Design Of Real-time Monitoring System For Turnout Rail Head Damage Based On Ultrasonic Guided Waves

As one of the main means of transports, the railway makes people's travel and freight faster and more convenient. However, rail damage is a key factor that affects the safety of rail transport. It seriously threatens the safety of train traffic, which is one of the important factors leading to major safety accidents. The turnout is the most important component of the railway track equipment and it is most difficultly maintained which is the weakest part of the railway track system resulting from its structural complexity. In addition, the damages are easily produced in the turnout. Therefore, it is of great significance to monitor the damage of track rails in real-time.Based on the ultrasonic guided wave detection method, the real-time monitoring system for turnout rail head damage is studied in this paper. Firstly, the system scheme and the detection algorithm are designed. In order not to affect the normal operation of the train and facilitate the fixed installation, the PZT piezoelectric ceramic ultrasonic probes are selected and installed in the side of rail head for solving the real-time detection problems of turnout rail head.Simultaneously, for the purpose of reducing the dead zone, the method of transmitting and receiving the probe is arranged respectively. Moreover, the excitation frequency of the ultrasonic transmitting probe is determined by experiment method whose value is 180 kHz. The cross-correlation algorithm based on the echo of the ultrasonic guided wave is used as the system damage detection method and its feasibility is verified by MATLAB simulation. On this basis, the hardware and software design of the system are accomplished in this paper. The ARM data processing module is regarded as the core in the system which includes the circuit of ultrasonic transmitter, the circuit of ultrasonic receiver, the circuit of FPGA data acquisition, the circuit of LCD display etc. The probes of ultrasonic guided wave are driven by the transmitting circuit including the signal isolation, driving and boost circuits. By using the limiter circuit and the active band-pass filter in the receiving circuit to implement the conditioning for the ultrasonic guided wave signals, we can ensure the normal acquisition for the signal data utilizing FPGA data acquisition circuit. At the same time, LCD is controlled by ARM in order to achieve waveform display, system parameter setting and system debugging. Finally, the software and hardware of the system are tested and the correctness of the hardware and software functions of the system is verified.The experimental results show that the system can operate normally and the relative error of the data processing of cross-correlation algorithm is less than 0.4% compared the ARM platform with the MATLAB platform, which meets the design requirements of the system. In addition, the feasibility of the monitoring system for head damage identification in the rail located in turnout is verified by the simulation experiment of man-made head damage.