Precision Compensation Method for Positioning Error of Working Table of Vision Measuring Machine Based on Machine Vision

The factors causing the positioning error of mobile instrument of vision measurement machine are analyzed. The positioning accuracy results are compared under the conditions of line ruler compensating the positioning error and without error compensation. In order to overcome the aiming error and alignment error caused by manual sampling when using line ruler compensation, we propose a method of using a template with array solid circles as the compensation standard precision parts to compensate for planar comprehensive positioning error. The method firstly carries out a template alignment. The solid circle image is obtained by image acquisition. And the circle center coordinate is calculated and drawn in the collected image in real time by image processing method. The circle center is marked, which is used as alignment reference to adjust the standard template position on the stage in order to make the motion coordinate system and the template coordinate system parallel. After alignment, the machine is move to the position where the circle center of each array is coincident with the center of the image. The corresponding coordinate point pair is recorded. And the fitting coefficient is obtained through the polynomial fitting method and used for machine positioning error compensation. The method is tested on the VMS300 vision measuring machine. After the compensation, the positioning accuracy of the instrument reaches 2 mu m, and the accuracy is effectively improved.