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Remote Controlled Mine Detector

One more variant of device design is the remote control scout of mine fields. To orientate on terrain and to define coordinates of searching objects, the self-propelled cart of the radar will be equipped with GPS and TV camera. Steering of the cart will be carried out with help of a remote control box. Possible design of the cart with the sensors, which are established on it, is presented in the Figure.

Wide-span System for Humanitarian Demining Operations

Introduction. Our team had taken an initiative in the development of MiRascan subsurface sounding radar to enable the operator to detect and identify objects buried under the ground at low depth (up to 20.0 cm) basing on their shape analysis. The operating principle of the radar design is based on the method of multi-frequency sounding of a condensed media (like building structures, grounds, etc.). The method offered has no counterpart in the world practice so far. (Russians Launch Anti-Bugging Radar. Microwave Journal, February 1998, Vol. 41, No. 2, pp. 47, 48). The creators of MiRascan radar are Russian Federation Government prize-winners in the field of science and technology for 1999.

One of the main problems while liquidating the aftereffects of local conflicts is mine clearance of the territories that were mined as a result of combat operations. The special difficulty in the process of humanitarian mine clearance is presented by the fact that minefields were laid as a rule chaotically, without compiling proper mine-field records (charts), as well as the fact that mines with antidisturbance fuses were also installed.

As a rule, the minefields are combined, which means that they include both antitank and anti-personnel mines. The major part of the mines has round cross-section view. The antitank mines have diameter of about 300 mm, and the average diameter of the anti-personnel mine amounts to 75 mm. Some types of the mines contain practically no metal, which substantially impedes their detection. In this case the key give-away factor lies in the blasting charges of the mines, the dielectric properties of which differ from analogous characteristics of the ground that covers them. Thus, relative permittivity e_r for the typical explosives is between 3.5 and 4.0. At the same time dielectric properties of the ground in the considered frequency range vary within a wide range from 2.6 to 25.0, depending on the composition and moisture content of the ground. The lowest value of the range is related to absolutely dry sand, which is found in the desert. In the overwhelming majority of cases er for the ground exceeds the analogous value for the blasting charge.

The heterogeneities of the surface, as well as a great number of foreign objects in the ground, especially in the urbanized localities create substantial difficulties in the mine detection operations. The dielectric contrast of these heterogeneities with reference to the ground frequently exceeds the contrast of the plastic-cased mines, which results in an inadmissible level of false alarms. At the same time, in accordance with the requirements of the UN, the probability of mine detection should amount to 99.6% at the low level of false alarms. But these requirements are not met by the existing technical means. Very often the mine-probing rod and snuffer dogs are the only aids of the sapper.

Description. The development of the wide span gears making the most of the spatial filtering to reduce the level of false alarms is one of the approaches to achieve the set aim. The mock-up of such mine detector using Russian-made mine detectors of the MMP type in the capacity of the search elements was designed in late 1980s.

The new design considers possibilities for the enhancement of efficiency of mine detection operations that thanks to usage of multifrequency SHF transducers coupled with metal detector and to generation of the radio images of the terrain in the lane of movement of a mine detector. An experimental mock-up with the transducer providing for scanning in two dimensions has been developed, and algorithms for the representation of information on the display screen in the form of animated images have been put forward. Proposed methods may find their use during peacekeeping and humanitarian operations. Fig. 1 presents the block diagram of the radar MiRascan.

The scanning in the lateral direction is carried out at the expense of electromechanical movement of the radar, and in the longitudinal direction due to the movement of the cart. The scanning results are displayed in the form of gray scale images on the monitor screen. Since it is difficult for an operator to perform a simultaneous analysis of all images on different frequencies, one animated image is formed in which sequential frames correspond to different frequencies.

The results presented in this paper do not reflect the obtained experimental information in full body as the MiRaskan display system is intended for the use of the present-day computer screens and information from mine detector is displayed as animation.

Possible design of the cart with the sensors, which are mounted on it, is presented in Fig. 5. The subsurface radar will have five to ten operational frequencies in the range of 1.5 - 2.0 GHz and transmits unmodulated signals at each frequency. Its signals are received in two polarizations. Power emitted by the generator on each frequency is switched in sequence. It amounts up to 10 mW, which provides for the complete safety of staff. The induction coil of the metal detector will be located on the butt end of the antenna of the ground penetrating radar, which provides spatial coincidence of received images from two channels of the mine detector. Operating frequency of the metal detector will be about 2 MHz, and the diameter of the induction loop is equal to 120 mm. The successive reception of signals on each frequency and in both polarizations of GPR and from the metal detector will be conducted in the process of scanning the ground surface. The frequency switching rate is such that it provides for the spatial matching for all radio images of the GPR separate frequencies and metal detector image.

The scanning results will be displayed in the form of gray scale images on the monitor screen for both channels. Since it is difficult for an operator to perform a simultaneous analysis of all images on different frequencies of GPR, one animated image will be formed in which sequential frames correspond to different frequencies. We shall have only one picture for the metal detector channel. The size of images in the lateral direction corresponds to scanning range of searching antenna, and in the longitudinal direction the length of the covered distance in the sweep defines the image.

To orientate on terrain and to define coordinates of searching objects, the self-propelled cart of the radar will be equipped with GPS and TV camera. Steering of the cart will be carried out with help of a remote control box.