Research On Edge Detection Technique Of Mechanical Part Image And Measuring System Development

In the measurement field of machine parts,machine vision technology is used to overcome the stress deformation of the traditional measurement methods,achieve the requirements of high precision and fast speed.It is applicable to the measurement of thin-walled parts,complex parts and irregular parts,etc.The research on edge detection method has been the hotspot of machine vision technology because the edge as important information in vision measurement contains the description of location and geometric features.At the same time,the methods of image registration and vector format conversion are got widespread concern increasingly to meet the automatic measurement demand and improve the compatibility of mechanical design drawings.This paper makes the exploratory and innovative work on the technologies of edge detection,image registration and vector graphics conversion which are involved by building high-precision image measurement system.On the basic of studies in mainstream pixel and sub-pixel edge detection technique,adaptive median filter method and Canny edge detection operator are used as the pixel-level edge detection method to meet the characteristics of mechanical parts image.In the field of sub-pixel edge detection,adaptive hybrid filter method and the zero-order spatial moment within nine windows method are proposed.Higher detection accuracy could be reached by calculating spatial moment operator along the normal direction of edge.For the image registration,a method based on the centroid and minimum bounding rectangle of the edge is proposed.This method firstly takes the image preprocessing,which means filtered and binarization,and then computes the affine transformation parameters through the location coordinates of centroid and the tilt angle of the minimum bounding rectangle between different images.Experiments show that this method has advantages of high accuracy,low computational complexity and high processing rate.As for the phenomenon of widespread using vector graphics as the mechanical design drawings,a method based on codec technology and file stream is developed to make the mutual conversion between DXF and bitmap format,which could enhance the compatibility of the image measurement system.Take gauge blocks and a number of mechanical parts images as test objects,parts drawings as vector graphics,and use the proposed methods of edge detection,image registration and format transform to do the experiments.The results show,the image measurement system can succeed in high precision edge detection,pixel-level image registration and conversion between vector and bitmap format.