应用于Lamb波的最小功率无畸变波束形成算法

Minimum Power Undistorted Beamforming Algorithm for Lamb Waves

在利用Lamb波进行板状结构损伤检测时,采用经典最小功率无畸变波束形成算法可以获得较高的损伤成像精度,但仍无法避免频散效应对成像精度的影响,且该算法存在谱矩阵求逆运算复杂、奇异谱矩阵无法求逆等缺陷,显著降低计算效率。为解决上述问题,本文提出了更适用于Lamb波检测的改进型最小功率无畸变波束形成算法。该算法在频域进行波束形成以解决频散对成像的影响,并结合最小二乘递推法与对角加载法来进行谱矩阵求逆,以提高计算效率。实验及仿真结果表明,该算法能有效去除频散对损伤成像结果的影响,从而有效地解决了传统波束形成算法的成像结果中存在伪影,且成像分辨率低的问题;同时解决了谱矩阵求逆困难的问题,使得计算时间显著缩减。

When using Lamb waves to detect the damage of the plate structures,the classic minimum power distortion beamforming algorithm can obtain good damage imaging accuracy,but it still can not avoid the influence of dispersion effect on the imaging accuracy.And this algorithm has shortcomings such as complex spectral matrix inversion operation and inability to invert singular spectral matrix,which may reduce computing efficiency significantly.In order to solve the above problems,this paper proposes an improved minimum power distortion beamforming algorithm that is more suitable for Lamb waves detection.The proposed algorithm performs beamforming in the frequency domain to solve the dispersion effect on imaging result,meanwhile combines the least square recursion method and the diagonal loading method to invert the spectral matrix to improve computational efficiency.Experimental and simulation results show that the algorithm can effectively remove the impact of dispersion on the imaging results of damage,thereby effectively solving the problems of artifacts and low imaging resolution in the imaging results of traditional beamforming algorithm.This algorithm also solves the problem of difficulty in inversion of the spectral matrix,which reduces calculation time significantly.