| High speed railway transportation industry is a vital link in China’s economic growth.The importance of ensuring railway transportation safety and preventing railway accidents is self-evident.Due to the fast running speed of high-speed railway train,it is difficult to make emergency braking in a short distance.Therefore,in order to prevent rear collision and other collision accidents and avoid irreparable consequences,it is of great significance to monitor the track occupation status.Track axle counting is one of the key technologies in the existing track occupation status monitoring.It uses sensors to sense the axle information of passing trains,so as to calculate the number of axles,and realizes the monitoring of track occupation status by comparing the number of axles at both ends of the monitoring section.However,at present,the axle counter sensor is mainly electromagnetic axle counter.Due to the poor anti-corrosion and anti electromagnetic interference ability of electrical sensor elements,the working reliability is greatly reduced in Thunderstorm and other bad weather.Fiber Bragg grating is a new type of sensor,which has strong anti-corrosion and anti electromagnetic interference ability,and can be well coupled with optical fiber,so as to overcome the defects of electromagnetic axle counter.However,the current track occupancy monitoring scheme based on Fiber Bragg grating sensing technology is difficult to have the performance advantages of high demodulation frequency,low cost and high stability,and can not meet the engineering needs of long-term monitoring of high-speed track occupancy.Under this background,this paper designs the fiber Bragg grating sensor with fault safety mode,and proposes to use the edge filter demodulation method combined with embedded technology to realize a track axle counter system with high demodulation frequency,low cost and high stability.The main research contents of this paper are as follows:(1)Demand analysis and sensor design of track axle counter system.The requirements of high speed,high sensitivity and high reliability of track axle counting system are analyzed in detail,and the design of track axle counting system based on Fiber Bragg grating is proposed;The sensing principle of fiber Bragg grating is analyzed,the fiber Bragg grating sensor with fault safety mode is studied and designed,the sensitivity of the sensor is improved through the structural design of sensitizer,and the temperature decoupling of the sensor based on temperature compensation grating is designed;This paper introduces the basic principle and implementation method of edge filter demodulation technology,and further improves the accuracy of sensor demodulation by studying and analyzing the spectral characteristics of fiber Bragg grating.(2)Research on high stability fiber Bragg grating track axle counting system.The temperature characteristics of linear optical filter are analyzed and studied,and the influence of temperature on its transmission spectrum is verified by simulation.A multi-channel optical path system is built according to the edge filter demodulation technology,and the temperature compensation algorithm is studied and designed to improve the high temperature stability of the system;Select the parameters of the key components of the circuit system,and design the circuit to meet the needs of high demodulation frequency and long-distance transmission of the system;Under the structure of two out of two safe track axle counting system,the dynamic threshold sequence axle counting algorithm and dynamic threshold real-time peak seeking axle counting algorithm are studied and designed to solve the problem of axle counting error when the train is running slowly.(3)Implementation of fiber Bragg grating track axle counting system.A set of fiber Bragg grating track axle counting system is built on Ordos Dazhun railway line.The basic functions and long-term demodulation stability of the system are tested on the spot.It is verified that the system has the function of monitoring sensor loosening/ falling off and has good long-term stability;After completing the basic function and stability test of the system,the actual axle counting test is carried out for the running trains under different vehicle weight,different vehicle speed,different driving direction and slow exit,so as to verify that the system has the axle counting ability for the trains under different vehicle conditions. |
