For decades, the underwater electromagnetic signatures generated by naval vessels have been easily detected by electromagnetic threats. Especially, the steel that is used in the construction of many vessels produces a magnetic field which can trigger sea mines present in the vicinity of the vessel. In order to reduce the possibility of detection of the ship or the triggering of the sea mines, vessels use both active and passive protective measures. The active protective measure comprises the installation of an on board degaussing system and the passive protective measures are achieved by appropriate design and by a demagnetization treatment of the entire vessel. The magnetic field generated by a vessel can be divided in two parts, an induced field and a permanent field. The computation of the induced magnetic field is now well known. However, the permanent part is impossible to evaluate with the deterministic calculation because we have no information on the magnetic history of the ferromagnetic material during the construction phase.
In this study, we propose the theoretical and experimental techniques for the separation of the permanent and the induced magnetic field from the measured magnetic signature of a scale model. Also, we describe the prediction method of the induced magnetic field for a scale model using the MAGNET software. From the separated permanent and induced magnetic field signature, we introduce the magnetic dipole modeling method for a scale model based on the singular value decomposition technique which could be applied to the prediction of the static magnetic signature distribution for the real vessel as well as a scale model vessel.
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