基于离散平稳小波变换的无线随钻系统测试信号处理

Signal Processing of Wireless Measurement While Drilling Based on Discrete Stationary Wavelet Transform

在无线随钻测量系统中,钻井液波信道中含有很强的噪声信号,为获得更好的钻井液脉冲信号,采用小波变换对该信道的信号进行处理。小波基的选取是否恰当对处理的最后结果有非常大的影响,以相关系数作为判断钻井液信道信号处理效果优劣的依据,将7种常用的小波基函数选取不同参数后分解重构的信号与原始信号进行了比较,通过相关系数的大小选定了适合处理该信号的最佳小波基函数及其参数,并对重构后的信号进行了阈值去噪试验。试验结果表明,小波变换去噪对钻井液信道信号的噪声有很好的抑制作用,Haar小波基对钻井液信道信号的去噪处理效果最佳;同时表明,相关系数作为两个信号波形的相似性的一种度量是合理的。

In the wireless measurement while drilling system, the mud signal contains strong noise. The wavelet transform was used to transform the mud signal for better mud pulse signal. The wavelet base selection plays a very important role in the result of the processed signal, The correlation coefficient was used to rank the drilling mud signal processing results. The commonly used 7 wavelet bases with different parameters were tested to reconstruct the signal and compared with the original signal; the correlation coefficient was used to identify the optimum wavelet base and associated parameters for this signal. The threshold method was used to de-noise the reconstructed signal. The experiments indicate that wavelet transform is very useful in restraining the noise in drilling mud signal. Haar wavelet base is the optimum in de-noising the drilling mud. It is reasonable to use correlation coefficient to determine the similarity of two signals.