Theoretical Analysis And Research Of Binocular Vision Measurement System To Measure Contact-Wire's Geometric Parameters

Contact-wire is an important component of electrified railway's power supply system which also named OCS(overhead contact system),it transports the electric power to locomotives by sliding friction contact to the pantograph.Geometric parameters of contact-wire(contact-wire height,stagger and wear)directly affects the reliability and stability of the friction contact between contact-wire and pantograph slider,so then affects the quality of current collection of electric locomotive,even the operation safety.Therefore,in the overhead contact systems construction,operation and maintenance,maintenance and other processes,the measurement of geometric parameters of contact-wire is an indispensable content.There are an important practical significance of engineering to research and development of portable measuring instrument with high measurement accuracy and efficiency,high degree of automation,and applicable for situ measuring.In this paper,a variety of existing contact-wire detection methods and instruments are comprehensive analysis and comparison.On this basis,considering the technical requirements of contact-wire detection and the characteristics of computer vision inspection,the method of measuring contact-wire parameters based on binocular vision measurement system has been established,and then completed the scheme design.This paper points out the optical design by using two reflection prisms to reflect light path,making the installation of two cameras back to back horizontally,its advantages are:(1)It is beneficial for camera installation and adjustment,Moreover,the camera is protected by hiding in the track gauge.(2)It also benefits to install and protect of the narrow-band filter in front of the camera.(3)It can reduce the optical path error by using two reflection prisms to reflect light path.Secondly,a general mathematical model is established using binocular vision method to measure geometric parameters of contact-wire.The relationship between the structural parameters and the camera's parameters of the binocular measurement system and the errors of the measurement is simulating by MTALAB.The result indicates that:(1)The measurement error caused by the error between the optical axis of the two cameras and the center-to-center distance is large;when the angle between the optical axes of the two cameras keep unchanged,the measurement error is not sensitive for the change of single camera tilt angles ?1 and ?2.(2)The measurement error can reduce effectively by choosing two lenses with good focal length consistency and compensating lens distortion.Thirdly,the camera imaging model and camera calibration method are analyzed and researched,the calibration method of binocular measurement system based on Two-Stages Camera Calibration From a Plane is determined.In the VC++ environment,the calibration program of binocular measurement system is developed based on Open CV and MFC.On the basis of theoretical analysis and research,a binocular vision measuring device is designed and manufactured.The experiment of binocular calibration and preliminary contact line physical measurement is carried out.Experimental results are coincident with the theoretical analysis.It provides theoretical basis for further research and development of instruments.