Post on 13-Feb-2017
WAR TANKER WITH AUTOMATIC SENSING OF HIT DIRECTIONS A PROJECT REPORT SUBMITTED TOWARDS PARTIAL FULFILLMENT FOR THE AWARD OF
BACHELOR OF TECHNOLOGY
IN
MECHANICAL ENGINEERING (MECHATRONICS)
BY
B HEMANTH KUMAR (11261A1406) BADI SAI NIHANTH REDDY (11261A1408) BANGARI SAI RAJ MICHAEL BABU THOMAS
(11261A1410) (11261A1443)
UNDER THE ESTEEMED GUIDANCE
OF
Dr. S. Madhava Reddy
Associate Professor
Department of Mechanical Engineering (Mechatronics) DEPARTMENT OF MECHANICAL ENGINEERING (MECHATRONICS)
MAHATMA GANDHI INSTITUTE OF TECHNOLOGY
(Affiliated to JNTU, Hyderabad) Accredited by NBA-
AICTE, New Delhi GANDIPET, HYDERABAD-
500075, TELANGANA www.mgit.ac.in
April 2015
DEPARTMENT OF MECHANICAL ENGINEERING (MECHATRONICS)
MAHATMA GANDHI INSTITUTE OF TECHNOLOGY
(Affiliated to JNTU, Hyderabad) Accredited by NBA-
AICTE, New Delhi GANDIPET, HYDERABAD-
500075, TELANGANA www.mgit.ac.in
CERTIFICATE This is to certify that this project titled “WAR TANKER WITH AUTOMATIC SENSING OF HIT DIRECTIONS” has been submitted by: B HEMANTH KUMAR (11261A1406)
BADI SAI NIHANTH REDDY (11261A1408) BANGARI SAI RAJ (11261A1410) MICHAEL BABU THOMAS (11261A1443)
We hereby accord our approval of it as project work carried out and presented in a manner required for its acceptance in partial fulfillment for the award of Bachelor of Technology in Mechanical Engineering (Mechatronics). The results and work embodied in this project have not been submitted to any other University or Institution for the award of any degree or diploma. INTERNAL GUIDE HEAD OF THE DEPARTMENT
(DR. S MADHAVA REDDY) (Dr.K.SUDHAKAR REDDY) INTERNAL EXAMINER EXTERNAL EXAMINER
ACKNOWLEDGEMENT We would like to express our gratitude to a number of people, to whom we owe the success of our project. We have great pleasure in expressing our indebtedness to our internal guide Dr. S. Madhava Reddy, Associate Professor, Department of Mechanical Engineering (Mechatronics) for his constant help at this stage. We thank Dr. K. Sudhakar Reddy, Professor and Head of the Department, Mechanical Engineering (Mechatronics) for guiding us through proper grooves and giving us the necessary support. We also thank Dr. G. Chandra Mohan Reddy, Principal MGIT for inspiring and motivating us throughout the work. We would also like to thank all the Faculty members and non-teaching staff of MGIT who helped for the completion of the present work directly or indirectly.
With gratitude,
B HEMANTH KUMAR (11261A1406) BADI SAI NIHANTH REDDY (11261A1408) BANGARI SAI RAJ (11261A1410) MICHAEL BABU THOMAS (11261A1443)
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ABSTRACT
The robot is equipped with gun mechanism can be controlled through RF based remote
controlled technology A toy gun arranged over the vehicle is designed to rotate freely for
hunting the enemies and is controlled through the remote. The system designed here can be
used for many applications; it can be used as a hunting robot at boarders to destroy the
enemies crossing the border. The same system can be used as warfare vehicle in war fields.
The system designed here is unmanned vehicle that is equipped with a toy gun is
controlled through the remote. The robot can be controlled in two formats i.e., one in
manual mode of operation and the other in automatic mode of operation. In the manual
mode of operation, the operator can control the tanker through remote and can chase the
rivals from a secured place. The vehicle can be controlled in all directions; similarly the
gun can be positioned towards the target through same remote. The gun moving mechanism
can be positioned towards the enemy direction through the remote itself.
In the automatic mode of operation, the operator can only control the robot (tanker)
movement i.e., forward, backward, right and left directions. The gun moving and firing
mechanisms are automatically taken care by the robot itself depending on the direction
from which the tanker is hit. Depending on the direction from which the tanker is hit, the
gun will be automatically moved or rotated to that particular direction and fires. When the
system is utilized at boarders, the system can be controlled from the bunker through remote
designed with ZigBee modules.
So the remote control unit is designed using push buttons and MEMS modules. The
push buttons are used to control the position of the gun in two axes along with the firing
mechanism. So a total of seven push buttons are used. The MEMS is used to control the
movement of the war tanker in four directions i.e., forward, backward, right and left.
MEMS (Micro Electro Mechanical Sensor) is the device often used as position
displacement sensor. The applications of MEMS are plenty and to prove the application
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practically this system is designed to control the robot by changing the position of MEMS
device. Micro Electro Mechanical Systems (MEMS) is the integration of the mechanical
elements, sensors, actuators and electronics on a common silicon substrate through micro
fabrication technology. The broadest requirement for these very small devices is ability to
sense the environment, to collect necessary data and to create a signal or action to make
desired changes to the environment. The MEMS is like a motion sensor. Slight variation in
the X, Y, or Z – axes gives the voltage variation that is fed to the ADC and the digital
information from ADC is fed to the controller. Depending on this data the controller
transmits the information through the ZigBee transmitter depending on which the tanker
will be controlled.
In this concept the operator is safe as he will be in bunker. The microcontroller used in
this project work is programmed to control the motors independently. Four DC motors with
inbuilt reduction gear mechanism are used to drive the complete mechanical transmission
section of the robot, depending up on the control signals generated and transmitted from the
remote. The robot moves in all directions and gun is also controlled independently. In the
four DC motors two are used for the robot movement and two are used for the gun
movement in vertical and horizontal directions.
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TABLE OF CONTENTS
1. INTRODUCTION 1
1.1 Potential of Unmanned Warfare 2 1.2 Need For Unmanned Applications 2 1.3 Unmanned Ground Vehicles 2
1.3.1 Tele Operated UGV 3 1.3.2 Autonomous UGV 3
1.4 Unmanned Warfare In Air 4 1.5 Lethal UAV 4 1.6 Naval Unmanned warfare 6 1.7 Under Sea Vehicles 6 1.8 Anti-Submarine Warfare 7
2. BRIEF INTRODUTION ABOUT WARTANKERS 8
2.1 Wartanker 8 2.1.1 Light Tanks 9 2.1.2 Heavy Tanks 10 2.2 History 10
3. FUNTIONAL DISCRIPTION 12
3.1 Remote Control Unit 12 3.2 ADC (Analog to Digital Convertor) 14 3.3 Clock Generator 17 3.4 Zigbee Module 18 3.5 Mechanical Actuation Section 20 3.6 DC Motor 22 3.6.1 DC Motor Specifications 25 3.7 H-Bridge 25 3.7.1 Basic Structure of H-Bridge 26 3.7.2 H-Bridge Operation Summary 27 3.7.3 Transistors As Switch 28 3.7.4 L293D H-Bridge(Driver) 30 3.8 Limit Switches 30 3.9 UM3562 (Gun Sound Generator) 32
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3.9.1 General Description 32 3.9.2 Features 32 3.9.3 Pin Description 33 3.10 Relay 34 3.11 Power Source 36
4. BLOCK DIAGRAMS AND CIRCUIT DIAGRAMS 37
5. DETAILED DESCRIPTION ABOUT MEMS 41
5.1 MEMS - An Overview 41 5.2 Advantages and Challenges MEMS 42 5.3 Fabrication Technologies 43 5.3.1 Bulk Micro Machining 43 5.3.2 Surface Micro Machining 44 5.3.3 Moulding 45 5.4 Actuation 46 5.4.1 Electrostatic Actuation 46 5.4.2 Thermal Actuation 48 5.5 MEMS in Optical Circuits 49 5.6 Sensors 50 6. BRIEF DESCRIPTION ABOUT ZIGBEE COMMUNICATION 52 6.1 ZIGBEE Networks 52 6.2 Architectural Overview 55 6.2.1 Physical Layer 56 6.2.2 MAC Layer 56 6.2.3 Network and Security layer 56 6.2.4 Application Support Sub-Layer 57 6.3 Application Framework 58 6.4 ZIGBEE Device Objects (ZDO) 58 6.5 Data Transfer Mode 58 7. DESCRIPTION OF H-BRIDGE 60
7.1 Introduction 60 7.2 Basic Theory 60 7.3 L293D Dual H-Bridge Motor Driver 63
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8. DC MOTORS 66 8.1 Overview 66 8.2 Principles of Operation 68 8.3 Types of DC Motors 69 9. DESCRIPTION OF MICRO CONTROLLERS 73 9.1 Introduction 73 9.2 Necessity of Microcontrollers 73 9.3 Features of Microcontrollers 73 9.4 Advantages of Microcontrollers 74 9.5 Features of 8051 Architecture 74 9.6 8051 Microcontroller Architecture 75 9.7 Pin Diagram 75 9.8 Functional Block Diagram of Microcontroller 77 9.9 Alternate Functions of Port3 Pins 77 9.10 The 8051 Oscillator and Clock 79 9.11 Types of Memory 79 9.11.1 Code Memory 80 9.11.2 Internal RAM 80 9.11.3 Special Function Registered Memory 80 9.11.3.1 Accumulator 80 9.11.3.2 B Register 81 9.11.3.3 Stack pointer 81 9.11.3.4 Data pointer 81 9.11.3.5 Program counter 81
9.12 I/O Ports 82 9.12.1 PORT 0 82 9.12.2 PORT 1 82 9.12.3 PORT 2 82 9.12.4 PORT 3 82
9.13 Interrupts 83
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10. HARDWARE DETAILS 85
10.1 Components used in the Project Work 85 11. SOFTWARE DETAILS 86 11.1 KEIL Software 86 11.2 Simulation 86 11.3 Use of Software for Execution of Microcontroller Programs 86 11.4 Problems Faced by Embedded Software Developers 86 12. CONCLUSIONS AND REFERENCES 88 12.1 Conclusions 88 12.2 References 88
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LIST OF FIGURES
FIGURE NO. TITLE PAGE NO.
2.1 War Tanker 08
3.1 Block Diagram for Converting Analog to Digital Form 15
3.2 Circuit Diagram of Analog to Digital Converter 16
3.3 H Bridge 26
3.4 Two Basic Stages of H Bridge 27
3.5 NPN and PNP Transistors switch configurations 27
3.6 DC Motor Control with H Bridge 29
3.7 L293D 29
3.8 Limit Switch 31
3.9 Schematic of Relay with Contact 35
4.1 Block Diagram of Vehicle Control Station 37
4.2 Block Diagram of Warfare Vehicle 38
4.3 Circuit Diagram Warfare Vehicle 39
4.4 Circuit Diagram of Vehicle Control Station 40
5.1 Titanium Mirrors Bulk Micromachining 43
5.2 Electrostatic Comb Drive Fabricated Using SUMMIT 45
5.3 Extremely Low Loss Coplanar Waveguide Using LIGA 46
5.4 Parallel Plate Actuator 47
5.5 Comb Drive Actuator 48
5.6 Types of MEMS Lens Arrays 49
5.7 Thermal Amplification Approaches 50
6.1 ZIGBEE Module 52
6.2 ZIGBEE Mesh Networking 53
6.3 ZIGBEE in Home Automation 54
6.4 Architectural Overview 55
6.5 Application Support Sub layer 57
7.1 H Bridge 60
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7.2 Transistors as H Bridge 62
8.1 DC Motors 69
9.1 Pin Diagram of AT89C51 76
9.2 Block Diagram of Microcontroller 77
9.3 Oscillator and Timing Circuit 79
LIST OF TABLES
TABLE NO. TABLE TITLE PAGE NO.
3.1 Configuration of MEMS Module 14
3.2 Specifications of DC motor 25
3.3 Voltages Supplied in H Bridge 26
3.4 Pin Description of UM 3562 33
6.1 ZIGBEE Specifications 59
7.1 Working Conditions of H Bridge 61
7.2 Truth Table of Half Enabled H Bridge 64
7.3 Truth Table of Full Enabled H Bridge 65
8.1 Types of DC Motors 71
9.1 Various Functions of Port 3 78
9.2 Interrupts and Their Addresses 83
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Chapter – 1
INTRODUCTION
Manpower scarcity has been a perennial problem for many armed forces around the
world. Over the years, there has been a decline in the absolute numerical make-up of these
organizations, which, if not managed properly, can affect their operational capabilities. This
scarcity is a situation that is unlikely to improve in the foreseeable future, given the current
low birth rates and conflicting demands for manpower.
From a numerical perspective, this constraint means that the armed forces cannot mass
together the sheer number of ground troops as before. From a risk perspective, every soldier
on the battlefield is now a precious resource which should not be exposed to unnecessary
risks. This translates into further constraints for battle planners, who may not have the
leeway to select the riskier but more expedient military options. Finally, from the skills
perspective, smaller population bases make it difficult to find, select, train and develop
specialized combatant resources like pilots and submariners.
Thus, it is crucial that new avenues be explored to circumvent this prevalent trend of
manpower shortages. One viable solution lies in exploiting technology and pushing the
limits of force multipliers. Within the domain of force multipliers, there lies a relatively
new discipline, unmanned warfare.
The definition of 'unmanned' chosen for this article is fairly loose, as the emphasis is not
solely on taking men out of machines but also on how to employ technology to make better
use of its manpower. Thus, while the focus is on unmanned warfare in its literal sense, the
article will also touch on some equipment or systems which result in lower manpower
usage (or higher operational capability with the same manning). In doing so, please accept
that some aspects of this article border on technological innovation as opposed to
unmanned warfare per se.
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1.1 Potential of Unmanned Warfare
Unmanned warfare is a relatively new approach in the conduct of warfare, where the
boundaries are not well charted and limited largely by our imaginations. Unmanned warfare
will not only help overcome manpower and resource constraints but will also enhance
operational capabilities, since it can now move into areas where mankind has previously
feared to tread. With unmanned warfare, the competitive advantage can be swung such that
human numerical superiority is no longer an overwhelming advantage or a pre-requisite for
victory.
1.2 Need for Unmanned applications
The impetus to go unmanned include optimizing the deployment of manpower,
enhancing operational capabilities and being able to venture into territory once out-of-
bounds to mankind (e.g. deep ocean, space, etc). In particular, unmanned systems should be
used to replace humans where the work is dangerous, dirty or dull.
Some specific advantages in going unmanned include:
• Reduction in manpower requirement
• Overcome fatigue and human error
• Minimize hazards
• Cost savings
• Decision making
• Applicability
Department of Defense (DOD) Unmanned Ground Vehicles (UGV) save lives and
improve national defense capabilities by providing agencies of the Department of Defense
(DOD) with the control system architectures, advanced sensor systems, research services,
and standards to achieve autonomous mobility for unmanned ground vehicles.
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1.3 Unmanned Ground Vehicles (UGV)
They are robotic platforms that are used as an extension of human capability. This type
of robot is generally capable of operating outdoors and over a wide variety of terrain,
functioning in place of humans.
UGVs have counterparts in aerial warfare (unmanned aerial vehicle) and naval warfare
(remotely operated underwater vehicles). Unmanned robotics is actively being developed
for both civilian and military use to perform dull, dirty, and dangerous activities. Some
UGVs are employed in War in Iraq. There are two general classes of unmanned ground
vehicles: Tele-operated ones and Autonomous ones. An unmanned ground combat vehicle
(UGCV) is an autonomous, all terrain unmanned ground vehicle designed for combat.
1.3.1 Tele-operated UGV
A tele-operated UGV is a vehicle that is controlled by a human operator at a remote
location via a communications link. All cognitive processes are provided by the operator
based upon sensory feedback from either line-of-sight visual observation or remote sensory
input such as video cameras. A basic example of the principles of tele-operation would be a
toy remote control car. Each of the vehicles is unmanned and controlled at a distance via a
wired or wireless connection while the user provides all control based upon observed
performance of the vehicle.
There are a wide variety of tele-operated UGVs in use today. Predominantly these
vehicles are used to replace humans in hazardous situations. Examples are warfare,
explosives and bomb disabling vehicles.
1.3.2 Autonomous UGV
An autonomous UGV is essentially an autonomous robot but is specifically a vehicle
that operates on the surface of the ground.
A fully autonomous robot in the real world has the ability to:
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• Gain information about the environment.
• Work for extended durations without human intervention.
• Travel from point A to point B, without human navigation assistance.
• Avoid situations that are harmful to people, property or itself, unless those are part
of its design specifications
• Repair itself without outside assistance.
• Detect objects of interest such as people and vehicles.
• A robot may also be able to learn autonomously
1.4 Unmanned Warfare in the air
Plagued with constraints of limited human resources and a sizable reduction in the pool
of youths who fulfill stringent recruitment requirements, air forces around the world will be
compelled to explore means to maintain or extend their operational capabilities with an
increasingly trim fighting force.
The employment of unmanned platforms in the modern battlefield serves to alleviate
problems caused by the shortage in manpower and resources. In employing unmanned
platforms, pilots may also be removed from aircraft penetrating defended enemy airspace,
thus reducing the danger arising from exposure to hostile fire.
The benefits are immediately obvious. First, human attrition will be reduced. Second, the
aircrew whose functions are now assumed by unmanned platforms can be channeled to
other crucial functions like air defense, C31 and transportation missions. Finally, planners
will be able to undertake more risky but decisive combat missions, such as SEAD, without
exposing aircrew to excessive risk.
UAVs can broadly be characterized as lethal and non-lethal systems. As its name
suggests, non-lethal UAVs refers to the class of UAVs used for reconnaissance,
surveillance, relay, target designation, ECM, SIGINT, ELINT, radar decoy and
meteorological surveillance. Lethal UAVs, of course, refer to the class of UAVs which
inflicts physical damage to enemy assets or installations operations.
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1.5 Lethal UAV
Lethal UAVs can best be looked at by dividing them into two distinct categories:
counter-air and strike. I will examine these two components separately and assess the
viability of UAVs to replace manned aircraft during wartime.
Air-to-air combat is very dynamic and dependent upon the pilot's judgment and skill to
outwit and out-manoeuver the aggressor so as to get into an advantageous position for the
kill. This applies even when an aircraft is armed with the most advanced AAMs, especially
if the enemy is similarly equipped. Furthermore, in an air battle, the air picture is usually a
complex one, with many real-time injects like weather, use of ECM or ECCM, changes in
tactics, attention, etc. The pilots, with the help of GCI, will have to make impromptu, split-
second decisions to circumvent the friction of war.
The use of UAV’s as interceptors will expose one of its biggest shortcomings; its lack of
decision making abilities. However advanced the UAV, it is still unable to replace the pilot
in a dog-fight. The situational awareness is just not the same. More often than not, UAVs
are very scenario dependent and operate well only in a predictable environment. The lack
of a human on board limits a UAV to perform mostly pre-programmed standard functions.
Although UAVs cannot replace manned fighters in air-to-air combat, they can be used as
decoys to reduce friendly losses. Decoys can be scrambled together with manned
interceptors to complicate the enemy's air picture, distracting their pilots or causing them to
expend their missiles on the decoys.
Strike missions are a hazardous task as the strike aircraft are susceptible to many threats:
enemy fighters, SAMs, AAA etc. A typical strike mission would involve a lot of resources.
Besides the strikers, sweepers are to fly ahead and clear the path for their transit. In
addition, to have accompanying escort fighters are needed to eliminate hostile aircraft that
slip through to threaten the strike aircraft.
UAVs can be used to reduce the heavy demands and risks of strike missions. Many
strike aircraft and bombers follow a pre-determined route into enemy territory and strike
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specific targets on the ground. The predictable nature of this task makes it suitable for UAV
execution. Technically, the cruise missile is a small, disposable UAV. These missiles are
cost-effective, proven in war, and do not need escorts or sweepers. Re-usable bomber
UAVs are also under development, but these are probably less flexible and effective than
missiles as they would require a great deal more support for them to fulfill their role.
A final benefit of using UAVs is that they are less dependent on runways. Most
unmanned platforms are easier to store and deploy than fixed wing aircraft, and many do
not need a long runway to launch from. Of particular significance, land or sea launched
cruise missiles would allow an armed force to retain a long-range strike capability even if
its runways were closed and its aircraft temporarily grounded.
1.6 Naval Unmanned warfare
Unmanned platforms are relatively new naval forces. Naval forces should consider
adopting more unmanned systems in the naval theatre, with manned warships deployed as a
controlling force or a follow-up strike force when a high casualty rate has been inflicted on
the opposing force.
They are the Unmanned Aerial Vehicle (UAV), Unmanned Undersea Vehicle (UUV)
and Sound Ocean Surveillance System (SOSUS). The following discusses the ways these
platforms can replace or supplement a navy's manned platforms and improve its operational
effectiveness.
1.7 Undersea Vehicles
The application of unmanned vehicles for underwater warfare is predominantly in the
area of mine clearance. Mine clearance in hostile waters can be fulfilled with the Self-
propelled Acoustic and Magnetic Minesweeping System (SAMMS). This unmanned,
remotely controlled mine sweeping craft is capable of establishing a safe route through
mined waters.
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Navies could consider acquiring a passive mine clearance capability so as to expand
their mine-sweeping versatility. The US Navy is currently developing a tactical scale
Unmanned Undersea Vehicle (UUV) to conduct covert, fully autonomous, long duration
mine warfare and tactical oceanography in littoral waters. To date, the UUV has
demonstrated a navigational accuracy of 0.18% of distance traveled. Such a vehicle allows
naval forces to conduct covert mine clearance and seabed surveys during POT when
aggressive counter-mine measures could not be conducted. Another advantage of the UUV
is that it can be launched covertly from a submarine.
1.8 Anti-Submarine Warfare
Manned assets are still largely used in the area of Anti-Submarine Warfare, as it remains
the playground for tacticians. However, SOSUS can be used to monitor submarine
movements at various key points in our area of operations. This will reduce the demands on
manned anti-submarine warfare assets. With further development in UAVs, ASW packages
can also be fitted onboard to provide an extended arm to airborne ASW.
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CHAPTER - 2
BRIEF DESCRIPTION ABOUT WAR TANKERS
2.1 War tanker
A tank is a tracked, armoured fighting vehicle designed for front-line combat which
combines operational mobility and tactical offensive and defensive capabilities. Firepower
is normally provided by a large-calibre main gun in a rotating turret and secondary machine
guns, while heavy armour and all-terrain mobility provide protection for the tank and its
crew, allowing it to perform all primary tasks required of armoured troops on the
battlefield.
Fig. 2.1
The tank remains the “King of the battle field” having come into its own during world
war. Designed initially to navigate the miles of trenches and obstacles along the western
front, the tank ( then known as the “Landship”) was first envisioned in an infantry support
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role. The first tank-versus-tank battle took place in the war between british and german
tanks with results being rather anticlimatic. As experience bagan to dedicate function, the
tank was later user to spearhead critical alied offensives in breaking down enemy positions
and causing general havoc. In the end, the armored vehicle became a permanent fixture of
the battlefield – evolvinginto the spearhed of any successful land campagin to date.
World War 1 saw the origins of the "Landship", which became the "tank" as we know it
- all thanks to British engineering out of Bovington, England.
World War 1 proved a testing ground concerning aspects related to modern warfare.
Poison gas, the flamethrower, the aircraft (as a fighter, light bomber and heavy bomber),
the machine gun and the "tank" were all born in their practical sense in during the dark days
of The Great War. Early "tanks", known then as "landships" after their sea-going battleship
counterparts, were largely pioneered by the British Navy and began life as awkward
rhomboidal-shaped steel beasts with side-mounted cannon and machine gun armament.
Such armored vehicles helped to break the stalemate along the Western Front for the Allies
and force the Armistice of November 1918. By the end of the war, the revolutionary French
Renault FT-17 Light Tank was in use and it brought about the revolving turret that proved a
common feature in all future tank developments since. Today's massive and powerful war
machines can all trace their roots back to these early ground-breaking initiatives.
2.1.1 Light tanks
Light tanks continued to be built, but for very limited roles such as amphibious
reconnaissance, support of Airborne units, and in rapid intervention forces which were not
expected to face enemy tanks. The Soviet PT-76 is a good example of a specialized light
tank. It is amphibious and has the firepower to kill other reconnaissance vehicles, but it is
very lightly armored. The US M551 Sheridan had similar strengths and weaknesses, but
could also be airdropped, either by parachute or LAPES.
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2.1.2 Heavy tanks
Heavy tanks continued to be developed and fielded along with medium tanks until the
1960s and 1970s, when the development of anti-tank guided missiles and powerful tank
guns rendered them ineffective in their role. The combination of large HEAT warheads,
with a long effective range relative to a tank gun, and with high accuracy meant that heavy
tanks could no longer function in the stand-off, or overwatch role. Much cheaper antitank
guided missiles could fill this role just as well. Medium tanks were just as vulnerable to the
new missiles, but could be fielded in greater numbers and had higher battlefield mobility.
Furthermore, the value of light tanks for scouting was diminished greatly by helicopters,
although many light tanks continued to be fielded.
2.2 History
The tank is the 20th century realization of an ancient concept: that of providing troops
with mobile protection and firepower. The internal combustion engine, armour plate, and
the continuous track were key innovations leading to the invention of the modern tank.
Armoured trains appeared in the mid-19th century, and various armoured steam- and
petrol-engined vehicles were also proposed. The first armoured car was produced in Austria
in 1904. However, all were restricted to rails or reasonably passable terrain. It was the
development of a practical caterpillar track that provided the necessary independent, all-
terrain mobility.
Many sources imply that Leonardo da Vinci and H.G. Wells in some way foresaw or
"invented" the tank. Da Vinci's late 15th century drawings of what some describe as a
"tank" show a man-powered, wheeled vehicle with cannons all around it. However the
human crew would not have enough power to move it over larger distance, and usage of
animals was problematic in a space so confined.
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The machines described in Wells's 1903 short story The Land Ironclads are a step
closer, in being armour-plated, having an internal power plant, and being able to cross
trenches. However, Wells's vehicles were driven by steam and moved on Pedrail wheels,
technologies that were already outdated at the time of writing. After seeing British tanks in
1916, Wells denied having "invented" them, writing, "Yet let me state at once that I was not
their prime originator. It is, though, possible that one of the British tank pioneers, Ernest
Swinton, was subconsciously or otherwise influenced by Wells's tale.
The "caterpillar" track arose from attempts to improve the mobility of wheeled vehicles
by spreading their weight, reducing ground pressure, and increasing their adhesive friction.
Experiments can be traced back as far as the 17th century, and by the late nineteenth they
existed in various recognizable and practical forms in several countries.
It is frequently claimed that Richard Lovell Edgeworth created a caterpillar track. It is true
that in 1770 he patented a "machine, that should carry and lay down its own road", but this
was Edgeworth's choice of words. His own account in his autobiography is of a horse-
drawn wooden carriage on eight retractable legs, capable of lifting itself over high walls. In
1903, a Captain Levavasseur of the French Artillery proposed mounting a field gun in an
armoured box on tracks. Major W.E. Donohue, of the British Army's Mechanical Transport
Committee, suggested fixing a gun and armoured shield on a British type of track-driven
vehicle. In 1911, a Lieutenant Engineer in the Austrian Army, Günther Burstyn, presented
to the Austrian and Prussian War Ministries plans for a light, three-man tank with a gun in
a revolving turret. In the same year an Australian civil engineer named Lancelot de Mole
submitted a basic design for a tracked, armoured vehicle to the British War Office.
All of these ideas were rejected and, by 1914, forgotten, although it was officially
acknowledged after the War that de Mole's design was at least the equal of the tanks that
were later produced by Great Britain, and he was voted a cash payment for his contribution.
Various individuals continued to contemplate the use of tracked vehicles for military
applications, but by the outbreak of the war no one in a position of responsibility in any
army had any thoughts about tanks.
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CHAPTER - 3
FUNCTIONAL DESCRIPTION
The functional description and working operation as per the block diagram is explained
below. The block diagram and the circuit diagram are provided in the next chapter.
As mentioned in the introduction the unmanned vehicles are either operated
autonomously or through tele-communications i.e., remote. The robot (war tanker)
designed here is the remote operated one. Through this remote the robot can be controlled
sitting at a safe place. The remote is designed with six control keys, MEMS, micro-
controller and the zigbee transmitter. Out of these seven keys, two keys are to rotate the gun
on the tank in clockwise and anti-clockwise directions. Two keys are used to set the tanker
in automatic or manual mode of operation. Two keys are used for the gun to lift up and
down in vertical direction and one key is used to start firing from the gun.
When automatic mode of operation is selected, the vehicle movement will only be
controlled where as gun firing will be done automatically depending on the target hit
direction. But in manual operation, everything is to be controlled through the remote itself.
And the vehicle movement is controlled using the MEMS module.
3.1 Remote control unit
The remote control unit is nothing but the transmitter unit through which the tanker is
controlled. The main components present in this unit are the push buttons, micro controller,
MEMS, ADC, 555 Timer chip, ZigBee transmitter and power supply unit for all these
components. As mentioned earlier, a total of seven keys (push buttons) are used to control
the vehicle and these are interfaced with the 89C51 micro controller. MEMS module is
used to control the robot and is interfaced with the 89C51 micro controller through ADC.
Depending on the MEMS moved, the ADC converts the analog voltage variation obtained
from the MEMS to digital data and feeds it to the controller. In the same way depending on
the key pressed, the controller generates a unique 8 bit binary code which is fed to the
Zigbee transmitter for modulation. A slightest tilt in the angle of the MEMS module, gives
12
the voltage variation to the ADC, by which the controller will identify what operation is to
be performed. Description about MEMS module is provided below.
MEMS (Micro Electro Mechanical Systems)
Micro - Small size, micro fabricated structures
Electro - Electrical signal / control (In / Out)
Mechanical - Mechanical functionality (In / Out)
System Structures, Devices, Systems, Control
MEMS is a class of systems that are physically small. These systems have both
electrical and mechanical components. MEMS originally used modified integrated circuit
(computer chip) fabrication techniques and materials to create these very small mechanical
devices.
Micro Electro Mechanical System or MEMS represent an extraordinary technology that
promises to transform whole industries and drive the next technological revolution. These
devices can replace bulky actuators and sensors with micron scale equivalents that can be
produced in large quantities by fabrication processes used in integrated circuit
photolithography. This reduces cost, bulk, weight and power consumption while increasing
performance, production volume, and functionality by orders of magnitude.
Sensors and actuators are the two main categories of MEMS. Sensors are non-invasive
while actuators modify the environment. Micro sensors are useful because their physical
size allows them to be less invasive while Micro actuators are useful because the amount of
work they perform on the environment is small and therefore can be very precise. MEMS is
very small in size with dimensions of less than 1 mm (1000 microns) and with feature sizes
on the order of microns (0.001 mm).
13
The pin configuration of MEMS module is given below:
Table 3.1
So from the pin configuration of the MEMS module, we can identify three output pins
i.e., X, Y and Z direction output voltages. As the controller cannot read the analog voltages,
these are given to ADC to convert the analog voltages to digital format and then fed to the
controller.
3.2 ADC (Analog to Digital Converter)
As the peripheral signals usually are substantially different from the ones that micro-
controller can understand (zero and one), they have to be converted into a pattern which can
14
be comprehended by a micro-controller. This task is performed by a block for analog to
digital conversion or by an ADC. This block is responsible for converting an information
about some analog value to a binary number and for follow it through to a CPU block so
that CPU block can further process it.
Fig. 3.1
This analog to digital converter (ADC) converts a continuous analog input signal, into
an n-bit binary number, which is easily acceptable to a microcontroller. As the input
increases from zero to full scale, the output code stair steps. Obviously for an input voltage
range of one LSB, the output code is constant. For a given output code, the input voltage
can be anywhere within a one LSB quantization interval.
The outputs of the MEMS module (X, Y, and Z) are fed to A/D converter. The channel
selection depends upon the address selection sent by the Micro-controller. This ADC is
having three address inputs to select one out of eight channels of the ADC. This ADC 0809
is a successive approximation type A/D converter and the clock rate at which the
conversion is fed from the IC 555 timer configured as Astable multivibrator. This is an 8-
channel IC, out of 8 channels only 3 channels are used for 3 parameters of the MEMS
modules. This is an 8-bit parallel ADC, and the conversion time is 110 microseconds
approximately. The digital output after conversion is fed to Micro-controller.
For ADC to start converting the data after selecting the channel by sending the address
inputs, the start conversion signal is to be sent by Micro-controller. Then ADC starts
converting the analog signals voltage into corresponding digital data.
15
After conversion, the ADC generates EOC (End of conversion). This indicates to Micro-
controller that the conversion is completed and takes the digital data corresponding to
analog input.A/D Converters are among the most widely used devices for data acquisition.
The output of any transducer or sensor is nothing but a physical quantity and it is converted
in to electrical signal in the form of either Voltage or Current. Therefore, we need an A/D
converter to translate the analog signals to digital numbers, so that the microcontroller can
read and process them. In this project work 8-bit ADC is used. The ADC chips are either
parallel or serial; in parallel ADC it is having more pins are dedicated to bring out the
binary data, but in serial ADC it is having only one pin for data out. The following is
Circuit diagram of A/D Converter along with its clock generator.
Fig. 3.2
Circuit Diagram of A – D Converter
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3.3 Clock Generator
The required clock for the ADC is generated using 555 Timer IC, which is configured as
Astable multi-vibrator (Self Oscillator). In this mode of operation the required frequency
can be adjusted using two external components i.e., resistor and capacitor. Keeping
capacitor value constant where as by varying the value of resistor the frequency can be
adjusted from 1Hz to 500 KHz. Here the required frequency is 100 KHz approximately.
In the above circuit diagram 555 timer IC is used for generating the required clock
pulses. Frequency can be adjusted using variable resistor 100K (RB). In this circuit the
external capacitor charges through RA+RB and discharges through RB. Thus the duty cycle
may be precisely set by the ratio of these two resistors. In this mode of operation, the
capacitor charges and discharges between 1/3 VCC and 2/3 VCC. As in the triggered
mode, the charge and discharge times, and therefore the frequency are independent of the
supply voltage. Here the timing resistor is now split into two sections, RA and RB, with the
discharge transistor (Pin 7) connected to junction of Ra and Rb. When the power supply is
connected, the timing capacitor C charges towards 2/3 VCC through Ra and Rb. When the
capacitor voltage reaches 2/3 VCC, the upper comparator triggers the flip-flop and the
capacitor starts to discharge towards ground through Rb. When the discharge reaches 1/3
VCC the lower comparator is triggered and a new cycle is started. The capacitor is then
periodically charged and discharged between 2/3 VCC and 1/3 VCC respectively. The
output state is high during the charging cycle for a time period t1, so that
t1 = (Ra + Rb) C1n
t1 = 0.693 (Ra + Rb) C
The output state is LOW during the dischage cycle for a time period t2, given by
t2 = 0.693 RbC
Thus, the total period charge and discharge is
T = t1 + t2
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= 0.693 (Ra + 2Rb) C (Seconds)
So that the output frequency is given as
3.4 ZIGBEE Module
The data-transmitting unit including 89C51 microcontroller designed to operate at 5V
DC, and required supply is derived from the mains. A small keyboard designed with 7 keys
is interfaced with this microcontroller. This keyboard is designed to generate the data that is
stored in RAM and it is delivered through output pin of the controller (transmitter).
The main function of the data transmitting section is to generate 8-bit binary code that is
to be transmitted through Zigbee transmitter. The 8-bit binary code produced by the
keyboard is fed to microcontroller, which functions as encoder; the data obtained from the
keyboard is stored and it is converted into 8-bit information which is transmitted through
amplified modulated input signal. If any key is pressed; that information is converted into
8-bit data. For example, if No.1 key is pressed, 00000001 code is generated. Likewise each
key function differs from another key to generate a different 8-bit code. Based on this code,
the other micro controller used in the receiving module, which is designed as 8-bit code
decoder, decodes this data and compares with the pre-defined program prepared in
assembly language and operates the vehicle (robot).
The output of the (Encoder) microcontroller is fed to Zigbee transmitter, for radiating
the pulsating energy into air. The function of a radio frequency (RF) transmitter is to
modulate, up convert, and amplify signals for transmission into free space. An RF
transmitter generally includes a modulator that modulates an input signal and radio
frequency power amplifier that coupled to the modulator to amplify the modulated input
18
signal. The radio frequency power amplifier is coupled to an antenna that transmits the
amplified modulated input signal.
The Zigbee transmitter used in our project is Tarang – F4. This RF transmitter transmits
data in the frequency range of 2.4 - 2.4835 GHz with a range of approximately 50-feet
(open area) outdoors. Indoors, the range is approximately 20 feet, and will go through most
walls. Tarang – F4 has features which includes small in size, low power consumption and
operates at 3.3 volts DC, excellent for applications requiring short-range RF signal.
The data receiving module consist Zigbee receiver, DC motors with their driving
circuits, gun firing sound simulator IC and limit switches that are interfaced with the 89C51
microcontroller as source of information at the receiving side. To control the moving
mechanism based on the input information, H-bridge IC’s are connected at the output of
microcontroller and these are used to control the DC motors ultimately, which controls the
robot as well as the gun firing and its direction. Over all function of the block diagram is to
install an electro-mechanical vehicle operated in all possible directions. The description is
as followed.
The RF signal transmitted by the transmitter is detected and received by this section of
the receiver. This binary encoder data is sent to the decoder for decoding the original data.
The receiver receives an RF signal, converts the RF signal to an IF signal, and then
converts the IF signal to a base band signal, which is then provides to the base band
processor. As is also known, RF transceivers typically include sensitive components
susceptible to noise and interference with one another and with external sources. The
Zigbee (RF) receiver is coupled to the antenna and includes a low noise amplifier, one or
more intermediate frequency stages, a filtering stage, and a data recovery stage. The low
noise amplifier receives an inbound RF signal via the antenna and amplifies it.
The program is fixed, it cannot be changed, depending up on the program prepared for
controller, and the information produced by the keyboard at transmitting end, the received
information if it is tallied with the pre-defined program, then the microcontroller at
19
receiving end energizes the DC motors driving circuit to control or operate the tanker
(robot) automatically.
3.5 Mechanical Actuation Section
The mechanical system is considered as motion converter, this can be created by
implementing electro-mechanical techniques. The concept is to transform the motion from
one form to some other required form by using suitable mechanical and electrical devices.
In this project work the technique of transform the rotational motion into circular and linear
motion is implemented. For this purpose DC motors are used to create the motion in the
gun mechanism of the tanker as well as its movement. These motors are constructed with
reduction gear mechanism which is built in with the motor internally. As the machine is
designed as prototype module, low rating motors are used to drive the mechanism.
The advantage of selecting reduction gear mechanism motors are that a small motor can
drive heavy loads, as these motors are purchased from local market, ratings regarding
torque is not mentioned. Only speed and operating voltage is specified, as per this data the
motor is designed to operate at 12V DC and the motor speed is 30 RPM.
The rotary motion can be transferred from one shaft to another by a pair of rolling gears.
Depending up on the ratio of final shaft speed, number of gears is arranged in group and is
called as gear trains. These gear trains are mechanisms which are widely used either to
increase or to decrease the final shaft speed. When the speed is increased torque will be
reduced, where as if the speed is decreased torque will be increased i.e., speed (RPM) and
torque are inversely related to each other. In general these teethed gear wheels are coupled
in between two parallel shafts. When two gears are in mesh, the larger gear wheel is often
called as crown wheel and the smaller one is called as pinion. The movement of the robot
will be started by pressing the control buttons in the remote and the DC motors keep on
rotating until the button is released (stop pressing) again.
To control the movement of the gun mechanism and the tanker in various directions, the
DC motors are driven through driver IC’s L293D. The push buttons in the remote are
20
nothing but the feather touch keys called as push to ON keys. A total of 4 DC motors are
used in this project work, in which 2 DC motors are connected to the right and left wheels
of the robot for the robot movement in forward, backward, right and left directions. And in
the remaining 2 DC motors, one is used to rotate the gun for almost 300 degrees, the other
to lift the gun up and down.
A total of 7 push buttons and MEMS are used to control these DC motors
independently. Each motor is connected with 2 push buttons for operating in clockwise and
anti-clockwise directions. By pressing the push button the H – Bridge IC provides supply to
the DC motor by which the motor rotates in a particular direction. To restrict the
mechanical movement when reached to extreme positions by the gun rotating motor, limit
switches are used to stop the DC motor. As the movement is to be restricted in both the
directions of this motor i.e., clockwise and anti-clockwise 2 limit switches are used.
Out of the 4 DC motors, two are used to control the robot movement and the rest for
controlling the gun of the tanker. The two motors in the gun are used for rotating and lifting
it at desired positions. As mainly load falls on these motors, these are connected with
mechanical gear drive mechanisms. Mechanical drives are used to provide variable output
speed from a constant speed power source. These mechanical gear drives are extensively
used in automobile industry. Mechanical drives provide simple control and are cheaper as
compared to electrical drives.
A gear drive is an assembly of gears turned by the motor to perform the specific task.
The first gear attached to the motor supplies the power and is known as input gear, while
the gear that amplifies the mechanical energy is called the output gear. There are various
types of gear drives such as harmonic drives, bevel gear drives, hypoid gear drives,
combination drives, worm drives, etc and many more. Description about types of gear
drives is provided in the further chapters.
When two gears are meshed with each other, a definite velocity ratio is obtained.
Velocity ratio (or gear ratio) is the ratio between the angular velocity of driving gear and
the angular velocity of driven gear.
21
Gears are typically used for short distance power transmission. They are compact and
have high transmission efficiency when compared to other power transmission systems. In
this project work we use worm gear drive mechanism in the gun lifting and rotating
mechanisms. And the tanker by chain drive mechanism is implemented with wheels
connected to the motors.
This configuration allows the worm to engage more teeth on the wheel, thereby
increasing load capacity. In worm-gear sets, the worm is most often the driving member.
However, a reversible worm-gear has the worm and wheel pitches so proportioned that
movement of the wheel rotates the worm. In most worm gears, the wheel has teeth similar
to those of a helical gear, but the tops of the teeth curve inward to envelop the worm. As a
result, the worm slides rather than rolls as it drives the wheel. Because of this high level of
rubbing between the worm and wheel teeth, the efficiency of worm gearing is lower than
other major gear types.
One major advantage of the worm gear is low wear, due mostly to the full-fluid
lubricant film that tends to be formed between tooth surfaces by the worm sliding action. A
continuous film that separates the tooth surfaces and prevents direct metal-to-metal contact
is typically provided by a relatively heavy oil, which is often compounded with fatty or
fixed oils such as acid less tallow oil. This adds film strength to the lubricant and
further reduces friction by increasing the oiliness of the fluid. The detailed description
about the worm gear drive mechanism is provided in the latter chapters. As mentioned
earlier all these mechanical gear drive mechanisms are driven by the electric motors.
3.6 DC Motor
An electric motor is a machine, which converts electrical energy into mechanical
energy. It is based on the principle that when a current-carrying conductor is placed in a
22
magnetic field, it experiences a mechanical force whose direction is given by Fleming’s
Left-hand rule and whose magnitude is given by
Force, F = B i L Newton
Where ‘B’ is the magnetic field in weber/m2.
‘i’ is the current in amperes and
‘L’ is the length of the coil in meter.
The force, current and the magnetic field are all in different directions.
If an Electric current flows through two copper wires that are between the poles of a
magnet, an upward force will move one wire up and a downward force will move the other
wire down.
A direct current (DC) motor is a fairly simple electric motor that uses electricity and a
magnetic field to produce torque, which turns the motor. At its most simple, a DC motor
requires two magnets of opposite polarity and an electric coil, which acts as an
electromagnet. The repellent and attractive electromagnetic forces of the magnets provide
the torque that causes the DC motor to turn.
In a magnet attraction between opposite poles and the repulsion of similar poles can
easily be felt, even with relatively weak magnets. A DC motor uses these properties to
convert electricity into motion. As the magnets within the DC motor attract and repel one
another, the motor turns.
A DC motor requires at least one electromagnet. This electromagnet switches the current
flow as the motor turns, changing its polarity to keep the motor running. The other magnet
or magnets can either be permanent magnets or other electromagnets. Often, the
electromagnet is located in the center of the motor and turns within the permanent magnets,
but this arrangement is not necessary.
23
Electrical current is supplied to the coils of wire on the wheel within the DC motor. This
electrical current causes a magnetic force. To make the DC motor turn, the wheel must
have be negatively charged on the side with the negative permanent magnet and positively
charged on the side with the permanent positive magnet. Because like charges repel and
opposite charges attract, the wheel will turn so that its negative side rolls around to the
right, where the positive permanent magnet is, and the wheel's positive side will roll to the
left, where the negative permanent magnet is. The magnetic force causes the wheel to turn,
and this motion can be used to do work.
When the sides of the wheel reach the place of strongest attraction, the electric current is
switched, making the wheel change polarity. The side that was positive becomes negative,
and the side that was negative becomes positive. The magnetic forces are out of alignment
again, and the wheel keeps rotating. As the DC motor spins, it continually changes the flow
of electricity to the inner wheel, so the magnetic forces continue to cause the wheel to
rotate.
DC motors are used for a variety of purposes, including electric razors, electric car
windows, and remote control cars. The simple design and reliability of a DC motor makes
it a good choice for many different uses, as well as a fascinating way to study the effects of
magnetic fields
DC motors are widely used, inexpensive, small and poweful for their size. They are
most easy to control. One DC motor requires only two singals for its operation. They are
non-polarized, means you can reverse the voltage without any damage to motor. DC motors
have +ve and –ve leads. Connecting them to a DC voltage source moves motor in one
direction (clockwise) and by reversing the polarity, the DC motor will move in opposite
direction (counter clockwise). The maximum speed of DC motor is specified in rpm
(rotation per minute). It has two rpms: no load and loaded. The rpm is reduces when
moving a load or decreases when load increases. Other specifications of DC motors are
voltage and current ratings. Below table shows the specifications of the motor used in the
project.
24
Parameter Value
Operating Voltage 12V DC
Operating Current 150 milli Amps
Speed 30 RPM
Table 3.2
3.6.1 DC Motor Specifications
Speed of the motor can be changed by changing the applied voltage across motor. DC
motors don’t have enough torque to drive the mechanism directly by connecting
mechanism with it. The motor driving circuit is designed with L293D chip; this is popularly
known as ‘H’ bridge device generally used to drive the low power DC motors.To drive
these motors independently in both directions, drive sequence is programmed depending up
on the information gathered from the transmitter.
3.7 H-Bridge (General description)
H-Bridge is an electronic circuit which enables a voltage to be applied on either side of
the load and the H-bridge DC motors allow the car to run backwards or forwards. H-Bridge
is a configuration of 4 switches, which switch in a specific manner to control the direction
of the current through the motor. Below figure shows simplified H-bridge as switches. The
states of these four switches can be changed in order to change the voltage across the
motor, of the current flow and the rotation of motor.
25
Fig. 3.3
H - Bridge
3.7.1 Basic Structure of an H-Bridge
In above figure, all switches are open and the motor terminals are disconnected from the
circuit. This state allows the motor to spin freely. If we open switches S1 & S4 and close
S2 & S3 as in first part of below figure there will be current flow across the circuit and
motor will run. But if S1, S4 are close and S2, S3 are open, the voltage across the motor
will switch around and that will cause the motor to rotate in the opposite direction. Below
table summarizes the basic operation of the H-bridge depending upon the voltage applied
across the switches.
S1 S2 S3 S4 Result
1 0 0 1 Motor moves right
0 1 1 0 Motor moves left
0 0 0 0 Motor free runs
0 1 0 1 Motor brakes
1 0 1 0 Motor brakes
Table 3.3
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3.7.2 H-Bridge Operation Summary
Figure 3.4
Two Basic States of an H-Bridge
To control the speed and direction of the DC motor from the microcontroller, this simple
H-bridge will be of no use. H-bridge which makes use of transistors works best for robotics
projects. These transistors work as switch and they can control the current flow in the motor
easily. Below figure shows transistor as a switch.
Fig. 3.5
27
PNP and NPN Transistor Switch Configurations
3.7.3 Transistors as a Switch
The difference between the mechanical switch and the transistor switch is that
mechanical switch can be turned on or off mechanically but a transistors switch can be
turned on or off by applying small current at the base. For an NPN transistor, when a small
current of 20mA is applied to the base of the transistor, current will flow from collector to
emitter. In case of, for PNP transistor, the current will flow from emitter to collector. For
transistor to work as switch, the applied voltage at base needs to be higher than collector
voltage for NPN transistor and lower than collector voltage for PNP transistor.
In this project, the dual H-bridge motor driver IC used is L293D. “The L293D is a
monolithic integrated, high voltage, high current, 4-channel driver”. The L293D supports
two DC motors. Pin 8 is voltage for the motors and pin 16 is the +5 voltage for the chip. So
with one IC we can interface two DC motors which can be controlled in both clockwise and
counter clockwise direction and if you have motor with fix direction of motion then we can
make use of all the four I/Os to connect up to four DC motors. First motor is connected
between pin 3 and 6. The motor is turned on by sending a high signal to both the enable
(pin 1) pin and one of the two direction pins, i.e. pin 2 or pin 7. To stop motor, the enable
pin is high and both pin 2 and pin 7 are low. L293D has output current of 600mA and peak
output current of 1.2A per channel. Moreover for protection of circuit from back EMF
output diodes are included within the IC. The output supply (VCC2) has a wide range from
4.5V to 36V, which had made L293D a best choice for DC motor driver.
28
Fig. 3.6
DC Motor Control with H-Bridge
The same goes for the other side of the chip. When using two motors, the best practice is
to connect pins 2 and 15 togather and pin 7 and 10. above figure shows the control of the
DC motors with L293D and microcontroller signal.
Fig. 3.7
Pin Diagram of L293D
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3.7.4 L293D H Bridge (Motor Driver)
Motor drivers are the simplest modules that provide power amplification for low-level
control singals like PWM and direction supplied by the user.
Depending on the command signals given from the remote, the controller decodes the
information and takes decisions appropriately. The vehicle (robot) movement is performed
using two DC motors driven by a single H - Bridge IC. So four keys in the remote control
the tanker directions i.e., forward, backward, right and left. One more H – Bridge IC is used
to drive the two DC motors for controlling the gun direction in rotational mechanism and
lifting up and down present on the vehicle itself. Out of the two DC motors, one motor is
used to to lift the gun to certain height and the second DC motor is used to rotate the gun to
desired position. The DC motor is also to be rotated in the reverse direction and by
reversing the polarities, the motor rotates in the reverse direction that is done by the
controller through the H - Bridge IC’s. The mechanical movements of the above mentioned
mechanism using two DC motors is designed using gear drive mechanisms for the required
mechanical motions.
3.8 Limit Switches
In engineering a limit switch is a switch operated by the motion of a machine part or
presence of an object. They are used for control of a machine, as safety interlocks, or to
count objects passing a point. A limit switch is an electromechanical device that consists of
an actuator mechanically linked to a set of contacts. When an object comes into contact
with the actuator, the device operates the contacts to make or break an electrical
connection. Limit switches are used in a variety of applications and environments because
of their ruggedness, ease of installation, and reliability of operation. They can determine the
presence or absence, passing, positioning, and end of travel of an object. They were first
used to define the limit of travel of an object; hence the name “Limit Switch.”
Miniature snap-action switch may be used for example as components of such devices
as photocopiers or computer printers, to ensure internal components are in the correct
30
position for operation and to prevent operation when access doors are opened. A set of
adjustable limit switches are installed on a garage door opener to shut off the motor when
the door has reached the fully raised or fully lowered position.
In this project work also the mechanical movements are restricted through limit switches
and these entire limit switches are interfaced with the H – bridge IC’s as input signals. As
mentioned earlier, 2 limit switches are used to restrict the mechanical motion by stopping
the DC motors when reached to maximum extent. This limit switch is having long lever
and when little pressure is applied to the lever, switch will be activated automatically. The
mechanical transmission section that moves the excavating robot arm in three degrees of
freedom activates these switches at various levels. The following is the diagram of limit
switch.
Figure 3.8
Limit Switch
The limit switch shown above is having long lever, like this ten limit switches are used,
and they are arranged at different positions of the mechanical structure to control the
movement of mechanical transmission section. The motion of the motor in the form
mechanical movement, if it touches to the lever, than the switch is activated and generates a
logic signal to the DC motor. Based on this signals produced by these limit switches, the
mechanical movements of entire machine are restricted by the DC motors.
31
3.9 UM 3562 (Gun Sound Generator)
3.9.1 General Description
The IC UM 3562 used in this project is a low cost, low power CMOS LSI designed for
use in toy application. Since the IC includes oscillating and selector circuits, a compact
sound module can be constructed with only a few additional components. The UM 3562
contains circuit to produce three gun sounds. The circuit constructed here has a facility to
adjust machine gun shooting rate. For this resistor R1 and R2 are given as optional with
dotted marking on PCB. If shooting rate is not to be adjusted then resistor R1 and R2 may
be omitted.
3.9.2 Features
• Three sounds can be selected
• Rifle Gun
• Machine Gun
• Laser Gun
• Typical 3V operating voltage
• RC Oscillator built-in
• A magnetic speaker can be driven by connecting NPN transistor
• Power ON reset.
32
3.9.3 Pin Description
Pin No. Destination Description
1 OSC
This pin is used for testing in normal
operation the pin is open.
2 SEL Sound effect select pin.
3 VSS Negative Power Supply
4 TRI Trigger pin
5 OUTPUT Monotone Output
6 ADJ Normally open, may connect a resistor to
ground to adjust machine gun shoots rates.
7 NC No connection
8 VDD Positive power supply
Table 3.4
A relay is used to activate this chip when gun firing is to be done. The controller control
the operation of the relay depending on the key pressed in the remote in manual operation.
Else in the automatic mode of operation also, depending on the direction of the hit target,
the controller automatically rotates the gun to that particular direction and activates this
chip through the relay to fire.
33
3.10 Relay
A relay is an electrical switch that opens and closes under the control of another
electrical circuit. In the original form, the switch is operated by an electromagnet to open or
close one or many sets of contacts. These contacts can be either Normally Open (NO),
Normally Closed (NC), or change-over contacts. A relay is able to control an output circuit
of higher power than the input circuit, it can be considered to be, in a broad sense, a form of
an electrical amplifier. So a relay can be defined as an automatic electromagnetic/electronic
switch, which can be used to make or break the circuit.
The relay used in this project work is electro-magnetic/mechanical relay. The
electromagnetic relay is basically a switch (or a combination of switches) operated by the
magnetic force generated by a current flowing through a coil. Essentially, it consists of
four parts an electromagnet comprising a coil and a magnetic circuit, a movable armature, a
set of contacts, and a frame to mount all these components. However, very wide ranges of
relays have been developed to meet the requirements of the industry. This relay is nothing
but a switch, which operates electromagnetically. It opens or closes a circuit when current
through the coil is started or stopped. When the coil is energized armature is attracted by
the electromagnet and the contacts are closed. That is how the power is applied to the
signals (indicators). The construction of the typical relay contains a code surrounded by a
coil of copper wire. The core is mounted on a metal frame. The movable part of the relay is
called armature. When a voltage is applied to the coil terminals, the current flowing through
the coil produces a magnetic field in the core. In other words, the core acts as an
electromagnet and attracts the metal armature. When the armature is attracted to the core,
the magnetic path is from the core through armature, through the frame, and back to the
core. On removing the voltage the spring attached to the armature returns the armature to its
original position. In this position, there is a small air-gap in the magnetic path. Hence, more
power is needed to pull in the armature than that needed to keep it held in the attracted
position
34
A relay is a device that opens or closes an auxiliary circuit under some predetermined
condition in the main circuit. The object of a relay is generally to act as a sort of electric
magnifier, that is to say, it enables a comparatively weak current to bring into operation a
much stronger current. It also provides complete electrical isolation between the controlling
circuit and the controlled circuit. The relay is operated like a switch to control the gun
firing sound generator IC. The controller controls the operation of the relay i.e., ON and
OFF by which the device is also controlled.
The relay contacts and the terminals are mounted on an insulated board. When no
current flows through the relay coil, the contact arm, or pole as it is called, mounted on the
armature, touches the “top” (N/C) contact. When the coil is energized by flow of current,
the armature along with the contact arm assembly moves downwards; so that the contact
arm touches the “bottom” (N/O) contact. When an electric current is flowing through a
relay coil, it is said to be energized, and when the current flow stops, the relay is said to be
de-energized. They have a set of parallel contacts, which are all pulled in when the
electromagnet pulls in the armature. On being energized, whether a relay makes contact(s)
or breaks them depends on the design of contact arrangements. Though the contacts are
open or close simultaneously, the sequence of operation cannot be guaranteed in this of
construction. To have a definite switching sequence, stacked contacts are used.
Fig. 3.9
Schematic of relay with contact
35
3.11 Power Source
The required power supply to drive the tanker is derived by 12V, 7 Ah (Ampere hour),
rechargeable, lead acid heavy duty battery. Here we require two different DC levels of +5V
and +12V. The battery as it is delivering 12V is used to drive the DC motors through the H
Bridge IC’s, where as for the remaining electronic circuitry consists of microcontroller,
LCD and RF receiver requires +5V constant source. To generate a stable supply of +5V,
7805 three terminal voltage regulator chip is used which provides constant supply, though
the battery terminal voltage falls down to 8V. The DC motors are designed to operate at
12V DC and each motor consumes a maximum current of 150 milli-amps, there by four
motors for the robot movement together consumes 600 milli-amps. Likewise by calculating
the current drawn by the entire circuit, the backup time of the battery can be calculated. The
relation for calculating the backup time is given as: The battery backup time = battery
rating in Ah/ consumed energy (current drawn by the entire circuit in Amps).
The power supply for the remote section is derived from the mains single phase supply.
For this a step-down transformer is used to decrease the voltage level to 12v Ac, which is
then fed to the rectifier to convert it into pulsating DC voltage.
36
CHAPTER- 4
BLOCK DIAGRAMS AND CIRCUIT DIAGRAMS
Fig. 4.1
Block Diagram of Vehicle Control Station
37
Fig. 4.2
Block Diagram of Warfare Vehicle
38
Fig. 4.3
Circuit Diagram of Warfare Vehicle
39
Fig 4.4
Circuit Diagram of Vehicle Control Station
40
CHAPTER – 5
DETAILED DESCRIPTION ABOUT MEMS
5.1 MEMS (Micro Electro Mechanical Systems) – An Over View
Micro Electro Mechanical systems, or MEMS represent and extraordinary technology
that promises to transform whole industries and drive the next technological revolution.
These devices can replace bulky actuators and sensors with micron-scale equivalents that
can be produced in large quantities by fabrication processes used in integrated circuit
photolithography. This reduces cost, bulk, weight and power consumption while increasing
performance, production volume, and functionality by orders of magnitude.
Micro electro mechanical systems are devices that have static or moveable components
with some dimensions on the scale of a micrometer to nanometer. For comparison, a human
hair is about 80 micrometers in diameter. MEMS combine micro- electronics and
micromechanics and sometimes micro optics and micro magnetics. While MEMS devices
will not be used as commonly as integrated circuits, they will be found in a great diversity
of products and installations. Just as most people in technological societies own products
with integrated circuits and micro lasers, pervasive ownership and use of MEMS are clearly
in prospect. It is estimated that there are 1.6 MEMS devices per person in the United States.
Micro-mechanical devices will both improve the performance of existing systems and
enable entirely new applications.
The integration of microelectronics and micromechanics is a historic advance in
the technology of small-scale systems and is very challenging for designers and producers
of MEMS. We will show examples of monolithic (single substrate) and hybrid (two
substrate) MEMS later in this review.
41
5.2 Advantages and Challenges of MEMS
The small size of MEMS is attractive for many applications because feature sizes are
typically as small as 1 micrometer or less. Hence, for optical applications, features may be
made with size on the order of the wavelength of light. Their small size also allows
applications to be developed which would otherwise be impossible. For example,
micromechanical switches fabricated as part of a communications circuit allow phase
shifting and signal switching at speeds that would be impossible to achieve using macro-
scale switches. To illustrate the scale of a typical micro system, Figure below shows a
micro machined mirror assembly next to a spider mite. The mirror assembly is about 100
micrometer wide, and it is dwarfed by the spider mite. The mechanical devices surrounding
the mirror allow it to be positioned accurately as part of an optical network.
Other advantages include the on-chip integration of electromechanical systems and the
circuitry used to control them, allowing further miniaturization. Furthermore, many MEMS
fabrication technologies allow parallel fabrication of thousands of systems by leveraging
the parallel fabrication techniques of the integrated circuit industry. This may lead to a
reduction in the manufacturing cost and improvement in reliability.
Like any technology, micro systems present some challenges. Because micro
mechanisms operate at a size scale far below that of typical mechanical devices, surface
forces such as adhesion and friction may dominate over other forces in the system, leading
to failure of the device. In many micro electromechanical systems, electrical or optical
signals are used to interface with, provide power to, and control the device, rather than
manual, hydraulic, or pneumatic control typically seen in macro-scale mechanical devices.
In addition, packaging of MEMS components has often presented a challenge because each
device must be packaged in a way that keeps the components clean and free from
contamination, while also allowing mechanical motion and, in many cases, interaction with
the environment. For example, a MEMS pressure sensor requires a package that exposes
the sensor to the ambient pressure while protecting the electronic circuitry from dust or
other particles. Finally, while parallel fabrication techniques can reduce the manufacturing
42
cost of many units, MEMS development may be more costly because few units are
produced at a time using complex and expensive fabrication equipment.
5.3 Fabrication Technologies
A large variety of fabrication methods have been employed for MEMS. However, many
of these methods may be broadly described under three headings: surface micromachining,
bulk micromachining, and molding.
5.3.1 Bulk Micromachining
Bulk micromachining, the oldest of the micromachining technologies, is accomplished
by removing material from a substrate to create holes, cavities, channels, or other desired
shapes. Early bulk micromachining was accomplished using isotropic or anisotropic wet
etching of silicon or glass substrates. In particular, several chemicals, such as KOH
(potassium hydroxide) or TMAH (tetra-methyl-ammonium hydroxide) etch a silicon
substrate preferentially depending on the crystalline planes in the direction of etching. The
etch rate for these chemicals is tens to hundreds of time faster in the [100] crystalline plane
compared to the [111] plane. This effect has been used to create a wide variety of features
using simple wet etching.
Fig. 5.1
Titanium mirrors bulk micro-machined using deep etching of a titanium substrate
Another important technology frequently used with bulk micromachining is wafer
bonding. After etching the desired parts in several different substrates, the substrates may
43
be bonded together to create systems incorporating several parts. In some cases, the wafers
are bonded using an adhesive, but this method often has poor accuracy in spacing and
alignment between bonded parts. Silicon and glass wafers can be bonded more accurately
by applying high temperatures (about 1,000 degrees C) to a clean interface between the
surfaces. In many cases, the bond generated in this way is as strong as the intrinsic strength
of glass or silicon. If high temperatures are not desired, anodic bonding can be using. In this
case, the wafers are pushed together at a lower temperature (about 400 degrees C), and then
a large voltage (about 1,000 V) is placed between the wafers. This generates a high electric
field at the interface, accelerating bonding even at the lower temperature. Wafer bonding
has also been explored as a way to create a vacuum package enclosing MEMS parts.
5.3.2 Surface Micromachining
Surface micromachining is one of the most common technologies used to manufacture
MEMS devices. In surface micromachining, films are deposited on a substrate and
patterned, using photolithography, to create micromechanical devices. The films normally
alternate between structural and sacrificial layers, with the MEMS parts being made from
the structural layers. The sacrificial layers serve to support the structural components
during fabrication. After the structural layers are patterned, the sacrificial material is
removed, often using wet chemical etching. The result is freestanding MEMS parts that can
move relative to the fixed substrate.
Most early surface micromachining used polycrystalline silicon (polysilicon) as the
structural layers and an oxide of silicon as the sacrificial material. However, as surface
micromachining has further developed, numerous other materials have been used.
Depending on the desired application, MEMS developers have used metals, oxides and
nitrides of silicon, and even polymers for both structural and sacrificial films. Several
foundry processes have also been developed to allow users to design their own MEMS and
having them fabricated using the foundry's fabrication facilities. For example, Fig. 8.3
shows a surface micromachined electrostatic drive manufactured using the SUMMiT
foundry process developed at Sandia National Laboratories. The device is made from two
44
layers of released polysilicon, with a layer of polysilicon. The fingers of the electrostatic
drive are about 35 micrometer long, and each layer is about 2 micrometer thick. The gaps
(between the substrate and the first layer, and between the two layers) are determined by
the thickness of the sacrificial oxide film - 2 micrometer.
Fig. 5.2
An electrostatic comb drive fabricated using SUMMIT, a surface-micromachining
foundry process.
5.3.3 Molding
Finally, MEMS parts are often made by creating a mold, which may then be filled to
create the desired part. Molds have been made from a variety of polymers, including some
types of photo-resist, as well as metal and deep-etched silicon wafers. Photolithography is
normally used to define the mold pattern. If metal parts are desired, the mold may be filled
by electroplating. Polymer parts may be created by pouring or pressing the precursor into
the mold. After the part has been molded, it may be removed from the mold by either
etching the mold away, or, if the mold is to be used again, by peeling away the mold.
Micro-molding was first performed in Germany, where it was called LIGA, an acronym
for the German words lithography, electroplating, and molding. The original LIGA process
required an X-ray source to fully expose thick layers of photosensitive material, but many
molding techniques have since been developed that use visible or ultraviolet light sources.
However, because of this history, many molding processes are still referred to as LIGA or
LIGA-like processes. Figure 4 shows a copper waveguide fabricated using true LIGA
45
technology. Because of its high thickness and exact specifications, the waveguide has very
low losses, especially compared to other micro-machined waveguides.
Fig. 5.3
An extremely low-loss coplanar waveguide fabricated using LIGA
5.4 Actuation
On-chip actuation of micro systems has been a particularly challenging aspect of MEMS
development. Common macro-level actuation approaches, such as hydraulics, pneumatics,
electric motors, internal combustion engines and turbines, are either too difficult to
fabricate at the micro level or do not work well at that scale. Electrostatic attraction is one
approach that has been widely used for actuation of micro systems. While electrostatic
actuation is suitable for many applications, some systems require either lower voltages or
higher output forces. Electrostatic and thermal actuation approaches are described in more
detail.
5.4.1 Electrostatic Actuation
The simplest type of electrostatic actuator consists of a movable plate or beam which is
pulled toward a parallel electrode under the application of a voltage difference. This type of
actuator is illustrated schematically in the Figure. The movable electrode is suspended by a
mechanical spring, which is often simply a micro machined beam. When voltage is placed
across the electrodes, opposite charges on each one attract each other. However, unless they
46
touch, the electrodes only draw sufficient current to charge the actuator's effective
capacitance, resulting in low power requirements. The attractive force is larger when the
movable electrode is closer to the fixed electrode, with the force proportional to the
reciprocal of the square of the gap.
Fig. 5.4
A parallel-plate actuator consists of two parallel electrodes. Attractive electrostatic
force pulls the movable electrode toward the fixed electrode.
Because of this inverse relationship, these parallel-plate actuators suffer from instability
for voltages beyond a threshold known as the "pull-in" voltage. For voltages beyond the
pull-in voltage, the electrostatic attraction grows more quickly than the mechanical
restoring force, causing the electrodes to crash into each other. Unless the electrodes are
protected with a dielectric coating or mechanical stops to prevent contact, this normally
results in catastrophic melting or vaporization of the actuator due to sudden current flow
between the electrodes..
Comb drive electrostatic actuators avoid the pull-in instability and remove the
dependence of the force on the deflection. As with parallel-plate actuators, comb drives
consist of one fixed and one movable electrode. Using straight combs, like those shown in
the figure results in an attractive force that is nearly constant over a wide range of
deflection of the movable comb. The attractive force falls rapidly when the combs
disengage and rises rapidly when the combs approach full engagement, but most comb
drives are designed to operate entirely in the constant-force region.
47
Fig. 5.5
A comb-drive actuator uses interdigitated comb electrodes to produce an attractive
force which does not depend on actuator displacement
Comb drives also suffer from instability when the applied voltage is too high, but this
instability is not directly related to the deflection of the movable comb. As long as each
comb finger is perfectly centered between two opposing comb fingers, the net transverse
force acting on that finger will be zero. However, it is common for the fingers to become
slightly off-center during motion. If the resulting transverse force is large enough, it will
either cause bending of the fingers or it will pull the entire comb in the transverse direction.
Hence, for sufficiently large applied voltage, the fingers on opposing combs can touch,
which is frequently catastrophic due to melting or vaporization of the fingers.
5.4.2 Thermal Actuation
A change in temperature causes an object to undergo a change in length, where the
change is proportional to the material's coefficient of thermal expansion. This length
change is usually too small to be useful in most actuation purposes. Therefore, a method of
amplifying the displacement is an essential part of thermal actuators. Figures 7a to 7d
illustrate four examples for achieving amplification of thermal expansion in micro
actuators.
Bimetallic devices use two materials with different coefficients of thermal expansion
that are fused together. As the temperature increases, one material expands more than the
other and the actuator bends to accommodate the different deflections.
48
5.5 MEMS in Optical Circuits
A wide variety of optical components may also be implemented in MEMS. For
example, the Digital Mirror Device discussed above uses micro machined mirrors to
redirect light. MEMS mirrors have also been used for optical switching applications,
allowing optical communication to be routed without requiring conversion to electrical
signals.
MEMS optical waveguides are often used to route optical signals within a MEMS
optical chip. These waveguides consist of a core with low loss at optical wavelengths.
Using micromachining, the waveguides can be patterned on the same chip as other optical
components. Both mechanically suspended and fixed waveguides have been demonstrated.
Suspended waveguides can also be designed to deflect mechanically.
Micro machined lens arrays have also been demonstrated for optical applications. Figure
below shows an example of three types of micro machined lens arrays. Similarly,
diffractive gratings can be made using the fine dimensional control available from
micromachining. These lens arrays and gratings have been used in optical filters and
switches.
Fig. 5.6
Three types of MEMS lens arrays: Cylindrical (top), Circular lenses, Square packed
(middle), and Hexagonal lens, Hex packed (bottom).
49
5.6 Sensors
A sensor is a device that responds to a physical input (such as motion, radiation, heat,
pressure, magnetic field), and transmits a resulting signal that is usually used for detection,
measurement, or control. A transducer (often used as a synonym for sensor) is a device that
is actuated by power from one system and converts it to a different form to another system.
Piezoresistive and capacitive sensing methods are among the most commonly employed
sensing methods in MEMS. Piezoresistance is the change in resistivity caused by
mechanical stresses applied to a material. Materials with high piezoresistivity (such as
some semiconductors which have more than an order of magnitude higher piezoresistivity
than metals) are useful for transducing mechanical deformation to electrical signals. This is
particularly useful in applications such as pressure sensors and accelerometers.
Fig. 5.7
Example thermal amplification approaches, including (a) bimetallic, (b) pseudo-
bimorph, (c) geometry-based amplification, and (d) a thermo mechanical in-plane
micro actuator (TIM).
50
While bimetallic actuators heat both materials to the same temperature but exploit their
differences in coefficients of thermal expansion, pseudo bimorphs use a single material
with a uniform coefficient of thermal expansion, but with different parts experiencing
different temperature changes. This approach makes it possible to construct an actuator
from a single layer of the same material. An example is the device shown in Figure which
has one leg thinner than the other. An electric current runs through the legs, but the thin leg
will have a higher electrical resistance and will heat up more than the wide leg. As the hot
leg expands it will cause the actuator to rotate in the direction shown.
Another approach for amplifying the thermal expansion is to use geometric constraints
that force the actuator to move in the desired direction. An example of this type of
amplification is the "bent beam" actuator, illustrated in Figure. As the thin legs heat up, the
expansion causes an amplified deflection in the direction shown.
The Thermo mechanical In-plane Micro actuator (TIM) also exploits geometric
constraints [12, 13], as illustrated in Figure. It consists of thin legs connecting both sides of
a center shuttle. The leg ends not connected to the shuttle are anchored to bond pads on the
substrate and are fabricated at a slight angle to bias motion in the desired direction. As
voltage is applied across the bond pads, electric current flows through the thin legs. The
legs have a small cross sectional area and thus have a high electrical resistance, which
causes the legs to heat up as the current passes through them. The shuttle moves forward to
accommodate the resulting thermal expansion. Advantages of this device include its ability
to obtain high deflections and large forces, as well as its ability to provide a wide range of
output forces by changing the number of legs in the design. A scanning electron
micrograph of a TIM is shown in Figure below.
51
CHAPTER – 6
BRIEF DESCRIPTION ABOUT ZIGBEE COMMUNICATION
The explosion in wireless technology has seen the emergence of many standards,
especially in the industrial, scientific and medical (ISM) radio band. There have been a
multitude of proprietary protocols for control applications, which bottlenecked interfacing.
Need for a widely accepted standard for communication between sensors in low data rate
wireless networks was felt. As an answer to this dilemma, many companies forged an
alliance to create a standard which would be accepted worldwide. It was this Zigbee
Alliance that created Zigbee. Bluetooth and Wi-Fi should not be confused with Zibgee.
Both Bluetooth and Wi-Fi have been developed for communication of large amount of data
with complex structure like the media files, software etc. Zigbee on the other hand has been
developed looking into the needs of communication of data with simple structure like the
data from the sensors.
Fig. 6.1
Zigbee Module
52
Zigbee is a low power spin off of WiFi. It is a specification for small, low power radios
based on IEEE 802.15.4 – 2003 Wireless Personal Area Networks standard. The
specification was accepted and ratified by the Zigbee alliance in December 2004.
Many years ago, when Bluetooth technology was introduced, it was thought that
Bluetooth would make WiFi redundant. Bluetooth is made with mobile phones as its centre
of universe enabling media transfer at rates in excess of 1 Mbps while Zigbee is built with
emphasis on low data rate control system sensors featuring slower data of just 250 kbps.
6.1 Zigbee Networks
Zigbee devices can form networks with Mesh, Star and Generic Mesh topologies among
themselves. The network can be expanded as a cluster of smaller networks. A ZigBee
network can have three types of nodes: Zigbee Coordinator (ZBC), Zigbee router (ZBR)
and Zigbee End Device (ZBE) each having some unique property.
Fig. 6.2
Zigbee Mesh Networking
Let us understand Zigbee through a typical usage scenario in a home automation system.
There can be only one ZBC in a network, the one that initiates the network in the first place
and stores the information about the network. This would be the main control panel or
remote control in the living room of each storey. All the devices in the network
53
communicate with this ZBC. It has routing capabilities and acts as a bridge to other
networks on other floors. A ZBR is an optional component used to extend the coverage,
say, providing access to the Zigbee receivers controlling the garage lighting and shutter
which is in the nearby shed. The router itself may host an application like a CC Camera
which is continuously in active monitoring state. It can also handle local address allocation
or de-allocation. A ZBE is optimized for low power consumption and is the cheapest
among the three node types. It communicates only with the coordinator and is the point
where sensors are deployed. Any end device like lighting units, air conditioning elements
etc. can be Zigbee End Devices. Unicast Device Discovery is done if Network ID is
available; else Broadcast Device Discovery is done. The Radio unit and the Processing unit
are often built into a single chip to reduce costs. When a car enters the premises, the radio
transmitter inside the car broadcasts its presence to the Zigbee Coordinator through routers.
The coordinator then binds the garage shutter’s receiver with the Car’s transmitter and all
packets from the Car transmitter are routed to the Shutter, which can then open and close
without stepping out of the car. The whole transaction can be automated such that by the
time the car reaches the garage door, it automatically opens.
Fig. 6.3
Zigbee in Home Automation
54
In a network, data traffic can be periodic, intermittent or repetitive. When data is
periodic, the application determines the rate of transfer. Intermittent data needs optimum
power savings and hence the data rate is stimulus dependent. For repetitive type of data,
guaranteed time slots are used, for example the air conditioning unit.
6.2 Architectural Overview:
Zigbee bases itself on the IEEE 802.15.4-2003 specifications which lay down standards
for the Physical and MAC layers. The protocol stack is completed by adding Zigbee’s own
Network and Application Layers. Drawing analogies from the OSI protocol stack simplifies
the study of Zigbee protocol. In the figure below, the two protocols are stacked up side by
side to see the similarity of roles of various layers.
Fig. 6.4
Architectural Overview
55
6.2.1 Physical Layer
Zigbee uses three frequency bands for transmission- 868 MHz band with a single
channel has a raw data rate of 20 kb/s. The 915MHz band with 10 channels has each
channel’s central frequency separated from the adjacent band by 2 MHz and data rate of 40
kb/s. BPSK modulated symbols are transmitted at 1 bit per symbol using Direct Sequence
Spread Spectrum (DSSS) technique with 15 bit chips. The 2.4 GHz ISM band with 16
channels, 5 MHz wide offers 250 kb/s data rate. It employs O-QPSK modulation with 4
bits/symbol transmitted using DSSS with 32 Bit chips. To reduce the transmitted power, the
Zigbee transmitters use Energy Detection (ED) and Link Quality Indication (LQI). It is the
responsibility of the physical layer to perform channel assessment.
6.2.2 MAC Layer
Channel access is primarily through Carrier Sense Multiple Access- Collision
Avoidance (CSMA-CA). On a node hop to hop basis, the MAC layer can take care of
transmitting data. Depending on the mode of transmission, i.e. Beacon or Non-Beacon
mode, the MAC layer decides whether to use slotted or unslotted CSMA-CA. The MAC
layer takes care of scanning the channel, starting PANs, detecting and resolving PAN ID
conflicts, sending beacons, performing device discovery, association and disassociation,
synchronizing network device and realigning orphaned devices on the network. Along with
this, the MAC layer also provides some standard security features like access control,
encryption of data, duplicate rejection and frame integrity. Like in the case of the standard
OSI MAC Layer, MAC layer in Zigbee also cannot take care of the situation when the
nodes have intermediate nodes between them. This functionality of routing the packets to
their destinations is provided in the network layer.
6.2.3 Network and Security Layer
The network layer takes care of network startup, device configuration, topology specific
routing, and providing security. On each node, the network layer is the part of the stack that
does the route calculations, neighbor discovery and reception control. All the nodes are
optimized using unique 64 bit addresses as per the IEEE 802.15.4 standard, supporting a
56
maximum of 65536, 16 bit network address devices which can have 256 sub addresses. The
network routing table is populated when the devices come alive in the network for the first
time by generating Broadcast Routing Request Packets (RREQ). Endpoint routers respond
to these packets as Routing Response Packets (RREP).
6.2.4 Application Support Sub-Layer
It interfaces the network layer and application layer providing a general set of services
through two entities, the APS Data Entity (APSDE) and APS Management Entity
(APSME) accessed through their respective Service Access Points (SAP). These provide
services like binding management, making application level PDU, group filtering, and
managing Object database called APS Information Base, providing reliability of transaction
etc. which are the necessary functions for an application to work properly.
Fig. 6.5
Application Support Sub-Layer
57
6.3 Application Framework
It is the environment to host application objects on a Zigbee device. Up to 240 distinct
application objects can be defined uniquely. It consists of the application profiles as the top
layer over ZDO which provides the base functionality.
Application Profiles define an accepted language for exchanging data and provide
interoperable services across different manufacturers. Zigbee Alliance has released several
Standard Profiles which contain different device descriptors which have unique identifiers.
6.4 ZigBee Device Objects (ZDO)
ZDO provides an interface between the application objects, the device profiles, and the
APS layer in Zigbee devices. It is located between the Application Profiles and the
application support sub-layer. The ZDO are responsible for initializing the APS, the
network layer, and the Security Service Provider, and also forming the configuration
information from applications to implement discovery, security, network and binding
management.
6.5 Data Transfer Modes
This data can be transferred in two modes: Beacon Mode and Non-beacon mode. In
beacon mode, the data is sent periodically over the network. In between the time period
when the devices are not sending data, they may enter a low power sleep state to minimize
power consumption. However, such close timing and network synchronization has precise
timing needs as the beacon period is of the order of milliseconds. This can pose design
constraints while reducing costs and eventually is a tradeoff between the design constraints
and costs involved. In a non-beacon mode, the coordinators and the routers active in the
network have to stay awake for most of the time to listen incoming data and hence need
robust power supplies. Hence, the end devices can sleep most of the time and wake up
solely for sending data, or on receiving a trigger, while the core devices need to be active,
creating an asymmetric power distribution in the network. This creates a heterogeneous
network.
58
Table 6.1
Zigbee Specifications
And why is Zigbee considered a possible competitor to Bluetooth technology? The
answer would be evident from a comparison between the two. This however should not be
the basis of deciding which technology is the best, but to decide, what technology is best
suited for the specific task. Eventually, it might coexist with Bluetooth just as Bluetooth
has come to live with WiFi.
59
CHAPTER – 7
DESCRIPTION ABOUT ‘H’ - BRIDGE
7.1 Introduction
Whenever a robotics hobbyist talk about making a robot, the first thing comes to his
mind is making the robot move on the ground. And there are always two options in front of
the designer whether to use a DC motor or a stepper motor. When it comes to speed,
weight, size, and cost. DC motors are always preferred over stepper motors. There are
many things, which we can do with DC motor when interfaced with a micro controller. For
example we can control the speed of motor, we can control the direction of rotation, we can
also do encoding of the rotation made by DC motor i.e. keeping track of how many turns
are made by the motors etc. So we can see DC motors are better than stepper motors.
7.2 Basic Theory
Fig. 7.1 H – Bridge
H - Bridge called a "full bridge". The H-bridge is so named because it has four
switching elements at the "corners" of the H and the motor forms the cross bar. The basic
60
bridge is shown in the figure above. The key fact to note is that there are, in theory, four
switching elements within the bridge. These four elements are often called, high side left,
high side right, low side right, and low side left (when traversing in clockwise order).
To power the motor, turn on two switches that are diagonally opposed. The current
flows and the motor begin to turn in a "positive" direction. Switch off these two switches
and switch on other two switches diagonally in other direction then the motor starts rotating
in opposite direction.
One more topic in the basic theory section is quadrants. If each switch can be controlled
independently then we can do some interesting things with the bridge, some folks call such
a bridge a "four quadrant device" (4QD). We can build a small truth table that tells us for
each of the switch's states, what the bridge will do. As each switch has one of two states,
and there are four switches, there are 16 possible states. However, since any state that turns
both switches on one side on is "bad", there are in fact only four useful states (the four
quadrants) where the transistors are turned on.
High Side Left
High Side Right
Low Side Left
Low Side Right
Quadrant Description
On Off Off On Forward Running
Off On On Off Backward Running
On On Off Off Braking
Off Off On On Braking
Table 7.1
Working Conditions of H - Bridge
61
In the above table the last two rows describes condition about short circuit the motor that
causes the motors generator effect to work against it. The turning motor generates a
voltage, which tries to force the motor to turn the opposite direction. This causes the motor
to rapidly stop spinning and is called "braking" on a lot of H-bridge designs. Of course
there is also the state where all the transistors are turned off. In this case the motor coasts
freely if it was spinning and does nothing if it was doing nothing.
• Using Relays A simple implementation of a H Bridge using four SPST relays is shown. Terminal A is
High Side Left, Terminal B is High Side Right, Terminal C is Low Side Left and Terminal
D is Low Side Right. The logic followed is according to the table above.
• Using Transistors:
We can better control our motor by using transistors or Field Effect Transistors (FET’s).
Most of what we have discussed about the relays H-Bridge is true of these circuits. See the
diagram showing how they are connected. We should add diodes across the transistors to catch the back voltage that is generated by the motor's coil when the power is switched on
and off. This fly back voltage can be many times higher than the supply voltage.
Don't turn on A and C or B and D at the same time.
Fig. 7.2
Transistors as H – Bridge
62
Transistors, being a semiconductor device, will have some resistance, which causes
them to get hot when conducting much current. This is called not being able to sink or
source very much power, i.e.: Not able to provide much current from ground or from plus
voltage.
MOSFET’s are much more efficient, they can provide much more current and not get as
hot. They usually have the fly back diodes built in so we don't need the diodes anymore.
This helps guard against fly back voltage frying our ICs.
To use MOSFET’s in an H-Bridge, we need P-Channel MOSFET’s on top because they
can "source" power and N-Channel MOSFET’s on the bottom because they can "sink"
power. It is important that the four quadrants of the H-Bridge circuits be turned on and off
properly. When there is a path between the positive and groundside of the H-Bridge, other
than through the motor, a condition exists called "shoot through". This is basically a direct
short of the power supply and can cause semiconductors to become ballistic, in circuits
with large currents flowing. There are H-bridge chips available that are much easier, and
safer, to use than designing our own H-Bridge circuit.
7.3 L293D Dual H-Bridge Motor Driver
L293D is a dual H-Bridge motor driver, so with one IC we can interface two DC motors,
which can be controlled in both clockwise and counter clockwise directions. Since the
device is having four half ‘H’ Bridges, thereby if required four motors can be driven
through this single device, moreover the task is to run all four motors in one direction only.
L293D has output current of 600mA and peak output current of 1.2A per channel.
Moreover for protection of circuit from back EMF output diodes are included within the IC.
The output supply (VCC2) has a wide range from 4.5V to 36V, which has made L293D a
best choice for DC motor driver.
In this IC there are two different power supplies (Vcc1 and Vcc2). Vcc1 is for logicinput
circuit while Vcc2 is supply for the output circuit. This means that we should applyabout
5V to Vcc1 and whatever voltage required by the motor (up to 36V max for this IC) to
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Vcc2. Each Half H-Bridge has an individual Ground. So we must ground the terminal
corresponding to the Half H-Bridge, depending up on the circuit design, if required all four
terminals of bridges can be connected to the ground.
Each Half H-Bridge has an Input (A) and output (Y). Also there are enable pins to turn
on the Half H-Bridges. Once a Half H-bridge is enabled, then the truth table is as follows:
INPUT A
OUTPUT Y
L L
H H
Table 7.2
Truth Table of Half Enabled H- Bridge
So we just give a High level when we want to turn the Half H-Bridge on and Low level
when we want to turn it off. When the Half H-Bridge is on, the voltage at the output is
equal to Vcc2.
If we want to make a Full H-Bridge, we must connect the motor (or the load) between
the outputs of two Half H-Bridges and the inputs will be the two inputs of the Half H-
Bridges.
Suppose we have connected Half H-Bridges 1 and 2 to form a Full H-Bridge. Now the
truth table is as follows
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INPUT
1A
INPUT
2A
OUTPUT
1Y
OUTPUT
2Y Description
L L L L Braking (both terminals of motor are
Gnd)
L H L H Forward Running
H L H L Backward Running
H H H H Braking (both terminals of motor at
Vcc2)
Table 7.3
Truth table of full enabled H – Bridge
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CHAPTER – 8 DC MOTORS
8.1 Overview
At the most basic level, electric motors exist to convert electrical energy into
mechanical energy. This is done by way of two interacting magnetic fields -- one
stationary, and another attached to a part that can move. A number of types of electric
motors exist, but most BEAM bots use DC motors in some form or another. DC motors
have the potential for very high torque capabilities (although this is generally a function of
the physical size of the motor), are easy to miniaturize, and can be "throttled" via adjusting
their supply voltage. DC motors are also not only the simplest, but the oldest electric
motors.
The basic principles of electromagnetic induction were discovered in the early 1800's by
Oersted, Gauss, and Faraday. By 1820, Hans Christian Oersted and Andre Marie Ampere
had discovered that an electric current produces a magnetic field. The next 15 years saw a
flurry of cross-Atlantic experimentation and innovation, leading finally to a simple DC
rotary motor. A number of men were involved in the work, so proper credit for the first DC
motor is really a function of just how broadly you choose to define the word "motor."
DC motors are configured in many types and sizes, including brushless, servo, and gear
motor types. A motor consists of a rotor and a permanent magnetic field stator. The
magnetic field is maintained using either permanent magnets or electromagnetic windings.
DC motors are most commonly used in variable speed and torque applications.
Brushed DC motors have built-in commutation, meaning that as the motor rotates,
mechanical brushes automatically commutate coils on the rotor. Brushless DC motors use
an external power drive to allow commutation of the coils on the stator. Brush-type motors
are used when cost is a priority, while brushless motors are selected fulfill specific requirements, such as maintenance-free operation, high speeds, and hazardous
environments where sparking could be dangerous.
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DC gear motors are configured in many types and sizes, including brushless and servo.
A DC gear motor consists of a rotor and a permanent magnetic field stator and an integral
gearbox or gear head. The magnetic field is maintained using either permanent magnets or
electromagnetic windings. DC motors are most commonly used in variable speed and
torque applications.
Motion and controls covers a wide range of components that in some way are used to
generate and/or control motion. Areas within this category include bearings and bushings,
clutches and brakes, controls and drives, drive components, encoders and resolvers,
Integrated motion control, limit switches, linear actuators, linear and rotary motion
components, linear position sensing, motors (both AC and DC motors), orientation position
sensing, pneumatics and pneumatic components, positioning stages, slides and guides,
power transmission (mechanical), seals, slip rings, solenoids, springs.
Motors are the devices that provide the actual speed and torque in a drive system. This
family includes AC motor types (single and multiphase motors, universal, servo motors,
induction, synchronous, and gear motor) and DC motors (brushless, servo motor, and gear
motor) as well as linear, stepper and air motors, and motor contactors and starters.
Permanent magnet DC motor responds to both voltage and current. The steady state
voltage across a motor determines the motor’s running speed, and the current through its
armature windings determines the torque. Apply a voltage and the motor will start running
in one direction; reverse the polarity and the direction will be reversed. If you apply a load
to the motor shaft, it will draw more current, if the power supply does not able to provide
enough current, the voltage will drop and the speed of the motor will be reduced. However,
if the power supply can maintain voltage while supplying the current, the motor will run at
the same speed. In general, you can control the speed by applying the appropriate voltage,
while current controls torque. In most cases, DC motors are powered up by using fixed DC
power supply, therefore; it is more efficient to use a chopping circuit.
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Consider what happens when a voltage applied to a motor’s windings is rapidly turned
ON and OFF in such a way that the frequency of the pulses produced remains constant, but
the width of the ON pulse is varied. This is known as Pulse Width Modulation (PWM).
Current only flows through the motor during the ON portion of the PWM waveform. If the
frequency of the PWM input is high enough, the mechanical inertia of the motor cannot
react to the ripple wave; instead, the motor behaves as if the current were the DC average of
the ripple wave. Therefore, by changing the width of pulse, we can control the motor speed.
At the most basic level, electric motors exist to convert electrical energy into mechanical
energy. This is done by way of two interacting magnetic fields -- one stationary, and
another attached to a part that can move. A number of types of electric motors exist, but
most BEAM bots use DC motors in some form or another. DC motors have the potential
for very high torque capabilities (although this is generally a function of the physical size of
the motor), are easy to miniaturize, and can be "throttled" via adjusting their supply
voltage. DC motors are also not only the simplest, but the oldest electric motors.
8.2 Principles of operation
In any electric motor, operation is based on simple electromagnetism. A current carrying
conductor generates a magnetic field; when this is then placed in an external magnetic field,
it will experience a force proportional to the current in the conductor, and to the strength of
the external magnetic field. As you are well aware of from playing with magnets as a kid,
opposite (North and South) polarities attract, while like polarities (North and North, South
and South) repel. The internal configuration of a DC motor is designed to harness the
magnetic interaction between a current -carrying conductor and an external magnetic field
to generate rotational motion. Let's start by looking at a simple 2-pole DC electric motor
(here dark black represents a magnet or winding with a "North" polarization, while light
colour represents a magnet or winding with a "South" polarization).
Every DC motor has six basic parts -- axle, rotor (a.k.a., armature), stator, commutator,
field magnet’s, and brushes. In most common DC motors, the external magnetic field is
produced by high-strength permanent magnets. The stator is the stationary part of the motor
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-- this includes the motor casing, as well as two or more permanent magnet pole pieces. The
rotor (together with the axle and attached commutator) rotates with respect to the stator.
The rotor consists of windings (generally on a core), the windings being electrically
connected to the commutator. The above diagram shows a common motor layout -- with
the rotor inside the stator (field) magnets.
Fig. 8.1
DC Motor
The geometry of the brushes, commutator contacts, and rotor windings are such that
when power is applied, the polarities of the energized winding and the stator magnet(s) are
misaligned, and the rotor will rotate until it is almost aligned with the stator's field magnets.
As the rotor reaches alignment, the brushes move to the next commutator contacts, and
energize the next winding. Given our example two-pole motor, the rotation reverses the
direction of current through the rotor winding, leading to a "flip" of the rotor's magnetic
field, driving it to continue rotating.
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In real life, though, DC motors will always have more than two poles (three is a very
common number). In particular, this avoids "dead spots" in the commutator. You can
imagine how with our example two-pole motor, if the rotor is exactly at the middle of its
rotation (perfectly aligned with the field magnets), it will get "stuck" there. Meanwhile,
with a two-pole motor, there is a moment where the commutator shorts out the power
supply (i.e., both brushes touch both commutator contacts simultaneously). This would be
bad for the power supply, waste energy, and damage motor components as well. Yet
another disadvantage of such a simple motor is that it would exhibit a high amount of
torque "ripple" (the amount of torque it could produce is cyclic with the position of the
rotor).
D.C. Motors with field coils are classified as series. Shunt, compound and separately
excited according to how the field windings and armature windings are connected. With the
series wound motor the armature and fields coils are in series. Such a motor exerts the
highest starting torque and has the greatest no-load speed. With light loads there is a danger
that a series wound motor might run at too high a speed. Reversing the polarity of the
supply to the coils has no effect on the direction of rotation of the motor, it will continue
rotating in the same direction since both the field and armature currents have been reversed.
With the shunt wound motor the armature and field coils are in parallel. It provides the
lowest starting torque, a much lower no- load speed and has good speed regulation.
Because of this almost constant speed regardless of load, shunt wound motors are very
widely used to reverse the direction of rotation, either the armature or field supplied must
be reversed. For this reason, the separately excited windings are preferable for such a
situation.
The compound motor has two field windings, one in series with the armature and one in
parallel. Compound wound motors aim to got the best features of the series and shunt
wound motors, namely a high starting torque and good speed regulation. The separately
excited motor has separate control of the armature and field currents and can be considered
to be a special case of the shunt wound motor.
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The torque-speed characteristics of the above motors and the speed of such D.C. Motors
can be changed by either changing the armature current or the field current. Generally it is
the armature current that is varied. The choice of motor will depend on its application. For
example, with a robot, manipulator, and the robot wrist might use a series wound motor
because the speed decreases as the load increases. a shunt wound motor would be used
where a constant speed was required, regardless of the load.
The speed of a permanent magnet motor depends on the current through the armature
coil. With a field coil motor either varying the armature current or the field current can
change the speed; generally it is the armature current that is varied. Thus speed control can
be obtained by controlling the voltage applied to the armature. However, because fixed
voltage supplies are often used, an electronic circuit obtains a variable voltage.
With an alternating current supply, the thyristor circuit can be used to control the
average voltage applied to the armature. However, we are often concerned with the control
of D.C. Motors by means of control signals emanating from microprocessors. In such cases
the technique known as pulse width modulation (PWM) is generally used. This basically
involves taking a constant D.C. supply voltage and chopping it so that the average value is
varied.
8.3 Types of DC Motors with Advantages and Disadvantages
Type Advantages Disadvantages
Stepper Motor
Very precise speed and
position control. High
Torque at low speed.
Expensive and hard to
find. Require a switching
control circuit
DC Motor with field coil
Wide range of speeds and
torques. More powerful
than permanent magnet
motors
Require more current
than permanent magnet
motors, since field coil
must be energized.
motors. More difficult to
obtain.
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DC permanent magnet
motor
Small, compact, and easy
to find. Very inexpensive
Generally small. Cannot
vary magnetic field
strength.
Gasoline (small two
stroke)
Very high power/weight
ratio. Provide Extremely
high torque. No batteries
required.
Expensive, loud, difficult
to mount, very high
vibration.
Table 8.1
Types of DC Motors
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CHAPTER – 9 DESCRIPTION ABOUT MICRO CONTROLLERS
9.1 Introduction
A Micro controller consists of a powerful CPU tightly coupled with memory, various
I/O interfaces such as serial port, parallel port timer or counter, interrupt controller, data
acquisition interfaces-Analog to Digital converter, Digital to Analog converter, integrated
on to a single silicon chip. If a system is developed with a microprocessor, the designer has
to go for external memory such as RAM, ROM, EPROM and peripherals.
Intel has introduced a family of Micro controllers called the MCS-51.The
microcontroller plays the major role in any embedded project. In this my project we use
three microcontrollers they are made by the ATMEL Company. In which two are
AT89C51/52 and the other is AT 89C2051.
9.2 Necessity of Microcontrollers
Microprocessors brought the concept of programmable devices and made many
applications of intelligent equipment. Most applications, which do not need large amount of
data and program memory, tended to be costly.
The microprocessor system had to satisfy the data and program requirements so;
sufficient RAM and ROM are used to satisfy most applications .The peripheral control
equipment also had to be satisfied. Therefore, almost all-peripheral chips were used in the
design. Because of these additional peripherals cost will be comparatively high.
9.3 Features of a Microcontroller
• 8/16/32 CPU
• Instruction set rich in I/O & bit operations.
• One or more I/O ports.
• One or more timer/counters.
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• One or more interrupt inputs and an interrupt controller
• One or more serial communication ports.
• Analog to Digital /Digital to Analog converter
• One or more PWM output
• Network controlled interface
9.4 Advantages of Microcontrollers
• If system is developed with a microprocessor, the designer has to go for external
memory such as RAM, ROM or EPROM and peripherals and hence the size of PCB
will be large enough to hold all the required peripherals. But, the micro controller
has got all this peripheral facility on a single chip o development of a similar system
with a micro controller reduces PCB size and cost of the design.
• One of the major differences between a micro controller and a microprocessor is
that a controller often deals with bits, not bytes as in the real world application, for
example switch contacts can only be open or close, indicators should be lit or dark
and motors can be either turned on or off and so forth.
9.5 FEATURES OF 8051 ARCHITECTURE
• Optimized 8 bit CPU for control applications and extensive Boolean
processing capabilities.
• 64K Program Memory address space.
• 64K Data Memory address space.
• 128 bytes of on chip Data Memory.
• 32 Bi-directional and individually addressable I/O lines.
• Two 16 bit timer/counters.
• Full Duplex UART.
• 6-source / 5-vector interrupt structure with priority levels.
• On chip clock oscillator.
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Now we may be wondering about the non-mentioning of memory space meant for
the program storage, the most important part of any embedded controller. Originally
this 8051 architecture was introduced with on-chip, ‘one time programmable’
version of Program Memory of size 4K X 8.
Intel delivered all these microcontrollers (8051) with user’s program fused
inside the device. The memory portion was mapped at the lower end of the
Program Memory area. But, after getting devices, customers couldn’t change
anything in their program code, which was already made available inside during
device fabrication.
9.6 8051 Micro controller architecture
The 8051 architecture consists of these specific features
• Eight –bit CPU with registers A (the accumulator) and B
• Sixteen-bit program counter (PC) and data pointer (DPTR)
• Eight- bit stack pointer (PSW)
• Eight-bit stack pointer (Sp)
• Internal ROM or EPROM (8751) of 0(8031) to 4K (8051)
• Internal RAM of 128 bytes:
1. Four register banks, each containing eight registers
2. Sixteen bytes, which maybe addressed at the bit level
3. Eighty bytes of general- purpose data memory
• Thirty –two input/output pins arranged as four 8-bit ports:p0-p3
• Two 16-bit timer/counters: T0 and T1
• Full duplex serial data receiver/transmitter: SBUF
• Control registers: TCON, TMOD, SCON, PCON, IP, and IE
• Two external and three internal interrupts sources.
• Oscillator and clock circuits.
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9.7 PIN DIAGRAM
Fig. 9.1
Pin Diagram of AT89C51
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9.8 Functional block diagram of Microcontroller
Fig. 9.2
Block Diagram of Microcontroller
9.9 Port 3 Pins Alternate Function
• P3.0- RxD (serial input port)
• P3.1 -TxD (serial output port)
• P3.2 -INT0 (external interrupt 0)
• P3.3- INT1 (external interrupt 1)
• P3.4 -T0 (timer 0 external input)
• P3.5 -T1 (timer 1 external input)
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• P3.6 -WR (external data memory write strobe)
• P3.7 -RD (external data memory read strobe)
• VCC: -Supply voltage
• VSS: -Circuit ground potential
All four ports in the 89C51 are bidirectional. Each consists of a latch (Special Function
Registers P0 through P3), an output driver, and an input buffer. The output drivers of Ports
0 and 2, and the input buffers of Port 0, are used in accesses to external memory. In this
application, Port 0 outputs the low byte of the external memory address, time-multiplexed
with the byte being written or read. Port 2 outputs the high byte of the external memory
address when the address is 16 bits wide. Otherwise, the Port 2 pins continue to emit the P2
SFR content.
All the Port 3 pins are multifunctional. They are not only port pins, but also serve the
functions of various special features as listed below:
Port Pin Alternate Function
P3.0 RxD (serial input port)
P3.1 TxD (serial output port)
P3.2 INT0 (external interrupt)
P3.3 INT1 (external interrupt)
P3.4 T0 (Timer/Counter 0 external input)
P3.5 T1 (Timer/Counter 1 external input)
P3.6 WR (external Data Memory write strobe)
P3.7 RD (external Data Memory read strobe)
Table 9.1
Various functions of Port – 3
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9.10 The 8051 Oscillator and Clock
The heart of the 8051 circuitry that generates the clock pulses by which all the internal
all internal operations are synchronized. Pins XTAL1 And XTAL2 is provided for
connecting a resonant network to form an oscillator. Typically a quartz crystal and
capacitors are employed. The crystal frequency is the basic internal clock frequency of the
microcontroller. The manufacturers make 8051 designs that run at specific minimum and
maximum
Fig. 9.3
Oscillator and timing circuit
9.11 Types of memory
The 8051 have three general types of memory. They are on-chip memory, external
Code memory and external Ram. On-Chip memory refers to physically existing memory
on the micro controller itself. External code memory is the code memory that resides off
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chip. This is often in the form of an external EPROM. External RAM is the Ram that
resides off chip. This often is in the form of standard static RAM or flash RAM.
9.11.1 Code memory
Code memory is the memory that holds the actual 8051 programs that is to be run. This
memory is limited to 64K. Code memory may be found on-chip or off-chip. It is possible to
have 4K of code memory on-chip and 60K off chip memory simultaneously. If only off-
chip memory is available then there can be 64K of off chip ROM. This is controlled by pin
provided as EA.
9.11.2 Internal RAM
The 8051 have a bank of 128 bytes of internal RAM. The internal RAM is found on-
chip. So it is the fastest Ram available. And also it is most flexible in terms of reading and
writing. Internal Ram is volatile, so when 8051 is reset, this memory is cleared. 128 bytes
of internal memory are subdivided. The first 32 bytes are divided into 4 register banks.
Each bank contains 8 registers. Internal RAM also contains 128 bits, which are addressed
from 20h to 2Fh. These bits are bit addressed i.e. each individual bit of a byte can be
addressed by the user. They are numbered 00h to 7Fh. The user may make use of these
variables with commands such as SETB and CLR.
9.11.3 Special Function registered memory
Special function registers are the areas of memory that control specific functionality of
the 8051 micro controller.
9.11.3.1 Accumulator (0E0h)
As its name suggests, it is used to accumulate the results of large no of instructions. It
can hold 8 bit values.
80
9.11.3.2 B register (0F0h)
The B register is very similar to accumulator. It may hold 8-bit value. The b register is
only used by MUL AB and DIV AB instructions. In MUL AB the higher byte of the
product gets stored in B register. In div AB the quotient gets stored in B with the remainder
in A.
9.11.3.3 Stack pointer (81h)
The stack pointer holds 8-bit value. This is used to indicate where the next value to be
removed from the stack should be taken from. When a value is to be pushed onto the stack,
the 8051 first stores the value of SP and then store the value at the resulting memory
location. When a value is to be popped from the stack, the 8051 returns the value from the
memory location indicated by SP and then decrements the value of SP.
9.11.3.4 Data pointer
The SFRs DPL and DPH work together work together to represent a 16-bit value called
the data pointer. The data pointer is used in operations regarding external RAM and some
instructions code memory. It is a 16-bit SFR and also an addressable SFR.
9.11.3.5 Program counter
The program counter is a 16 bit register, which contains the 2 byte address, which tells
the 8051 where the next instruction to execute to be found in memory. When the 8051 is
initialized PC starts at 0000h. And is incremented each time an instruction is executes. It is
not addressable SFR.
9.12 I/O Ports
One major feature of a microcontroller is the versatility built into the input/output (I/O)
circuits that connect the 8051 to the outside world. The main constraint that limits
numerous functions is the number of pins available in the 8051 circuit. The DIP had 40 pins
and the success of the design depends on the flexibility incorporated into use of these pins.
For this reason, 24 of the pins may each used for one of the two entirely different functions
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which depend, first, on what is physically connected to it and, then, on what software
programs are used to “program” the pins.
9.12.1 PORT 0
Port 0 pins may serve as inputs, outputs, or, when used together, as a bi directional low-
order address and data bus for external memory. To configure a pin as input, 1 must be
written into the corresponding port 0 latch by the program. When used for interfacing with
the external memory, the lower byte of address is first sent via PORT0, latched using
Address latch enable (ALE) pulse and then the bus is turned around to become the data bus
for external memory.
9.12.2 PORT 1
Port 1 is exclusively used for input/output operations. PORT 1 pins have no dual
function. When a pin is to be configured as input, 1 is to be written into the corresponding
Port 1 latch.
9.12.3 PORT 2
Port 2 may be used as an input/output port. It may also be used to supply a high –order
address byte in conjunction with Port 0 low-order byte to address external memory. Port 2
pins are momentarily changed by the address control signals when supplying the high byte
a 16-bit address. Port 2 latches remain stable when external memory is addressed, as they
do not have to be turned around (set to 1) for data input as in the case for Port 0.
9.12.4 PORT 3
Port 3 may be used to input /output port. The input and output functions can be
programmed under the control of the P3 latches or under the control of various special
function registers. Unlike Port 0 and Port 2, which can have external addressing functions
and change all eight-port b se, each pin of port 3 maybe individually programmed to be
used as I/O or as one of the alternate functions. The Port 3 alternate uses are:
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Pin (SFR) Alternate Use
P3.0-RXD (SBUF) Serial data input
P3.1-TXD (SBUF) Serial data output
P3.2-INTO 0 (TCON.1) External interrupt 0
P3.3 - INTO 1 (TCON.3) External interrupt 1
P3.4 - T0 (TMOD) External Timer 0 input
P3.5 – T1 (TMOD) External timer 1 input
P3.6 - WR External memory write pulse
P3.7 - RD External memory read pulse
Table 9.2
Uses of Port – 3
9.13 Interrupts
Interrupts are hardware signals that are used to determine conditions that exist in
external and internal circuits. Any interrupt can cause the 8051 to perform a hardware call
to an interrupt –handling subroutine that is located at a predetermined absolute address in
the program memory.
Five interrupts are provided in the 8051. Three of these are generated automatically by
the internal operations: Timer flag 0, Timer Flag 1, and the serial port interrupt (RI or TI)
Two interrupts are triggered by external signals provided by the circuitry that is connected
to the pins INTO 0 and INTO1. The interrupts maybe enable or disabled, given priority or
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otherwise controlled by altering the bits in the Interrupt Enabled (IE) register, Interrupt
Priority (IP) register, and the Timer Control (TCON) register. . These interrupts are mask
able i.e. they can be disabled. Reset is a non maskable interrupt which has the highest
priority. It is generated when a high is applied to the reset pin. Upon reset, the registers are
loaded with the default values.
Each interrupt source causes the program to do store the address in PC onto the stack
and causes a hardware call to one of the dedicated addresses in the program memory. The
appropriate memory locations for each for each interrupt are as follows:
Interrupt Address
RESET 0000
IE0 (External interrupt 0) 0003
TF0 (Timer 0 interrupt) 000B
IE1 (External interrupt 1) 0013
TF1 (Timer 1 interrupt) 001B
SERIAL 0023
Table 9.3
Interrupts and their Addresses
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CHAPTER – 10
HARDWARE DETAILS
The IC’s and other important components used in this project work, procured from the
Hyderabad Electronics Market. The details or data sheets of the IC’s are down loaded from
the Internet. The following are the web sites that can be browsed for collecting the data
sheets.
• www.texas Instruments.com
• www.national semiconductors.com
• www.fairchild semiconductors.com
•
10.1 Components used in the project work
• Atmel 89C51 Micro Controller
• Atmel 89C2051 Micro Controller
• L293D H – Bridge IC’s
• Voltage Regulator IC 7805
• BC 547 NPN Transistor
• Relay
• Zigbee Tarang
The required PCB’S (Printed Circuit boards) for the project work fabricated by SUN RISE
CIRCUITS, Kushaiguda Industrial Estate, Hyderabad. Kushaiguda Industrial Estate is very
famous for fabricating the Industrial grade PCB’s.
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CHAPTER – 11
SOFTWARE DETAILS
11.1 SOFTWARE DESCRIPTION
In our project we used software that is Keil micro vision for the simulation of the
program.
11.2 Keil Software
Keil development tools for the 8051 Microcontroller Architecture support every level of
software developer from the professional applications engineer to the student just learning
about embedded software.
The industry-standard Keil C Compilers, Macro Assemblers, Debuggers, Real-time
Kernels, Single-board Computers, and Emulators support all 8051 derivatives and help you
get your projects completed on schedule.
11.3 Simulation
The µVision Simulator allows you to debug programs using only your PC using
simulation drivers provided by Keil and various third-party developers. A good simulation
environment, like µVision, does much more than simply simulate the instruction set of a
microcontroller — it simulates your entire target system including interrupts, startup code,
on-chip peripherals, external signals, and I/O.
11.4 Use of software for execution of microcontroller programs
Keil development tools for the MC architecture support every level of software
developer from the professional applications engineer to the student just learning about
embedded software development.
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The industry-standard Keil-C compilers, macro assemblers, debuggers, real, time
Kernels, Single-board computers and emulators support all microcontroller derivatives and
help you to get more projects completed on schedule. The Keil software development tools
are designed to solve the complex Problems facing embedded software developers. Those
are listed below.
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CHAPTER – 12
CONCLUSIONS AND REFERENCES
12.1 CONCLUSION
The project work is designed and developed successfully. For the demonstration
purpose, a prototype module is constructed; and the results are found to be satisfactory.
Since it is a prototype module, a simple war tanker is constructed, which can be used for
many applications. In this concept the warfare vehicle is controlled by a remote that will be
operated by the operator and also has the provision to operate automatically. The triggering
of the gun can also be done through the remote by which the gun sound simulator IC
produces the gun shot sensation.
The employment of unmanned platforms in the battlefield serves not only to overcome
the constraints arising from manpower and resource shortages, but also increases the
operational capability of a fighting force. They will provide tangible increases in combat
range, firepower, speed, element of surprise, command and control, etc. As unmanned
warfare and the mastery of unmanned technology will become increasingly important parts
of a nation's strategic architecture, here armed forces and defence industries will need to
pay appropriate attention to this aspect of warfare.
While designing and developing this proto type module, we have consulted few experts
those who are having knowledge in Mechatronics, and these professionals working at
different organizations belongs to Hyderabad helped us while fabricating this project work.
Since it is a prototype module, much amount is not invested. The whole machine is
constructed with locally available components, especially the mechanical components used
in this project work are procured from mechanical fabricators and they are not exactly up to
the requirement. Some of the modifications must be carried out in design to make it as real
working system.
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