Research Of Calibration System For Wheelset Wear Online Measurement Of Locomotive

In the railway operation system, wheel set is one of the most important factors for train running safety. The condition of wheel set is directly related to the safety of train running. Therefore, wheel set wear measurement is an important measure for ensuring the safe running of train.A calibration system applied to wheel set wear online measurement was designed. In this calibration system, camera calibration and dynamic calibration of entire measuring process were carried out. Main parts of this paper were described below.(1) A camera calibration method was proposed based on perspective projection principle of pinhole camera and iterative calculation method. The transformational relation between physical coordinates and pixel coordinates was determined according to the actual camera pinhole model. The space angles and object distance of camera were calculated by iterative calculation method. The camera parameters provided calculation method for acquiring the wheel set wear parameters from wheel set image.(2) A dynamic calibration method of entire measuring process was proposed according to the online feature of wheel set wear measurement. The linear relation between wheel set base point and trigger position was determined according to wheel set motion model. According to the actual pixel coordinates of wheel set base point, the deviation of trigger position was obtained by iterative calculation. The deviation value was used to correct the acquiring moment in wheel set wear measurement process.(3) The characteristic parameters of calibration system components were designed, including space position parameters of laser source and camera, field of view of CCD and focal distance of lens, asynchronously triggering method of camera, test method of locomotive speed and calibration machinery.(4) The calibration system software was designed according to camera calibration method and dynamic calibration method. The calibration software included camera calibration software and dynamic calibration software. The function of image acquiring, image processing and data analysis was achieved in the calibration software. (5) Experiments of camera calibration, laser source and image processing were carried out. The experiment results showed that calibration precision achieves 0.2mm and meet the precision demand of wheel set wear measurement.