Research On Panoramic Generation Of Train Wheel Tread Under Machine Vision

Train wheel detection is one of the important part of train safe testing.Currently,the static manual detection is getting replaced by the dynamic wheel detection in the nation so as to improve the efficiency of detection.For dynamic wheel detection,the thesis focues on panorama generation of wheel tread under machine vision.The main work has studied by three aspects of wheel tread extraction,tread panorama generation and dynamic detection system.Tread extraction of train wheel.For fixed image formation of captured system,wheel tread pre-region is splitted.According to the value and the change rate of gray projection,the gray level projection is applied for re-locating the tread region.Based on the change of the tread edge gradient,the edge of tread is detected via Canny operator.By the chain code dectection,the direction values of gradient for each edge point is calculated and tracked so that the edge point is determined for extracting the edge line of wheel tread.Finally,the complete edge line of wheel tread is generated by using the least square fitting method.Tread panoramic generation of train wheel.By the Zhang's calibration,the mapping of the feature point of center of circle in round calibration plate is built between imaging plane coordinate system and the world coordinate system.Through inverse transformation matrix,the real coordinates of wheel edge points are obtained for surface correction of the wheel tread.The histogram equalization is adopted to improve the illumination quality of tread images.The panoramic generation methods both the feature point-based and the space-based pixel matchings are studied.According to partitioned capture of tread images,the space-based pixel matching is then used to calculated the difference between grey level values in the overlapped region of neighboring tread images.Based on the difference and minimum smoothing width,the overlapped region is smoothed and the tread image is then jointed to generate tread panoramic images.Realization and upgrade of train wheel dynamic detection system.The train wheel dynamic detection system is developed in which the dynamic capture of wheel tread and panoramic generation of tread are upgraded.This system developed have high robustness and better results and now is pilot running in on-line dectection in rail detection center,Jinan.The testing results have better ablity of detection and are satisfied with the requirement of system indexs.