基于极低频电磁场的水下目标跨界定位机理研究

Since the strategic focus moving to the ocean, the underwater monitoring and detection techniques have been extensively studied. As an important supplement to the acoustic technology, extremely-low-frequency (ELF) electromagnetic (EM) field is being paid more attention to by numerous countries due to its characteristics of high-penetration ability and the minor effects from the interfaces and multi-path phenomenon. As early as 1970s, USA and Russia have studied the ability of ELF EM technology to communicate with underwater nuclear submarines. It is pointed out in open literatures that the underwater vehicles would produce ELF EM signals which can be modelled as a simple combination of various magnetic dipoles. This project would study the possibility of transboundary localization techniques with ELF EM technology by first studying charateristics of the shaft-rate EM field produced by the underwater targets and the corresponding magnetic model. Then the transmission matrix would be studied theoretically and experimentally with the investigation of the EM field distribution produced by the previous magnetic dipole model. At the same time, the localization techniques would be studied on the basis of the transmission matrix which would be simplified into a nonlinear unconstrained optimization problem. The study of this project is an elementary part to the alert and precautin techniques of the future naval war, which shows great theoretical significances and promising application prospects.

国家海洋战略方针的提出使得海洋监控技术受到广泛重视。作为声纳技术的有力补充，电磁技术在探测、导航与通讯方面受到了极大的关注。由于极低频电磁场对海水较强的穿透力、较强的跨界面传播性能以及多径效应影响小等特点，早在上个世纪末美俄等国便已着手开展诸如极低频对潜通信与导航技术的研究。本项目在对现有磁定位技术广泛调研后针对相关研究仅局限在同媒质环境等问题，结合近期关于水下航行器具有极低频电磁辐射等现象的研究，拟从机理出发探讨极低频跨界定位方法的可行性。通过研究舰艇的轴频电磁辐射现象及其对应的磁偶极子辐射源模型获得极低频电磁场的传输矩阵，并在此基础上对定位问题进行研究，将相关问题简化为非线性无约束的最优化问题。针对此问题，拟通过全局优化与局部优化算法融合的方式实现水下目标的快速定位。本项目的研究方向是未来海上战争预警与防备的重要一环，具有重要的理论意义和军事应用前景。

在近海防御体系中，极低频电磁技术已是传统探测技术的重要补充。而由于传统声/磁异常定位方法在浅海环境中的自身缺陷，如何利用极低频电磁技术优势进行水下目标的浅海定位问题受到海内外各界的持续关注。.针对以上研究背景，围绕项目研究目标，开展了极低频跨界定位方法的研究。首先，在研究水下目标的极低频电磁场源辐射机理的基础上提出了基于分层介质中水平偶极子的辐射模型，并利用空气-海水-海床分层介质模型计算极低频电磁场空间分布，获得场的传播损耗模型参数。其次，在研究传统磁定位方法的基础上结合理论模型建立了目标信息未知情况下的阵列式传感定位方法，并构建分布式单轴传感定位系统。同时，在分析研究现有定位方法的基础上针对定位非线性无约束优化问题提出了基于遗传-高斯牛顿混合优化算法以及后续改进的蚁群-LM混合优化算法，实现了快速定位。深入分析了环境噪声、源磁矩以及传感器布局等对定位精度的影响，为以后海洋传感器网络的设计提供参考。最后，通过陆地试验与湖上试验验证了分布式极低频电磁场定位的可行性。.通过本项目的研究构建的水下极低频电磁场源及其场分布计算模型，极低频电磁波跨界面损失模型基础上构建的极低频电磁场定位模型以及搭建的阵列式传感器探测系统可用于未来海上预警与防备，具有重要的理论意义和军事应用前景。同时，项目的研究对于跨界目标探测定位、跨界极低频通信提供重要的理论基础和试验依据。