Research Of Fiber Bragg Grating Axle-counting Systems Based On Shear Measurement

In recent years, with the occurrence of "10.29" and "7.23", the importance of railway signal train track occupancy detection technology is increasing day by day. The axle-counting technology is a significant technology in the field of track occupancy detection. The traditional axle-counting equipment adopts the principle of electromagnetic induction, and it is difficult to make an accurate judgment on the track occupancy after the interference of lightning and other electromagnetic physical quantity. But now widespread use of fiber Bragg grating sensing technology has a lot of advantages, such as high sensitivity, strong anti-interference ability, high reliability and low cost, which can meet the requirements of track state long term online monitoring.This paper relies on the the Shuohuang railway development limited liability company project Monitoring system of railway signal based on optical fiber sensor hosted by Shijiazhuang Tiedao University, then studies and designs a new axle-counting system based on Fiber Bragg grating sensing technology. The system can use fiber Bragg grating sensor for measuring steel rail deformation state of shear stress, and by decoding and processing the data of optical signal, it carries shear force changes. Then it can accurately calculate the number of axles through axle region, finally completing on the track occupancy monitoring. The work mainly includes the following aspects. Firstly, this paper describes briefly the development of application of axle counting technique and fiber grating sensor in rail transportation, and analyzes the defects of the existing axle counting equipment. Secondly, it theoretically analyzes the sensing principle of FBG and the principle of axle through the measurement of shear from the point of statics. At the same time, it finishs the calculation of shear type sensor from the point of materials mechanics and the wheel pressure of rails under stress model by finite element simulation, determining the layout angle and position of fiber grating sensor. Thirdly, it completes the set of fiber grating demodulation system and designs a dedicated acquisition module of fiber grating wavelength demodulation instrument to output signal and upload to the PC. Forthly, it describes the understanding of interference noise model of system output signal, then uses the EMD method to deal with filtering output Signal, realizing the signals of wavelength reconstruction and improving the precision of demodulation greatly. Finally, it uses LabVIEW as the host computer programming software to finish the data processing of the demodulation system output signal, the TCP/IP data communication and the human-computer interaction section module designing.The research findings of this paper are both innovative and practical in some extent, which is of a certain value for the future railway signal track occupancy detection field, and make some contribution to ensuring the safety of railway traffic.