Local navigation methods for metal detectors
Petr Nováček · Czech Technical University Digital Library (Czech Technical University in Prague) · 2017
This dissertation addresses the implementation of navigation capabilities for metal detection, in particular landmines. The precise aim of this thesis is to find a professional handheld metal detector search head position. This allows the creation of a magnetic image of the area searched, which opens a new prospective to increase the discrimination ability of metal detection between conductive scrap and the surveillance of unexploded ordnance. This thesis has two parts. The first and main part focuses on the enhancement of professional handheld metal detector discrimination functionality. This was the main stream of my research work. The second part deals with position estimation as a tool to reach the objectives of the first part. The navigation is based on low-cost MEMS inertial sensors of angular rate and acceleration, which have minimum metal content. The required precision, in centimetres, can only be achieved by using calibration and signal enhancement procedures. The utilization of the magnetic position markers directly detected by a metal detector itself is my main original scientific contribution to the knowledge in the scientific area of aiding navigation. Position markers with specific characteristics are placed in a known location and are recognised by a metal detector during its overhead movement. The metal position markers described are a connection link between the navigation part and the part dealing with metal detector enhancement. Their usage is only enabled due to previous research made on the signal dependency of the metal detector’s output on a detected object’s material, size and distance from the detector’s search head. Metal position markers are a by-product of this research, which focuses in particularly on the improvement of metal detector discrimination abilities. The ability of metal detector discrimination can also be increased by using several excitation signal frequencies. The methods published up to now use multitone signals composed of sinewaves with two to four frequencies. In the presented papers we show that using sin(x)/x excitation signal brings new possibilities in this area.