Rail Corrugation Measurement Based On Multi-line Structured-light Vision

In recent years,with the rapid development of China's railway transportation,the requirements of the train for the rail corrugation are getting higher and higher.Theoretical research and engineering practice show that the rail corrugation is difficult to control and its mechanism is complicated.It is the main cause of train running noise,contact resonance of wheel and rail in the natural frequency,and brings too much damage to rail and vehicle,environmental vibration and noise problems.Therefore,high-precision dynamic rail corrugation measurement techniques are critical to guide rail maintenance.In this paper,some traditional corrugation measurement detection methods are firstly introduced and analyzed in detail,especially the inertial reference method and chord-based method.Because of the lower precision problem caused by the random vibration of onboard system in the current measurement method,a novel method for rail corrugation measurement based on multi-line structured-light vision is proposed,and the experimental platform for precision analysis experiment is built in this paper.Firstly,multiple line lasers are used to vertically project the light plane to intersect the rail.After the camera takes a laser stripe image from another position,to extract the center line of the light stripe containing profile information,a series of graphic preprocessing processes are performed: Hough transform to detect the rail boundary line,threshold segmentation,image denoising,and image refinement.And then the three-dimensional reconstruction process of the profile curve is completed by the structured-light three-dimensional vision measurement system.Then,because of the problem of profile distortion caused by the random vibration of onboard system,a distortion calibration method based on profile projection is proposed in this paper: we establish an auxiliary plane perpendicular to the rail longitudinal direction using the characteristics that the line between rail jaw points of several measurement profiles is parallel to the longitudinal direction,and we project measurement profiles to the auxiliary plane to calibrate profile distortion;Next,we accurately and gradually align the measurement profiles with reference profile through the hierarchical registration;Finally we precisely locate the point of corrugation measurement by using the fixed distance along the crosstie direction fromit to the center of the arc in rail waist area,and the vertical distance between two points is regarded as the corrugation value of this section.Finally,the precision analysis experiment of rail corrugation measurement method in this paper is carried out,and the experimental results show the influence of vibration on the measurement data can be inhibited effectively by our proposed method.The deviation between the calibrated measured value and the reference value is less than 0.3mm,the root mean square error is reduced to 0.19 mm,and the experimental standard deviation is reduced to 0.17 mm.The experimental results of continuous point precision analysis show that compared with the grinding ruler,the difference between the over-limit ratios in the wavelength range is not more than11.2%.So the corrugation measurement method in this paper provides a new idea and technical reference for the application of multi-line structured-light technique in the high-precision dynamic rail corrugation measurement.