Research On Broken Rail Detection Algorithm Based On Barker Code Excitation

As an important pillar of our national economy,rail transportation provides great convenience for people's daily production and life.When the train is running,the rail plays the role of carrying and guiding.Whether the rail is in a healthy state directly affects the safety of the train.The broken of rail on railway operation line seriously threatens people's lives and property safety.Therefore,it is of great significance to study rail damage detection.In order to solve the shortcomings of traditional single pulse excitation and combind with the application of coded excitation in medicine,the code excitation technology is applied to the detection system of ultrasonic guided wave track breaking in this paper.Firstly,based on the experimental data of four kinds of distance,the relationship between the attenuation of ultrasonic guided wave and the distance is studied,and the rail channel is modeled with the theory of multipath effect.Secondly,based on the established rail channel model,the Barker code,Golay code and chirp signal are analyzed and compared,and the Barker code is selected as the ultrasonic excitation signal according to the characteristics of the rail broken detection system and the coding.Then,at the receivers,the matched filtering and the weighted matched filtering are selected for pulse compression simulation.In addition,in order to solve the problem that the resonance frequency of the sandwich piezoelectric ultrasonic transducer deviates under the interference of the external environment,the frequency tracking method is used to determine the optimal transmission frequency of the ultrasonic guided wave in the rail.At the same time,the number of bits and periods of Barker code are discussed according to the simulation and experimental results.Finally,the coded excitation algorithm and pulse compression algorithm are verified based on the rail broken detection system.The simulation and experiment results of 1m and 50m rails show that the signal amplitude of Barker code excitation after pulsed compression by matched filtering is much higher than the received signal of single pulse excitation.The normalized waveforms of the two signals are almost completely coincident in the time domain,the similarity between the two signals in the simulation and experiment results is reached 99.39%,99.29%and 96.77%,91.08%respectively.The simulation and experiment of 50m and 500m weighted matched filtering show that compared with the original matched filtering,the received signal after weighted matching can reduce the sidelobe by 12dB,11dB and 29dB,21dB respectively.The conclusion can be drawn that using Barker code as excitation to obtain UGW is feasible and the Barker code excited UGW can be applied in broken rail detection.