Improving the Quality of Magnetic Signature Reproduction by Increasing Flexibility of Multi-Dipole Model Structure and Enriching Measurement Information

Jaroslaw Tarnawski,Krystian Buszman,Adam Cichocki,Tomasz Adam Rutkowski,Miroslaw Woloszyn

doi:10.1109/access.2020.3031740

Jaroslaw Tarnawski, Krystian Buszman + Show 3 more

Open Access

https://doi.org/10.1109/access.2020.3031740

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Abstract

The paper presents the construction of a multi-dipole model that allows reproducing magnetic signatures of ferromagnetic objects. The virtual object used in the paper is an ellipsoid, which is the source of synthetic data. To make the situation more realistic, noise is added to the synthetic data. Two significant improvements compared to previous work are presented. Three-axial magnetometers are introduced instead of uniaxial magnetometers. However, a more important change is the modification of the model structure that allows placing dipoles on the entire plane, e.g. object's deck. The multi-dipole model consists of an a priori assumed number of permanent and induced single-dipole models. Each single dipole is described by three magnetic moments and, depending on the applied approach, one or two dipole position parameters. The non-linear least-squares optimization method is used to determine model parameters. To assess the quality of magnetic signature reproduction, qualitative and quantitative forms are used. The final quality assessment is based on differences between the reference fields and the fields determined from the multi-dipole model. The applied modifications bring significant improvement, however, only their combined application allows to restore magnetic signatures with good quality for directions other than for which the data were available.

Highlights

All naval objects, such as e.g. ships, which are built or consist of any ferromagnetic elements disrupt natural Earth’s magnetic field in their own surrounding. This disorder in the underwater environment is defined as the ship’s own magnetic field, identified by its complex magnetic signature [1], [2]. To minimize this magnetic signature, navy ships have a degaussing system, which consists of coils with currents controlled by a specialized controller depending on the ship’s course
The magnetic signature technology has practical significance for analysing the behaviour of naval ferromagnetic objects in the magnetic field of Earth, The associate editor coordinating the review of this manuscript and approving it for publication was Wen-Sheng Zhao
The induced magnetization is directly related to the current geographical position and orientation of the ship in the Earth’s magnetic field - current heading of the ship [4]

Summary

INTRODUCTION

All naval objects, such as e.g. ships, which are built or consist of any ferromagnetic elements disrupt natural Earth’s magnetic field in their own surrounding. Where BxE,i, ByE,i, and BzE,i are the components of the vector of ambient Earth magnetic flux density BE at the location of i-th induced dipole, and the values of factors f1 and f31 depend on shape and size of the ellipsoidal object (Appendix). For the simulation studies described in the paper, the access to the data from a virtual, simulated measuring range with three three-axis magnetometers in each direction (working in the cross configuration) was assumed. Such magnetic data with additional noise, according to Scheme (14), was used as synthetic data for further analysis with a multi-dipole model. It was done intentionally to comply with the modelling approach based on the possessed measurement data

NUMERICAL CALCULATIONS

CONCLUSION