Research On External Thread Parameter Detection Technology Based On Image Processing

Tubing thread because of its good leakproofness and resistance to pressure has been widely used in oil fields.Today in the world,the demand for energy is more and more urgent,so the growing demand for tubing thread is more and more greater at home and abroad,while the quality requirements are more strict.Traditionally tubing thread detection is manually done by workers,the process is complicated,time-consuming and laborious.And when workers evaluate the results,due to the lack of strict and normal scale,experience of the workers will have an important effect on the final measuring results.In recent years,computer vision and image processing technology,namely machine vision technology,develop quickly and have become a kind of advanced detection method.Machine vision technology has the advantages of high efficiency,high speed,non-contact detection,intelligence.Using the technology to detect the external thread has become an important research content for universities and research institutions.This paper mainly studies the external thread parameter detection system based on digital image processing technology.Firstly,the optical imaging system is constructed,CCD camera is used to obtain the digital image of tubing thread,then image processing technology is used to get the contour of thread edge,mainly including image preprocessing,binarization,edge detection and sub-pixel location.After analyzing the effects of the several edge detection algorithms,the topic uses Canny detection algorithm to extract edge contour,and then we use sub-pixel technology to obtain the precise edge information of thread.After this,the fitting method of linear fitting and circle fitting is selected to fit the edge contour.In addition,the calibration technology is used to obtain the pixel size equivalent of CCD.Finally on the basis of understanding the geometrical characteristics of tubing thread and the measurement methods proposed by American Petroleum Institute(API),parameters of the external thread are obtained through a certain algorithm,and the error analysis is carried out.At the same time,the Visual C++ is used as development language of the detection system,and the relatively simple operation interface is designed.The experimental results show that the detection system based on machine vision technology can realize the measurement of external thread parameters.The detection schemes and related algorithms of this paper can provide certain reference for other related research.