Research On Autonomous Train Location Mehtod Based On Image Features

Comprehensive monitoring train is an important infrastructure detecting facility which ensures normal operation of highspeed railway.Accurate position is the basis of precise detection.A research on autonomous train location method is of great theoretical and practical significance for localization of comprehensive monitoring train and enhancing the infrastructure detecting level of existing line.This dissertation analyses position requirement of comprehensive monitoring train. It puts forward the concept of Visual Balise(VsB) for the first time.A novel positioning method to identify trackside and track-own VsB with map matching and image recognition is proposed.The identified VsBs with accurate position are used to calibrate odometer accumulative error.There are 3 steps of this method:determination of VsB capture area;recognition and location of VsB image features,and VsB's actual precise position calculation.To determine the VsB capture area,the train rough position should be estimated. Firstly,A sparse grid map matching method is presented for initial train positioning. Then,the nearest point estimation and maximum posterior probability estimation are used for estimating train position based on GPS output and track's mathematics model. And a position estimation method based on curvature and course combined matching is also proposed in curve tracks.As for trackside VsB,a mechanism for restricting searching area with virtual track is introduced to improve searching speed.In the restricted area,grey projection is used for partitioning VsB features out of whole image.Finally,the partitioned VsBs are classified and identified by SVM.As for track-own VsB,the frog of turnout is firstly abstracted as intersection of straight tracks.Then a straight track candidate pool is generated by grey projection of image line scan,and Hough transform is used to verify the authenticity of candidate tracks.Since the defects of heavy calculation load for standard Hough transform is overcomed and the anti-noise advantage of Hough transform is used to verify the authenticity of tracks,this method can quickly and accurately detect the straight tracks in images.For calculating actual precise position of VsB,a simple 1-D calculation model based on single image is used to reduce calculation load.Theoretic error arising from height and lean angle of camera is discussed.Another 3-D triangle positioning method with gauge constant is also discussed.Both theoretical calculations and experimental results show that calibration of odometer error with Visual Balise(VsB) identified by map matching and image recognition can meet train positioning requirement.And it provides a high-precision and low-cost solutions for precise autonomous train location.