Reconstruction And Positioning Of Rail Fasteners Based On Line Structure Light Vision

In recent years,with the continuous expansion of the field of engineering measurement and the requirements for measurement accuracy in 3D design and manufacturing,traditional measuring instruments have been unable to meet the needs of high-precision three-dimensional coordinate acquisition.Compared with traditional measurement techniques,structured light vision technology has great technical advantages,especially in data acquisition.Its high efficiency,fast,accurate and simple features make it widely used in various fields.The biggest advantage of structured light vision technology is that it can quickly scan the object under test and directly obtain high-precision 3D coordinate data without the need for a reflective prism.The paper takes the rail fastener as the research object,and deeply discusses the related technology of the line structure light three-dimensional reconstruction system.Applying the existing 3D measurement technology to the actual engineering background of the railway,the reconstruction and positioning of the rail fasteners is realized.The main work of this paper is as follows:(1)The research status of structured light vision technology and the principle of line structure light 3D reconstruction system are introduced in detail.The advantages and disadvantages of direct laser triangulation method and inclined laser triangulation method in laser triangulation measurement are analyzed.According to the actual application scenario,the direct laser triangulation method is finally selected for measurement.(2)According to the mathematical model of line structured light sensor,image coordinate system,camera coordinate system and world coordinate system are established.The advantages and disadvantages of common camera calibration methods are analyzed,and the principle of Zhang Zhengyou's calibration algorithm is introduced in detail.Combining with the actual experimental environment of the system,Zhang Zhengyou's calibration algorithm is finally used as the camera calibration method of the system.(3)The algorithm of extracting the center line of light fringes is studied and discussed.Experiments are carried out by maximum method,gray center of gravity method and Hessian matrix method respectively.The effect of the three algorithms is analyzed and compared.Finally,the gray center of gravity method is used as thealgorithm of extracting the center line of the system.(4)Through the system motion information,the camera motion direction information is obtained.The two-dimensional pixels are converted into spatial three-dimensional coordinates,and the fasteners are three-dimensionally reconstructed.The round surface of the fastener nut is extracted according to the three-dimensional profile of the fastener.The paper analyzes the common circle fitting method,fits the circular plane,locates the center of the circle,and analyzes the experimental results.(5)A rail fastener positioning system platform was built.Using software development tools such as MATLAB and Microsoft Visual Studio 2010,the function of the software is designed with C++ programming language.The center positioning experiment was carried out on the software program to verify the feasibility of the system.