Locating and identifying compact ferrous objects

Abstract

A solution is presented to the problem of magnetostatic location and identification of compact ferrous objects of arbitrary shape. It is shown that, in practice, the inversion of the magnetostatic dipole field or field gradient is a necessary first step toward determining object location and identity. Several iterative and noniterative methods of determining the dipole moment and location from field or gradient measurements are described and compared. It is shown that given the dipole-moment estimates, it is possible to determine the identity of the dipole source in practical situations by pattern recognition. A unique prototype total field magnetometer is described, which is capable of explicitly and accurately locating and identifying axially symmetric compact ferrous objects. It has performed well in preliminary tests using spheres and spheroids.

A novel test ground for the equipment qualification of magnetic gradient sensors used for unexploded bomb detection

“…For a survey see e.g. the paper of McFee et al (1990). Electromagnetic induction methods are methods of choice for the detection of buried ordnance, lying in lower depth (see for instance Friedel et al, 2012).…”

“…For the detection of unexploded bombs it is commonly used that the massive steel or iron shell of the bombs is magnetized (a) unintentionally during the fabrication process (remanent magnetization) and (b) as a consequence of the susceptibility of the steel or iron shell in the earth magnetic field (induced magnetization) (Billings, 2004;McFee et al, 1990). Using the stray magnetic field of the resulting magnetic moment, the position of the bomb in the ground may be found by scanning the ground level by one or more fluxgate gradient sensors.…”

Detection of ferromagnetic objects in local magnetic anomaly of the Baltic Sea

“…4). The measures of the magnetic field near the object allow to detect, to localize and to identify it [5]. The influence of the strong local magnetic anomaly on the magnetic measurements, with systems installed on planes and helicopters, was presented in this paper.…”

Magnetic Field Sensors Based on Microelectromechanical Systems (MEMS) Technology

“…These magnetic field sensors find employment for the detection of compact ferrous objects (McFee et al 1990). Such objects are of major concern in a number of applications.…”