基于边界等效源的舰艇磁异常推算技术研究

Research on the magnetic field extrapolation of ships based on boundary equivalent magnetic source method

用等效源法实现舰艇磁异常推算通常将等效源置于舰艇所占空间内,其位置分布参数常依赖人为经验确定,从而直接影响了等效源法在舰艇磁异常推算中的通用性。针对该问题,从边界积分理论及等效原理出发,分别建立了以边界单层源、双层源和混合源为未知量的边界等效源舰艇磁异常推算模型。与应用于舰艇磁场建模中传统等效源法相比,其等效源只需分布于边界面上,从而大大降低了人为因素的影响。基于磁场测量值来求解边界等效源磁性参数属磁场逆问题,磁场测量数据中信息量的不足通常使其表现出一定的病态性。为减小测量误差等因素对计算结果的影响,应用截断奇异值分解方法对模型进行了求解,并分析了所用磁场数据类型对建模的影响;采用数值算例和船模实验对边界等效源舰艇磁异常模型进行了分析比较。结果表明,基于截断奇异值分解方法求解的边界等效源舰艇磁异常模型,可有效克服传统等效源法在舰艇磁异常建模中的不足,推算结果令人满意。

It is convenient to extrapolate magnetic field of ships based on equivalent source method.However,the location of the equivalent sources is usually determined by experience,so the application of equivalent source method in magnetic field extrapolation of ships is not generalized.In order to overcome the above disadvantage,models of the single,double or mixed layer boundary equivalent source were adopted to extrapolate the magnetic field of ships based on the boundary theory and equivalent principle.Compared with the traditional equivalent source method,the equivalent sources in boundary equivalent source method are only distributed on the boundary.So experience can be eliminated in these new models.Due to measurement error and lack of enough physical information,the above magnetic inverse models are usually ill-posed.In order to obtain reliable results,truncated singular value decomposition technique was applied to enhance the robustness of the inverse models.And the influence of the different types of magnetic fields to models was analysed.It is shown by a numerical example and a mock up experiment that the proposed boundary equivalent source method is satisfying in magnetic field extrapolation of ships.