基于VMD的多相介质超声回波检测技术
Ultrasonic detection research on multiphase medium based on VMD
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摘要: 提取多相介质中有效超声回波信号是实现煤岩界面识别的关键技术。利用超声波探测煤岩介质所获取的回波信噪比低且为非平稳、非线性信号,难以有效准确的获取煤岩界面的回波波形,进而无法有效判断煤岩分界面。传统的小波分析手段需要根据信号特点选取特定的小波基,EMD,EEMD等自适应信号分解方法存在模态混叠及虚假分量等现象。提出利用VMD(变分模态分解)分析超声回波信号的组成成分,准确获取煤岩界面的首次回波的波形与时间,以达到识别不同介质界面和判断介质相关参数的目的。模拟仿真及实验表明,VMD可实现更优化的信号分解效果,实现对煤岩界面首波波形和首波时间的检测,达到准确识别以煤岩介质为代表的多相介质分界面的目的。Abstract: The detection of effective ultrasonic echo about multi-component is the key point to realizing coal-rock inter-ference recognition. In actual ultrasonic detection,as the echo received is the signal composed of multi-component which is low SNR,non-stationary and non-linear,it’ s hard to accurately and efficiently get the waveform about the coal-rock boundary. Traditional wavelet transform method requires that the specific wavelet base is selected according to the characteristics of signals. Frequency aliasing and illusive components exist in adaptive decomposition methods such as EMD,EEMD etc. VMD (Variational Mode Decomposition) is proposed to analyze the components of the ultra-sonic echo signal and precisely obtain the waveform and time of the first echo signal about coal-rock boundary so as to realize the interface recognition among different components as well as make the judgement of related parameters. Sim-ulation and experiments demonstrate that VMD,able to achieve a more optimized signal decomposition effect,makes a difference in accurately identifying the interface of multi-components as represented by coal-rock.