Data processing technology of electromagnetic ultrasonic testing based on improved EMD
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摘要: 为提高电磁超声检测信号的精确度,提出了一种基于改进EMD(经验模式分解)的数据处理方法。针对IMFs(本征模态函数)筛选中容易丢失高频有用信息的问题,建立了一个基于欧式距离的IMFs分量筛选准则,并结合小波阈值滤波方法以实现噪声去除和微小有用信号的有效提取。为验证该算法的有效性,对厚度为10,15 mm的铝板进行了测厚试验,采用改进EMD算法对检测到的数据进行处理并提取峰值点位置,通过相邻峰值点的时间差计算厚度值,进行多组试验并计算误差。试验结果表明,提出的方法能够提高电磁超声检测的精度,同时提高了回波信号的信噪比,对于10 mm厚的铝板最小误差为0.1%,对于15 mm的铝板最小误差为0.3%。Abstract: In order to improve the accuracy of electromagnetic ultrasonic testing signal, a data processing method based on improved EMD was proposed. Aiming at the problem of losing high-frequency useful information in IMFs screening, an Euclidean distance based IMFs component screening criterion was established, and wavelet threshold filtering method was combined to achieve noise removal and effective extraction of small useful signals. In order to verify the effectiveness of the algorithm, thickness measurement experiments were carried out on 10 mm and 15 mm aluminum plates. The detected data were processed by using the improved EMD algorithm and the peak position was extracted. The thickness value was calculated by the time difference between adjacent peak points. Multiple groups of experiments were carried out and the error was calculated. The experimental results show that the proposed method can improve the accuracy of electromagnetic ultrasonic testing, and improve the signal-to-noise ratio of echo signal. The minimum error can reach 0.1% for 10 mm aluminum plate and 0.3% for 15 mm aluminum plate.
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