面向机器人精密装配的高精度圆片位姿视觉检测

High-Precision Wafer Pose Visual Detection for Robot Precise Assembly

为了引导机器人精密装配过程的轴孔自动对中,提出一种高精度圆片位姿视觉检测算法。根据圆片的几何性质,对采集图像进行圆片轮廓提取、上表面轮廓椭圆检测和亚像素精度优化,从而获得能高精度拟合圆片上表面的轮廓椭圆方程。基于该椭圆方程,利用圆锥曲线透视投影原理建立了从2D椭圆到3D空间圆的位姿转换数学模型,可以根据圆片表面轮廓椭圆方程和圆片半径解算圆片上表面圆心坐标和圆片轴线方向向量,并提出两个轮廓点筛选准则以消除图像中部分非高斯噪声的干扰。针对位姿解算的二义性问题,提出一种利用圆片下表面圆心重投影的二义性消除方法,其优势在于无需增加环境约束。仿真分析和视觉检测实验结果表明,所提出算法鲁棒性好且检测精度达到:圆片上表面圆心的x,y轴位移检测精度0.01 mm,圆片轴线方向向量的角度检测精度0.7°。

In order to guide the automatic alignment of axis and hole in the process of robot assembly,a high-precision visual detection algorithm of wafer pose is proposed.According to the geometric properties of the wafer,the contour of the wafer in the captured image is extracted,the upper surface of the wafer is detected and the sub-pixel edge point is searched,so as to achieve the high-precision fitting of the contour ellipse equation of the upper surface of the wafer.Based on the fitted ellipse equation and the perspective projection principle of conic curve,the mathematical model of pose transformation from 2D ellipse to 3D space circle is established,which can solve the center coordinates of the upper surface and the direction vector of the axis of the wafer according to the ellipse equation of the surface contour and the radius of the wafer.Two contour points’screening criteria are proposed to eliminate the interference of some non-Gaussian noise in the image.To deal with the ambiguity of pose solution,an ambiguity elimination method based on the reprojection of the circle center on the lower surface of the wafer is proposed.Its advantage is that it does not need additional environmental constraints.The simulation analysis and visual inspection experimental results show that the proposed algorithm has good robustness,and the detection accuracy is as follows:the detection accuracy of x and y axes of the center on wafer’s upper surface is 0.01 mm,and the angle detection accuracy of the axis direction vector of the wafer is 0.7°.