In this paper, we first study the applicability and stability of the Tikhonov regularization method (TRM) and the truncated singular value decomposition method in ship’s magnetic signature inversion modeling. To further improve the noise immunity and robustness of the model, we apply an iterative regularization algorithm based on the conjugate gradient least squares (CGLS) method. Numerical simulation shows that the proposed algorithm is more applicable and can obtain better results of ship’s magnetic field extrapolation under different noise backgrounds. In the ship model experiment, the errors of the TRM and CGLS method for magnetic signature extrapolation are, respectively, 4.77% and 3.67%, showing that the proposed algorithm can improve the inversion effect of the ship model magnetic field.
A real-time magnetic localization method based on unscented particle filter (UPF) is proposed to solve the problem for real-time localization of underwater non-cooperative magnetic targets. The state space model of non-cooperative magnetic targets is set up according to its motion characteristic, and the state is estimated in real time by UPF. In order to improve the observability of the system, the particle state is constrained and magnetic moment is inverted by the least square method. The simulation results and ferromagnetic object localization experimental results show that the method is good in localization precision and real-time performance, which can be applied to the real-time magnetic localization in near field.
Accurate magnetostatic field computation for complex 3D ferromagnetic objects can be widely used to solve various engineering problems, while mesh quality is a key factor that can greatly affect the calculation precision. For complex shaped 3D objects, their mesh quality can be improved greatly by using hybrid mesh strategy with the advantages of hexahedral elements and tetrahedral elements. In this paper, a hybrid mesh integral equation method (IEM) for 3D magnetostatic field computation is realized based on mixed mesh with hexahedrons and tetrahedrons. Furthermore, computational accuracy of the proposed method is demonstrated by simulation and experimental examples with 2.10% and 3.20%, respectively. Thus, foundations for the mixed mesh strategy for the complex shaped 3D objects and fast computational methods with hybrid mesh IEM are established.
Improving the magnetic stealth capability of ships [7]is of great importance to the safety of ships. The comprehensive degaussing method is an important method of ship degaussing. This paper mainly introduces the principle, coil classification, key and difficult factors of the comprehensive degaussing method and its application prospect in China.
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