Mine detection and marking robot.pdf

AM 20

MINE DETECTION AND MARKING ROBOT

PREPARED BY-

NYEIN CHANN

In partial fulfillment of the

requirements for the Degree of Bachelor of Engineering

DEPARTMENT OF MECHANICAL ENGINEERING

NATIONAL UNIVERSITY OF SINGAPORE

SESSION 2006/2007

Landmine detection and marking robot Summary

Summary

The purpose of this project is to design a robot which is capable of detecting

buried landmines and marking their locations, while enabling the operator to control

the robot wirelessly from a distance. This is a collaboration project between DSTA

and NUS.

This is a pioneer project in NUS and therefore the development of the robot

had to be initiated from the very basic steps. The project was started from the brain

storming phase together with the research phase and then proceeded into the

conceptualization or designing phase. The ideas and concepts from the theoretical

stages are shaped into the physical hardware components by fabrication of a

prototype and then software programs are integrated into the system so as to test and

experiment the concepts that had been developed.

The designed robot is capable of detecting a buried mine, marking the exact

location of the buried mine, and controlling itself from stepping over it and detonating

the mine. The detection of the buried mine is done by using metal detectors since

most land mines contain metal components. The marking of the location of the

possible buried mine area will be done by spraying distinctive colour paint onto that

location. With the use of interchangeable four pairs of wheels, the avoiding of the

possible buried mine location can be executed without requiring the robot to dodge

around that spot.

I

Landmine detection and marking robot Summary

The robot will travel in a straight line path, marking the possible buried mine

spots and clearing 1.2 meter wide lane in one pass. The system allows the operator to

stay at a safe distance by enabling him to control the robot wirelessly or remotely.

The robot travels at 0.3 km/h and therefore it can clear a distance of 100 meters (with

a width of 1.2 meter) in approximately about 20 minutes.

The reliability of the robot depends upon the type of sensors or detectors

being used. Therefore, the robot platform has been designed to be versatile enough to

work with any detectors installed onto it. This project has opened up a new area of

research to be explored.

II

Landmine detection and marking robot Acknowledgements

Acknowledgements

I would like to express my sincere gratitude to Associate Professor Gerard

Leng, for his invaluable guidance and advices. His guidance has paved me to handle

the project professionally and his advices have been a great help in executing the

project.

I would like to thank sincerely to the stuff of Dynamics and Vibrations Lab

for helping me in not only technical matters but also administrative matters.

I would also thank DSTA (Defence Science & Technology Agency) for

giving me a chance to participate in great research project and providing project

funding.

Last but not least, I would like to express my gratitude to my peers who have

helped tremendously and the friendly postgraduates who had shared their opinions

openly.

III

Landmine detection and marking robot Table of contents

Table of Contents Contents Page No Summary ………………………………………………I Acknowledgement ………………………………………………III Table of content ………………………………………………IV List of figures ………………………………………………VI List of Tables ………………………………………………VIII List of Symbols ………………………………………………IX Chapter 1: Introduction…………………………………………..……1

1.1 Purpose ………………………………………………………1 1.2 Objectives………………………………………………………1 1.3 Scope ………………………………………………………2 1.4 Challenges ………………………………………………2

Chapter 2: Literature survey ..………………………………..……4 Chapter 3: Design conceptualization ..………………………..……7

3.1 The detector ………………………………………………7 3.2 A carrying vehicle ………………………………………9 3.3 Data processing unit ………………………………………11 3.4 Designing location marking mechanism ………………14 3.5 Designing location marking mechanism ………………15

Chapter 4: Fabrication of the prototype ……………………..……18 4.1 The scanner ………………………………………………20 4.2 The location marking mechanism ………………………21 4.3 The body ………………………………………………………22 4.4 The processing unit ………………………………………30

Chapter 5: Experimental results ……..…………………..……35 Chapter 6: Conclusion ………………..………………………..……37 Chapter 7: Recommendations ………..………………………..……38 References …………………………..……………………..……39

IV

Landmine detection and marking robot Table of contents

Appendices ………………………..………………………..……40 DC motor selection table ………………………………………A Recommendation on the use of infrared thermal imaging camera ………………………………C Detecting the mine by sniffing for the explosive inside the mine ………………………………………G Off the shelf metal detector used in the prototype ………………………………………………I Alternative detection system for the robot ………………………J Engineering Drawings ………………………………………K

V

Landmine detection and marking robot List of figures

List of Figures

1. M14 Antipersonnel mine

2. M15 Anti-tank mine

3. Use of metal detector

4. Ground Penetration Radar (GPR)

5. Thermal image of buried landmines

6. Comet III, Landmine detecting walking robot

7. Landmine detection robot equipped with metal detector

8. Algorithm of processing unit

9. The sequence of detected mine avoiding mechanism

10. Four different views of the prototype

11. Top view of the prototype

12. General view of 3D model

13. General view of the prototype

14. Metal detectors on the prototype

15. Small vehicle that shuttle inside the scanner, carrying the detectors from end

to end

16. Simplify circuit diagram of paint spraying unit

17. The base structure of the prototype

18. Support plate that carries one front wheel and one rear wheel

19. ¾” C-channel attached onto the supporting plate in order to prevent deflection

20. Mine avoiding mechanism

VI

Landmine detection and marking robot List of figures

21. Mine avoiding mechanism, Inside set of wheels are lifted up to avoid mine

that might lies on their path

22. Front wheel motor with speed controller

23. Processing unit comprises of a 12-remotely controlled relays unit and a

programmable micro-controller

24. Simplify connections of inputs and outputs at the micro-controller

VII

Landmine detection and marking robot List of Tables

List of Tables

1. Comparism of Thermal imaging cameras provided by two different companies

VIII

Landmine detection and marking robot List of symbols

List of Symbols

W : Weight

F : Force

g : Acceleration due to gravity

I : Moment of inertia

L : Length

m : Mass

P : Power

r : Radius

v : Linear velocity

ω : Angular velocity

μ : Static coefficient of friction

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Landmine detection and marking robot

Chapter 1 Chapter 1: Introduction

1.1 Purpose

The landmine crisis is globally alarming since there are presently 500 millions

unexploded, buried mines in about 70 countries. Governments are looking into this

situation seriously since landmines are claiming the limbs and lives of civilians

everyday. Singapore Armed Forces (SAF) is trying to explore this area and work

jointly with National University of Singapore (NUS) to develop a land mine detection

unit. The purpose of this project is to design a robot which is capable of detecting

buried land mines and marking their locations, while enabling the operator to control

the robot wirelessly from a distance.

1.2 Objectives

1. A land mine detection robot is needed to be designed to employ in peace

support operations and in the clearance of contaminated areas.

2. The robot shall be able to detect 90% of landmines (Anti-personnel mines and

Anti-tank mines) and mark the locations of the mines within a tolerance of

5cm.

3. For the safety of the operator, the designed robot must be able to operate

remotely, moreover, must be equipped with wireless data transmitting

capabilities.

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Chapter 1 4. The robot shall not detonate the mines while scanning the area and marking

the locations of the mines.

1.3 Scope

The information gathered through research is presented in chapter 2. The

analysis and discussion upon the acquired data are also included. Based on the data

accumulated, the sequence of conceptualization of the final design of the robot is

articulated in chapter 3. After the final design had been decided and built on the 3D

virtual CAD software, a prototype was built to represent the design concept of the

finalized design. This process is explained in detail in chapter 4. It is followed by

discussion and interpretation of experimental results in chapter 5. The chapter 6

presents the conclusion of this project, while chapter 7 offers recommendations for

further improvement for this project.

1.4 Challenges

Not only is the presence of the mine is required to be discovered, it also needs

the robot to mark the location of the mine with an accuracy of 5cm radius.

Such accurate location marking system is needed to be designed and installed

on the robot.

The geographical nature of the mine field is expected to be a little rough with

grass or gritty ground. Therefore, a minimum clearance height from the

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Chapter 1 ground to the bottom of the vehicle is required and a suspension system is

required in the vehicle.

To avoid detonating the land mines, either the wheels must be lifted from the

ground or the vehicle has to be driven around the mines. At the same time, the

robot must be able to mark the locations of the detected mines.

To enable a wireless communication system, places for radio transmitters and

receivers will have to be incorporated.

The budget is constrained to $4000 Singapore dollars to create a prototype

mine detection and marking module.

In order to fulfill the objectives and overcome the challenges, the following

steps are carried out carefully.

A thorough research was carried out in order to gather information regarding

the existing systems and other solutions relating to the problems. The accumulated

data was analyzed thoroughly and ideas generated through brain storming. The

generated ideas were filtered through the criteria required by the project objectives.

After a series of reviewing and revising, a final design was produced as a 3

dimensional solid model on CAD software known as Pro-E. The components were

fabricated according to the 3D model and equipments were purchased and installed

according to the final design. Several tests were carried out at in-between stages to

ensure the workability of each mechanism inside the robot. After a complete

assembly of the robot, test runs were carried out to determine the reliability of the

robot.

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Landmine detection and marking robot Chapter 2

Chapter 2 : Literature Survey

Landmines are easy-to-make, cheap and effective weapons that can be

deployed easily over large areas to prevent enemy movements. Mines are often laid in

groups, called mine fields, and are designed to prevent the enemy from passing

through a certain area, or sometimes to force an enemy through a particular area.

While more than 350 varieties of mines exist, they can be broken into two categories,

namely, anti-personnel mines and anti-tank mines.

Anti-personnel mines are designed to

kill or injure enemy combatants. They are

usually buried 10mm to 40mm beneath the soil

and it requires about 9 kg minimum pressures to

detonate them. The face diameter of most the

anti-personal mines ranges from 5.6cm to

13.3cm.

Figure 1. M14 Antipersonnel Landmine

Figure 2. M15 Anti-tank Landmine

An anti-tank mine is a type of land mine

designed to damage or destroy vehicles

including tank and armored fighting vehicles.

An applied pressure of 158 kg minimum is

required to detonate it; hence the footstep of a

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person won't detonate them. Most anti-tank mines possess a larger face diameter

compare to anti-personal mines, usually around 33.7cm.

“The landmine is eternally prepared to take victims.” It is true that the

forgotten landmines are taking the lives of civilians every now and then. Thus,

different counties use different methods to deal with buried landmines which possess

potential danger to the lives of its own civilians. The most commonly used methods

are as followed.

Probing the ground ; For many years, the most sophisticated technology used for

locating landmines was probing the ground with a stick or bayonet. Soldiers are

trained to poke the ground lightly with a bayonet and search for buried mines.

Metal Detectors ; The detectors try to discover a buried mine by sensing the metal

components inside the mines.

Ground Penetrating Radar ; This equipment detects the inconsistencies in the soil

and tries to identify the differences in the densities of the soil and a buried mine.

The use of trained dogs and rats ; They are trained to sniff out vapors coming from

the explosive ingredients inside the landmine.

Moreover, various on-going researches are being carried out around the world

either trying to improve the existing methods of sniffing for buried mines or hoping to

discover new methods of detecting buried mines with better accuracy.

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At the same time, landmine detection robots are created by various

organizations trying to solve the “forgotten landmines” problems. Some of the above

mentioned mine detection methods are installed onto uniquely designed robots to

perform the desired jobs, finding the mines without detonating them. Wheeled robots

are mainly used to dodge around the possible mine buried spots, while some tracked

robots are designed to possess weight lighter than detonating pressure and then they

roll over the mines after marking the possible spots. Unmanned aerial vehicles (UAV)

are also deployed to scan the mine fields. The most advanced carrying vehicle is a

walking robot with mechanical legs.

Different combinations of mine detecting unit and carrying vehicle are

employed with the aim of detecting all the mines in the desired direction and

precisely pin-pointing their locations, with efficiency.

The reliability on a landmine searching robot is highly dependent upon the

performance of the detector with respect to the landmines, whereas, the purpose of

the carrying vehicle is to provide the require pattern of movement in such a way that

the detector can do its job. A data processing unit is needed on board, to process the

input data from the operator and to send out output data to the specific mechanism to

perform the necessary function.

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Chapter 3 : Design conceptualization

As mentioned in chapter 2, a land mine searching robot must comprise of

three basic features, namely; the mine detector, a carrying vehicle and a data

processing unit.

3.1 The detector

For the past decade, landmines, both anti-personnel

and anti-tank mines, are made in metal casings. Therefore, the

detection of landmine by using metal detectors is a simple and

workable method. However, nowadays, the mines

manufacturers tend to use as little metal as possible to

redundant the use of metal detectors and so that their

landmines will serve their purpose.

Figure 3. Use of Metal detector

Moreover, the metal detectors give out false signals upon sensing every

presence of metal pieces instead of only when detecting the real mine. In statistical

language, it can be said that 100 to 10,000 false signals are sent out before detecting a

real landmine.

Due to the above reasons, using a metal detector as a mine detector in the

robot has become an unfavorable option.

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Figure 4. Ground Penetration Radar (GPR)

Another proposal to search for a buried mine

is the use of ground penetrating radar (GPR). This

equipment detects the inconsistencies in the soil and

tries to identify the differences in the densities of the

soil and a buried mine. This concept is theoretically

workable; however, it is not an absolute fool-proof

system since natural inconsistencies in the soil can trigger a false alarm. On going

researches are carried out around the world in order to rectify the false alarms and to

detect the buried mines without missing it.

Figure 5. Thermal image of buried

landmines

The third concept comes with a simple

physics theory. Each element or each material has

their own thermal properties, such as thermal

conductivity, rate of heat absorption and thermal

radiation. A buried landmine comprises of different

materials from the surrounding soil and they will

react to the surrounding heat in a different manner

from the soil. They will absorb the heat slower or faster than the surrounding soil and

they will release or radiate the contained heat slower or faster than the surrounding

soil. Therefore, at any point of time, the land mine will possess slightly different

temperature form the surrounding, due to the constantly varying heat supply from day

time and night time.

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Therefore, thermal imaging Infra Red camera is the best option for this

project. They provide us with thermal images whose displays enable us to

differentiate objects with different temperature profiles. However, on the other hand,

the prices of the thermal imaging cameras are expensive; they range from $40,000

and above. Due to budget constraints, the idea of employing and experimenting with

the thermal imaging cameras is saved for the next stage of this project. The same

applies for GPR (ground penetration radar) since the equipment is expensive and

requires military clearance in order to purchase one. Hence, even though metal

detectors may seem inferior in performance to thermal imaging cameras and GPR,

they are the most suitable to be used in the first stage of this venturing project.

3.2 A carrying vehicle

A transport system is required to carry and transport the mine detection unit.

The mine fields are expected to have plain, leveled but mildly rough terrains.

Figure 6. Comet III Landmine detecting

walking robot

The very first proposal of transport unit

is a walking robot, either four legged or six

legged. Using legged robots will give great

advantages in walking though rough terrain

since it has the ability to balance itself and

ability to avoid holes and small obstacles.

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However, the draw back is the designing of the robot. It can cost nearly a million

dollar to build a smart robot and will take more than a year’s time to do so. The robot

idea had to be abandoned due to the financial constraint and time constraint.

Moreover, the smarter the robot is, the more complex its mechanisms will be, and the

main objective of designing a land mine detection unit might be sidetracked and

instead more efforts will be put into designing the robot.

Unmanned aerial vehicle (UAV) was taken into consideration while

brainstorming for the transporting unit for the system. It possesses attractive

advantages over land vehicles such as; ability to fly over a mine field without having

to worry about detonating the mines. However, the difficulty to maintain the air lift at

a constant height and the difficulty to maneuver the vehicle at low speed have put

negative weight from selecting it. Some UAVs can be as complex as a walking robot

in their own way; more time might have to be spent on designing it rather than

working on detection of land mines.

Figure 7. Landmine detection robot

equipped with metal detector

Therefore, the goal is a simple yet

workable concept. A vehicle with tracks system or

wheels hints as a correct choice. Since a decent

design can give good fraction, enough torque to

overcome obstacles and easy maneuvering ability,

this idea seems promising. Moreover, the

designing and fabricating a vehicle will be much

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cheaper and less time consuming than making a robot. Choosing between tracks or

wheels is not difficult since tracks system is usually more complex than wheels and

they both serve nearly identical purposes in this case. Therefore, it was decided that

the vehicle with wheels will be employed as a transporting unit for the mine detection

system.

After wheeled vehicles are chosen, the next stage of the challenge is avoiding

the mines. Dodging the robot around the mines in the mine field is not a smart option.

Therefore, a new way of avoiding the suspected mine buried spots was thought of.

The idea is to lift up the wheels on whose path lays a buried mine and another set of

wheels will touch down on the ground without having to move the robot. In other

words, there will be a mechanism to interchange between two sets of wheels, if there

lays a mine on the original path.

3.3 The data processing unit or control unit

A processing unit, installed on the robot, will be transmitting data from the

robot to the operator, such as images from the cameras, and it will receive and

process the commands from the operator to the robot. These signals will be

transmitted and received through radio channels and the command signals received

by the robot will be redistributed to the respective mechanisms to carry out the

required processes.

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The aim of the processing unit is to synchronize the movements of the

mechanisms to perform the desired job. This mine detection robot is intended to

detect the buried mines, make a mark on their locations and then continue looking for

another mine without disturbing the marked mine.

Firstly, the scanner which is located at the front of the robot processes a metal

detector that will scan and clear the path of 1.2m width. The scanner will stop

scanning if there is no detection of a mine, and the robot will advance one step

forward by activating the forward motor for 5 seconds. After which, the scanner will

restart its scanning sequence. The robot would move forward again with no detection

of mine. This scanning loop will continue until the scanner detects a mine.

Once the scanner detects a mine, the robot comes to a standstill and sends out

signals back to the operator by both illuminating the Light Emitting Diode (LED) as

well as beeping. The operator will then have to decide if it is a false alarm or a real

detection of a mine. If the operator takes the warning as a false alarm, he will ignore

it and restart the scanning loop. If warning is taken as a real detection of the mine, the

operator has to send a command to the robot to mark the location by spraying

distinctive colour paint on that spot.

Another decision that has to be made by the operator is if the detected mine

lies on the path of the wheels which are currently on the ground, he has to send out a

command to the robot to interchange with the other set of wheels. The command will

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set in motion the rolling down of the other set wheels and the lifting up of the set of

wheels that were originally on the ground. Now, the location of the detected mine has

been marked and the robot is ready to advance forward to search for another mine

without having to detour from its path.

Figure 8. Algorithm of the Processing Unit

POWER

START STOP

Scanner moves from L-R or R-L

No detection Detection of possible mine

Keep scanning until the scanner hits the other end

Position switch has been triggered

Stop the movement of the scanner

Change the direction of the scanner

Forward wheels activated for 5 sec

Light up LED

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In conclusion, our robot comprises of three major components, namely; a

carrying vehicle (wheels), a data processing unit and a mine detection unit.

3.4 Designing the location marking mechanism

After the location of a land mine has been exposed, it is required to mark the

position of the mine in order to facilitate the follow up demining process or to warn

the marching troops. The suggested ideas for mine location marking process will be

as followed.

Use GPS (Global Positioning System) to mark the location digitally.

Use Flags to indicate the location visibly.

Use bright color paints to highlight the location of a buried mine.

The first idea of using GPS to mark the location digitally might have been a

good idea if satellite communication system is easily accessible in any region of the

world. Moreover, the complexity of communication device that the robot needs to

carry will put some negative votes towards the idea. Demining will be difficult since

there is no visual indication of the exact location of the mine.

Indicating the location of discovered mines by flagging will be the best way to

warn the troops and the best way to initiate the demining. Nevertheless, the

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mechanism that the robot might possess in order to set up a flag upon finding mine

can be quite complicated and can cost a lot of time designing it.

The third idea of using paint to indicate the presence of a land mine could be a

simple and workable idea. Droplets of bright color paint will be dispersed from a

nozzle, right onto the soil that is covering a land mine. A simple mechanism

comprises of an electric motor, paint container, a few pipes and a nozzle, could be

able to perform the desired job. Paint will give out visual warning and indication of

the presence of a buried land mine.

3.5 Designing the mine avoiding mechanism

The first priority of the land mine detection robot is to expose the location of

the buried mines. Then it will be followed up by marking the location of the mine.

However, in order to sweep the whole mine field at one travel, the robot need to avoid

from detonating or stepping over the buried mines. In another words, the robot is

expected to sweep the mine field without detonating the marked mines. It needs to

avoid them, at the same time sweeping the mine field without leaving an undetected

square inch. In order to perform so, the robot must be capable of dodging the mines or

going over the mines without touching them.

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Dodging around the mine won’t be a good idea since it might lead to leaving

some undetected spots. Moreover, there is high possibility of detonating the mines

while trying to dodge around the mines.

The second option of the robot going over the mines without touching them

seems a complicated idea comparing to the idea of going around the mines. However,

a creative designing and careful consideration can give us a workable solution with

reliable mechanism. The suggested idea is described as followed.

There will be eight wheels suspended from the frame of the robot. Four

wheels at the front and four at the rare. Since the wheels are operating independently

from each other, some wheels can be lifted up in order to avoid the buried mines

while the rest will stay on the ground to support the robot.

At the start of the operation, only four outermost wheels will be placed on the

ground. If the detector has found a mine which lies on the path of either most-left

wheels or most-right wheels, the robot will stop from moving. It will put down the

rest four wheels onto the ground and now all eight wheels are on the ground. Then,

the robot will lift up the most outermost four wheels, leaving the center four wheels

on the ground to continue the mine sweeping operation. In this way, the mine which

lay on the path of either most-left or most-right wheels can be avoided. The robot will

repeat the operation from inside wheels to outside wheels if the detector finds mines

laying on the path of center wheels.

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Buried mine

Shaded block – Wheel touching the ground

Unshaded block – Wheel lifted up

Figure 9. The sequence of detected mine avoiding

mechanism

Outmost wheels are lifted up and center wheels touch the

ground.

Mine lies on the path of inside wheel.

Center wheels are lifted up and outmost wheels touch the

ground.

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Chapter 4 : Fabrication of the Prototype

Due to the factors of financial limitations, fabrication facilities limitations and

time constraints, the making of the actual robot has to be done in the later phase of the

project. Instead, a prototype is developed to represent the performance of the actual

robot. In the making of the prototype, care is taken to ensure that it closely resembles

the intended actual robot. Therefore, the prototype is of the same size as the actual

robot and the number of components is the same. The components in the prototype

are chosen or made as their functions are capable of performing as close as possible

to the real robot.

Figure 10.

Four different views of the prototype

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Figure 12. General view of 3D model

Figure 13. General view of the prototype

Figure 11. Top view of the Prototype

Components

- The Scanner

- The Location Marking Mechanism

- The Body

- The Processing Unit


4.1 The Scanner

Figure 14. Metal detectors on the prototype

Figure 15. Small vehicle that shuttle inside the

scanner, carrying the detectors from end to end

off-the-shelf metal

to represent the

etector on the actual robot. The metal

detectors consist of metal coils which

creates electric fields around the

detector. These electric fields are used

to detect any presence of conductive

materials or metals nearby. The

scanning width of the path is 1.2meters

and therefore by installing 2 metal

detectors separated 50centimeters apart,

instead of only one, will cut down the

scanning time by half. There are position

switches on both ends of the scanning

mechanism which guides it to move

from left to right and right to left as

every time the scanning mechanism

reaches the edge.

The detector is in constant communication with the processing unit and upon

sensing the metal in near proximity, the detector will alert the processor and it will

Two

detectors are deployed

d

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21

Figure 16. Simplify circuit diagram of paint

it

rocess. Consecutively, the output from the detector will be used to

eep to inform the operator. The detector

ommand from the operator to resume the

e warning signal, the operator has to decide

ccept that a mine has been detected. If he

e location marking mechanism will come

nsist c

is

tor

the

e is

hich

detected mine. Therefore,

lready positioned to mark the

spected area.

stop the scanning p

light up the LED and activate the warning b

will stop all motion and awaits the c

scanning sequence.

4.2 The Location Marking Mechanism

After the detector has sent out th

whether to ignore the warning or to a

decides that a mine has been detected, th

into use.

The location marking mechanism co

pump and a hose with nozzle.

The relay indicated in the figure

controlled wirelessly and once the opera

sends out a command, the relay will close

circuit and activate the pump. The nozzl

attached right next to the metal detector w

is now above the

s of a paint container, an electri

spraying unthe nozzle is a

su

-+

PUMP

RELAY


4.3 The Body

The purpose of the body is to house the components or mechanisms which are

required for the prototype to function.

The first concern in fabricating the body of the prototype is the material

es of alloys which cannot be selected for the fabrication of the prototype.

e, dimensionally unstable materials such as plastics and polymers are

not a b

l features. Hence, aluminium is the best choice.

ro-E), a solid model of the prototype

led drawings of the components are

te the fabrication of the components.

awings of the machined components.

that they are simple enough to be

in t

e 3-D model.

The body consists of the base structure and 2 major mechanisms. The purpose

of the base structure is to provide reliable support for the mechanisms and to

selection. This is due to the constraints of the fabricating facilities and the

complexities of the components. It is necessary to choose materials which are easy to

machine, cut and form. Thus, high strength materials such as steel, cast iron and

certain typ

At the same tim

etter option as well since some components in the body of the prototype

requires near precise dimensiona

By using 3-dimensional CAD software (P

is first created virtually. The engineering detai

created from the 3-D model in order to facilita

Please refer to the appendix for the detailed dr

The components are designed in such a way

fabricated with minimum requirement of mach

and fitting test are also carried out virtually in th

ing facilities. The interference tes

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23

accommodate d

Figure 17. The base structure of the prototype

re of the robot are mainly

fabricated with simple shearing

machine, electric cutting saw and

manual filing. Off-the-shelf

fasteners are used to assemble the

components while not forgetting to

consider the minimum strength

requirements of the structure.

ifferent devices intended for different purposes. The first mechanism

is the m tor that lift up or roll down the legs for mine avoiding purposes. The other

mechan

he components for the

structu

Howev

75 Mpa.

σyield = 110 Mpa

The req

o

ism is the robot legs with motorized wheels.

T

er, adjustments had to be made to the design of the components according to

the available raw material and components. The shaft of the rotating wheel is a good

example in this case.

Total weight of the vehicle, Wtotal = 16 kg

There will always be minimal of 4 wheels on the ground at any time.

Therefore, weight carried by each wheel or each shaft, Wshaft = 16 / 4 = 4 kg

The yield strength of the Brass (copper alloy) rod, 110 MPa to 2

uired diameter of the rod, R = ?

By using the safety factor of 2,


Let’s consider failure by shear,

σshear = Safety factor * (weight / cross sectional area)

σyield / 2 = 2 * (4*9.81 / π R2 )

Figure 18. The support plate that carries one front

and one rear wheel

π R2 = 4 * (4*9.81 / σyield )

1 / σyield )

m diameter rod is safe to use for this purpose.

eel possesses 2.5mm diameter through hole.

ize of the coupler which will connect the motor

ence, a 3mm rod is selected instead of 1mm

th virtual

R2 = (4 / π) * (4*9.8

R = 6.739 x 10-4 m

R ≈ 0.67 mm

It can be safely concluded that a 1m

However, the available rim for the wh

Moreover, the minimum available s

and shaft is also 3mm to 3mm. H

diameter copper rod.

Another good example to show

structure will be the deflection of the plate connecting the front wheel and rear wheel.

e lack of reality of the modeled 3-D

24


25

ate the possible deflection caused by the load from

deflection in the

support g pla

ssum heel be simple, single point support and the

load fro the le point loads. Assuming the load is

equally istribu ical design.

ortion of the robot + weight of the lifted up two other plates

a = 140 mm = 0.14 m

l = 600 mm = 0.6 m

I = (b * h3) / 12 = (0.08 * 0.0033) / 12 = 1.8 x 10-10 m4

E = 73.1 GPa (63 GPa – 73.1 GPa) [ Higher value is take because 3D model

doesn’t show any sign of deflection.]

By using the formula from “Mechanical Engineering Design, 7th edition”_

Deflection at the ce

y substitution of the numerical values,

y = 0.01198 m ≈ 12mm

3-D model did not indic

top. However, from the simplified free body diagram below, the

in te will be analyzed.

A ing that the support at the w

m lifting screws also be simple, sing

d ted due to symmetr

There will always be two plates at anytime, supporting the weight of 11 kg

(weight of the upper p

with four wheels)

Hence, W = 11 / 4 = 2.75 kg

nter, y = {(Wa) * (3l2 – 4a2)} / (24*E*I)

B


26

Figure 19. ¾” C-channel attached onto the

supporting plate in order to prevent deflection

Figure 20. Mine avoiding mechanism

tem to be

unstabl

ated as well. Components are created using materials available off

the she trength of the structure.

otor that

lift up

avoidin

ough a

plate. T

At any

on the

up. Wh

Above calculation has shown that

there will be deflection in the supporting plate

which in turn can cause the sys

e. Therefore, a ¾”C-channel is added

to reinforce the supporting plate to prevent it

from bending.

As per the above careful considerations, selection and fabrication, other

components are cre

lf without compromising the s

The first mechanism is the m

or roll down the legs for mine

g purposes. One front and one rear

wheel are paired up and connected thr

hus, there are four pairs of wheels.

point of time, two pairs of wheels are

ground while the other two are lifted

en a mine is detected in the line of


27

the lai

em. The lifting of each

late is executed by two 200rpm DC

motors. These motors will be activated by the

irelessly controlled relay.

he selection of the motors for this purpose is done by the following calculation.

, 10seconds.

s used to lift up one supporting plate, 2 motors.

d-down wheels, the other two

pairs of wheels will be rolled down

and the previously laid ones will be

lifted up. Each pair of wheels is lifted

up by means of threading up the plate

that connects th

pFigure 21.

Mine avoiding mechanism Inside set of wheels are lifted

uw p to avoid mine that might lies on their path

T

Weight of each supporting plate with front and rear wheel at the edge, 2.5 kg.

The height of the wheel needed to be lifted up, 4cm.

Desired time spending on lifting up the wheels

Number of motor

Motor

Threaded shaft Applied torque by the motor, T Angular velocity of the shaft, ω

Exerted force on the weight, F Moving up velocity, v

Weight to be lifted


28

Figure 22. Front wheel motor with speed controller

cm / 10 s = 0.4 cm/s = 4 x 10-3 m/s

per cm = 0.4 * 60 * 8 = 192 rpm

* (2π / 60) = 20.1 rad/s

ω

*

= 2.44x10-3 Nm

= 0.025 kg.cm

are followers of the front ones.

These 30rpm DC motors are

controlled by the processing unit.

The processing unit will close the

circuits for the front wheels’

motors momentarily in order to move

the robot one step forward between the

Power input equals output,

T * ω = F * v

F = weight carried by each motor = 2.5 k

v = moving up velocity of the weight = 4

RPM of the shaft = v * 60 * no. of thread

[ M8 , 1.25 thread is used.]

Angular velocity of the shaft , ω = RPM

Hence torque exerted by the motor, T = (F * v) /

= (12.2625

g / 2 = 1.25 kg = 12.2625 N

4x10-3) / 20.1

Hence, the motor with 206 rpm and 1.3 kg.cm torque is selected. ( Refer to the

appendix for the table of the selection of motors.)

The front wheels are

motorized whereas the rear wheels


scanning sequences. To turn the robot left and right, skid steer method is used. For

, it will be carried out separately by the remotely controlled relay and

e installed right

with the

ful calculation and

lculations are as follows.

N

rete pavement is between

on the

lue and usually it is between 0.016

nd 0.05, therefore μ = 0.05

= F * v

e ground at any time, whereby only two is

equired to be generated by each motor, P motor =

nd the power is defined as, P = T * ω , where

this movement

independent from the processing unit. The speed controller circuits ar

before the motors to fine tune each rotational speed in order to synchronize

other motors.

The selections of the motors were made after care

determination of the specifications required. The ca

For the forward moving motors-

Total weight of the robot, WT ≈ 16 kg * 9.81 = 156.96

Static fractional coefficient between the rubber and the conc

0.6 to 0.8 for the case of dragging motion, however, for the case of rolling moti

coefficient of friction doesn’t reach to its max va

a

Frictional force, F = W * μ

Velocity of the robot, v

Power required to move the robot, P

There are always four wheels on th

powered by motors. Hence, power r

(F*v)/2

The relationship between the torque a

ω = the angular velocity of the wheel

29


30

Figure 23. Processing unit comprises of a 12 remote-controlled relays unit and a programmable

micro-controller

= 0.235 Nm

= 2.4 Kg.cm

pm.

y plate is used to accommodate the processing unit,

is electrically conductive,

stem. They combine

ommands. Assembly

Hence, (F*v) / 2 = T * ω

T = (F*v) / (ω * 2)

= (F * r) / 2 , where “r” is the radius of the wheel

= (156.96 * 0.05 * 0.06) / 2

The required torque for the motor is decided as 6 kg.cm with the speed of 30 r

The free space on the bod

electrical circuits and battery packs. Since aluminium

insulating layers are installed in between the electrical components and the

aluminium body plate.

4.4 The Processing Unit

The main components

of the prototype processor are

the 16 legs microprocessor and

12 channels remote control

relay sy

together to process the input

data and generate the output

c

Programmable micro-controller

Remote control

12 remote-controlled relays unit


Figure 24. Simplify connections of inputs

ts at the microcontroller

e program according to the algorithm that had been

enerat . Th o the processor are as followed. The scanner

of the scanner

The output signals go to the scanning

echanism, th motors, the paint pumps and the lifting mechanisms.

l

ts at the microcontroller

e program according to the algorithm that had been

enerat . Th o the processor are as followed. The scanner

of the scanner

The output signals go to the scanning

echanism, th motors, the paint pumps and the lifting mechanisms.

l

language is used to write up thlanguage is used to write up th

g ed e input signals intg ed e input signals int

activation command from the operator, signals from position switchesactivation command from the operator, signals from position switches

and feed back signals from the detectors. and feed back signals from the detectors.

m e front wheels’ m e front wheels’

and outpu

PINS

Inputs ( excluding power supply pins )

1. left side push button

2. right side push button

3. main switch from remote contro

4. from metal detector

utpu

PINS

Inputs ( excluding power supply pins )

1. left side push button

2. right side push button

3. main switch from remote contro

4. from metal detector

pins 3 output pins 4 input

From L ft Side e Push button

From Right Side Push button

From Main switch ( remote )

From Metal detector

Rotate left

Rotate right

To wheel motor

Microcontroller

31


Outputs

5. rotate left

6. rotate right

7. to wheel motor

32


Alg

wh 1. initialize one direction ( either turn on P5 or P6 )

2. check P3 until it is high, once high, go to step 2. no need

check again.

2. ( internal ) put a flag inside microcontroller to give direction. When

initializing the direction, or whenever there is a change in P1 or P2, this flag

will change to give the direction. The flag will be either high or low to give

right or left to go. Set this direction flag ( DF ), to “low” if the first

initialization is to left direction, or “high” if initialization is to right. Once P1

is set ( high voltage ), set DF to high, and if P2 is set, set DF to low. The flag

should not be changed until the next change occurs at P1 or P2 ( it should

hold its state until microcontroller is turned off ).

3. check the direction flag ( DF ) all the time ( by using some looping ),* if it is

low ( say representing “left” ), then turn on P5 ( give a high voltage ) , and if it

is high ( say representing “right” ), then turn on P6 ( give a high voltage ) .

Either P5 or P6 will turn on at a time, not both. Important Once the flag

is detected with change in voltage, turn off both P5 and P6 for about 5

seconds ( let’s call this wheel moving time ). ( need to use buffer to check

the change in DF: store current state in something, when the loop checks

the DF again, check that value with the previously stored value. If it does

not change, then overwrite stored value with the currently checked one.

Then loop again ) Do not check the flag during this time (wheel moving

time). And during this time, turn on P7 ( which is connected to wheel

orithm

en power up

to

33


motor ). REASON : pause the scanner and move forward. Then turn off P7

4. check P4 all th

P6, P7. No nee , except P3. wait until P3 is set. If it is set, go

and *do direction change.

e time. Once it is set, stop everything, meaning : turn off P5,

d to check inputs

to step 2.

34


Chap

e

actual r l

detecto they are made of cheap components and thus the reliability is

ncertain. They are only able to detect metals that are larger than M8 nut. Sometimes,

false alarms are given out due to detecting its own metal component from the circuit.

However, this problem is solved by separating the detecting coil from the circuit with

the use of plastic plates.

Another problem arises from the detector is that after the location of the metal

has been marked, the scanning mechanism is supposed to restart and continue looking

for another buried metal, however, it detects back the marked metal which is still in

its close proximity. The warning alarm keeps on signaling without the scanner

moving away from the marked area. This is solved by temporarily switching off the

detectors while the scanning mechanism moving away from the detected metal.

The third problem occurs in the DC motors. These motors are not precision

displacement providing motors. They are made to provide speed and torque closest to

their specifications, but not the exact amount. Therefore, the motors installed on the

front wheels are rotating at slightly different speeds which cause the robot to sway

towards the slower rotating wheel’s side. At the same time, the lifting up process of

the wheels and interchanging process of the sets of wheel in order to avoid the mines,

ter 5: Experimental Results

The test runs carried out with the prototype assure us of the success of th

obot, except for some minor problems. The first problem arises from the meta

rs. Since

u

35


are also disturbed by the misalignment caused by the different in speeds of the lifting

otors. Thus, speed controller circuits are installed prior to the motors in order to m

synchronize their speeds before using them in the mine searching process.

However, these minor problems won’t occur in the actual robot since they are

caused by the poor quality of the equipments not due to the concept or design of the

robot.

36


Chapter 6: Conclusion

It has been successfully proven through the prototype that the proposed theory

and concepts for a landmine exploring platform works perfectly. The prototype is

capable

e path with 1.2m width at one go. With the use of interchangeable four

wheels, the marked locations can be avoided without requiring the prototype to dodge

around that spot. And most importantly, the prototype is controlled wirelessly by the

operator from a safe distance. The greatest advantage that this robot offers is the

safety for the soldiers. Not only does it mark the possible locations of buried mines, it

also rolls over the places that it deems as safe thus acting as a sacrificial object. This

means that if the operator or the soldiers follow the tire tracks, they are perfectly safe

since the robot has already rolled over it.

Thus, the proposed design for landmine detection and marking module had

opened up a new area for the researchers to explore. Saving the lives and limbs of

innocent civilians becomes one step closer.

of detecting the buried metal pieces, marking the exact location with

distinctive colour paint, and controlling itself from stepping over it. It is also able to

clear th

37


Chapter 7: Recommendations

d be carried out on the performance of

Infrared Thermal Imaging cameras relative to the landmines. The literature research

informa

This project has fulfilled most of its objectives and has even gone beyond in

some aspects. The requirement whereby it states that the robot must detect 90% of the

mines is beyond the limitations that are set by the circumstances of this project.

Among all the detectors, metal detectors are the most unfavorable type as most of the

mines are made with plastic bodies. The other options which are the use of GPR

(ground penetration radar) and thermal imaging cameras are beyond this project’s

budget and moreover they require military clearance from the United States

Government. Therefore, the research on the detection of mines and differentiation of

false alarm versus real warning was unable to be carried out and that objective was

compromised. However, the literature survey has been done on the performance of

Infrared Thermal Imaging cameras and its results are promising. Thus, it is

recommended that further research shoul

tion is attached in the appendix.

38

Landmine detection and marking robot References

References

1. Making landmine detection and removal practical

http://www.llnl.gov/str/Azevedo.html

2. “Landmine detection in bare soils using thermal infrared sensors” by

Sung-ho Hong, Timothy W. Miller, Brian Borchers, and Jan M.H. Hendrickx

New Mexico Tech, Socorro NM 87801

TNO Physics and Electronics Laboratory, The Hague, The Netherlands.

Henk A. Lensen, Piet B.W. Schwering and Sebastiaan P. van den Broek

3. Use of Unmanned Aerial Vehicles (UAVs) for Land Mine Detection

http://www.mondialogo.org/129.html

4. How stuff works.

www.howstuffworks.com

5. Ugural, A.C, “Mechanic of Materials” , McGraw-Hill, 1993

6. Beer, Ferdinand P. and Johnston, E. Russel Jr., “Vector Mechanics for Engineers –

Statics” , McGraw-Hill, Toronto, 1998

7. Beer, Ferdinand P. and Johnston, E. Russel Jr., “Vector Mechanics for Engineers –

Dynamics” , McGraw-Hill, Toronto, 1999

8. Shigley, Mischke, Budynas., “Mechanical Engineering Design”. Seventh Ed,

McGraw-Hill.

9. Serway, Beichner., “Physics for Scientists and Engineers with Modern Physics”.

Fifth ed, Saunders college Publishing.

39

Landmine detection and marking robot Appendices

Appendices

40


A

N37-GR GEARED MOTOR

MOTOR SPECIFICATION

D.C 6V D.C 12V D.C 24V

CURRENT SPEED TORQUE OUTPUT EFF DESCRIPTION

A RPM g-cm Watt %

6V 0.20 6200

12V 0.12 6200 NO LOAD

24V 0.06 6200

6V 0.79 5140 54.5 2.87 60.67

12V 0.47 5100 59.81 3.14 55.60 AT MAX.EFF

24V 0.212 5000 61.67 3.17 62.31

6V 3.50 320

12V 2.20 340 AT STALL

24V 0.9 320

GEARED MOTOR SPECIFICATION Possible to producting for needs of ratio beside bellow chart.

RATIO V 1/

6

1/

10

1/

18 1/

30

1/

40

1/

60

1/

80

1/

100

1/

120

1/

150

1/

180

1/

200

1/

250

1/

300 1/

400

1/ 1/ 1/

500 600 750


B

"L"-SIZE 24.8 27.3 29.8 32.3

6 1033 620 344 206 155 103 78 62 51 41 34 31 24 21 15 12 10 8

12 1033 620 344 206 155 103 78 62 51 41 34 31 24 21 15 12 10 8 NO LOAD

(RPM) 24 1033 620 344 206 155 103 78 62 51 41 34 31 24 21 15 12 10 8

6 856 514 285 171 128 85 64 51 43 34 28 26 21 17 13 10 8.6 6.8

12 850 510 283 170 128 85 66 51 43 34 28 26 21 17 13 10 8.5 6.8 AT MAX.EFF

(RPM) 24 833 500 277 166 125 83 63 50 41 33 27 25 20 16 12 10 8 6.5

6 0.2 0.4 0.7 1.2 1.4 2.1 2.8 3.5 3.8 4.8 5.8 6.0 6.0 6.0 6.0 6.0 6.0 6.0

12 0.3 0.5 0.8 1.3 1.5 2.3 3.1 3.9 4.2 5.3 6.0 6.0 6.0 6.0 6.0 6.0 6.0 6.0

TORQUE

(Kg-cm)

24 0.3 0.5 0.8 1.3 1.6 2.4 3.2 4.0 4.3 5.4 6.0 6.0 6.0 6.0 6.0 6.0 6.0 6.0

The selection of motors for the mine avoiding mechanism.


Specifica on an lection of lable Infra-r hermal imagiti d Se avai ed T ng

camera

f e a d m a a a r a t w

ifferent purposes. They can be categorized into four types according to their

of in a g e l

Monochromatic; contain a single type of sensor responding to single

es are represented as black,

white or gray according to the intensity of the radiation of the objects. They are

mostly used as night vision cameras.

Color cameras; complex construction of various sensors responding to various

ranges of infrared radiation. However, these cameras display the colors in order to

indicate the intensity of the radiation from the objects and hence different color

represents different temperature range.

Cooled infrared detector; the sensors are contained in a vacuum-sealed case

and cryogenically cooled. Since the temperature of the sensors are much lower than

that of the object, their sensitivity is increased. However, they are expensive to

produce and time consuming to use, since they are required to cool down before put

to use.

Di

serve d

fer nt types of infr re ca er s are m nuf ctu ed round he orld to

methods

captur g and portr yin the th rma images.

wavelength range of infrared radiation. The captured imag

C


Uncooled infrared detector; uses the sensors operating at ambient temperatur

These unc

e.

ooled infrared sensors are capable of measuring the intensity of the thermal

red to cool down with cryogenic cooler.

This is done by using the Micro-Bolom

era which possesses medium range sensitivity to

differentiate the objects having a

radiation intensities of the objects. Color

infrared cameras are best at describing the differences in the thermal profiles of the

objects sin

e. While, uncooled infrared detector offers

medium sensitivity at lower cost.

radiation of an object without being requi

eter as sensor which is a form of particle

detector. They are small in size and not expensive to produce.

In our case, we require a cam

slight temperature difference.

Monochromatic cameras are used mainly as night vision cameras since their

display can’t provide clear differentiation of

ce they indicate the warmest parts are customarily colored white,

intermediate temperature objects as reds and yellows, and the coolest parts as blue.

Cool infrared detector provides us with great sensitivity; however it comes together

with higher cost and longer preparation tim

Therefore, it will be wise to choose color infrared camera with uncooled

detector since this combination can provide us with good thermal profile display to

identify land mine among surrounding soil and rubbish, at a cheap price.

D


There are a few infrared camera suppliers in Singapore and the following is

the comparison of two reputable infrared cameras available in Singapore.

NEC TS 9100 M Electrophysics PV-320 T

E


F

Table 1. Comparism of Thermal imaging

cameras provided by two different companies

V 320 T Brand / Model NEC / TS9100M Electrophysics / P

Measuring Range - 20°C to 100°C - 10°C to 500°C

lution 0.06° C 0.08° C Reso

Accuracy ±2°C or ±2 % ±2°C or ±2 %

Detector Uncooled Bolometer Uncooled BST

Spectral Range 8 to 14μm 8 to 14μm

Frame Time 60 frames / sec 30 Hz

Thermal Image Pixels 320 (H) x 240 (V) pixels 320 (H) x 240 (V) pixels

Interface RS-232C or Ethernet USB 2.0 High Speed

Operating Temperature -15 to 50°C -20 to 45°C

Dimensions ( 12 (H 140 (W) x 114 (H) x 114 ( 99 W) x 1 ) x 206 (D)

mm

D)

mm

Weight 2.6 kg 1.2 kg

Price

From the above comparison, even though different camera models are produced by

different manufacturers, their capabilities and services are tailored for certain range of

application. Hence, we are only required to choose according to their availability,

prices and compatibility with others equipments in our robots.


D mine b he explosivetecting the y sniffing for t e inside the mine

Although up to 53% of minefields are unstructured terrain in uneasy

ccessible areas, often covered by thick ve ost of the machines proposed to

e used in humanitarian demin t, regular terrain,

lready cleared from vegetation. The f crawling inside the thick

nto

sors to the

minefield by carrying them on a suitable platform, while the other method consists in

bringing air samples from the minefield to the sensors, located in a remote safe place.

a getation, m

b ing are designed to operate on fla

refore, new means oa

vegetation have been considered and applied to the robots presented.

The solutions proposed encompass two methods of locating landmines, both using

sensors detecting traces of explosives escaping from mine casing into the soil and i

the air over the landmine. One method consists in bringing the sen

G


This second method is called REST (Remote Explosive Scent Tracing); it is currently

used by two demining agencies.

H


I

Off the shelf metal detector used in the Prototype


Alternative detection system for the robot

The robot equipped with infrared thermal imaging cameras

The basic structure of the robot without processing unit and detection unit

J


K

Documents

Mine detection and marking robot.pdf