Contact Wire Geometry Parameters Of Binocular Vision Measurement System Research

Contact wire is an important part of the contact net of electrified railway. While the locomotive is running, its pantograph contacts with the wire and gets electrical energy from the wire. Being affected by open-air atmosphere and sliding friction, contact wire’s geometric parameters, such as its height, stagger, and wear, are very easy to change. In order to ensure that the locomotive runs safely, it is necessary to inspect wire’s geometric parameters regularly, so that the wire can be maintained and protected from potential safety hazard.Based on the analysis for existing methods to measure contact wire’s geometric parameters, this thesis deeply researches into the measurement performances and main technical target of a binocular measuring system for the wire’s geometric parameters.In the first place, the theoretical relationship between the effective field of view & resolution of a binocular measuring system and the system’s structure parameters and camera optical parameters has been analyzed. The simulating calculation on the effective field of view and resolution under different structure parameters and optical parameters are done by use of MATLAB. The results show that, (1) once the CCD is determined, the effective field of view will increase with the increase of the camera’s focus; (2) if the focus does not change, the effective field of view and resolution will decrease and increase respectively with the increase of the camera’s optical-axis slant angle.Secondly, the theoretical formula between the measuring error and such parameter errors as the system’s structure parameter (the space between the centers of two CCD, the slant angle of tow camera) errors, the focus error, and the image position error of the wire on two CCD have been derived. Then, the measuring error analysis is simulated by use of MATLAB. The results provides theoretical foundation for optimizing measuring system’s design and determining allowance error reasonably under requiring measuring accuracy.Then, the position relations between the images of contact wire and messenger wire on two CCD have been simulated, and the feasibility and concrete methods to distinguish those two wires have been analyzed.On the basis of theoretical analysis, a preliminary measuring device has been built up and used to verify the feasibility. Visual C++has been used to develop the program of image acquisition, image pre-processing, object identification, and parameter calculating. Aimed at the characteristics of contact wire’s image, it is analyzed in theory that how to identify the wire.