Recent improvements for solving inverse magnetostatic problem applied to thin shells

Abstract

In this paper, we propose a new approach to solve the magnetostatic inverse problem. The goal of the work is, from measurements of the magnetic field in the air, to rebuild a model for the magnetization of a ferromagnetic shell structure. It's then possible to calculate the field where sensors cannot be placed. This problem is usually ill posed or rank-deficient, it's then necessary to use mathematical regularizations. These techniques are based upon the injection of knowledge about the mathematical behavior of the solution. We preferred to add physical information. This solution allows us to get a faithful solution and to reduce significantly the number of sensors. Moreover, our method has been tested on a mock-up with real measurements and led to very promising results.

A Magnetic Field Separation Technique for a Scaled Model Ship through an Earth's Magnetic Field Simulator

“…If the hull thickness is relatively small and its permeability is high, the direction of the magnetization can be considered parallel to the hull surface, and its magnitude can also be assumed constant [3,4]. When the magnetization distribution on the hull is given under the above assumption, the perturbation field is easily calculated by: (4) where, V is the volume enclosed by the hull surface S, r is the distance between an observation point and the hull magnetization, and n is the unit vector normal to the hull surface [4].…”

“…Even though its magnitude is much smaller than that of the Earth's magnetic field, it can activate underwater weapon systems equipped with high-sensitivity magnetic sensors, such as influence mines, or underwater detecting equipment. To protect the ship from these threats, it is necessary to establish proper countermeasures against the detection sensors of an influence mine or an underwater detection system [1][2][3][4][5][6][7][8][9].…”

Ships Magnetic Anomaly Computation With Integral Equation and Fast Multipole Method

“…This method is already well-known for its efficiency to solve such problem and has been mainly used recently to solve the inverse problem, meaning the identification of the magnetization starting from magnetic measurements around the hull [5]- [7]. The main advantage is that no mesh of the air region is needed so the method ensures a really good ability to compute accurately stray magnetic field.…”

Identification of Unknown Remanent Magnetization in the Ferromagnetic Ship Hull Utilizing Material Sensitivity Information Combined with Magnetization Modeling

“…This magnetic anomaly depends on the hull's magnetization, which can be classified as induced and remanent magnetization [1][2][3][4][5][6]. The calculus of the induced magnetization is easy to compute [1,2]. On the other hand, the remanent magnetization depends on the magnetic history, such as mechanical and thermal stresses, etc.…”

“…When a ship is placed in the earth's magnetic field, steady-state magnetic signatures are created around the hull. This magnetic anomaly depends on the hull's magnetization, which can be classified as induced and remanent magnetization [1][2][3][4][5][6]. The calculus of the induced magnetization is easy to compute [1,2].…”