How to well pose a magnetization identification problem

Abstract

Abstract-This paper presents an original approach for determining the unknown magnetization of a ferromagnetic shell. Magnetic measurements using sensors close from the device under test are used to rebuild distributions located on the shell. These distributions are representative of the magnetization and tangential moments or charges can be used. This identification problem is a particular case of an inverse problem and is generally ill posed. Instead of using classical mathematical tools to solve such a problem, we preferred to change it in a better posed one by adding our physical knowledge of the problem. All our results have been validated on a mockup with real measurements.

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].…”

“…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].…”

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

“…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].…”

“…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.…”