Study On Modulation And Demodulation Of Ultrasonic Guided Wave Communication In Rail

Rail in service is easily damaged by environment and huge pressure.If it can not be detected and dealt with in time,it will lead to traffic accidents.In order to solve this problem,experts put forward various theories and implementation methods of rail damage detection,among which the ultrasonic track breaking detection system has become a research hotspot.The modules of this system usually use digital transmission modules to communicate with each other.This paper proposes to use ultrasonic waves to communicate in the rails,so that the ultrasonic track breaking detection system can communicate with each other while performing damage detection,which can realize the system integration and enhance the stability of the system.Based on the research of ultrasonic track breaking detection system,This paper analyzes and compares the modulation and demodulation methods of ultrasonic communication.Firstly,the optimal excitation frequency range is determined by frequency scanning experiment,and the carrier frequency of ultrasonic communication is determined according to the frequency range and the characteristics of ultrasonic transducer.Then,in Simulink,based on the multi-channel attenuation and electrical model of transducer,the three modulation modes of 2PSK,2ASK and 2FSK are simulated and compared,and a frequency signal demodulation method is proposed aiming at the disadvantages of non-coherent demodulation.Finally,the modulation and demodulation circuit of ultrasonic communication based on arm microcontroller is designed,which is divided into two parts:transmitter and receiver.The transmitter achieves channel coding and signal modulation through software and power-amplifies and boosts the modulated signal through full-bridge inverters and the pulse transformers.The boosted modulated signal excites the ultrasonic transducer.The demodulator firstly preprocesses the receiving signal through programmable amplifier circuit,the automatic gain control circuit,the bandpass filter and the bias circuit,then collects the signal through ARM microcontroller,demodulates the signal,decodes the channel and displays the signal by softwareAfter completing the software and hardware design,the functions of each module is verified in the laboratory.Then the platform of the ultrasonic communication is built to verify the overall function.Finally,a large number of experiments were carried out on the railway site.The experimental results show that ultrasonic communication in the rail should adopt 2PSK modulation and non-coherent demodulation.The communication rate of the system is up to 714bps and the error rate is 0.006.