Theoretical Analysis And Experimental Study On Measurement Of Geometric Parameters Of Contact Wire By Binocular Vision

This thesis makes a comprehensive and in-depth analysis on the research status of the measurement technology and instrument of geometry parameters of contact wire. Theoretical analysis and experimental research on the portable measuring system for measuring geometric parameters of contact wire based on binocular vision are carried out deeply.First of all, through analysis of binocular vision measurement principle and the contact wire detection technology requirements, the mathematical model for measurement of geometry parameters of contact wire based on binocular vision are established. And the theoretical formulas of measuring geometric parameters of contact wire and effective field of view are derived individually by binocular measurement system structure parameters, camera optical parameters and image processing results; the overall structure design of portable measuring device for measuring geometric parameters of contact wire are completed.Secondly, the error and sensitivity of measurement of geometric parameters of the contact wire by using the binocular vision method is simulated by Matlab. The results show that the sensitivity of change of the contact wire height is much lower than that of the change of the staggers in this binocular vision system, so the error of the measurement of the contact wire height is much larger than that of the staggers. The measures to improve the measurement accuracy of the two measures are given: using image processing to achieve sub pixel resolution, increasing the base distance of two cameras and the camera tilt angle α; increasing the focus of camera lens f.Thirdly, under the VC++ environment, based on the Microsoft foundation class library MFC and OpenCV open source computer vision library to complete the system software design. Using the sub-pixel edge detection and least square method to fit lines to the image edge of the contact wire, improve the calculation accuracy of imaging position of the measured point in the two cameras effectively, then improve the measurement accuracy of the geometric parameters of the contact wire.Finally, the experiment device of measuring system was designed, and the experiment was carried out in the laboratory environment, and the error analysis and compensation of the experimental results were carried out. Compared with the measurement results of the handheld laser range finder, in the binocular system, the measurement accuracy of the pull out value is in the range of ±2mm, and the accuracy of the contact wire height is in the range of ±4mm. Moreover, repeated experiments are stable, which verifies the feasibility and validity of the binocular vision method to measure the geometric parameters of the contact wire. The practical scheme is provided for the development of portable measuring instrument.