A calibration method of robot kinematic parameters by drawstring displacement sensor

Yahui Gan,Jinjun Duan,Xianzhong Dai

doi:10.1177/1729881419883072

Abstract

Calibration of robot kinematic parameters can effectively improve the absolute positioning accuracy of the end-effector for industrial robots. This article proposes a calibration method for robot kinematic parameters based on the drawstring displacement sensor. Firstly, the kinematic error model for articulated robot is established. Based on such a model, the position measurement system consisting of four drawstring displacement sensors is used to measure the actual position of the robot end-effector. Then, the deviation of the kinematic parameters of the robot is identified by the least-squares method according to robot end-effector deviations. The Cartesian space compensation method is adopted to improve the absolute positioning accuracy of the robot end-effecter. By experiments on the EFORT ER3A robot, the absolute positioning accuracy of the robot is significantly improved after calibration, which shows the effectiveness of the proposed method.

Highlights

In recent years, with the continuous development of the robot industry in China, the application range of robots has become more and more extensive
According to the positioning error data of the sampling point of the robot before and after calibration, the maximum positioning error of the sampling point of the robot in the X-axis direction is reduced from 3.4526 mm to 1.9688 mm, which is reduced by 42.98%; the average positioning error is reduced from
The maximum positioning error in the Y-axis direction decreased from 5.3287 mm to 2.1470 mm, which is reduced by 59.71%; the average positioning error decreased from

Summary

Introduction

With the continuous development of the robot industry in China, the application range of robots has become more and more extensive. According to the principle of differentiation calculation, the two end-effector of the transfer matrix between adjacent link coordinate systems are differentiated to obtain d ii[1] T , as shown in the following equation. Db ð25Þ n in which d is the deviation value of the robot end-effector position, Ma, M a , Md, M q , and M b are the matrix obtained by the simplification according to equation (24), which is the coefficient matrix of the kinematic parameter deviation of the robot. According to equation (26), the coordinates of the robot end position measurement point can be calculated as follows x 1⁄4 ðla þ rÞ cos b 1⁄4. By the above equations (27), (31), and (38), the position coordinate (x, y, z) of the measured point of the robot end-effector can be obtained.

Experiments

Findings

Conclusion