Mine Detecting Unmanned Rover Using Vapour Capturing and GPS Tracking
Landmines are explosive containers, placed just underground, which detonate when triggered due to contact with a person or a vehicle. During wars or security threats, the soldiers lay many anti-personal mines to prevent the enemy –army from advancing in their region. But these mines pose a serious threat to their own troops in the post-war scenario. Thus it is quite essential to detect the landmines and remove them without causing detonation. This is one of the major technological challenges for the army. One of the ways to detect the landmines is through vapour capture method. This paper proposes a solution to the above-mentioned problem using the vapour-capture method & GPS tracking. The landmine detector discussed here is an unmanned ground vehicle which uses GPS technology to locate the mine and internet-based receiver transmitter circuit to control the robotic vehicle. Through vapour-capture technology, the explosive vapours are collected at the locations where metal is detected by the robotic vehicle. Thus using this concept, the detection and removal of landmines become easier. The paper also discusses various methods for explosive vapour detection. A comprehensive compilation of all the technologies used in the process is presented. The future scope of the study is also discussed.
In war-prone areas, it is quite common for enemy nations to plant mines to prevent enemy troops from infiltrating into their territories. Landmines are explosive charges concealed just underground which detonate when triggered when a person or vehicle comes in contact. A mine usually contains explosive matter enclosed within some form of the casing (wood, metal or plastic), and a fusing mechanism to detonate the main explosive charge. Some mines are buried under the ground (15-30 cm deep), while others are fixed to objects above the ground. They can be activated by many mechanisms such as pressure, tripwire, magnetic influence or electrical command. Some mines can also be activated using other forms of electronic sensors.
Landmines are generally classified into two categories:
• Anti-tank (or anti-vehicle) and
Figure 1: Landmine Types
These mines are quite destructive and are capable of causing fatalities to military forces and also civilians living near minefields. Various methods have been developed to detect mines. Usually, metal detectors are used for the purpose of landmine detection but they do not provide accurate results. In this proposal, we will be using the vapour capture method to check for the impurities and then check the samples into the lab using sensor or dogs and then scanning the specific areas where the test results were positive.
Existing Detection and Detonation Technologies
Landmine detectors are used to detect the explosives (mines).They are actually metal detectors. The most important task is to detect the landmines and remove them by process of demining. Electromagnetic induction spectroscopy provides a solution to detect landmines. In present times, minesweepers either depend on metal detectors or vehicles with a large variety of mechanical tools attached to them. When a metal detector sweeps over a mine, the metal present in (can be the metal body or the crash pin) it induces a second magnetic field, which, when received by the detector sets off a buzzer. However, this is applicable to other metal pieces too. Other detection methods include TNT-seeking insect, antibodies, neutron analysis, reversal electron attachment detector and canine nose (dogs or rats). These animals with their acute sense of smell can detect the various impurities present in vapours surrounding the landmine
Once the mine is detected, it can be then detonated by following methods:
· Manual disarmament.
The explosive is burnt remotely.Care should be taken to avoid detonation. A compound called DETA i.e. Diethylenetriamine reacts with TNT and generates heat. The product thus formed in the reaction is combusted without detonation.
· The mine is burnt while avoiding high-order detonation. Holes are created in the mine without detonating its explosive contents
The next section discusses the proposed solution for Landmine Detection.
Vapour capture method is used to detect the landmines. This technique is innovative economical and easy to use. The idea discussed here explains the process of detecting the mines without detonating them.
The components used here are:
· IP Camera and metal detector
· Internet-based Receiver-Transmitter circuit
· GPS module
· Vacuum pump to capture vapour
The landmine detector is a robotic vehicle that hovers over the area to detect the mine. The robotic vehicle has a camera mounted over it so as to capture images while the vehicle moves on the ground. On the rear part of the vehicle, a vacuum pump is mounted. The front portion comprises of a metal detector plate. The vehicle is carefully designed so that it does not detonate the mine while moving on the surface.
Studies show that the presence of various explosive impurities present in the vicinity of a landmine can be detected. The amount of explosive vapour present in the surrounding environment is directly proportional to the temperature of the area.The robot is designed in a manner in which it can take the vapour samples using an air filter and then the filter is tested using various techniques such as electrochemical, chromatographic techniques or X-ray diffraction. Use of various canines can also be used to detect the presence of an explosive impurity. This helps us in deciding areas in which landmines are present. These areas which give positive test can be scanned with the help of a metal detector.
This is achieved by allowing the rover to moves on the land as per directions by a computer. The images are captured by the camera mounted on top of the vehicle. Once the robot enters the area, the vacuum pump will be switched on. The vacuum pump would suck in air. The air moves through the filter and the air particle are trapped within the wire mesh.The filter is then taken out from the pump and put in the units where dogs are made to smell the filters so that the presence of explosives can be determined. Other vapour testing methods can also be performed on the filters
GPS Technology (Global Positioning System)
The global positioning system is a satellite-based navigation system used to locate positions anywhere on earth. This kind of technology can be used in various areas like military, commercial usage and civil services all over the world.
Since there is a need for precise location of the mines we tend to use the geostationary satellites for determination of the location of the bot. These satellites are at a specific distance above the earth’s equator and follow the direction of the Earth’s rotation. The data is sent to a central PC by a network of base stations on the ground. The information is then sent to the geostationary satellite. Thereafter, it is broadcasted back down to GPS receivers.
In the rover, we use the REES52 NEO-6M U-BLOX NEO-6M GPS Positioning Module to Serial TTL. This GPS module continuously receives information from the orbiting satellites and is used to pinpoint the location of the rover detecting the mine. The minesweeper hovers over the area where mines are located, as soon as the metal detector detects a mine, the camera snaps a picture and the GPS sends the location of the rover so as to locate and carry out the demining procedure with ease.
The receiver transmitter circuit to be used here is essentially an Internet-based remote programming system which is named 8051 NET-ISP. The system comprises of an Ethernet communication module and an applicable microcontroller which is capable of ISP functions. The user can update any assembled hex-code program of 89C51.The user can thus control the applicable circuit through the internet without reaching the system.
This system enables the user to remotely read, write and erase program memory of the microcontroller unit. The user can thus remotely control the applicable circuit if all the related control functions are written. The remote user can reach connection through the internet with the help of system’s specific IP address and thus can remotely program the AT89C51 MCU.
The LNMS (local network management system) handles remote user’s request for connection. The remote user can thus control the nodes that are in the same LAN or LNMS.
Thus by using such a system, various applications can be combined such as updating as well as controlling simultaneously. It uses TCP/IP network for communication and control.
The user would thus send a signal through a computer which would reach the receiver mounted on the vehicle. The signal sent would direct the motion of the vehicle. Thus using the internet, the vehicle can be controlled even when the user is far away from the location where the device is being sent for detection of landmines.
Vapour Content Analysis
The vapour capture method is a very innovative technology to detect explosives. The air is trapped in the wire mesh of the vacuum pump and thereafter the filter inside the vacuum pump is removed and taken to a unit where the presence of explosives can be detected. There are various methods available to detect the explosives.
Some crucial factors governing the process include very low detection limits, good baseline stability, a short-detector response time for operations, minimum interferences from surroundings etc. The explosives vapour pressure is very low; therefore the vapour concentration around mines is also low. Hence the detection process is not easy.
The most commonly used explosive in landmines is TNT. Estimates show that almost 80% of the total landmines deployed contain TNT. There are many other impurities accompanying the explosive charge such as 2,4-DNT, 2,6-DNT, 1,3-DNB etc. These impurities generate much higher amounts of vapours than the main constituent of explosive 2,4,6-TNT itself. Recent studies suggest that the explosive techniques are beneficial to detect 2,4-DNT, 2,3-DNB vapours, and thus detect TNT explosives.
There are many methods for detection. Few have been discussed here.
1. Explosive vapour generation: Explosives do not emanate large quantities of vapour in the atmosphere. It is very necessary to generate vapours for proper detection. Various methods are used for the same. Vapour generation is the key factor governing the process of vapour detection.
2. Electrochemical detection: In this method, explosives are detected by measuring the current in the electrochemical cell, between the sensor electrodes and the counter electrodes at a specific voltage.
When explosives are thermally decomposed over heated noble metal surfaces, some characteristic pyrolysis products are formed which can be easily detected by amperometric sensors. This effect was also used to detect TNT vapours in the soil.
3. Fluorescence Techniques: Studies show that fluorescence polymer-based sensor prototype serves as an excellent landmine detection tool. The sensor is known to be ultrasensitive towards landmine detection. It detects the ultra-trace concentrations of TNT vapours and other explosive materials.
One of the two sensor types is chemoselective for nitroaromatic compound vapours, while the other sensor type is non-specific and cross-reactive array. The fluorescence patterns are recorded before, during, and after vapour exposure. This is done to record and analyse time-dependent vapour response patterns. This detection system has also been used to detect the presences of 2,4-DNT on the soil surface of landmines.
The process of demining carried out since ever is humanitarian. The idea proposed here is a robotic system for demining operations. Some studies have been carried out to develop an autonomous vehicle called “Gryphon”. It is designed to work efficiently in uneven terrains and is economic as well. Moreover, since the provision of energy is not an issue, it is feasible to use this vehicle.
Gryphon is quite similar to commercially available All-Terrain Vehicle (ATV).A long-reach robotic manipulator carrying a mine detector is mounted on it that automatically scans the terrain without any sort of human intervention. Stereo vision camera is used to obtain three-dimensional topographical information of the area to be scanned. The operator then carefully inspects the recorded dataand marks down the suspect spots onto the minefield with an onboard paint or plate-marking system. Additionally, an optional RTK-GPS localization system records the location of the marked spots,
• The Mobile Platform
The mobile platform is 4-wheeled ATV powered by a gasoline engine.
• The Manipulator
The manipulator, also called “Field Arm”, is composed of a weight-compensated mechanism and consists of a counter-balanced pantographic arm with 3 degrees of freedom, which allows taking advantage of a reduced power consumption and improved insensitivity towards the ATV’s suspension.
• The Stereo Vision Camera
Stereo vision camera is used to analyse the trajectory of the mine detector over the terrain.
• The Marking Systems
Two different marking systems have been developed. The first one, based on water-soluble color paint, has a nozzle attached to the mine detector. The second marking system operates by dispensing a marking plate onto the correct position.
The manipulator has sufficiently enough degrees of freedom (DOF) to operate and end-effecters optimized for removing the mines. It has a proper mechanism to minimize its power consumption. Since single-end effecters is not efficient to perform the task, the concept of Field –Arm is brought into use. The control systems of Gryphon and Field Arm work independently. Each control system computes its kinematics from sensors and uses Controller Area Network (CAN) to communicate its status to the other. It is necessary for human controllers to check the circumstances in which field arm operates. The cameras are mounted in front, back, both sides of the buggy and near the end effecters.
The platform is kept moving along the border of the safe area with the manipulator works on the minefield. This is done to prevent the robot from damages. The first prototype of ‘Field Arm” was made up of pipes of composite material and aluminum nodes. The selection of material is a crucial step since it is to be designed in a manner to work on all terrains. Once the arm is designed, it is easy to carry out the demining process efficiently.
Thus, a buggy-type robot for mine removal work has been proposed here. Though various techniques have been developed, there are some difficulties. The detection device needs to be designed differently for different terrains i.e. different kinds of devices are needed for sandy soil, fertile lands etc. It is a difficult task to develop a single device to work for all the different nature of soil and grounds. The analysis of manipulator along with its control system is under process. In near future, it is expected that end- effecters that should be used in real mine operations will be developed. But nevertheless, it is a reasonable system which if successfully implemented would be a great achievement in the field of landmine detection and demining. With advancements in technology, we would be able to develop a single device that works for all terrains and is accurate, power and energy-efficient as well as economical and carries landmine detection and demining action simultaneously.
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