固定翼时间域航空电磁探测的整体反演方法研究

The problem of shortage of mineral resources arises seriously in China, which restricts the socio-economic development and even threatens national security. The strategy of "exploration for deep mines and blind ore" is an important approach to solve this issue. Fixed-wing time-domain electromagnetic system has the advantage of lager penetrating depth and keen conductivity distinguishing ability, which is crucial for rapid survey for deep mines and blind ore. However,the system geometry of fixed-wing time-domain electromagnetic system, with the yaw, pitch and roll of transmitting coil and receiver coil and three dimensional separations between these coils, is changing continuously during the flight, which affects the data seriously. The system calibration model is introduced into the conventional inversion to represent parameters of system geometry. The holistic inversion is proposed to invert the entire dataset simultaneously merging system geometry calibration into inversion based on smooth continuous model. In this project, B-spline theory is used to develop the smooth continuous three-dimensional earth model and system calibration model to realize respectively the spacial constraints of the earth model and the time constraints of the calibration model. Then, based on the preconditioned conjugate gradient method，entire dataset inversions for three components are resolved. This holistic algorithm avoids the inconsistent results inverted from different components caused by calibrated alone in conventional inversion. The implementation of this project will provide a set of holistic inversion algorithm for fixed-wing time-domain electromagnetic data including the system geometry calibration. This will lay a significant foundation of science and technology for the rapid exploration of mineral resources in China.

我国矿产资源保障能力不足，严重制约国家社会经济发展，甚至威胁国家安全,"攻深探盲"战略是解决矿产资源紧缺的重要途径。固定翼时间域航空电磁系统具有探测深度大、导电率识别能力强的优势，是深部矿产资源快速勘查的重要手段。本项目针对固定翼时间域电磁系统在飞行探测过程中，发射与接收线圈相对位置、姿态等发生变化等问题，将代表系统装置参数的"系统校正"模型引入常规反演，提出基于光滑连续模型的"校正-反演"一体化的整体反演方法。采用B样条理论建立测区的光滑连续三维大地模型及系统校正模型，实现测区范围内大地模型的空间约束及系统校正模型的时间约束，基于预处理共轭梯度研究大型矩阵计算技术，进行测区所有数据的三分量同时反演，避免了各分量由于校正误差不一致而带来的反演结果不一致等问题。本项目的实施将提供一套集校正、反演于一体的固定翼时间域电磁探测的整体反演算法，为提高我国矿产资源的快速勘查能力奠定重要的技术基础。

固定翼时间域航空电磁探测是深部矿产资源勘查的重要技术手段。本项目针对固定翼时间域电磁系统在飞行探测过程中系统参数以及发射接收线圈的姿态变化，将代表系统装置的系统校正模型参数引入到常规反演中，提出了基于光滑连续模型“校正-反演”一体化的整体反演方法。本项目以固定翼时间域三分量电磁正演计算、系统参数对电磁响应影响分析、系统校正模型与大地模型参数的网格化、整体反演计算方法研究以及模拟飞行实验为主要研究内容，采用从全测线的拟二维约束反演，推进到带系统校正模型的拟二维、拟三维整体反演的递进研究方法，达成了项目的研究目标。.本项目推导了固定翼航空电磁探测任意发射线圈、接收线圈姿态角度和吊舱摆动角度情况下三分量电磁场正演计算公式，分析了发射线圈、接收线圈姿态和吊舱摆动对电磁响应的影响，确定了吊舱同向摆动以及发射、接收线圈的俯仰角度为系统校正参数；采用B样条理论建立了整个测区的光滑连续三维大地模型及系统校正模型，实现了模型的参数化和网格化；基于正则化反演理论，设计了整体反演的目标函数，引入模型同测点的纵向约束、邻测点的横向约束、邻测线的水平约束和先验信息作为约束项，建立了反演迭代方程；在反演迭代中，采用超松弛预处理共轭梯度算法，求解大型稀疏迭代矩阵，通过对系数矩阵的预处理，矩阵条件数以平方根规律下降，加快了收敛速度；在反演计算中，利用多步长累加算法求取雅克比矩阵，采用线性搜索自适应迭代方法自动选取正则化因子，增强了反演计算的稳定性。.本项目分别对大地模型进行一维、二维、三维正演计算，通过正演数据以及加噪数据的整体反演实验，完善并验证整体反演算法；同时搭建了模拟飞行实验平台，模拟飞行数据的整体反演结果进一步表明了本项目研究的反演算法的有效性。项目组共发表学术论文11篇，申请发明专利3项，授权1项，软件著作权2项，研究成果获得省部级奖励3项，项目执行期间培养硕士研究生3名，博士研究生4名，其中已毕业博士3名，已毕业硕士2名。