Study On Non-contact Measurement Technology Of Rail Head Profile Based On Machine Vision

Rail profile measurement plays an important role in guiding the rail grinding and ensuring the safe operation of the train.At present,the domestic rail profile measurement mainly uses the contact measuring tool,which has low measuring efficiency.The measuring tool can be worn and can't achieve full automatic measurement.The non-contact measurement method based on machine vision can improve the measurement efficiency.But it is difficult to determine the measurement datum automatically.And rail wear size can't be obtained directly.In addition,the image is affected by illumination,which increases the difficulty of laser stripe extraction.This thesis focuses on the above problems,the main work and innovation are as follows:Firstly,based on the principle of machine vision,a dual camera measurement scheme is established,and the non-contact measurement system of rail head profile was developed.According to the principle of laser ranging,the rail profile reduction is completed in the similar polar coordinate.Automatic determination of measurement datum is also realized.Through the automatic matching measuring benchmark and standard profile,the automatic measurement of rail head profile is achieved.Secondly,aiming at the image processing which is the key link of the measurement system,the corresponding processing flow is developed.Focus on the effect of illumination,Gamma correction method and Michelson contrast method are used.Combined with the characteristics of laser light source,the illumination factors can be eliminated effectively and the laser stripe can be extracted accurately.In order to improve the measurement accuracy,fringe thinning algorithm is studied.The normal direction mean method is proposed for this system.The feasibility of the method is proved by experiments,and the extraction of single pixel fringe is realized.Finally,the non-contact measurement software of rail head profile based on MFC control is compiled.And the automatic measurement of rail head profile is realized under laboratory conditions.The robustness of the algorithm and the feasibility of the measurement system are verified by the experimental results.