Position error calibration of industrial robot based on binocular vision with reference length constraint

Abstract

The position error on the end of the industrial robot is an important specification for evaluating its accuracy performance. In the ISO 9283 standard, the laser trackers and the binocular vision measurement methods are recommended to calibrate the positioning error. The calibration accuracy measured by using the laser tracker method is superior to that by using the binocular vision measurement method. Thus, this paper emphasized to study how to improve the calibration accuracy of the end position error by using the binocular vision measurement system. The high precision lengths as reference are introduced to combine with a conventional binocular vision system to make a new measurement system. The system errors of the binocular vision system can be corrected. In order to verify the correction effect, taking the industrial robot as an experiment example, the experimental results show that the absolute position error on the end of the industrial robot by using the binocular vision system with reference length constraint can reduce from 0.491 mm to 0.330 mm, and the repetitive positioning error reduced from 0.116 mm to 0.023 mm. The accuracy improved by about 33% and 80% respectively. Compared with the laser tracker measurement results under the same experimental conditions, the difference between the two are 0.34 μm and 7.80 μm. It can be considered that the corrected binocular vision calibration method can achieve the same accuracy with the laser tracker. It can be widely used for high-precision calibration of industrial robots as a means of balancing economics and precision.