Research On Technology Of Fiber Grating Sensors In Railway State Monitoring

Since the features of high-sensitivity, high speed, large quantity information storage capacity, ease of contributing large-scale networking and other advantages, optical fiber sensing technology have drawn widely attention. Fiber sensing technology provides effective solution for rational state of the track structure and effective monitoring mechanism. However, existing research lack fundamental application theory, feasibility research and application experience.Based on the study of fiber grating sensor theory, combined with application features of fiber Bragg grating sensor, the thesis concentrate on the feasibility of the FBG sensing technology using in the wheel tread defects Monitoring. On analyzing existing method for high-speed wheel tread defects monitoring, consulting optical fiber sensing technology its own characteristics and practical engineering applications requirement, the thesis formulate detection scheme for high speed wheel tread defects based on fiber sensing technology.The front part of the thesis research on the feasibility of the FBG sensing technology using in the wheel tread defects monitoring based on fiber grating sensor theory and application features of fiber Bragg grating sensor.At the second part, the author make detection scheme for high speed wheel tread defects based on fiber sensing technology. Compared to the electric sensors which is widely used in wheel tread monitoring system currently, FBG sensor is out of zero drift phenomenon since it is not affected by electromagnetic interference. Furthermore, fiber sensing technology is convenient to form the large scale distributed network. The thesis formulate detection scheme for high speed wheel tread defects based on fiber sensing technology and realize some functional modules using FPGA as digital control core unit.According to the design target, thesis set up multi-channel FBG sensing simulation model. Firstly, the impact response model of wheels based on fiber grating sensor is built. Then, another model is found to simulate PPM demodulation method in F-P demodulation module. Compare the wavelength shift graph with the actual impact response curve to verify the feasibility of demodulation method used in design. At last, thesis apply voltage controlled oscillator to simulate the actual frequency scanning procedure. Corresponding the center wavelength scanning process to frequency scanning process with voltage controlled oscillator, and the actual wavelength shift △λm to frequency shift △ω of simulated electric signal.