robotic landmine detector final report

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Robotic Landmine Detector Final Report

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Table of Content

Executive Summary..page 3

Statement of Need..page3

Project Specs/Technical Specs......page 4

Preliminary Designpage 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 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 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 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 with another to

facilitate motion. The robots 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 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

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 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 Desert terrain and sandy environment

Temperature range 30- 110F

Storage Temp -50-150F

Vibrations Withstand being dropped from 1.5 ft

Moisture Can withstand being wet on the exterior but not to the interiormechanics and circuitry

Durability Transported with minimal roughness

Weight Withstand being carried by 2 health individual

Cost requirement Within the ECE department

Area covered 25 meter squared in less than 1 hour, due to battery life

System Overview

Preliminary Design

Originally the team decided on having a robotic vehicle that will consist of tracks. 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 theOOPic microcontroller, which is programmable in C, Java, or Basic and sounded

like a more opportune option. 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

Chassis

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24V 1500 mAHrNiMH Battery Pack

IG32P GearMotors

OOPIC IIMicrocontroller

Paint valve

GoldPIC IIPI Metal Detector


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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. 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 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 what 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, 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 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 other 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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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 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 on to the sand. 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, metal-

cased 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 metal, but if only the detonating tube and firing pin

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(weighing approximately 0.6 g in an M14, and even less0.35 gramsin 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 undesired 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), pulse-

induction (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 shift but

are slow to react to current change, while those with high resistance have smaller phase

shift and are faster to react. VLF uses this property to discriminate most metals that vary

both in inductance and 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 object is metallic. However, BFO

does not have the same level of control in terms of sensitivity based on its functionality.

PI metal detectors, unlike VLFs, 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 of 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 of the circle. The

nails should slant out of the circle by a few degrees.

3. Wind exactly 27 turns around the nails, flush with the board. 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 a spiral of twine around the coil, tightly

grouping the windings together. Fasten the ends by knotting.

6. Remove the remaining nails.

7. Add another tight spiral of twine and secure 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. 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 object-

oriented language. This PIC can be programmed in C, or Java, and since one member of

the group is a CSE major and the other members are familiar with C it was an obviouschoice. 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 Event-

Driven by tying programmed procedures into the virtual circuits to trigger interrupts.

Any PIC where the interrupts can be easily 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. 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

Fall 2004 Winter Break

Sept October November December January

W3 W1 W2 W3 W4 W1 W2 W3 W4 W1 W2 W3 W4 W1 W2

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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Completed

Currently working on

Estimated Budget

Materials PriceAcrylic $70

Two 24VDC 190 RPM IG32P Gear

Motor

$45

Motor Housing $60

Wheels and Axils $40

Wheel encoder $30

OOPic II w/ Cables $70

Batteries $60

Hardware $20Metal Detector $70

Search Coils $10

Miscellaneous $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 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 help to find landmines that consist of no metal.

Nonetheless, this device will be a significant start for any future developments.

DATA SHEET

DC Motors

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24VDC 5kgf-cm 190 RPM Gear Motor-Characteristics

ReductionRatio

RatedTorque

RatedSpeed

RatedCurrent

No LoadSpeed

No Load Current

kgf-cm rpm mA rpm mA

1:27 5.0 190


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robotic landmine detector final report

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