EMT用于金属结构裂纹图像重建的仿真研究

针对港口企业对港机探伤可视化的需求,进行了电磁层析成像(EMT)技术用于港机金属结构裂纹成像的仿真研究。Landweber迭代算法是一种常用的经典图像重建算法,但用于EMT金属结构探伤成像中则多有不足。为了提高图像重建质量,首先对经典Landweber算法进行了改进,根据传感结构的特点定义了图像重建的"感兴趣区域",通过裂纹定位、移位等过程使其位于"感兴趣区域",然后再进行Landweber图像重建;这种改进后的Landweber图像重建效果较好,但缺点是不能一次成像。然后,基于金属结构裂纹稀疏分布的特性,采用一种稀疏重建方法,即子空间追踪(SP)算法对裂纹进行图像重建,仿真结果表明,SP算法在图像重建质量、算法鲁棒性等方面明显优于经典Landweber算法,且重建过程耗时短,可以一次成像。

Simulation study on EMT image reconstruction of metal structure flaw

To meet the demand of visualization in port machinery flaw detection, the electromagnetic tomography (EMT) technology is projected to detect and reconstruct metal structure flaw. Landweber iterative algorithm is a kind of traditional image reconstruction algorithm in research of EMT, but it does not work well when it is used directly in image reconstruction of metal flaw. Firstly, the region of interest is defined according to the characteristics of the sensor. On the supposition that the flaw has been detected and moved into the region of interest, the Landweber image reconstruction is carried out which gives better result, but the shortcoming is that the flaw detection and image reconstruction cannot be fulfilled at the same time, which means that the whole process is time consuming. Then, based on the characteristics of the sparse distribution of the metal structure flaw, the subspace pursuit (SP) algorithm which is a kind of sparse reconstruction method is used for flaw detection and image reconstruction. The simulation results show that the SP algorithm performs is better than the classical Landweber algorithm in the aspects of image reconstruction quality, algorithm robustness and so on, the flaw detection and the reconstruction are accomplished simultaneously.