Rail Fastener Center Positioning System Based On Binocular Vision

At present,the rail fasteners are mostly completed manually,which efficiency is low and intensity is large.Therefore,it is very practical to develop a set of automatic fastening system for rail fasteners.In this paper,binocular vision is applied to the automatic fastener disassembly system to solve the three-dimensional coordinate positioning problem of the fastener center in the disassembly system.In view of the problem of binocular positioning in the center of the fastener,the following aspects were studied:(1)Study the camera imaging principle and analyze the relationship between the object imaging points in four coordinate systems.A parallel binocular vision model was applied to the center of the fastener.(2)According to the actual needs of the automatic fastening system of the rai l fasteners,the parallel binocular vision test platform was designed and built to simulate the centering process of the fasteners.(3)Research the binocular camera calibration theory.The binocular camera is calibrated by Zhang's calibration method to obtain the internal and external parameters of the binocular camera.(4)In reality,binocular camera placement does not form an ideal parallel binocular stereo vision model.The left and right images are stereo-corrected by using the calibrated external parameter matrix to improve the imaging quality of the binocular image of the fastener and the positioning accuracy of the binocular vision.(5)The principle of stereo matching algorithm is studied,and the feature points of left and right image of fasteners are detected by SIFT stereo matching algorithm and matched.For the matching feature points,the feature point screening method of RANSAC is adopted to eliminate the mismatched points and improve the correct rate of matching points.(6)Aiming at the three-dimensional coordinate positioning problem of the fastener center.Firstly,using the characteristics of the SIFT feature point coordinates of the fastener surface,the feature points are screened to obtain the feature points in the top circle of the fastener.Then,in the feature point set,find two points with the largest difference in distance as two endpoints on the diameter of the top circle.The midpoint of these two points is also the center point of the circle,which is the center point of the fastener.Finally,the three-dimensional coordinates of the center of the fastener can be calculated.(7)The design of the fastener center center binocular vision positioning system was carried out to verify the feasibility and accuracy of the binocular vision positioning fastener center.The experimental results show that the binocular vision positioning system designed in this paper can locate the three-dimensional coordinates of the center point of the fastener and can meet the project precision requirements.