基于机器视觉的半球面微小孔位置的精密测量系统（英文）

A Machine Vision System for Position Measurement of Small Holes on Spherical Surface

针对精密零件的半球表面上微小功能孔的位置测量需求,研制了一套基于二维扫描机构、图像获取单元和精密隔振工作台的机器视觉测量系统.本文提出了基于二维正交旋转扫描测量微小孔孔间位置的理论方法和数学模型,探讨了在图像处理过程中小孔边缘的提取算法以及小孔空心位置的计算方法.为了验证测量系统对半球面微小孔位置的测量能力,实验中选用了半球面半径为60 mm、小孔半径为2 mm的工件作为测量对象;利用光学准直仪验证了小孔位置的测量重复性和测量精度等性能指标,实验结果显示测量重复性误差为1.0″和1.4″,在微孔位置测量偏差的极大值为2.13″和4.13″.

This paper presents a machine vision system for the position measurement of small holes fabricated on a spherical surface. The machine vision system consists of two rotation stages to rotate the measurement sample, an imaging sensor to scan the surface profile of the small hole under detection and a vibration-isolation table to reduce the disturbance of the measurement environment. In this paper, the approach to measuring the spatial position of small holes was firstly introduced based on the method of orthogonal rotary scanning. Due to that the image quality around the hole edge was influenced by the machining defects and machining marks, the image processing algorithm to search the hole edge and to determine the hole centre was described in detail. Then, to verify the feasibility of the machine vision system, the position measurement of a hemispherical artifact, of which the radius was 60 mm and on which the surface was fabricated with small holes with radius of 2 mm, was carried out. Furthermore, the measurement repeatability of the spatial position of small holes was experimentally investigated, and the measurement accuracy of that was also studied by an optical autocollimator. Experimental result indicates that the repeatability errors were 1.0″ and 1.4″, the maximum deviations of the hole position measurement were 2.13″ and 4.13″.