Emi Detection And Discrimination Of Uxo Using An Array Of Fluxgate Magnetic Sensors

While existing technologies have proved successful in establishing the location of metal objects and scrap, additional measurements are required in order to discriminate shape and size of targets. The advantages of a fluxgate magnetometer as the sensor in EMI metal detection are established in a series of observed profiles over dummy UXOs, and a related set of modeling studies. A series of model studies was conducted to establish what improvement in target orientation information could be achieved with single or multiple vector fluxgate sensors compared with commercial conventional single-component single-sensor systems. The model studies use a novel fast approximation for a permeable prism which is capable of modeling the non-linear or frequencydependent magnetic properties of steel objects. The model studies show that when the target size is known, the use of a single vector sensor delivers an order of magnitude greater accuracy in location in 3D space and orientation of the target, compared with the use of vertical-component only data in conventional metal detectors. When the target size is unknown, a single vector sensor can produce accurate location, but is likely to produce unstable orientation estimates. We conclude that an array of receiver sensors is preferable. Comparison of a single vector sensor versus an array of three vector sensors in model studies shows that the array of three vector sensors has the advantage of delivering accurate and stable estimates of both location and orientation of the target, even when target dimensions are unknown.