分析了影像测量仪移动机台定位误差的成因, 比较了无误差补偿和采用线纹尺进行定位误差补偿两种情况下机台的定位精度。为了克服线纹尺补偿时由人工采点造成的瞄准误差和摆正误差, 提出了采用阵列实心圆标准精密样板对进行平面综合定位误差补偿的方法。该方法首先进行样板摆正, 通过图像采集获取实心圆图像, 通过图像处理的方法获取每个圆心坐标, 并实时记录在采集图像中, 该圆心标记用于为调整样板坐标系与移动坐标系平行而转动标准样板时的摆正比对。摆正后, 通过移动机台到每个阵列圆圆心与图像中心重合的位置, 记录对应的坐标点对, 通过多项式拟合的方法获取拟合系数, 并用于机台的定位误差补偿。采用该方法在VMS300影像测量仪机台上进行测试, 经过补偿后仪器的定位精度可以达到2 μm。

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 μm, and the accuracy is effectively improved.