Collaborative robots can be remarkably applied in various industries, for example, medical treatment, 3C electronics, and public service [1, 2]. To avoid injury from robots, the collision detection technology of robots has attracted extensive attention. Collision detection based on a motor current should predict interference and assembly error model to accurately estimate torque [4]. To resolve these problems, many scholars have embedded a joint torque sensor into robot joints [5, 6]. The harmonic drive is widely used in collaborative robots because of its high gear-reduction ratio and high torque ability in a compact geometry. During the operation of the harmonic driver, the elliptical wave generator facilitates the periodic deformation of the flexspline

Methods

Results

Conclusion