基于经验小波变换的煤岩界面识别超声回波处理方法研究  

Signal processing method on ultrasonic echo from coal-rock interface based on EWT

作　　者：李力[1,2] 刘佳鹏 魏伟 LI Li;LIU Jiapeng;WEI Wei(College of Mechanical and Electrical Engineering,Central South University,Changsha 410083,China;State Key Laboratory of Deep Sea Mineral Resources Development and Utilization Technology,Changsha 410012,China)

机构地区：[1]中南大学机电工程学院,湖南长沙410083 [2]深海矿产资源开发利用技术国家重点实验室,湖南长沙410012

出　　处：《煤炭学报》2019年第S01期370-377,共8页Journal of China Coal Society

基　　金：国家重点基础研究发展计划(973计划)资助项目(2014CB046305);国家自然科学基金资助项目(51434002)。

摘　　要：煤岩界面的识别问题属于世界性的难题。利用超声回波检测技术识别煤岩界面存在回波信噪比低,模态混叠严重,难以准确获得煤岩界面回波波形的问题。因此,准确提取煤岩界面有效超声回波信号是识别煤岩界面的关键。变分模态分解(Variational Mode Decomposition,VMD)已成功用于提取煤岩界面超声回波的有效回波信号,但VMD十分依赖于输入参数的选取,不适当的输入参数会严重影响信号的分解效果。考虑到矿井现场需要对煤岩界面超声回波信号进行实时处理,VMD并不满足要求。因此,提出利用经验小波变换(Empirical Wavelet Transform,EWT)方法提取煤岩界面有效超声回波信号。经模拟仿真及实验数据表明,作为一种自适应信号处理方法,经验小波变换(EWT)无需输入参数即可实现对信号的自适应分解,准确提取煤岩界面有效回波,满足矿井现场对煤岩界面超声回波信号进行实时处理与成像的要求。经EWT提取的有效超声回波信号包络顶部存在波形畸变,严重影响煤层厚度计算。因此,提出引入权重系数的最优化迭代法对回波包络进行非对称高斯模型拟合,再利用拟合得到的回波包络计算煤层厚度,结果表明该方法可以有效地减小煤厚计算的误差。最后利用峰值聚焦成像技术对处理得到的拟合回波包络进行成像,用以提高煤岩界面超声成像的距离分辨率。经验证,该方案可达到准确识别煤岩界面的目的。Coal-rock interface recognition has always been a worldwide difficulty in mining.The echo reflected from coal-rock interface has the problems of low SNR,mode mixing,and being hard to obtain the accurate waveform of the echo from the coal-rock interface.Therefore,it is important to extract the useful component from the original echo.Variational Mode Decomposition(VMD)has been successfully applied to extract the useful component from original signal.However,it relies much on the parameter selection.Inappropriate parameters will severely affect the performance of VMD.Considering that the real-time processing of ultrasonic echo is required in underground mine sites,VMD doesn't meet the requirement.Therefore,Empirical Wavelet Transform(EWT)is proposed to extract the useful echo signal from coal-rock interface.Based on the simulation and experiment data,as an adaptive signal processing method,EWT achieves adaptive decomposition and accurately extracts useful component without any input parameters,which satisfies the requirements of real-time processing and imaging of echo signal.Based on the simulation and experiment data,EWT can effectively extract the useful echo signal.In addition,concerning that the processed echo signal has the problem of wavelet distortion,an optimal iterative method with weighted coefficients is proposed to fit the echo envelope based on asymmetric Gaussian model.Finally,a peak focalization imaging method is proposed to make image with the fitted echo envelope.Processed results indicate that this method can achieve the goal of recognizing the coal-rock interface accurately.

关 键 词：煤岩界面识别 超声检测 经验小波变换 峰值聚焦成像 

分 类 号：TD652[矿业工程—矿山机电]