基于磁场梯度张量的多磁源目标反演方法研究

Magnetic Source Inversion method interprets magnetic sources' position and magnetic moment information through measurement and analysis of data sets of limited points in the magnetic field. In the past, it is commonplace to employ methods involve magnetic vector or scalar in magnetic interpretation. To introduce magnetic gradient tensor (MGT) into such methods is recently favored. Comparing with magnetic vector, magnetic gradient tensor has more advantages in multi-aspects, that is not susceptible to the total magnetization. Its eigenvalues and rotational invariant can interpret source parameters more easily. Detector's orientation is not strictly restricted and contour of sources under subsurface can be well depicted. Also such methods is unsusceptible to interference from random noise or magnetic sources in the distance. At the present time, though it is efficient to use MGT methods to solve single source inverse problems, it is still far from well resolved in multi source problems, which is confronted in kinds of inverse theories. ..This study will investigate into the multi static magnetic sources inverse theory and measurement methods based on MGT, and also some must experiments will be performed. In such way we can discriminate multi magnetic sources precisely and solve the conundrum of multi source inversion. Anticipated theory product would be used in areas such as large scale mineral detection, submarine detection in cluttered environments, mineral detection on adjacent planets and status monitor of complicated instruments, etc.

磁源反演，是指通过对空间有限点处磁场数据的测量和分析，来计算推演空间中磁源的位置和磁矩。以往的磁源反演主要采用测量磁场矢量或分量的方法，利用磁场梯度张量反演磁源是一种磁源反演的新方法。相对于磁场矢量的测量，磁场梯度张量受磁化方向影响小，其特征根和旋转不变量能更好地反演场源参数，能够排除随机噪声和远处磁源的干扰，测量精度较高。目前，基于磁场梯度张量的磁源反演方法用在单个磁源的反演方面较为有效，而在多个复杂磁源的情况下分辨能力较弱，这也是各种静磁测量、反演理论普遍面临的问题。.本项目在已有的欧拉磁源反演方法的基础上，提出基于磁场梯度张量的多静态磁源目标反演方法，同时设计出测量方法，进行软件仿真和实验验证，达到准确有效的分辨多个磁源的目的，解决多磁源反演的难题。本项目未来可应用于磁性细节测量、大面积地矿探测、复杂情况下潜艇探测等。

磁源反演技术作为一种探测技术，在资源勘探、生物探测等多个领域具有重要的应用价值，但对多磁源场反演理论的研究，目前还处于初级阶段，缺少深入的研究。.本文研究了通过测量物体周边磁场对物体内部主要磁源进行分辨的问题。在理论分析上，首先根据等效磁偶极子近似建立起多磁偶极子模型，并论证了多磁偶极子分辨的有效性和非唯一性问题；选择了欧拉反褶积方法作为分辨过程中的初步反演算法，并据此设计了网格式的测点方法，进行了初步反演计算；针对矢量磁场和磁场梯度张量的测量问题，提出了矩阵式矢量磁场连续扫描方法，利用MATLAB对常用的十字形和六面体两种不同数据计算结构进行了比较，分析了基线距离对磁场梯度张量计算的影响。.根据计算结果，并从实际条件出发，发展了复合式欧拉反演方法、双面式欧拉反演方法等衍生方法。仿真结果证明，该方法能够较为准确地计算出部分磁源的位置参数。.然后将欧拉反演方法的计算结果作为初始参数，代入遗传算法，以磁场测量值与计算值误差为目标函数，进行了优化分析。结果表明，数值分析可以最终准确地计算出大部分磁源的位置和磁矩参数，计算精度完全满足试验要求，由此达到了对目标区域内多个磁偶极子进行准确分辨的目标。.在理论分析取得良好结果的条件下进行了试验验证，试验取得了与数值模拟较为一致的结果，证明了多磁源反演方法的有效性。