Research On Measurement System Of Geometric Parameters For Railway Overhead Line System

Overhead line system is the high voltage transmission line which is set up over therailroad tracks for the train pantograph to take the electric current. It bears theimportant task of transporting the electric energy obtained from the traction substationdirectly to electric locomotives. The reliable contact of catenary wire and thepantograph relates directly to the regular and safe operation of the railway, so accuratemeasurement of the geometric parameters of overhead line is critical, and it is themain theoretical basis of catenary repair and maintenance as well as the importantsafeguard of the safe operation of trains.In conventional catenary geometry measurement method, the measurementefficiency and accuracy is not high. Aiming at solving this situation, this articledesigned a real-time, high-precision geometric measurement system for overhead line.First, according to the feature of high speed and high accuracy of visual measurement,measurement scheme is established based on binocular stereo vision; making analysisof measurement requirements and site restrictions, we set up a measurement systemconsist of two high-resolution digital cameras, a high-power LED light source, alarry-car and a computer used for controlling the cameras and storing images. As thesystem can only be taken one-time calibration before measurement, the mechanicalstructure of the system is designed purposefully to fulfill rapid disassembling andinstallation. Calibration method of the measurement system is studied, and thecalibration of camera intrinsic parameters based on dimensional control field as wellas the calibration of camera extrinsic parameters based on bundle adjustment isanalyzed respectively. Three coordinates mentioned in the measurement areintroduced, and the definition and establishment methods of railway center coordinateand the unification of these coordinate systems are explained in detail. According toimages taken in the field, center extraction algorithm of the line based on edgedetection is designed compared to extraction of center of the light strip. Andexperiment is done to verify the feasibility of the extraction algorithm. The matchingalgorithm based on epipolar constraint is studied and verified.After site experimental verification, the measurement accuracy of the system canreach±1mm and the repeatability accuracy of the system can reach1mm. Both of them meet the measurement need, so the real–time and reliable measurement ofgeometric parameters of the overhead line system is achieved.