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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
IX
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.
1
Landmine detection and marking robot
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
2
Landmine detection and marking robot
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.
3
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
4
Landmine detection and marking robot Chapter 2
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.
5
Landmine detection and marking robot Chapter 2
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.
6
Landmine detection and marking robot Chapter 3
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.
7
Landmine detection and marking robot Chapter 3
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.
8
Landmine detection and marking robot Chapter 3
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.
9
Landmine detection and marking robot Chapter 3
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
10
Landmine detection and marking robot Chapter 3
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.
11
Landmine detection and marking robot Chapter 3
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
12
Landmine detection and marking robot Chapter 3
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
13
Landmine detection and marking robot Chapter 3
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
14
Landmine detection and marking robot Chapter 3
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.
15
Landmine detection and marking robot Chapter 3
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.
16
Landmine detection and marking robot Chapter 3
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.
17
Landmine detection and marking robot Chapter 4
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
18
Landmine detection and marking robot Chapter 4
19
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
Landmine detection and marking robot Chapter 4
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
20
Landmine detection and marking robot Chapter 4
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
Landmine detection and marking robot Chapter 4
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
22
Landmine detection and marking robot Chapter 4
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,
Landmine detection and marking robot Chapter 4
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
Landmine detection and marking robot Chapter 4
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
Landmine detection and marking robot Chapter 4
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
Landmine detection and marking robot Chapter 4
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
Landmine detection and marking robot Chapter 4
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
Landmine detection and marking robot Chapter 4
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
Landmine detection and marking robot Chapter 4
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
Landmine detection and marking robot Chapter 4
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
Landmine detection and marking robot Chapter 4
Outputs
5. rotate left
6. rotate right
7. to wheel motor
32
Landmine detection and marking robot Chapter 4
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
Landmine detection and marking robot Chapter 4
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
Landmine detection and marking robot Chapter 5
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
Landmine detection and marking robot Chapter 5
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
Landmine detection and marking robot Chapter 6
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
Landmine detection and marking robot Chapter 7
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
Landmine detection and marking robot Appendices
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
Landmine detection and marking robot Appendices
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.
Landmine detection and marking robot Appendices
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
Landmine detection and marking robot Appendices
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
Landmine detection and marking robot Appendices
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
Landmine detection and marking robot Appendices
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.
Landmine detection and marking robot Appendices
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
Landmine detection and marking robot Appendices
This second method is called REST (Remote Explosive Scent Tracing); it is currently
used by two demining agencies.
H
Landmine detection and marking robot Appendices
I
Off the shelf metal detector used in the Prototype
Landmine detection and marking robot Appendices
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
Landmine detection and marking robot Appendices
K