一种新的超声导波信号小波阈值去噪方法

摘要

In order to get an effective ultrasonic guided wave signal,the denoising measure of ul-trasonic guided wave in the broken rail detection is an essential part,and the efficiency of the de-noising directly affects the precision and reliability of the test results.These traditional threshold function methods have some shortcomings in signal denoising,so that a new novel threshold function is proposed in this paper to further improve denoising effect.This paper briefly describes the principle of this kind of new wavelet threshold function,and completes the related simulation and analysis,of which a comparison is made of the denoising effects by this method with those by the traditional soft and hard threshold function method.The ultrasonic guided wave signal is de-noised with these three methods respectively.The simulation results show that,compared with the soft threshold function method,the SNR of the signal dealt with novel threshold function method is improved by 6%~1 5%,the mean square error is reduced by 1 4% or so,and compared with the hard threshold function method,the signal SNR is improved by 8%~2 5%,the mean square error is reduced by 20% or so,and the amplitude of the denoising signal dealt with the no-vel method is very close to that of the original signal.In a word,this new ultrasonic guided wave wavelet threshold method has an obvious improvement of the denoising effect compared with those traditional threshold function methods.%在断轨检测中，为了获取有效的超声导波信号，必须对超声导波进行相应的去噪工作，而去噪效果的好坏直接影响到测量结果精度和可靠性。为了进一步提高去噪效果，本文针对传统的阈值函数法的不足，进行适当的改进，即提出一种新的小波阈值函数来提高去噪效果。文中简述了该种小波阈值函数的原理及构建，并进行了相关的仿真和分析；将该种方法的去噪效果与传统的软、硬阈值函数法去噪效果进行比较。结果表明，相对软阈值函数法，新阈值函数方法去噪后信号信噪比提高6％～15％，均方误差降低14％左右；相对硬阈值函数法，新阈值函数方法去噪后信号信噪比提高8％～25％，均方误差降低20％左右，并且新阈值函数方法去噪后信号幅值非常接近原始信号幅值，即该种超声导波小波阈值法相对于上述传统阈值函数法去噪效果有明显提升。