Estimation of Dipole Magnetic Moment Orientation Based on Magnetic Signature Waveform Analysis by a Magnetic Sensor

Abstract In this paper, we propose a measurement procedure to estimate the magnetic moment orientation (MMO) of a dipole. Theoretical analysis indicates that magnetic field in each orthogonal direction Bi (i=x, y, z) is found to be a superposition of its three basic elements Bij (i=x, y, z and j=1, 2, 3) along certain direction, allowing the obtained dipole signature to be decomposed of 9 basic elements. An orthogonal energy ratio (OER) algorithm is used to infer the MMO by calculating the signal energy distribution along each axis. A standard OER database is developed which provides a reference to be compared with the measured OER. The one having the smallest variance is determined as the estimated MMO. Owing to space symmetric property, it generally introduces 8 possible solutions. Then, a mathematic method is presented to define the common characteristics of the magnetic signature in the 8 octants, which is able to identify the octant of unknown target based on detected Bi field. As a result, the unique MMO can be estimated. The experimental results show good estimation accuracy for the dipole orientation with average error of 3.5°. In particular, the algorithm is independent of changing CPA and velocity, which is demonstrated in simulation and experiment.