Research On Full Section Measurement Technology Of Rail Profile With Line Structured Light

Line structured light rail profile full section measurement technology is based on the principle of triangulation.The point cloud data of rail profile is obtained by structured light sensor,and is registered with the rail standard profile template,so as to obtain the rail vertical wear and side wear and other parameters.These parameters can not only be used to master the service state of rail,but also guide rail grinding operation,which is a key technology of railway.It is an important means of operation and maintenance.The measurement technology has the characteristics of high speed,high precision and noncontact,which is the mainstream way of dynamic detection of rail profile at home and abroad.However,in the field application,due to the interference of imaging quality,system calibration error,contour stitching error and curve profile measurement error,the measurement accuracy of rail profile is affected.Therefore,reducing the interference of these factors and realizing high-precision measurement of rail profile is the focus of this paper.The main contents and innovations of this paper are as follows:(1)In view of the blank situation in the field of simulation research of rail profile full section measurement system,a simulation model of rail profile full section measurement system based on ZEMAX is proposed.From the image acquisition module,the system calibration module and the contour measurement module,the model is built in turn.The simulation model has the functions of image acquisition,system calibration and rail profile full section measurement.It can be used to simulate the process of rail profile full section measurement with line structured light.It can be used for the analysis of related problems,experimental verification and result prediction of rail profile full section measurement.It provides theoretical support for the accuracy improvement and reliability evaluation of rail profile full section measurement system.(2)Aiming at the problem of abnormal local exposure of rail laser cross-section image in field application,polarization imaging technology is applied to rail profile measurement system,and a full section imaging method of rail profile based on polarization fusion is proposed to optimize the full section imaging system of rail profile.The image fusion algorithm of polarization component is constructed through the reliability evaluation of light stripe.After fusion,the phenomenon of local over exposure and local under exposure is effectively eliminated,and the image quality is significantly improved.This method effectively overcomes the influence of abnormal local exposure on the results of light strip center extraction,improves the accuracy and stability of profile detection under complex conditions,especially after rail grinding,ensures the effectiveness of profile analysis,comparison and evaluation,and lays a foundation for improving the accuracy of rail profile full section measurement.(3)There is a lack of effective evaluation methods for laser plane attitude,including whether the laser is coplanar or not,and whether the laser plane is vertically installed with the rail,both of which will lead to errors in system calibration.A visual adjustment method of laser plane based on plane target and a calibration method of rail longitudinal parameters based on plane target are proposed.The attitude information of laser planes on both sides of rail is obtained by three plane targets in real time,and the laser coplanar evaluation method is constructed by plane normal angle and plane distance to guide the coplanar adjustment operation of two line lasers.The longitudinal direction vector of the rail is obtained by the form that the plane target is close to the rail surface,and the perpendicularity evaluation method of the laser plane and the rail longitudinal is established by using the correlation between the rail longitudinal and the normal of the laser plane.Through these two methods,the laser coplanar adjustment and component installation and other calibration links are upgraded from the original visual evaluation with low accuracy,poor real-time performance and subjectivity to the computer vision evaluation with high accuracy,strong real-time performance and objectivity,so as to reduce the calibration error caused by system calibration.This method provides a theoretical basis for the accuracy improvement and reliability evaluation of rail profile measurement system,and lays a foundation for the subsequent measurement system calibration and error correction.(4)Aiming at the measurement error of rail profile caused by laser non coplanar installation,a correction method of laser non coplanar error based on rail longitudinal direction is proposed.The auxiliary plane perpendicular to rail longitudinal direction is established by using rail longitudinal parameters and origin of world coordinate system,and the laser non coplanar error correction is completed by projecting the profile of half sections on both sides of rail onto the auxiliary plane.On the premise of ensuring the accuracy of rail profile measurement,this method does not need the laser planes on the left and right sides of the rail to be coplanar accurately,and only needs to be roughly aligned,which greatly reduces the requirements of assembly processing accuracy and field installation environment,and avoids the tedious and time-consuming laser plane fine-tuning process on site.(5)In order to solve the problem of large error in curve rail profile measurement,two error correction methods are proposed,one is based on the combination of virtual and real rail profile measurement error correction method,the other is based on double line structured light rail profile measurement error correction method.In the first method,the virtual rail is generated by using the actual measurement profile and the attitude parameters of the auxiliary plane.The optimization objective function is constructed by the coincidence degree of the virtual rail and the actual rail.The optimal auxiliary plane is solved,and the actual measurement profile is projected onto the optimal auxiliary plane to complete the profile correction.In the second method,the virtual rail is generated by using the first laser plane actual measurement profile and the auxiliary plane attitude parameters,and the auxiliary rail is generated by using the first laser plane and the second laser plane actual measurement profile and the two plane attitude parameters.The optimization objective function is constructed by the coincidence degree of the virtual rail and the auxiliary rail,and the optimal auxiliary plane is solved Projection to the optimal auxiliary plane to complete the contour correction.The two methods get the vertical plane of rail from three-dimensional angle,which provides a new way to solve the problem for the research of rail profile measurement error analysis and correction.