Research On The Double Joint Steel Rail Profile Detection System And Matching Algorithm

The geometry and wear of the rails have a crucial impact on the safety of the line.In order to ensure the good geometry of the rails and find and evaluate the rail wear in time,it is necessary to check the rails regularly.The efficient and accurate rail profile detection system is in line with the trend of high-speed and digitization in China.Rail profile,the outer profile of rail cross section.Rail profile detection technology is a technology that uses measuring tools or instruments to extract coordinates of outline points on rail cross-section,and reconstructs rail profile by reverse engineering,so as to truly reflect the geometric shape and rail profile.Rail wear detection technology is a technology that uses tools or instruments to measure the wear between the measured rail profile and the design profile at specific points.The main concern of rail profile measurement is the outline shape of the rail head,which can be described as a complex plane curve.The actual rail profile and the designed rail profile curve often need to be translated and rotated properly,and described by their matched difference characteristics.Rail wear measurement can be carried out on the basis of complete rail profile measurement,or only for specific points of rail profile.The biggest difference between wear measurement and rail profile measurement is that wear measurement provides specific measurement and calculation benchmarks for the matching of actual rail profile and designed rail profile.Because of the special shape of the rail head,most of the existing rail profile detection systems in the industry can not measure the jaw of the rail,so the waist or the bottom of the rail are often used as the reference for rail profile matching.However,the purpose of rail wear measurement is to evaluate and ensure the strength and stiffness of rail head.Considering that the relative position between rail head and rail waist or rail bottom is often affected by machining errors or stress and deformation.The industry standard"JJG 1127-2016 Rail Abrasion Measuring Instrument Verification Regulations"stipulates that the rail wear is measured and calculated based on the outer rail sill of the rail head.The theoretical basis is more scientific and reasonable than the rail waist or rail bottom.Based on this,a double-joint rail profile detection system is proposed,which is mainly composed of double-joint rail profiler and corresponding upper computer software algorithm.It can measure the rail profile of outer rail jaw with rail head quickly and accurately,and use the rail jaw as matching datum to match the measured rail profile with the designed rail profile accurately.At the same time,the geometrical shape and wear value of the rail profile can be obtained.The rail profiler adopts the contact method of double-joint mechanism.The angle data at two joints are obtained by high precision incremental photoelectric encoder.Combining with the size of measuring arm length,the mathematical model of rail profiler measurement is established.The measured angle data are transformed into two-dimensional point coordinates in Cartesian coordinate system by modifying the end point of the probe,and the spatial position of the contact point between the probe and the rail is reflected in real time.In order to ensure that the measuring range of the rail profiler can cover the outer rail jaw of the rail head,the measurement model is solved inversely,and the mechanism is simulated and optimized by using the code written by matlab.It is found that the arm length between 130mm and 200mm can meet the requirements of the measuring range,and 160mm is an ideal design.Therefore,it is determined that the rail profiler adopts the design scheme of equal arm length with 160mm measuring arm length.Because the incremental photoelectric encoder is used in the angle measurement of the two joints,the zero position of the joint angle measurement needs to be calibrated before the formal measurement.In order to obtain accurate rail profile measurement data,it is necessary to know the initial position data of the rail profiler,including that the rail profiler is installed on the rail profiler,in order to obtain the attitude relative to the cross section of the line.According to the measurement model,angle measurement of two joints is defined as angle?₂₀ between the arms of the rail profiler and angle?₁₀ between the arms and the connecting lines of the left and right sides of the rail profiler.These parameters can be obtained directly by calculating the size of the mechanical structure if a fixed and measurable initial position of the rail profiler is given by appropriate method,but this will improve the installation and machinery.Processing accuracy requirements.In view of this,a simple and easy single point calibration method is proposed.The zero point of?₂₀ can be automatically calibrated by using the rail profiler to measure the same point in two different postures.At the same time,a method of contour calibration is proposed,which can realize zero point calibration of?₁₀.The experimental verification shows that the measurement accuracy of the rail profiler after calibration is 0.026 mm.The rail profile measurement data is the basis of the rail profile matching.In order to improve the matching accuracy,it is necessary to effectively extract the turbulent measurement data.The validity of the point is judged by the central distance method.After denoising and simplification,the cubic spline function is used to realize the segmentation fitting of the rail profile.The calculation of wear is based on the matching of rail profile.A matching method based on the two straight lines at the bottom of rail jaw and the side of rail head is proposed.Hough transform is used to detect the straight line and get the intersection point of the straight line.The translation and rotation of rail profile are calculated.According to the principle of coordinate transformation,the precise matching between the measured rail profile and the designed rail profile is realized.The experimental results show that the matching accuracy can reach 0.04°,the wear of the experimental rail profile is 7.11mm.