Sensor For Landmine Detection Research Articles

Characterization of Electromagnetic Properties of In Situ Soils for the Design of Landmine Detection Sensors: Application in Donbass, Ukraine

To design holographic and impulse ground penetrating radar (GPR) sensors suitable for humanitarian de-mining in the Donbass (Ukraine) conflict zone, we measured critical electromagnetic parameters of typical local soils using simple methods that could be adapted to any geologic setting. Measurements were recorded along six profiles, each crossing at least two mapped soil types. The parameters selected to evaluate GPR and metal detector sensor performance were magnetic permeability, electrical conductivity, and dielectric permittivity. Magnetic permeability measurements indicated that local soils would be conducive to metal detector performance. Electrical conductivity measurements indicated that local soils would be medium to high loss materials for GPR. Calculation of the expected attenuation as a function of signal frequency suggested that 1 GHz may have optimized the trade-off between resolution and penetration and matched the impulse GPR system power budget. Dielectric permittivity was measured using both time domain reflectometry and impulse GPR. For the latter, a calibration procedure based on an in-situ measurement of reflection coefficient was proposed and the data were analyzed to show that soil conditions were suitable for the reliable use of impulse GPR. A distinct difference between the results of these two suggested a dry (low dielectric) soil surface, grading downward into more moist (higher dielectric) soils. This gradation may provide a matching layer to reduce ground surface reflections that often obscure shallow subsurface targets. In addition, the relatively high dielectric deeper (10 cm–20 cm) subsurface soils should provide a strong contrast with plastic-cased mines.

Monte Carlo modelling of a neutron-induced gamma-ray sensor for landmine or explosive detection

Monte Carlo simulations were carried out to model a thermal neutron-induced gamma-ray sensor for anti-personnel-landmine (APM) or explosive detection. This is done by employing the thermal neutron prompt gamma activation (TNPGA) technique. The neutron capture reaction on nitrogen 14N(n,γ)15N is analyzed to detect the subsequent characteristic 10.8 MeV gamma rays. This is done by modelling a suitable geometry consisting of a point 252Cf source placed inside a sphere of lead (Pb) which is contained in a cylinder of high density polyethylene (HDPE), together with a NaI (Tl) detector. The sensor geometry was optimized and the optimal configuration was selected to scan a plastic APM buried (2–10) cm. The Monte Carlo results obtained in terms of variations of the signal-to-background ratio, indicated the feasibility of employing 14N(n,γ)15N neutron capture reaction for landmine detection and the suitability of the proposed sensor for airport explosives as well.

The COMRADE System for Multirobot Autonomous Landmine Detection in Postconflict Regions

We consider the problem of autonomous landmine detection using a team of mobile robots. Previous research on robotic landmine detection mostly employs a single robot equipped with a landmine detection sensor to detect landmines. We envisage that the quality of landmine detection can be significantly improved if multiple robots are coordinated to detect landmines in a cooperative manner by incrementally fusing the landmine-related sensor information they collect and then use that information to visit locations of potential landmines. Towards this objective, we describe a multirobot system called COMRADES to address different aspects of the autonomous landmine detection problem including distributed area coverage to detect and locate landmines, information aggregation to fuse the sensor information obtained by different robots, and multirobot task allocation (MRTA) to enable different robots to determine a suitable sequence to visit locations of potential landmines while reducing the time required and battery expended. We have used commercially available all-terrain robots called Coroware Explorer that are customized with a metal detector to detect metallic objects including landmines, as well as indoor Corobot robots, both in simulation and in physical experiments, to test the different techniques in COMRADES.

Magnetic viscosity of tropical soils: classification and prediction as an aid for landmine detection

SUMMARY Electromagnetic induction (EMI)-based metal detectors are the most widely used sensing techniques in landmine clearance operations; however, they are negatively influenced by frequency dependence of magnetic susceptibility. A total of 466 rock and soil samples collected from across the tropics are investigated in this study. The data show that frequency-dependent susceptibility depends on the parent material as well as on the degree of weathering. Ultramafic and mafic rocks and their derivatives have higher susceptibility and absolute frequency dependence than material originating from intermediate, felsic and sedimentary rocks. Within each parent material group, absolute frequency dependence increases steadily with increasing alteration from unweathered rock to topsoil. This effect is likely due to either the residual enrichment of weathering resistant ferrimagnetic minerals including superparamagnetic (SP) grains, the comminution of larger ferrimagnetic minerals or the neoformation of SP minerals during soil formation. Relative frequency dependence is generally lower than 15 per cent for the investigated samples with a few exceptions. It increases with alteration for igneous rocks but remains at the initially high level for sediments. This finding indicates that the relative concentration of SP minerals changes with respect to the total magnetic fraction for igneous rocks but remains constant for sediments. Soils derived from ultramafic, mafic and intermediate rocks show low relative frequency dependence, and their magnetic susceptibility is mainly the result of multidomain lithogenic minerals. In contrast, soils derived from felsic rocks and sediments show the highest values, and their susceptibility is due to SP minerals that are either formed during pedogenesis or residually enriched. Theaverageandextremevaluesoftheabsolutefrequencydependencewithineachsubgroup, based on parent material and alteration grade, are used to design a prognosis system for assessing the impact of the subsurface on EMI sensors for landmine detection. In general, intermediate, felsic and sedimentary rocks have no influence on the detectors and only a weak influence inthemostextreme cases.Soilsderived fromtheserockstypically have noinfluence; however, they can have a very severe influence in a few cases. In contrast, ultramafic and mafic rocks typically have a moderate influence and a very severe influence in extreme cases, with the associated soils resulting in a severe influence in general. The deduced prognosis system can be used by demining organizations to help them predict metal detector performance in tropical regions on the basis of geologic and/or soil maps, which do not supply information on electromagnetic properties. In this way, such a system may eventually help with the planning of demining campaigns and selection of appropriate sensors.

Combined seismic, radar, and induction sensor for landmine detection

An experimental system to collect co‐located ground penetrating radar (GPR), electromagnetic induction (EMI), and seismic data was developed to investigate possibilities of using the sensors in a cooperative manner and to investigate the benefits of the fusion of the sensors. These sensors were chosen because they can sense a wide range of physical properties. The seismic sensor is sensitive to the differences between the mechanical properties of a landmine and the soil while the GPR is sensitive to the dielectric properties, and the EMI sensor is sensitive to the conductivity. In the experiments, a range of mines and clutter objects were buried at various depths in a sandbox. Multiple burial scenarios were investigated with a variety of antipersonnel and antitank mines and typical clutter objects. The GPR makes use of modified resistive‐vee antennas. The EMI sensor collects broadband data so that the relaxation spectra of the buried targets can be used to aid discrimination. The system uses electrodynamic shakers to generate seismic waves, and a radar is used to measure the displacement of the surface caused by the seismic waves. The responses of each of these sensors to the buried targets will be shown. [Work supported by ARO.]

Generalized two-sided linear prediction approach for land mine detection

Ground penetrating radar (GPR) is a widely used sensor for land mine detection. However, GPR signal return is very susceptible to ground bounce and reflection of clutter objects, which makes the detection a difficult problem to date. In this paper, we propose to utilize two-sided linear prediction (LP) to model the background interference and then employ the residue energy to generate the test statistic. It is demonstrated from real GPR data that the proposed scheme is able to significantly suppress the interference due to ground reflection and is superior to the adaptive ground bounce removal and one-sided LP methods.

Joint TNT and RDX detection via quadrupole resonance

Quadrupole resonance (QR) technology has been receiving increasing attention for explosive detection in applications including landmine detection. It can be used as a confirming sensor for buried plastic landmine detection by detecting the explosives within the mine. Since a single mine can contain more than one type of explosives (e.g., trinitrotoluene (TNT) and (RDX) compound), a detector designed to detect only one type of explosive may not provide the best detection. We focus herein on the joint detection of TNT and RDX explosives for the landmine detection via the QR sensor. To mitigate the RF interferences (RFIs) associated with the QR measurements, we apply a doubly constrained robust Capon beamformer (DCRCB) to perform the spatial beamforming by exploiting the spatial correlation of the RFIs. Based on the output of the spatial DCRCB, we devise a generalized likelihood ratio test (GLRT) for the joint TNT/RDX detection, which is referred to as the DCRCB-GLRT detector. We show that our detector has the constant false alarm rate (CFAR) property and that the detection variable obeys a x <sup xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">2</sup> -mixture distribution in the mine-free scenario. The effectiveness of the proposed DCRCB-GLRT detector is demonstrated with the experimental data collected by Quantum Magnetics, Inc.

Investigation of microphones as near-ground sensors for seismic detection of buried landmines

Commercially available microphones were investigated as near-ground sensors to measure the acoustic pressure and the vertical pressure gradient of evanescent air-acoustic waves associated with audio-frequency seismic waves. Measurements in close proximity to the surface and the use of waveguides were found to improve the microphone signal's quality, the comparison of its seismic sensitivity to its sensitivity to propagating sound (ambient acoustic noise and nonseismic reverberation). Landmine images formed using microphone data collected in a laboratory experimental model clearly locate buried inert landmines but exhibit more clutter than images of the same objects formed with seismic displacement data collected using other techniques.

GPR Signal Processing with Geography Adaptive Scanning using Vector Radar for Antipersonal Landmine Detection

Ground Penetrating Radar (GPR) is a promising sensor for landmine detection, however there are two major problems to overcome. One is the rough ground surface. The other problem is the distance between the antennas of GPR. It remains irremovable clutters on a sub-surface image output from GPR by first problem. Geography adaptive scanning is useful to image objects beneath rough ground surface. Second problem makes larger the nonlinearity of the relationship between the time for propagation and the depth of a buried object, imaging the small objects such as an antipersonnel landmine closer to the antennas. In this paper, we modify Kirchhoff migration so as to account for not only the variation of position of the sensor head, but also the antennas alignment of the vector radar. The validity of this method is discussed through application to the signals acquired in experiments.

GPR Signal Processing on Geography Adaptive Scanning with Vector Radar

Ground Penetrating Radar (GPR) is a promissing sensor for landmine detection, however there are two major problems to overcome. One is the non-planer (e.g. rough and/or undulating) ground surface. It remains unremovable clutters on a sub-surface image output from GPR. Geography adaptive scanning is useful to image objects beneath non-planer ground surface. The other problem is the distance between the antennas of GPR. When imaging the small objects such as an anti-personnel landmine buried in shallow depth, it increases the nonlinearity of the relationship between the time for propagation and the depth of a buried object. In this paper, we modify Kirchoff migration so as to account for not only the variation of height and pose of the sensor head, but also the antennas alignment of the vector radar. The validity of this method is discussed through application to the signals acquired in experiments.

An investigation of surface-contacting sensors for the seismic detection of buried landmines

Techniques have been studied for the detection of buried landmines with acoustic/seismic interrogation signals. Much of this work has involved full wave-field imaging from local measurements of ground motion using noncontact sensors. These offer inherent safety for the system operator and accommodate the need to make measurements over rough ground surfaces. The system requirement is, however, only that a sensor does not intrude on the measurement rather than that it not contact the ground. An experimental investigation was conducted into the feasibility of an array of ground-contacting sensors for use in a seismic landmine-detection system that exploits full wave-field imaging. The main considerations in the design of the array sensor were safety, sensitivity, fidelity, reproducibility, and sensor-to-sensor interaction. A relatively simple and inexpensive sensor was demonstrated in an experimental simulation of a landmine-detection system. The sensor, which is suitable for inclusion in a large planar array that could be used for detection confirmation, exerts a safe normal force at the point of contact and enables detection performance comparable to that which could be achieved using noncontact techniques.

Landmines Ground-Penetrating Radar Signal Enhancement by Digital Filtering

Until now, humanitarian demining has been unable to provide a solution to the landmine removal problem. Furthermore, new low-cost methods have to be developed quickly. While much progress has been made with the introduction of new sensor types, other problems have been raised by these sensors. Ground-penetrating radars (GPRs) are key sensors for landmine detection as they are capable of detecting landmines with low metal contents. GPRs deliver so-called Bscan data, which are, roughly, vertical slice images of the ground. However, due to the high dielectric permittivity contrast at the air–ground interface, a strong response is recorded at an early time by GPRs. This response is the main component of the so-called clutter noise, and it blurs the responses of landmines buried at shallow depths. The landmine detection task is therefore quite difficult, and a preprocessing step, which aims at reducing the clutter, is often needed. In this paper, a difficult case for clutter reduction, that is, when landmines and clutter responses overlap in time, is presented. A new and simple clutter removal method based on the design of a two-dimensional digital filter, which is adapted to Bscan data, is proposed. The designed filter must reduce the clutter on Bscan data significantly while protecting the landmine responses. In order to do so, a frequency analysis of a clutter geometrical model is first led. Then, the same process is applied to a geometrical model of a signal coming from a landmine. This results in building a high-pass digital filter and determining its cutoff frequencies. Finally, simulations are presented on simulated and real data, and a comparison with the classical clutter removal algorithm is made.

Radio Frequency Interference Suppression for Landmine Detection by Quadrupole Resonance

The quadrupole resonance (QR) technology can be used as a confirming sensor for buried plastic landmine detection by detecting the explosives within the mine. We focus herein on the detection of TNT mines via the QR sensor. Since the frequency of the QR signal is located within the AM radio frequency band, the QR signal can be corrupted by strong radio frequency interferences (RFIs). Hence to detect the very weak QR signal, RFI mitigation is essential. Reference antennas, which receive RFIs only, can be used together with the main antenna, which receives both the QR signal and the RFIs, for RFI mitigation. The RFIs are usually colored both spatially and temporally, and hence exploiting only the spatial diversity of the antenna array may not give the best performance. We exploit herein both the spatial and temporal correlations of the RFIs to improve the TNT detection performance.

An abrupt change detection algorithm for buried landmines localization

Ground-penetrating radars (GPRs) are very promising sensors for landmine detection as they are capable of detecting landmines with low metal contents. GPRs deliver so-called Bscan data which are, roughly, vertical slice images of the ground. However, due to the high dielectric permittivity contrast at the air-ground interface, a strong response is recorded at early time by GPRs. This response is the main component of the so-called clutter noise and it blurs the responses of landmines buried at shallow depths. The landmine detection task is therefore quite difficult. This paper proposes a new method for automated detection and localization of buried objects from Bscan records. A support vector machine algorithm for online abrupt change detection is implemented and proves to be efficient in detecting buried landmines from Bscan data. The proposed procedure performance is evaluated using simulated and real data.

2P1-C37 ベクトルレーダによる地形適応走査時の地中レーダ信号処理

Ground Penetrating Radar (GPR) is a promising sensor for landmine detection, however there are several problems to overcome. One is adaptability to non-planer(e.g. rough and/or undulating) ground surface. It remains unremovable clutters on a sub-surface image output from GPR. Geography adaptive scanning is useful to image objects beneath non-planer ground surface. The other problem is the distance between the antennas of GPR. When imaging a small object such as an anti-personnel landmine close to antennas, it increases the nonlinearity of the relationship between the time for propagation and the depth of a buried object. In this paper, we modify Kirchoff migration so as to account for not only the variation of height and pose of the sensor head, but also the antennas alignment of the vector radar. The validity of this method is discussed through application to the signals acquired in experiments.

Canadian teleoperated landmine detection systems. Part II: Antipersonnel landmine detection

Continuing with the description of the Canadian teleoperated mine detection systems, in this paper we will focus on systems developed primarily for antipersonnel (AP) landmine detection. The Articulated Robotic Scanner (ARS) is a system approach that uses a generic robotic device capable of automatically moving a landmine detection sensor over natural ground surfaces in a manner similar to an operator. Exploiting the cost efficiency of proven high sensitivity commercial-off-the-shelf sensors, such as the metal detectors widely employed by military and humanitarian deminers, the high-precision automation of the ARS can be utilized to provide a low cost and low weight scanning imaging sensor that can be carried on a small autonomous platform. Concurrent with the ARS project, Defence R&D Canada – Suffield has maintained an active programme in the development of portable AP landmine detection systems, a number of which will be described. Together, these projects inspired a more ambitious vision, the Canadian Sensor Integration Concept (CANSIC), which applies the successful multi-sensor landmine detection approach to a small autonomous vehicle, using complementary sensors designed for antipersonnel landmine detection. Using a high-mobility robotic platform, the envisioned system incorporates five separate technologies: two hyper-spectral cameras, thermal and visual/near infrared, along with a scanning sensor imaging system mounted on a purpose build articulated robotic scanner, working in conjunction with a nuclear imaging confirmation sensor. Designed to provide clearance options for areas off established roadways, the goal is not only to operate in all environments and conditions that a deminer is able to, but also to extend the demining capabilities of military commanders and humanitarian demining project managers to situations where there is a high probability of casualities.

Detection of aromatic nitro compounds with electrode polarization controlling sensor

The global demands for landmine abolition become stronger, whereas the development of landmine detection technology progresses slowly. At present, the detection activities are mainly performed by means of a metal detector or a well-trained dog that needs much time and cost. Therefore, a more efficient landmine detection technique is desired. Most landmines contain aromatic nitro compounds, such as 2,4-dinitrotoluene (DNT) and 2,4,6-trinitrotoluene (TNT) as explosive charges; therefore, these substances are clues for landmines. In this study, we tried to detect amount of aromatic nitro compounds high-sensitively using a surface-polarization controlling method that measures electrochemical impedance of an electrode surface where explosive compounds adsorbed. As a result, we could detect the aromatic nitro compounds at detection limits of sub-μM level and distinguish the aromatic nitro compounds from other aromatic compounds at 100 μM at least. Furthermore, in order to improve specificity and sensitivity to aromatic nitro compounds, the electrode surface was modified with arenes that makes charge-transfer complex with aromatic nitro compounds. We adopted anthracene as the arene to functionalize the electrode surface. The modified electrode makes it possible to detect the aromatic nitro compounds selectively. This method enables us to develop a sensor for landmine detection.

Surface plasmon resonance immunosensor for highly sensitive detection of 2,4,6-trinitrotoluene

We have examined the sensing characteristics of a surface plasmon resonance (SPR) immunoassay for the detection of 2,4,6-trinitrotoluene (TNT) using an immunoreaction between 2,4,6-trinitrophenol–ovalbumin (TNP–OVA) conjugate and anti-2,4,6-trinitrophenol antibody (anti-TNP antibody). TNP–OVA conjugate was attached to a SPR-gold sensing surface by means of physical immobilization, which undergoes binding interaction with anti-TNP antibody. Both the immobilization and binding processes were studied from a change in the SPR-resonance angle. The quantification of TNT is based on the principle of indirect competitive immunoassay, in which the immunoreaction between the TNP–OVA conjugate and anti-TNP antibody was inhibited in the presence of free TNT in solution. The decrease in the resonance angle shift is proportional to an increase in concentration of TNT used for incubation. The immunoassay exhibited excellent sensitivity for the detection of TNT in the concentration range from 0.09 to 1000 ng/ml with good stability and reproducibility. The immunosensor developed could detect TNT as low as 0.09 ng/ml, within a response time of ∼22 min. The sensor surface was regenerated by a brief flow of pepsin solution, which disrupts the antigen–antibody complex without destroying the conjugate biofilm. Cross-reactivity of the SPR sensor to some structurally related nitroaromatic derivative and the detection of TNT in the presence of these nitroaromatic compounds were investigated. The cross-reactivity of the SPR sensor to 2,4-dinitrotoluene (2,4-DNT), 1,3-dinitrobenzene (1,3-DNB), 2-amino-4,6-dinitrotoluene (2A-4,6-DNT) and 4-amino-2,6-dinitrotoluene (4A-2,6-DNT) were very low (≤1.1%). The analytical characteristics of the proposed immunosensor are highly promising for the development of new field-portable sensors for on-site detection of landmines.

An acoustic landmine detection confirmatory sensor using continuously scanning multibeam LDV

Acoustic-to-seismic coupling technology using an LDV as a vibration sensor has proved itself as a potential confirmative sensor for buried landmine detection. One of the most important objectives of this technology is to increase the speed of measurements. Traditionally used point-by-point scanning LDVs cannot provide fast measurements. A moving platform that uses 16 LDVs and a continuously scanning single-beam LDV has been used to increase the speed of detection of buried landmines. Recently a multibeam LDV simultaneously probing 16 positions on the ground has been developed and successfully used for landmine detection. In this work, we report the use of a continuously scanning multibeam LDV as a confirmatory sensor for acoustic landmine detection. The multibeam LDV simultaneously illuminates the ground in 16 points spread over a 1-m line. A scanning mirror moves all 16 laser beams across the line. An airborne sound source in the frequency range of 80–300 Hz has been used to excite vibrations in the ground. The system enables scanning a 1-m by 1-m area and provides the vibrational pattern at the surface of the ground in a much shorter time than with previous scanning techniques.

Investigation of a combined seismic, radar, and induction sensor for landmine detection

An experimental system to collect co-located ground penetrating radar (GPR), electromagnetic induction (EMI), and seismic data was developed to investigate the benefits of the fusion of these sensors. In the experiments, a range of mines and clutter objects were buried at various depths in the sandbox at Georgia Tech. Multiple burial scenarios were investigated with a variety of antipersonnel and antitank mines and typical clutter objects. The seismic system used in these experiments is an extension of our existing seismic mine detection system. The system uses electrodynamic shakers to generate a seismic wave which propagates across the simulated minefield, and a specially designed radar is used to measure the displacement of the surface caused by the seismic wave. The GPR makes use of modified resistive-vee antennas and operates over the frequency range of 500 MHz to 8 GHz. These antennas are very clean in that they have very little self-clutter and very low radar cross section to lessen the reflections between the ground and the antennas. The EMI sensor collects broadband data (300 Hz to 100 kHz) so that the relaxation frequencies of the buried targets can be used to aid discrimination. [Work supported by ARO.]