Robotic Landmine Detector Final Report

Robotic Landmine Detector Final Report

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Table of Content Executive Summary…………………….…….page 3 Statement of Need…………………………..…page3 Project Specs/Technical Specs/Technical Specs………..……....page 4 Preliminary Design……………………………page 4-5 Final Design…………………………………...page 5 Chassis…………………………………..……..page 6 Motors………………………………………....page 6-7 Batteries………………………………….……page 8 Mark Area………………………………..……page 9 Landmine/Metal Detector……………..…...…page 9-12 Microcontroller……………………………......page Microcontroller……………………………. .....page 12-13 Testing……………………………...………..…page 14 Timeline………………………………… …….page 14 Budget………………………………………….page 15 Conclusion………………………………….…..page 15 Data Sheet……………………………………....page 16 Reference……………………………………….page 17

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Robotic Landmine Detector Project Executive Summary This project involves designing and constructing con structing a robotic vehicle that will scan a predetermined area and detect any landmines that might be present.  The primary areas being searched will be sandy and rough terrain-like environment.  Upon detecting a landmine the robot will mark the location where the landmine is detected.  This   This robot will be autonomously navigated by the use of a PIC microcontroller.  Two internal DC Motors will drive the robot.  Each motor will connect to a wheel coupled cou pled with another to facilitate motion.   The robot’s electrical system will control the robot to stop upon detection of a mine and mark the location where the mine was detected.  The system will then enable the robot to continue scanning the area until another mine is detected and the routine continues.

Statement of Need Landmines are efficient weapon used by approximately 48 countries throughout the world.  Over 100 companies are still producing landmines.  These weapons have a lifespan that is far beyond most of the conflict they are deployed for.  Therefore, these weapons will typically end up killing numerous civilians after the conflict than soldiers. It is estimated that 70 people are killed or injured by landmines everyday throughout the world.  Anyone who falls victim to a landmine will only have a 50% chance ch ance of survival and even if an individual does survive, they will suffer great personal and long-term injuries. The detection and removal of landmines posses a formidable challenge to the world, and there exists a need for a device that can find mines before they claim another victim.  Due to the widespread usage of landmines, there are many diverse environments that a detection device would have to be able to work in.  Also, due the many different variations and depth of mines, the device used to detect these mines would have to be precise and be able to penetrate various diverse environments.

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Project Description/Components Description/Components Project Specifications The electrical engineering department of the University of Connecticut requires the design of an operational prototype of a robotic landmine detector.  The landmine detector  will find landmines that are constructed of metal.  By   By knowing where the landmine is, a trained professional can disarm and remove the mine from the ground. The landmine detector will operate in a sandy environment that is characterized as being relatively flat.  The robot must have an internal motor to facilitate motion coupled with either wheels or a track and these motors will be controlled by the microcontroller.  It is also necessary for the robot to have an electrical system that will stop the robot when a mine is found.

Technical Specifications : Location Temperature range Storage Temp Vibrations Moisture Durability Weight Cost requirement Area rea cove covere red d

Desert terrain and sandy environment 30 - 110 F -50 -150 F Withstand being dropped from 1.5 ft Can withstand being wet on the exte xterior but but not to the interior  mechanics and circuitry Transported with minimal roughness Withstand being carried by 2 health individual Within the ECE department ent 25 meter eter squa square red d in less ess than than 1 hour hour,, due due to bat batter tery life ife °

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System Overview Preliminary Design Originally the team decided on having a robotic vehicle that will consist of tracks.  We   We wanted to implement tracks because of the sandy terrain the vehicle will be

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operated in.  After doing research and trying to locate tracks we did not come up with too many options.  Most individuals using tracks for their robots today construct them from rubber and wires, which is time consuming.  We wanted to focus most of our research and design on programming the microcontroller and the metal detector and not the tracks.  Through some research we found that if we use wheels that are big enough that they will navigate through sandy environment with no problems, so we decided to use 4 large tires instead of the tracks. Also the original microcontroller that was going to be used was the PIC16F874 used in ECE 266 and programmed using assembly language.  However, neither of the members of the group is comfortable programming using assembly language so we decided to look at some other options.  After doing some research we found the OOPic microcontroller, which is programmable in C, Java, or Basic and sounded like a more opportune option.  This   This microcontroller also has an I/O voltage regulator, which would be convenient for our design. Another change that we made to the design was using a remote.  We were going to use a remote controller because of our minimal experience with programming the PIC16F874, but after changing to the OOPic we can eliminate the remote control and make the robot completely autonomous.

Final Design The landmine detector consists of five major subsections including: vehicle chassis, batteries, motors, metal detector circuitry, and a PIC Microcontroller. Block Diagram

24V 1500 mAHr  NiMH Battery Pack 

IG32P Gear  Motors

GoldPIC II PI Metal Detector 

OOPIC II Microcontroller  5

Chassis

Paint valve

The body of the robot will be constructed with acrylic material.  The dimensions are 14” x 18”.  We chose this material because it is easy to work with and lightweight, which is what we want because we are operating in sandy environment.  We also had the choice of using Plexiglas but others experience with Plexiglas is that it is very difficult to work with and it shatters if not drilled properly. properly.  We could have also used aluminum but that might interfere with the metal detector circuitry and we did not want to take the risk.  The wheels whee ls that we are using are 3.5 inch in diameter, which is big enough to traverse through sand and rough terrain.  These wheels also come with a wheel encoder to facilitate navigation.

Motors

The motors will be used to physically navigate our robot around by driving four wheels. We have decided to use two motors where each motor would power one wheel coupled with another.  When we were exploring options in regards to wh at kind of  motor will be used, we thought that either DC motors or stepper motors would make the best choices.  This was due to the fact that the robot will be carrying all of its power on board in the form of batteries.  Therefore, it would be illogical to choose a motor that does not use DC, if an AC motor were chosen, then the motor would require an extra circuit to change from DC to AC. Knowing that DC motors and stepper motors would provide the best options, we then looked at each type of motors characteristics of operation.  Obviously,  Obviously, within the general title of DC motors there exists a wide variety of subsets but the chief types

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consist of permanent magnets and field coil.  In   In general, DC motors are characterized by possessing high torque from standstill and are easily controlled by varying the applied voltage.  A DC motor with a permanent magnet seems like a better choice due to the fact that it is lighter than a DC motor with a field coil.  The stepper motor  also provides many advantages, such as its precise speed control, and a large amount of torque.  The only disadvantage is that it requires a switching circuit.  With these ideas in mind, we came to the conclusion that a DC motor with a permanent magnet would provide the best results.  This was due to the fact that we will not need the precision of a stepper motor and by using a DC motor with a permanent magnet we will get adequate enough torque for our robot.  Also, implementing our design with DC motors as appose to stepper motors avoids o ther circuits to be built, thus keeping our design simple. The DC motors we will use for our design are the 24VDC 190-RPM IG32P Gear Motor  shown below.

Fig 2. IG32P Gear Motor

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Graph 1.  Torque / Current Curves for IG32P Gear Motor (1 lb is ~453 grams)

The chassis of our robot will weight about 2 lb and in addition with the other parts of our  design the overall weight of the robot will be close to the ideal operation opera tion characteristics of these DC motors.  By operating the IG32P Gear Motor at the current that best correlates with the weight of the robot we will achieve the torque and speed that we desired from these motors. Batteries

There are a wide variety v ariety of batteries to choose from.  To narrow our search, we wanted a battery that would be rechargeable due to the fact that we will be performing extensive testing on the robot and it will be costly to replace batteries after ever run. Also, another benefit to using rechargeable batteries is the fact that they are more economical than other batteries in the long run.  The two most common rechargeable batteries are Nickel-cadmium (NiCad) or Nickel-metal Hydride (NiMH).  NickelCadmium batteries were found to have memory problems.  If you consistently topped off a NiCad battery when it was only on ly partially discharged, the battery would quickly lose its full original capacity. capacity.  Because of this memory issue we decided to use the NiMH battery pack for use in our design.  We will use a 24V 1500 mAHr  NiMH Battery Pack as shown below. below.

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Fig 3. 24V 1500 mAHr NiMH Battery Pack 

The batteries are arranged in a 2x10 array of AA batteries interconnected by soldered strips and covered with PVC wrapping.  These batteries are convenient due to their  compact packaging, reducing the hassle of recharging individual batteries. Mark Area

The paint portion of our design will be used as the means to mark the spot of the mine. To do this, we will use a plastic line connected at one end to a small container of  paint and at the other end en d placed in the middle of the metal detectors coil.  When metal is detected, and the user knows about where the metal is, he or she will flip a switch in order to allow paint to drip out o ut on to the sand.  Paint   Paint will drip out because we will allow air to flow into the paint container and gravity will then be able to draw the paint out. Landmine/Metal Detection

Although not all landmines are made of metal, those that have metal casing or  have substantial metallic content are among the prevalent in most minefields. The detection of landmines made of materials other than metallic requires many types of  sensors and detection technologies such as thermal, chemical, or ground penetrating radar  imaging. They pose a great deal of complexity for landmine detection. However, metalcased landmines can be detected quite readily with a metal detector. Non-metallic cased mines such as plastic mines contain varying degrees of metal. It is still possible to be detectable if the fuse is made of o f metal, but if only the detonating tube and firing pin

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(weighing approximately 0.6 g in an M14, and even less0.35 gramsin a PMA3) are metal, it would be difficult to detect. Increasing the sensitivity of the metal detector may allow us to detect the firing pin when adjusted appropriately. However, this would cause the sensor to pick up u ndesired small metal objects, which in turn results in a high false alarm rate. Nevertheless, metal detectors remain the most widely used tool in the detection of landmines. Therefore, due to the limitations of various factors including our  budget and to prevent over-complexity of our project, we have decided to make our  robotic landmine detector to be one that finds metallic landmines rather than those that are made of any other materials.

Fig 4. Garrett PI Metal Detector

There are various methods and technologies used for metal detection. Three of the most used are: very low frequency (VLF), beat frequency oscillation (BFO), pulseinduction (PI). VLF metal detector is the most commonly used metal detector. It relies on phase shifting to detect metal. Objects with high inductance have larger phase ph ase shift but are slow to react to current change, chan ge, while those with high resistance have smaller phase shift and are faster to react. VLF uses this property to d iscriminate most metals that vary both in inductance and an d resistance. The most basic way to detect metal is to use BFO. BFO has coils that are connected to an oscillator that generates pulses in the kilohertz range. The magnetic field caused by the current flowing through the coil creates B-field in the object and then interferes with the frequency of the oscillator. This deviation in

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frequency allows BFO metal detector to determine the o bject is metallic. However, BFO does not have the same level of control in terms of sensitivity based on its functionality. PI metal detectors, unlike VLF’s, use a single coil to both transmit electromagnetic pulse and receive any detected induced eddy current by the pulse in the underground metal objects. This technology is widely used by hobbyists as coin detectors on the beach and is commercially available. After researching and comparing these three types o f methods, we have found the PI sensors are better in areas that have highly conductive materials in the soil and the general environment. The pulse-emitted signals can penetrate deeper and cover larger  areas in less time without missing deeply buried objects. The fact that this type of metal detector is available commercial facilitated our decision to go with the PI metal detector.

Fig 5. GoldPic 3 PI  Metal Detector Circuit

The metal detector of choice was the GoldPic 3 Pulse Induction Metal Detector. We have selected this particular metal detect circuit because of it is easy to build and much more inexpensive than to purchase a fully functional metal detector such as the Garrett PI metal detector seen in (Fig 4). With the GoldPic 3 PI metal detector, we are able to adjust the sensitivity of the detector to suit our purpose of landmine detection. We will also have the flexibility of making our own shaft and search coil that would be appropriate for our robot. The suggested coil consists of 27 Turns of 0.5mm enameled single strand copper wire with a diameter of 190mm. (7.6 inches). The recommended method of winding the coil is: 1. Draw a 190 mm diameter circle on a piece of wood or board.

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2. Knock in a small nail every 30mm around the circumference circumference of the the circle. The nails should slant out of the circle by a few degrees. 3. Wind exactly 27 turns around the nails, flush with with the board. Leave Leave +/- 10cm long flying leads for soldering to at the start and finish of the winding. 4. Pull out every other nail. 5. Using twine and a sewing needle, ‘sew’ ‘sew’ a spiral spiral of twine twine around the coil, tightly grouping the windings together. Fasten the ends by knotting. 6. Remove the remaining remaining nails. nails. 7. Add another tight tight spiral of twine and secure the the flying leads in place. We will be experimenting and adjusting the sensitivity of our metal detector  extensively as soon as we receive the parts. Central Controls/Microcontroller

The brain of our robot will be the PIC microcontroller. microcontroller.  The PIC will be the central control for the metal detector and the motors.  The DC motors, paint valve and the metal detector will be interfaced with the PIC; when the robot is in motion and a mine is detected the PIC will prompt the motors to stop.  The paint valve will then open, marking that spot as a hazard area for a potential mine.  After marking that location, the robot will turn left or right depending on current position; it will then continue to scan the area.  These functions will be carried out by means of the PIC microcontroller. The PIC that we chose for the design is the OOPic II, which can be seen below.

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Fig 6.  OOPIC II Microcontroller

This microcontroller was chosen for several reasons.  One reason is because of its objectoriented language. This PIC can be programmed in C, or Java, and since one member of  the group is a CSE major and an d the other members are familiar with C it w as an obvious choice.  This familiarity with the C compiler will allow us to program the PIC quickly allowing us more time for testing the individual components and associated programs. Another practical reason for using this PIC is that the Objects within the OOPic can be connected together to create a Virtual Circuit.  This virtual circuit operates in the background as your program tends to other tasks.  The programs can even be EventDriven by tying programmed procedures into the virtual circuits to trigger interrupts. Any PIC where the interrupts can be easily e asily controlled would be ideal for robotics projects. The OOPic II object oriented microcontroller is the primary MCU of our design.  The OOPic will control the PWM controlling the motors and the valve to mark the location of  the mine; it will take the inputs from the metal detector circuitry.

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FIG 7. Schematic of OOPic II Input/Output ports Testing

Each component of the robot will be tested individually. individually.  The metal detector circuitry will have to be tweaked to suit what we are trying to accomplish.  We want the detector to penetrate the ground as far as it could, but at the same time we want to eliminate any small metal objects that might not be a landmine.  The robot chassis itself be assembled and tested in sandy environment to make sure that that wheels are sufficient enough for searching the path.  The microcontroller where we predict we will be spending the most time will be programmed and interfaced with the motors and the metal detector circuitry. Timeline

Sept W3 W1

October W2 W3

Fall 2004 November W4 W1 W2 W3 W4

Research Metal Detector  Sensors Remote Control Locomotion Body Design Metal Detector  Remote Control Locomotion Body Ordering Parts Testing Implementation Written Report Project Statement Project Specs Project Proposal Final Report Weekly Report Schedule

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Winter Break December January W1 W2 W3 W4 W1 W2

Completed Currently working on

Estimated Budget

Materials

Price

Acrylic

$70

Two 24VDC 190 RPM IG32P Gear Motor Motor Housing Wheels and Axils Wheel encoder OOPic II w/ Cables Batteries Hardware Metal Detector Search Coils Miscellaneous

$45 $60 $40 $30 $70 $60 $20 $70 $10 $50 TOTAL = $525

Conclusion

The basic project requires the assembly of a device to help facilitate the removal of landmines in a sandy environment. The area searched will be 25 meters squared in approximately 45 minutes or less.  We  We believe that the device will be able to search a larger area but we are going to test the robot in an actual site before we modify our  specifications in this particular area.  Future work could be done in trying to figure out a way in which this robot could c ould help to find landmines that consist con sist of no metal. Nonetheless, this device will be a significant start for any future deve lopments.

DATA SHEET DC Motors 15

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24VDC 5kgf-cm 190 RPM Gear Motor Characteristics

Reduction Rated Ratio Torque 1:27

Rated Speed

Rated Current

No Load Speed

No Load Current

kgf-cm

rp rpm

mA

rpm

mA

5.0

190

<900mA

223

<450mA

OOPic Specs Programming Connector. Connects to the PC's Printer Port. (5 Pins) Power Connector. Connects to any power supply of 6-15 Volts DC. (2 Pins) I/O Connector. Provides connection to all I/O. (40 Pins) Memory Sockets. 2 Sockets for program and data EEPROM. (8 Pins) Network Connectors. 2 Connectors for I2C network cables. (5 Pins) Prototyping Area 76 Proto holes + 34 signal & 24 power connections 16 Mechanical layout. 2 inches X 3-1/2 inches x 5/8 inch.

Reference www.thebotshop.com

OOPic II and Cables & Chassis www.allproducts.com

24VDC 190 RPM IG32P Gear Motor 

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