The Research On The Detection Techniques Of Machined Surface Quality Based On Digital Image Processing

The surface roughness is the micro geometric feature which is composed by small spacing and peak valley.With the development of industrial technology,the precision and surface roughness of the product are becoming more and more important.In view of the improvement of measuring accuracy and measuring speed of the contact measuring instrument,the develop ment of non-contact nondestructive testing technology is promoted.The theory and technique of digital image processing have been introduced to study detection of metal surface roughness in this thesis,and the main contents and results are as follows:(1)The development of surface roughness detection,the application of digital image processing technologies in surface roughness measurement,and the basic principles of some digital image methods and their difference are firstly reviewed in this thesis.(2)The method of digital image technologies is applied to the image analysis of metal surface such as gray level transformations,gray stretching and so on.The suitable image processing method has been selected according to the gray histogram of the processed image and the effect of the image.The method of calculation and digitization for the value of the surface roughness Ra and Rz are investigated and proposed.(3)The classification of image noise is introduced and the appropriate filtering methods are suggested in according with different types of noise for the sake of getting better reduction effect.(4)The method of feature texture extraction is studied for the metal surface image based on the traditional method of surface roughness measuremen t.Employing the least squares principle to analyze the distribution characteristics of the surface texture map and carry on the statistics of texture characteristics of workpiece,the value of surface roughness and the final measurement method are obtained respectively.(5)The program of measuring surface roughness based on the Open CV software platform is developed by C++,including a series of function,such as,the machined surface images achievement,the surface texture feature extraction,and automatic measurement.Furthermore,the measured data are comparing with the actual surface roughness test data by parameter regression analysis method,and then the final result are carried out and implements the calibration of the system.The digital image processing technology that is combined with the detection of metal surface roughness has been employed to study the surface roughness of the workpiece by programming and calculating,at the same time,the program can realize the pre-treated of image,extract the texture features,and achieve the value of surface roughness that proves the feasibility of the method is obtained in thesis.The result has an important practical significance for the future development of the surface roughness detection.