Study On The Wear Inspection Technology For The Contact Wire Of Straddle-type Monorail Based On Stereo Vision

Contact wire is an important part of Chongqing rail transit power supply system to ensure the normal running of the train. Contact wire will be wired inevitably while the train operates. When the wear extent reaches a certain degree will affect the power collection quality between the pantograph and contact wire and accident such as blot or nets hang may happen. Consequently real-time monitor of the wear extent is the most important of the contact wire inspection items. At present, the contact wire wear detection mainly relies on manual inspection. This method takes the disadvantages of low efficiency, poor reliability and safety concerns. Therefore, the automatic detection technology research of the urban monorail contact wire has important practical significance.The straddle-type monorail wear detection system studied in this paper which is based on the linear array stereo vision principle acquire the contact wire image using two linear array cameras. Firstly,we obtain the depth information of the contact wire through the camera calibration and the stereo matching technology. Then, we calculate the actual high residual value of the contact wire using the clustering algorithm. Finally, the catenary wear information are obtained. In this paper, the main research work includes:We analyze the difference between the electrified railway and the straddle-type monorail catenary in the structure, and the corresponding difference and relation in the catenary wear detection technology. We design and construct the detection system based on the principle of the stereo vision system, and then collect high quality image of the catenary by using the system.We analyze and research the calibration technology of the linear array stereo vision system. We introduce the difference and relation between the plane array camera and the linear array camera model. The camera calibration method was reviewed and summarized comprehensively. Finally, we calibrating the stereo vision under laboratory conditions and obtain the inner and outer parameters of the camera and the location parameters between cameras.Stereo matching technology was studied deeply. We present a fast stereo matching algorithm based the initial match of the SURF primary direction for the catenary image, after analyzing and comparing of various kinds of stereo matching algorithms. The FAST algorithm was used to extract feature points in the proposed algorithm, and then SURF feature descriptor was constructed for the feature points that is extracted. Finally, the stereo matching of the catenary image was accomplished based polar constraint and the SURF primary direction. The experimental results show that the algorithm is of high match precision and speed and can obtain a dense disparity map, which is suitable for stereo matching of the catenary images.The depth value of the catenary can be calculated from the disparity map based on the principle of stereo vision and the high residual values of the contact wire can be calculated by using K-means clustering algorithm. Experiment results show that this design of monorail contact wire wear test validation system can match the requirement of the project. This has laid a solid foundation for the further practical design of the contact wire wear detection system.