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i
“I hereby declare that I have read this thesis and in my opinion this thesis is
sufficient in terms of scope and quality for the award of the degree of
Bachelor of Electrical Engineering (Mechatronics)”
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DEVELOPMENT OF POLE BALANCING
MOBILE ROBOT
NOORAZMI B AB RAHMAN
Submitted to the Faculty of Electrical Engineering
in partial fulfillment of the requirement for the degree of
Bachelor in Electrical Engineering (Mechatronics)
Faculty of Electrical Engineering
Universiti Teknologi Malaysia
MAY 2009
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I declare that this thesis entitled “Development of Pole Balancing Mobile Robot” is
the results of my own research except as cited in the references. The thesis has not
been accepted for any degree and is not concurrently submitted in candidature of any
other degree.
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To my beloved father and mother
Abdul Rahman Bin Hj. Salleh
Faridah Bte Majid
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ACKNOWLEDGEMENT
All praise to the Almighty Allah, the Most Gracious, Most Merciful and Most
Benevolent for giving me an opportunity to study for higher education and giving me
strength and patience in completing this final year project report.
First of all, I would like to take this opportunity to thank my project
supervisor, Associate Professor Dr. Rosbi Bin Mamat whom had actually provided
me with all the valuable, precious information to complete this report of PSM 2,
which carries up to four credits. Without the passionate supports, guidance
encouragement and advices given by him, it would have been very hard to complete
this project. As such this report is very important to me.
My outmost thanks also go to my course mate for all their support and helps
given to me while my project is still in progress for their guidance, support and not to
forget their precious time spent for me to provide information and equipments
needed. Their views and tips are useful definitely.
Next up, I would like to thank to all my friends for their continuous support
and encouragement. Thanks to my parents, Ab Rahman & Faridah Bte Majid, for
their unconditional love and support, I would not have made it this far without their
sacrifices. Finally, thanks to individuals that has contributed either directly or
indirectly to make this thesis project. From the bottom of my heart, thank you once
again.
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ABSTRACT
The research on balancing robot has gained momentum over the last decade
in a number of robotics laboratories around the world. This is due to the inherent
unstable dynamics of the system. Recently many robots have widely been used
anywhere especially in manufacturing and industrial sectors. In recent years,
researchers have applied the idea of a mobile inverted pendulum model to various
problems like designing walking gaits for humanoid robots, robotic wheelchairs and
personal transport systems. All of this uses a concept of ability to balance freefalling pole on its wheels and spin on the spot similar to inverted pendulum. This
mobile robot has become much more familiar nowadays since it is already equipped
with lots of intelligences where it is beneficial to human.
In conjunction with the development of balancing system on the robot itself,
the pole balancing mobile robot has been successfully designed for this project. In
this project, microcontroller PIC 16F877A is used as the brain of the robot to control
the robot’s movements where all the data and information would be processed. It is
also equipped with potentiometer 50k as a sensor of the balancing mobile robot. It
gives a reading of differential angle to the microcontroller as it process the data to
moves the DC motor with a correct PWM reading. To complete this, a pole must
mounted to the potentiometer as the differential angle reading are comes from the
movement of the pole. C language is used to program this microcontroller via
MicroC, so that it will properly function as desired.
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ABSTRAK
Penyelidikan dan pembangunan berkenaan keseimbangan robot telah
menerima impak momentum yang ketara sejak sedekad yang lalu seiring dengan
pertumbuhan makmal robotik di seluruh dunia. Hal ini adalah disebabkan oleh faktor
semulajadi ketidakseimbangan sistem dinamik. Baru-baru ini aplikasi penggunaan
robot semakin bertambah dan global terutamanya dalam bidang pembuatan dan
sektor industri. Sejak beberapa tahun ini, penyelidik telah berexperimentasikan
penggunaan idea berkenaan model tiang diseimbangkan pada robot gerakan bebas
untuk pelbagai masalah dan penggunaan seperti keseimbangan pergerakan bagi robot
manusia, kerusi roda robot dan sistem pengangkutan persendirian. Robot ini akan
lebih bermakna dan digunakan selalu jika ia dilengkapi dengan sistem pintar dan
berguna untuk kemudahan manusia.
Bersempena dengan pembangunan sistem keseimbangan pada robot itu
sendiri, robot gerakan bebas berasaskan keseimbangan telah berjaya direkabentuk
untuk projek ini. Dalam projek ini, mikropengawal PIC 16F877A digunakan sebagai
otak kepada robot ini untuk mengawal pergerakan robot dimana semua data dan
informasi diproses. Ia turut dilengkapi dengan perintang boleh laras 50k sebagai
pengesan untuk keseimbangan robot gerakan bebas ini. Ia memberi bacaan bezaan
sudut kepada mikropengawal dimana data akan diproses untuk member nilali bacaan
PWM yang betul kepada DC motor. Pelengkap bagi sistem ini ialah sebatang tiang
yang akan dicantum dengan perintang boleh laras sebagai pembaca data Bahasa C
telah digunakan untuk memprogram mikropengawal menggunakan Mikro C supaya
ia dapat berfungsi seperti yang diingini.
viii
TABLE OF CONTENTS
CHAPTER
TITLE
PAGE
TITLE PAGE
ii
DECLARATION
iii
DEDICATION
iv
ACKNOWLEDGEMENT
v
ABSTRACT
vi
ABSTRAK
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TABLE OF CONTENTS
Error! Bookmark not defined.i
1
2
LIST OF FIGURES
xi
LIST OF TABLE
xii
LIST OF ABBREVIATIONS
xiv
INTRODUCTION
1
1.1
Robot and Mobile Robot Definitions
1
1.2
Balancing Robot
2
1.3
Objectives of Research
3
1.4
Problem Statement
4
1.5
Scope of Work
4
1.6
Research Methodology
6
LITERATURE REVIEW
7
2.1
Segway HT
9
2.2
Balance Bot
12
2.3
Nbot Balancing Robot
13
2.4
Scaled Down Prototype of a Digital Signal Processor
Controlled Two-Wheel Vehicle
15
ix
2.5
3
5
16
ROBOT DESIGN
17
3.1
Robot Structure
18
3.2
Mechanical Design
20
3.2.1
21
Motor Positioning and Installation
3.3
Base
21
3.4
Gearbox
22
3.5
DC Motor
23
3.5.1
24
Pulse with Modulation
3.6
Pole
25
3.7
Main Electronics Component
25
3.7.1
Motor Driver (L298)
26
3.7.2
Potentiometer
27
3.7.3
Microcontroller
28
3.7.4
Power
31
3.7.5
Voltage Regulator
31
3.7.6
Wheel
32
3.8
4
Summary
Conclusion
33
CIRCUIT DESIGN
35
4.1
Overview
35
4.2
L298 and Potentiometer Circuit
35
4.3
Main Controller Circuit
37
4.4
Connecting the Microcontroller to PC Circuit
39
SOFTWARE DEVELOPMENT
41
5.1
Overview
41
5.2
Microsoft Excel
41
5.3
MicroC
42
5.3.1 PWM Change Duty via MikroC
43
x
6
5.4
WinPic800
45
5.5
Programming Languages
47
RESULT AND DISCUSSION
49
6.1
Overview
49
6.2
Calibration
50
6.3
Calculation and Analysis
51
6.3.1
Speed versus Angle
53
6.3.2
Control system
53
6.4
7
Programming
54
CONCLUSION AND RECOMMENDATION
57
7.1
Conclusion
57
7.2
Recommendation
58
REFERENCES
59
APPENDICES
60
Source code for Pole Balancing Mobile Robot
61
xi
LIST OF FIGURES
FIGURE NO.
TITLE
PAGE
Figure 1.1
Flow Chart for Project Methodology
6
Figure 2.1
Segway HT
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Figure 2.2
Features of Segway HT.
10
Figure 2.3
Balance Sensor Assembly
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Figure 2.4
Balance Bot
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Figure 2.5
Nbot Balancing Robot
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Figure 2.6
Scaled Down Prototype of a Digital Signal Processor Controlled Two-
Figure 3.1
Figure 3.2
Wheel Vehicle
14
Mechanical Structure Plan-Views
19
Base of the Project (in the beginning)
19
Figure 3.3
DC Motor (Gearbox) Positioning
20
Figure 3.4
Gearbox of Control Racing Car
22
Figure 3.5
System Inside Gearbox
23
Figure 3.6
PWM Signal of Varying Duty Cycles
24
Figure 3.7
Rod Aluminium
25
Figure 3.8
Main Electronic Components
26
Figure 3.9
Motro Driver (L298)
27
Figure 3.10 Potentiometer and its Symbol
27
Figure 3.11 PIC 16F877A
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Figure 3.12 PIC 16F877A Pin Notation
30
Figure 3.13 Battery Nickel-Cadmium 9.6V
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Figure 3.14 Voltage Regulator Circuit
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Figure 3.15 Pole Balancing Tire
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Figure 3.1
Side View
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Figure3.2
Back View
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Figure 3.3
Front View
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Figure 3.4
Plan View
34
Figure 4.1
L298 and Potentiometer Circuit
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Figure 4.2
Block Diagram of L298
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Figure 4.3
Real View of L298 and Potentiometer Circuit
37
Figure 4.4
Basic PIC Microcontroller Circuit
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Figure 4.5
PIC Microcontroller Circuit
39
Figure 4.6
Real View of PIC Microcontroller Circuit
39
Figure 5.1
MicroC
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Figure 5.2
WinPic800
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Figure 5.3
PIC detected 16F877A
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Figure 5.4
Writing HEX File Succeds
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Figure 6.3
Graph of Angle versus Voltage(in dec)
52
Figure 6.4
Block Diagram of Closed-Loop System
54
Figure 6.5
Flow Chart of the Programming
55
xiii
LIST OF TABLES
TABLE
TITLE
PAGE
Table 3.1.3
PIC 16F87XA features
30
Table 6.1
Table of Angle versus Voltage
50
Table 6.2
Table of hex value
51
xiv
LIST OF ABBREVIATIONS
d.o.g
-
degree of freedom
DC
-
Direct Current
PIC
-
Programmable Interface Controller
UTM
-
Universiti Teknologi Malaysia
MCU
-
Microcontroller Unit
HT
-
Human Transporter
BSA
-
Balance System Assembly
EEPROM
-
Electrically Erasable ROM
MIN/MAX
-
Minimum/Maximum
IC
-
Integrated Circuit
EMF
-
Electric Magnetic Field
LED
-
Light Emitter Diod
e.g
-
exempli gretis
EPROM
-
Erasable Programmable ROM
MCU
-
The Microcontroller Unit
VBA
-
Visual Basic for Application
ADC
-
Analog-Digital Converter
xv
DEC
-
Decimal
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CHAPTER 1
INTRODUCTION
Balancing robots are characterized by the ability to balance on its two wheels
and spin on the spot similar to inverted pendulum. The inverted pendulum problem is
common in the field of control engineering thus the uniqueness and wide application
of technology derived from this unstable system has drawn interest from many
researches and robotics enthusiasts around the world. In recent years, researchers
have applied the idea of a mobile inverted pendulum model to various problems like
designing walking gaits for humanoid robots, robotic wheelchairs and personal
transport systems.
Balancing is one of the main functions in making a robot. It uses a sensor as a
balance orientation. There are many types of balancing sensor in this robotic area.
Examples of the sensors are accelerometer, inclinometer, tilt sensor, gyroscope and
potentiometer. Balancing systems that are now having an enormously influence
towards world development and technologies promising to change and upgrade the
dynamic of the systems to be more stable and balance. In this project, the inverted
pendulum was replaced with a pole as it function are exactly the same and
importantly more suitable for this project.
This chapter will discuss definition of robot, objective of research, scopes of
research, literature review and thesis outline. Literature review will focus on pole
balancing mobile robot and other mobile robot which functioned and equipped with
balancing system that have been researched earlier.
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1.1
ROBOT AND MOBILE ROBOT DEFINITIONS
In this project, it involves mobile robot as a transport and a medium to balance
the pole. Before going any further, let’s define what the meaning of robot and mobile
robot is. From the website it state that, “A robot is a machine designed to execute
one or more tasks repeatedly, with speed and precision. There are as many different
types of robots as there are tasks for them to perform. A robot is a machine that
resembles a human and does mechanical, routine tasks on command or any machine
or mechanical device that operates automatically with humanlike skill.”
Definition robot from the Longman Dictionary is “machine that can move and
does of the work of a person and usually controlled by a computer.” Based on the
definition of the two facts collect from the net and one from the dictionary, as a
conclusion, a robot must be an automatic machine and be able to deal with the
changing information received from the environment.
As for the mobile robot (type of robot) it has the capability to move around in
their environment and is not fixed to one physical location. It can move freely in any
directions; forward, backward, left, and right and also in any angle as long as it is
programmed to move so. Mobile robots can be found in the industry, military,
security environment and in local universities labs which it is used to some research
programmed. For people who like to play with something, mobile robot can be used
in robot competition.
1.2
BALANCING ROBOT
Balance has a difference meaning according to Oxford Fajar Dictionary. The
best meaning contribute to this project is “keep or put in a state of balance or be or
put something in a state of balance”. According to the definition of robot before it
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can be conclude that pole balancing robot is an any mechanism which supports an
inverted pendulum or pole which is free to swing around a horizontal this with one
degree of freedom and balances it to keep it vertical by moving the point of support.
In this project a mobile robot will be used to balance the pole that place on
top of it. The mobile robot drove back and forth in response to tipping movements of
the pole as sensed by a potentiometer at its base. In order to move from one place to
another, the mobile robot (car) had to drive it away from the goal to unbalance the
pole toward the goal. In order to balance again at the destination, the car moved past
the destination until the pole was upright again with no forward velocity. It then
moves back to the goal. The pole balancing model would become important for
studying balancing in legged locomotion has been widely recognized since 1938.Late
1970s that experimental work on balancing for legged systems gained momentum.
1.3
OBJECTIVES OF PROJECT
The objectives of this project is to design and develop a mobile robot which
equipped with a pole on top of it, mounted to a potentiometer where it able to
measure the differentiate angle given as it was the mobile robot sensor balancing.
Besides, it also has been one of the objectives in this project to design and construct a
motherboard consists of microcontroller, motor driver (LM298) and other electronic
components such as potentiometer sensor and regulator.
Other objective is to
investigate the feasibility of PIC programming in balancing pole upon the hardware
platform. To let the functions properly, enable to get the relationship between angle,
voltage and velocity in order to balance the pole. Of course after all of this done,
programming the robot using C language is needed to test the balance of the system.
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1.4
PROBLEM STATEMENTS
To start making this project there are many things need to be consider.
Firstly, is the size of the robot. This mobile robot with a small space and dimension
hold a 60mm length of pole. In order to maintain the position of pole the base must
made from strong structure likes Perspex and aluminum. The Perspex will be cut into
rectangular shape to be the base of the mobile robot. Two holes were made to place
the back tire position For the front tire, use a bolt and nut to combine it with the
Perspex. This part is a little bit difficult because it must be done correctly without
mistake to avoid wrong size fitters after cutting the Perspex. After that mounted the
pole on the potentiometer. To do this make a hole on the bottom of the pole with a
diameter smaller than the shaft potentiometer diameter Then, push the shaft into the
hole until it stuck and manage to move easily(right and left). Lastly, solder the
potentiometer terminal to the motor driver circuit that already install on the mobile
robot base. For the PIC circuit, it is easier to locate it at the front of the robot, and
link it with a motor driver circuit that located at the middle of the base. The balance
happens here because the gearbox and the motor are located at the back of the robot.
1.5
SCOPE OF WORKS
In this project, there are four major scopes of works, which are focusing on
the concept of pole balancing mobile robot, designing and develop a small hardware,
an autonomous pole balancing robot(move on microcontroller) and the control
system(close loop system).
General idea of creating this pole balancing robot is making a mobile robot
balancing a pole that mounted on potentiometer on top of the base mobile robot. In
response to the tipping movements of the pole(tip forward and backward) , the
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mobile robot as known as the car will move faster to straight up again the pole,
means that the angle and the velocity is (0) zero. If the pole tipping forward, the car
will move forward in order to get its origin position. This concept is similarity to the
Fuzzy Logic Controller concept.
For mechanical parts, focusing on designing and developing the base of the
robot, the location of the pole and how to mount it on potentiometer and the most
appropriate material that can be used to develop the body of the robot have become
the aims of this project. While constructing the mechanical parts of the robot, it is
also required to know the best location of most of electronics board and other
components to be located at the base. It is essential to ensure that the robot does not
look messy and crowded eventually. For the pole, this robot used an aluminum rod,
length of 60mm to control the movement of the car either forward or backward. All
outputs are depend on the input that microcontroller received.
An autonomous pole balancing robot means that the robot move depend on
microcontroller decisions. For microcontroller, this project will focusing on PIC
microcontroller, PIC 16F877A as the main component, studying how it can
interfaced with potentiometer as the important item in this balancing project. The
designed programming in C language however should be able to control the
movement of the wheel and DC motors, which control the balance of the pole. All
these components have to be properly interfaced together so that the robot will only
be function, implement the tasks as programmed without error.
However, for the control systems, this project use close loop system as it is
required to balance the pole. From the origin center, if there if a forces applied and
the pole tipping (means there is a different in an angle value), the sensor will give a
signal to the PIC microcontroller. The brain processed the signal and give
appropriate value of PWM to the output. If there is an error of actual angle the
system wills doing again the same procedure until the pole come back to its initial
position.
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1.6
RESEARCH METHODOLOGY
Start
Title, objective and scope
of the project was given
Search literature review focus on pole
balancing mobile robot
Mechanical design
Designing the circuit of the
motor driver and PIC
Redesign
Decide material
Suitable and easy to construct
Not suitable/expensive
Built mobile robot and circuit
Improvement of the robot
YES
Troubleshooting
Programming
NO
Ok?
YES
End
Figure 1.1: Flow Chart for Project Methodology
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Methodology and procedure to perform this final year project must be
systematic to ensure the healthy progress of the project. First of all, title and
objective of the project will be searched and discussed with the supervisor to get
some opinion about the effectiveness of the title
After the title was confirm, literature review must be done. Some project
which was related to the title chosen is revised to get an idea, concept and theory in
order to design our own project. Information or finding of this project can be found
in books, articles, internet, e-books and etc.
The next step is to understand the project. This project was about building
and develops a pole balancing mobile robot. The structures and behaviors of the
autonomous mobile robot will be explained and should be already determined in by
now before designing the circuit.
After circuit is designed, the fabrication of the autonomous mobile robot can
be constructed using specific hardware materials. This is the most important part in
building and constructing the robot. Several basic movements will be programmed
and burned to the microcontroller chip to test the autonomous mobile robot. The
mechanical and electronic design will be changed whenever there are errors in the
testing phase.
Just after completing the design of mechanical and electronics parts, it
proceeds to built and constructs the motherboard followed by developing the
software in C programming. Trouble shoot will always be done as long as there is an
error in final testing to get the final result.
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CHAPTER 2
LITERATURE REVIEW
Literature review is vital to the research because from the previous
researches, it can be guidelines to this project. In other words, it can bring a various
idea and method to make this project a success. It also become a study case for this
project to overcome with the new idea and different design compared to the previous
project. Otherwise, from the literature review references it can develop the contents
to this research. Below is a few listing that been done from the previous project.
This chapter focuses on the related fields and knowledge pertaining to the
accomplishment of the thesis itself. Reading includes such as reference books,
papers, websites, conferences articles and any documentation concerning the related
applications and research works.
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2.1
SEGWAY HT
Figure 2.1: Segway HT
As can be seen from Figure 2.1 above, the Segway Human Transporter
[11]
(HT) is a truly 21st-century idea. A similar and commercially available system,
‘SEGWAY HT’ has been invented by Dean Kamen, who holds more than 150 U.S.
and foreign patents related to medical devices, climate control systems, and
helicopter design. A two-wheeled electric vehicle that's practical, efficient, slightly
miraculous, and an undeniably fun way of getting around, it's as different from a
bicycle or motorcycle as the original personal computers were from their lumbering,
mainframe predecessors. The ‘SEGWAY HT’ is able to balance a human standing on
its platform while the user traverses the terrain with it. This innovation uses five
gyroscopes and a collection of other tilt sensors to keep itself upright. Only three
gyroscopes are needed for the whole system, the additional sensors are included as a
safety precaution. Below are the features that this robot has:
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Controller board
Gearbox battery
Balance Sensor Assembly
Battery pack
Motor
Figure 2.1.2: Features of Segway HT
 Emissions free, powered by rechargeable NiMH battery packs.
 To balance the robot, it uses five gyroscopes and a collection of other tilt
sensor.
 Two sophisticated controller boards from Delphi Electronics provide both
brains and brawn for the system. Delphi Electronics was chose in the
production of high-volume, high-quality automotive electronics for such
demanding applications as airbag modules.
 The tire are from Michelin company designed using a unique tread
compound, a silica-based compound giving enhanced traction and minimized
marking on indoor floors.
 The motors use brushless servo technology.
 Gearbox that use a thermoplastics rim injection molded around a forged steel
hub.
11
Focusing on the sensor system, Segway HT has a powerful balance sensor to
achieve the goal of this system. Figure 2.1.3 shows the Segway HT sensor system,
Figure 2.1.3: Balance sensor assembly
The Balance System Assembly (BSA), supplied by Silicon Sensing Systems,
is an elegantly designed, extremely robust, and yet incredibly sensitive piece of
equipment. This small cube, 3 inches on a side, is packed with five solid-state,
vibrating-rings, angular-rate sensors ("gyroscopes") that use the Coriolis Effect to
measure rotation speed. These tiny rings are electromechanically vibrated in such a
way that when they are rotated, a small force is generated that can be detected in the
internal electronics of the sensor. Each "gyro" is placed at a unique angle that allows
it to measure multiple directions. Segway's onboard computers constantly compare
the data from all five gyros to determine if any of the five is supplying faulty data--in
this condition, it can compensate and use data from the remaining sensors to continue
balancing through a controlled safety shutdown. Two tilt sensors filled with an
electrolyte fluid provide a gravity reference in the same way your inner ear does for
your own sense of balance. The BSA is monitored by two independent
microprocessors and is split into two independent halves for redundancy. Even the
communication between sides is performed optically to avoid electrical faults on one
side propagating to the other.
12
2.2
BALANCE BOT
Figure 2.2: Balance Bot
The Balance Bot
[8]
is a computer-controlled motorized cart that balances a
thirty inch long aluminum pole, much like balancing a broomstick on your finger. So
far this model has the best design and development for the pole balancing mobile
robot. The brain of the Bot is a high speed SX52 microcontroller made by Ubicom.
To monitor the tilt of the pole and produce correction signals to the wheel motors, a
fuzzy logic program is used.
13
In operation, the fuzzy logic program takes into account both the angle and
angular velocity of the pole to calculate the appropriate voltage for the wheel motors.
Actually, the SX52 continuously applies correction voltages to the motors, at the rate
of hundreds of times per second, until the pole is finally standing upright.
The tilt of the pole is measured by a low-noise optical angle sensor. The
sensor signal is digitized and sent to the SX52. Angular velocity of the pole is
calculated over a six millisecond period and sent to the fuzzy logic. Two external
EEPROMs are used to store lookup tables in order to reduce the calculation time.
The fuzzy logic translates the input signals into five-member antecedent functions,
and then applies twenty-nine rules with a MIN/MAX algorithm to produce a fivemember consequent output. The output functions are combined using a set of Center
of Gravity values stored in the 32K EEPROM. The final "crisp" output value is
loaded into one of the SX52 timers which produce a pulse-width-modulated drive
signal for the motors. The whole process takes about 550 microseconds with the
SX52 running at fifty megahertz.
Below are the lists of features of Balance Bot;
 SX52 microcontroller made by Ubicom
 The tilt sensor is a low-noise optical angle sensor
 Two external EEPROMs
 high-speed servos and used direct motor control with a Pololu serial motor
controller
 two easy roller motor wheel 12V, 200rpm
 dual motor driver, L298
 potentiometer 1k, 3 turn
14
2.3
nBot BALANCING ROBOT
Figure 2.3: nBot Balancing Robot
Another one example of the balancing robot is nBot balancing robot [4]. This
robot was featured as NASA's Cool Robot of the week for 19 May 2003. The basic
idea for a two-wheeled dynamically balancing robot is pretty simple: drive the
wheels in the direction that the upper part of the robot is falling. If the wheels can be
driven in such a way as to stay under the robot's center of gravity, the robot remains
balanced. In practice this requires two feedback sensors: a tilt or angle sensor to
measure the tilt of the robot with respect to gravity, and wheel encoders to measure
the position of the base of the robot. Four terms are sufficient to define the motion
and position of this "inverted pendulum" and thereby balance the robot. These are 1)
the tilt angle and 2) its first derivative, the angle velocity, and 3) the platform
position and 4) its first derivative, the platform velocity. These four measurements
are summed and fed back to the platform as a motor voltage, which is proportional to
torque, to balance and drive the robot.
15
This balancing mobile robot uses the gyroscope and accelerometer combined
with complementary filters to provide an inertial reference sensor. The ADXL202
accelerometer provides accurate static tilt information, when the robot is not
accelerating. The gyroscope can be integrated to provide accurate dynamic tilt
information, but the integration tends to drift over time. Combining the two sensors
provides a robust inertial measurement.
2.4
SCALED DOWN PROTOTYPE OF A DIGITAL SIGNAL
PROCESSOR CONTROLLED TWO-WHEELED VEHICLE
Researchers at the Industrial Electronics Laboratory at the Swiss Federal
Institute of Technology have built a scaled down prototype of a Digital Signal
Processor controlled two–wheeled vehicle[4] based on the inverted pendulum with
weights attached to the system to simulate a human driver.
Figure 2.4: Prototype of Digital Signal Processor controlled two-wheel vehicle
16
A linear state space controller utilizing sensory information from a gyroscope
and motor encoders is used to stabilize this system. Advantage of this system
prototype is it uses gyroscope as it balancing sensor. Gyroscope capable of detecting
angular input rates about two orthogonal axes without the use of slip rings.
2.5
SUMMARY
From the literature review discussed in this chapter, it shows only a few of
the researcher do the balancing mobile robot by using a pole. It is hard to find a
model that would become my references to this project. However, the input and
information given really helps me in improving my robot development.
17
CHAPTER 3
ROBOT DESIGN
Inherently, robotics is an interdisciplinary field that ranges in scope from the
design of mechanical and electrical components to sensor technology, computer
systems and artificial intelligence. The mechanical and electrical components include
mechanical frame, motor, pole and wheel while the electrical components consists of
microcontroller and sensing system. The sensing system will allow the robot to
interact directly with environment.
18
3.1
ROBOT STRUCTURE
The structure of the robot can be classified into two parts:
1) Mechanical Design
2) Electrical design
3.2
DESIGN MECHANICAL
Mechanical structures should be designed as accurate as possible to avoid
unbalancing while robot starts its movement. All the possibilities should be aware
and taken seriously because minor mistakes will cause a major trouble to the robot
system. The selection of the best materials that will be used should be done wisely.
The pro and cons of any taken action influence the performances of the robot later on
The mechanical structure of the balancing mobile robot consists of the chassis
of the mobile robot, pole for the balancing system and the driving mechanism, which
is one DC, motors (gearbox) and wheels. Perspex is used for the body structure as it
is easy to fabricate, light and worked on. Weight is an important factor here, as the
robot will need to move smoothly. To catch up the tipping pole, the robot must move
faster so it must be made by a light material. An aluminum rod is chosen for the pole
because it is light, firm and easy to mount on potentiometer. These conditions are
important because in order to balance the pole, its material must be easy to move to
get back to its initial condition (straight).
19
These projects only have one layer and it consists of PIC microcontroller and
motor driver circuit, potentiometer and a pole. (Refer to Figure 3.1)
The pole
Motor Driver and sensor
circuit
Figure 3.1: Mechanical Structure-Plan View
PIC microcontroller circuit
Figure 3.2: Base of the project (in the beginning)
20
3.2.1
MOTOR POSITIONING AND INSTALLATION
Gearbox is located
at the back side
Figure 3.3: DC Motor (Gearbox) Positioning
There is one DC motor in a gearbox used in Pole Balancing Mobile Robot.
Function of this motor is to make the mobile robot move forward and backward. It
located at the back side of the robot. The reason of using only one DC motor is
because the motor is capable enough to move the four tires that the robot have.
Secondly it can reduce the weight of the robot as the circuit overall situated at the
front of the robot. It makes the weight in front and the back of the mobile robot
balance as it is important due to the balancing factor.
Generally, the DC motors are used in drive systems for two reasons. The first
reason involves the relationship between the speed and the torque of the DC motor.
The torque of the DC motor can change over a wide range of application. That is, as
the load applied to the motor increases, the torque at the motor also increases.
Nevertheless, this increased torque tends to slow the motor down. Additional current
supplied to the motor will overcome the torque and keep the speed of the motor
21
constant. The second reason DC motors are used is that DC motors can easily be
interfaced with electronic components.
The DC motor was recognized because it is small, light and of course it is
available at market with reasonable price compare to the others. Furthermore, the
programming to operate DC motor is quite simple compare to stepper motor. DC
motor must attach to gear to make it ABLE to carry more loads. If it is not attach to
gear, maybe the robot cannot move at all. The supply voltage for each DC motor is 5
Volts.
3.3
BASE
It is important to choose a suitable shape in making a robot especially when it
involves a balancing part. A rectangular is choose to be the shape of the body
because it is balance and have a much space for the mechanical and electrical
component to place on compare to other shape. In fact, a four tires mobile robot
looks stable and neatness with the shape that have four edges.
The purpose of this project is balancing. With a proper shape and design of
the mobile robot base, it helps a lot in maintaining the stability of the system. The
base will be equipped with four pairs of infrared sensors tracking lines purposes. A
pole is located on top of the robot, mounted on the potentiometer in a same circuit
with a motor driver. All of this is attached together on the base and that is why the
base must have a large space and rectangular shape is the answer of the problem.
22
3.4
GEARBOX
Figure 3.4: Gearbox of Control Racing Car
A gearbox is an enclosed system of assembled gears that transmits
mechanical energy from a prime mover to an output device. A gearbox can also
change the speed, direction, or torque of mechanical energy. In this project, a
gearbox from the remote control racing car is chosen to be the gearbox of the robot.
The advantage is, it cost no money because it is free (gift from friends). Below are
the features of gearbox;
 Gear set
 Nozzle
 Cylinder
 Piston
 M100 Spring
 Metal bushings
To know the gearbox features, below is the figure show the system of the
gearbox.
23
Cylinder/piston
Gear
Nylon/electrics
Trigger
Motor
3.5
Figure 3.5: System inside Gearbox
DC MOTOR
Refer to the Figure 3.5; the DC motor is in the gearbox. It stores in the same
casing because both of the material are coming from the same remote control racing
car. Motors are inductive devices since they draw mush more current at startup that
when they are running at a steady speed. Generally, a DC motor has two terminals on
it. If the positive and negative leads from a power source (battery, power supply) are
connected to the terminals of the motor, the motor will spin in one direction. If the
connections are swapped, the motor will spin in the opposite direction.
A few things that should be known about the motor that will be used as the
following; what voltage it is designed to work at, how much current it draws when
running, and how much current it draws at stall. For this project, the DC motor has a
starting current more than 1.5A, need a power of 12V and it has a small torque.
24
3.5.1
PULSE WIDTH MODULATION
Figure 3.6: PWM signals of varying duty cycles
Pulse Width Modulation (PWM) allows microcontrollers to dim lights,
control motor speeds, fan speeds and generate analog voltages. By changing the
length of the pulse, the output can be controlled. The pulse occurs at a regular
frequency, the modulation frequency. The length of the pulse ratio to period time is
called the duty cycle. The larger the duty cycle the higher the output is.
PWM is a powerful technique for controlling analog circuits with a
microprocessor’s digital outputs. PWM is employed in a wide variety of application
ranging from measurement and communication to power control and conversation.
The PWM signal is still digital because, at any given instant of time, the full
DC supply is either fully on or fully off. The voltage or current source is supplied to
the analog load by means of a reporting series of on and off pulses. The on-time is
the time during which the DC supply is applied to the load, and the off-time is the
periods during which that supply is switched off. Given a sufficient bandwidth, any
analog value can be encoded with PWM.
25
Figure 3.7 shows three different PWM signals. For the first, it shows a PWM
output at a 20% duty cycle. That is, the signal is on for 20% of the period and off the
other 80%. Next PWM outputs at 50% and 80% duty cycles, respectively. These
three PWM outputs encode three different analog signals values.
3.6
POLE
From a definition a pole (rod aluminum) is a long (usually round) rod of
wood or metal or plastic. In this project, rod aluminum with a length of 60mm is
used to be the pole of the balancing mobile robot. It is light, has a round shape, cheap
and easy to get. Below is the picture of rod aluminum.
Figure 3.7: Rod Aluminum
3.7
MAIN ELECTRONIC COMPONENTS
26
POWER SUPPLY CIRCUIT
SENSOR/POTENTIO
METER
MICROCONTROLLER
MOTOR DRIVER
CIRCUIT
Figure 3.8: Main Electronic Component
3.7.1
MOTOR DRIVER (L298)
To control the movement of motor this project needs motor driver, L298 to
do the job. The L298 is a strong, useful dual-motor driver IC but it’s tough to use by
it. The L298 chip is the bigger brother to the L293 chip (a popular small-motor driver
IC), but the L298 handles more current, and more voltage. The motor operates in a
high current and high voltage and L298 is perfect enough to be its motor driver
because it can function in high current until 4A. L298 can drive inductive loads such
as relays, solenoids, DC and stepping motors. Two enable inputs are provided to
enable or disable the device independently of the input signals. It is a Bidirectional
DC motor control means that Dual L298 Motor Driver can control four DC motors.
The most important thing about L298 is, it easy to mounting and setup on the
circuitry board.
Below are the characteristics of L298;
 6 to 26V operation,
27
 4A total drive current
 Accessible 5V regulated voltage
 Motor
tor direction indicator LEDs
 EMF protection diodes
 Small 40mm (1.527”) square footprint
Figure 3.9: Motor Driver L298
3.7.2
POTENTIOMETER
Electronic symbol
(Europe)
(US)
Figure 3.10: Potentiometer and Its symbol
28
A potentiometer is a three-terminal resistor with a sliding contact that forms
an adjustable voltage divider. If only two terminals are used (one side and the
wiper), it acts as a variable resistor or Rheostat. Potentiometers are commonly used
to control electrical devices such as a volume control of a radio. Potentiometers
operated by a mechanism can be used as position transducers, for example, in a
joystick. Potentiometers are rarely used to directly control significant power (more
than a watt). Instead they are used to adjust the level of analog signals (e.g. volume
controls on audio equipment), and as control inputs for electronic circuits. For
example, a light dimmer uses a potentiometer to control the switching of a TRIAC
and so indirectly control the brightness of lamps.
Potentiometers are sometimes provided with one or more switches mounted
on the same shaft. For instance, when attached to a volume control, the knob can also
function as an on/off switch at the lowest volume.
In this project, potentiometer 50k is chosen to be the sensor because it is easy
to get, mounted with a pole and has a tolerance of 5%-10%.
3.7.3
MICROCONTROLLER
A microcontroller is a computer-on-a-chip. It is a type of microprocessor
emphasizing high integration, low power consumption, self-sufficiency and costeffectiveness, in contrast to a general-purpose microprocessor (the kind used in a
PC). In addition to the usual arithmetic and logic elements of a general purpose
microprocessor, the microcontroller typically integrates additional elements such as
read-write memory for data storage, read only memory, such as flash for code
storage, EPROM for permanent data storage, peripheral devices, and input/output
29
interfaces. Power consumption while sleeping may be just nano watts, making them
ideal for low power and long lasting battery applications.
This project used PIC16F877A, manufactured by Microchip has been chosen
as the main controlling unit of pole balancing robot. This chip was selected based on
several reasons

It is small in size and equipped with enough input\output ports

Free samples can be applied from the Microchip website

It has interrupt capabilities

Easy-learning programming language
Figure 3.11: PIC 16F877A
Below is the figure of PIC pin notation and its features.
30
Figure 3.12: PIC 16F877A pin notation
Figure 3.13: PIC 16F87XA features
31
3.7.4
POWER
There are many powers offered in market nowadays. It is included power
such AC-DC Adapter, Transformer, Rechargeable Battery, Lead Acid Battery, LiPo
Battery Charger and Cell Battery respectively. In making decision on which power is
more appropriate, few specifications should be revealed such as per-cell voltage,
amp-hour current, weight and reusability. For this project, battery nickel-cadmium
9.6V has been chosen as the power supply since it is cheap, light, powerful, small,
easy to carry and easy to design.(see figure 3.14)
Figure 3.14: Battery Nickel-Cadmium 9.6V
The battery that being used as the input power supply is +9.6 V. This circuit
is to generate 5V which is needed by the PIC 16F877A Microcontroller from a 9V
battery. Terminal positive of the battery is connected to “+9V” and the terminal
negative of the battery is connected to “ground”.
3.7.5
VOLTAGE REGULATOR
PIC microcontroller needs constant 5V power supply. So, there is additional
circuit that will supply this amount of voltage. This circuit will change 9.6V power
32
supply from the battery to constant 5V by using voltage regulator LM 7805. Figure
3.15 shows the voltage regulator circuit.
Voltage regulator
9.6V
Figure 3.15: Voltage Regulator Circuit
3.7.6
WHEEL
Figure 3.16: Pole balancing tire
At the beginning, it was hard to find an exact tire for the mobile robot. A few
factors have to analyze before the base can be installed by a tire. The factors are;
 Small and sturdy
 Easy to spin forward and backward
 Match with the robot shape and look neat
 Flexible
33
After making some choices, finally the result is to use a tire from the same
remote control racing car that the gearbox and motor was taken. It fixes to all criteria
that been analyze before.
3.8
CONCLUSION
As a conclusion for this chapter, the pole balancing mobile robot mechanical
and electronic structure manages to combine together and form the robot
successfully. To see the result, below is the figure showing of the complete robot of
pole balancing robot.
Figure 3.17: Side View
Figure 3.18: Back View
34
Figure 3.19: Front View
Figure 3.20: Plan View
35
CHAPTER 4
CIRCUIT DESIGN
4.1
OVERVIEW
In this chapter, it will discuss all the circuits that had been used for this
project. The circuits are microcontroller circuit, sensor (potentiometer) circuit and
motor driver circuit.
4.2
L298 AND POTENTIOMETER CIRCUIT.
Figure 4.1 is a L298 and sensor (potentiometer circuit). In This project, one
L298 and one potentiometer will be used for controlling the movement of the mobile
robot and the balancing of the pole. There are fifteen pins in LM298 and each of the
pins has a function to do. The statements below are the pin and their function. Figure
4.2 shows the pin of the L298
36
All of this pin must connect correctly because if wrong the L298 will short
circuit and the device cannot be use again. As we can see, the middle pin of
potentiometer will be connected to pin RAO from the PIC to convert the analog
value to digital value. Other pins are connecting to Vcc and ground. To control the
PWM of the motor, enable pin from the L298 must interface with enable pin from
the PIC microcontroller. This will control the speed of the motor. Output pin will
connect to motor to give directly signal from PIC. Input pin will change the direction
of the motor either it want to move forward or backward. It also setting the time
delay between the changing directions happens.
Figure 4.1: L298 and Potentiometer Circuit
37
Figure 4.2: Block Diagram of L298
Figure 4.3: Real view of L298 and Potentiometer circuit
38
4.3
MAIN CONTROLLER CIRCUIT
Figure 4.4: Basic PIC Microcontroller Circuit
Figure 4.4 is the basic microcontroller circuit. The Microcontroller Unit
(MCU) main circuit consists of crystal, reset switch, and 5 volts supply from voltage
regulator. Crystal is connected to the OSC1 and OSC2 pins to establish oscillation.
Figure 4.4 shows the basic PIC microcontroller circuit. Pins 11 and 32 is connected
direct to 5 volts voltage regulator (not shown in figure), and pins 12 and 31 is
grounded.
The configuration of crystal and reset switch is shown in the Figure 4.4. Vdd
is 5 volts regulated voltage from voltage regulator circuit. A 20 MHz crystal is
choose as the oscillator to ensure the execution time of each instruction is fast
enough. By referring to PIC16F877A datasheet, it is necessary to connect 1533picoFarad ceramic capacitors to increase the stability of the oscillator. Figure 4.5
shows the overall circuit for the PIC microcontroller circuit and figure 4.6 shows the
real view for this circuit.
39
Figure 4.5: Main Controller Circuit
Figure 4.6: Real View of Main Controller Circuit
4.4
CONNECTING THE MICROCONTROLLER TO PC CIRCUIT
This project need some circuit to interfacing data from computer to
microcontroller. The PIC 16F877A is requires either TTL or CMOS logic, therefore
before connecting direct to RS232 port, max 232 is using to transform the RS232
level into 0 and 5 Volts since RS232 has some electrical specifications as below:
40
Logic 0: between +3V and +25V
Logic 1: between -3V and -25V
The region between +3V and -3V is undefined
MAX232 has two receives and transmitters in the same package that proves
need in this system.RS232 is the most known serial port used in transmitting the data
in communication and interface. Even though serial port is harder to program than
the parallel port, this is the most effective method in which the data transmission
requires less wires that yields to the less cost. The RS232 is the communication line,
which enables the data transmission by only using three wire links. The three links
provides ‘transmit’, ‘receive’ and common ground.
41
CHAPTER 5
SOFTWARE DEVELOPMENT
5.1
OVERVIEW
There are three software are used in this project. Microsoft Excel is used for
the calculation of data and graph plotting before it can transfer the data to do a
programming. Second is MikroC compiler used to compile the C code to the hex
code, and WinPic800 which used to load program into the microcontroller.
5.2
MICROSOFT EXCEL
Microsoft Excel is a spreadsheet-application written and distributed by
Microsoft for Microsoft Windows and Mac OS X. It features calculation, graphing
tools, pivot tables and a macro programming language called VBA (Visual Basic for
Applications). It has been the most widely used spreadsheet application available for
these platforms since version 5 in 1993. Excel is part of Microsoft Office.
42
5.3
MIKROC
MikroC is a powerful, feature rich development tool for PIC microcontrollers
developed by mikroElektronika. It is designed to provide the programmer with the
easiest possible solution for developing applications for embedded systems, without
compromising performance or control.
MikroC provides a lot of useful and handy libraries for example, LCD
interface, UART, I2C, SD card access and many more. Below is the MikroC sample
for sending "Hello World!" to LCD.
Lcd_Init(&PORTB); // Initialize LCD connected to PORTB
Lcd_Cmd(Lcd_CLEAR); // Clear display
Lcd_Cmd(Lcd_CURSOR_OFF); // Turn cursor off
Lcd_Out(1, 1, "Hello World!");
Code Explorer
Code Editor
Debugger watch
Error Window
Figure 5.1: MikroC
window
PIC and C fit together well. PIC is the most popular 8-bit chip in the world,
used in a wide variety of application, and C, prized for its efficiency, is the natural
43
choice for developing embedded systems. MikroC provides a successful match
featuring highly advanced IDE, ANSY compliant compiler, broad set of hardware
libraries.
MikroC allows user to quickly develop and deploy complex applications. The
C source code can be written using the built-in Code Editor (Code and Parameter
Assistants, Syntax Highlighting, Auto Correct, Code Templates, etc.). The MikroC
libraries are also included to dramatically speed up the development; data acquisition
memory, displays, conversions, communication and many more. Practically all PIC
series likes P12, P16, and P18 chips are supported.
In this project, C language will be used in programming this Pole Balancing
Mobile Robot. So, the MikroC software is needed to compile the C-language into
machine code before programmed into microcontroller. This compiler provides a
number of useful libraries for user to use as ADC and USART. By using this library
user do not need to configure the register of the microcontroller manually if they
want to use say the ADC module of the microcontroller, the compiler will do it for
the user. What users have to do is to know how to use the library.
5.3.1
PWM CHANGE DUTY VIA MIKROC
To control the speed of the motor, it depends totally from the PWM. By using
mikroC, PWM can be control by changing its duty ratio. In PWM programming there
are four terms that are important;
 PWM_Init
 PWM_Start
 PWM-Change_Duty,
44
 PWM_Stop
First thing that has to been set up is PWM_Init. PWM_Init initializes the
PWM module with duty ratio 0. Parameter freq is a desired PWM frequency in Hz
This routine needs to be called before using other functions from PWM Library. This
is an example of PWM_Init;
Initialize PWM module at 5 KHz:
Pwm_Init(5000);
Secondly, after call the PWM_Init, PWM_ Start have to been to call to start
the PWM. PWM_Init must been call first before to write this function. It is written as
below;
Pwm_Init(5000);
// Initialize PWM module
}//~
void main() {
InitMain();
j = 80;
// Initial value for j
oj = 0;
// oj will keep the 'old j' value
Pwm_Start();
// Start Pwm
Lastly, is PWM_Change_Duty. It is important to know that this function
changes PWM duty ratio. Parameter duty takes values from 0 to 255, where 0 is 0%,
127 is 50%, and 255 is 100% duty ratio. Other specific values for duty ratio can be
calculated as (Percent*255)/100. Requires for this function is Pwm_Init must be
called before using this routine. Example below;
Set duty ratio to 75%:
Pwm_Change_Duty(192);
PWM_Stop is required to stop the PWM.
45
The example changes PWM duty ratio on pin RC2 continually. If LED is connected
to RC2, you can observe the gradual change of emitted light.
// microcontroller: P16F877A
// PWM module is set on RC2.
unsigned short j, oj;
void InitMain() {
PORTB = 0;
TRISB = 0;
ADCON1 = 6;
PORTA = 255;
TRISA = 255;
PORTC = 0xFF;
TRISC = 0;
Pwm_Init(5000);
}//~
void main() {
InitMain();
j
= 80;
oj = 0;
Pwm_Start();
// Set PORTB to 0
// PORTB is output
// All ADC pins to digital I/O
// PORTA is input
// Set PORTC to $FF
// PORTC is output
// Initialize PWM module
// Initial value for j
// oj will keep the 'old j' value
// Start PWM
while (1) {
// Endless loop
if (Button(&PORTA, 0,1,1))
// button on RA0 pressed
j++ ;
//
increment j
if (Button(&PORTA, 1,1,1))
// button on RA1 pressed
j-- ;
//
decrement j
if (oj != j) {
Pwm_Change_Duty(j);
oj = j;
PORTB = oj;
}
Delay_ms(200);
// If change in duty cycle requested,
//
set new duty ratio,
//
memorize it,
//
and display on PORTB
// Slow down a bit
}
}
WINPIC800
WinPIC800 is software that used in this project to load the hex file into the
microcontroller. This software will be used together with the programmer which
being called JDM programmer or also it can be used with the USB programmer.
Below are the figures about the process of WinPIC800
46
Figure 5.2: WinPIC 800
Click here
Figure 5.3: PIC detected 18F452
47
Click here to program all
Figure 5.4: Writing HEX file succeeds
5.5
PROGRAMMING LANGUAGES
Programming languages are used to facilitate communication about the task
of organizing and manipulating information, and to express algorithm precisely.
In this project, C programming language had been chosen to code the major
task including interpret the data from the potentiometer and control the PWM to
perform desired task.
The advantages of using C programming language are:
 It is a general purpose programming language that provides code
effectively, elements of structured programming and has a rich set of
operators.
48
 Convenient and effective programming solution for a wide variety of
software task.
 Can be written faster than assembly code thus reduces cost and easier to
be understood.
49
CHAPTER 6
RESULT AND DISCUSSION
This chapter will discuss about the result and finding of this project. Besides,
the analysis conducted in this project also will be presented.
6.1
OVERVIEW
This chapter will discuss the result, findings and the assessment from the
analysis conducted in this project. After the design and development of the Pole
Balancing Mobile Robot took place, the robot will be analyzed to measure the
effectiveness, stability and to ensure the objectives successfully achieved. There are
four steps to do before the final result obtain. The steps are;
 Calibration
 Calculation and analysis
 Programming
 Testing
50
6.2
POTENTIOMETER CALIBRATION
This is a first step in finding the result of the project. An experiment must be
done to calibrate the value of voltage correspond to the different angle given from
the potentiometer. It takes at least three times calibration before going to the next
step. Below are the table of the data contain of the different angle of potentiometer
and its voltage.
Angle,(θ)
Voltage,(V)
-20
2.23
-15
2.30
-10
2.41
-5
2.47
0
2.55
5
2.65
10
2.75
15
2.86
20
2.93
Figure 6.1: Table of Angle versus Voltage
To write a programming about the input voltage comes from the
potentiometer to the PIC , the analog value that comes from the sensor must be
convert to digital value. Figure 6.2 shows the digital value of the analog voltage. The
hex value will be compare to the reference voltage or full scale voltage. In this
project the full scale voltage is 5V. It means for the 5V analog value it is same as
1024 in hex values. (Refer to the PIC 16F877A datasheet)
51
Analog
Calculation
Hex value
2.23Volt
2.23V  1024
 456.7
5V
$1C8
2.30Volt
2.30V  1024
 471.04
5V
$1D7
2.41Volt
2.41V  1024
 493.57
5V
$1ED
2.47Volt
2.47V  1024
 505.86
5V
$1F9
2.55Volt
2.55V  1024
 522.24
5V
$20A
2.65Volt
2.65V  1024
 542.72
5V
$21E
2.75Volt
2.75V  1024
 563.2
5V
$233
2.86Volt
2.86V 1024
 585.73
5V
$249
2.93Volt
2.93V  1024
 600.06
5V
$258
value
Figure 6.2: Table of hex value
6.3
CALCULATION AND ANALYSIS
After get the hex value, the complete data will be measured through
Microsoft Excel. All the calculation and plotting the graph will be done by the
52
software. Figure 6.3 shows the graph resulting from the angle versus voltage (in
decimal value).
angle vs voltage(in dec)
y = 0.273x - 143.7
25
20
15
Equation of
the graph
10
angle
5
0
0
100
200
300
400
500
600
700
Series1
-5
-10
-15
-20
-25
voltage(in dec)
Figure 6.3: Graph of angle versus voltage (in decimal value)
From the graph, it can be analyze that the angle is directly proportional to the
voltage. The result produce a straight line graph shows the system will possibly
result a stable condition among both value. It also yields a linear line equation that is
Y=0.273x-143.7
Y = angle
X = voltage (in decimal)
53
6.3.1
SPEED VERSUS ANGLE
For this data, the calibration cannot be done because it is difficult and take a
lot of time to do it. To make the analysis easier, the same concept of Fuzzy Logic
Controller was use to obtain the relationship between speed/PWM and angle. The
Fuzzy Logic Controller is given in the form of If-Then rules a shown:
-
If θ is medium negative and dθ is medium negative then the force is large
negative.
-
If θ is 0 and dθ is medium negative then the mobile moving backward
-
If θ is small negative and dθ is small negative then the mobile also moving
backward with a medium speed
-
If θ is 0 and dθ is 0 then the speed also zero
-
If θ is small positive and dθ is small positive then the mobile moving
forward with a medium speed
-
If θ is small negative and dθ is small positive then the speed is zero
-
If θ is medium positive and dθ is medium positive then the mobile moving
forward with a high speed
From this, assumption can be making and the PWM can be set and control
according to the corresponding different angle given.
6.3.2
CONTROL SYSTEM
After getting all the data needed, it is important to initialize the control
system in this project. The control system in this project is a closed loop system
which is automatically changes the output based on the difference between the
feedback signals to the input signal. Below is the figure of the close loop system for
this project.
54
Initial
condition,
θ=0
θ
+
-
PIC
Speed/
PWM
Angle from
potentiomet
er
Error of actual angle
Figure 6.4: Block Diagram of the Closed Loop System
At first the pole is in initial condition whereas θ=0. After giving some forces
to the mobile robot, the pole will began tipping. The angle of the pole change and it
also change the voltage of the potentiometer. This signal was sent to the PIC to
process the data as it was programmed before. With a Fuzzy Logic Controller
concept before, the motor will moving according to the If-Then rule. It will straight
up again the pole until the pole comes back to its initial condition. If there is an error
occur, which the mobile robot too fast or too slow, this error will feedback again the
system and be anew input for this system until the θ=0.
6.4
PROGRAMMING
After finish the calibration and calculation, all the input will be programming
using MikroC. Figure 6.5 show the flow chart of the programming.
55
NO
YES
Move backward
with high speed
PWM=200
NO
YES
Move backward
with high speed
PWM=200
56
NO
YES
Stay with 0
speed PWM =0
NO
YES
Move backward
with high speed
PWM=200
Figure 6.5: Flow chart of the programming
This flow chart was not show all the data programming but overall the
programming is the same.
57
CHAPTER 7
CONCLUSION AND RECOMMENDATIONS
7.1
CONCLUSION
This project discusses the development of Pole Balancing Mobile Robot
which actuated DC motor, L298, a pole, and a Potentiometer. The potentiometer is
an easy and a cheap sensor together comes with a full package to be the balancing
sensor. Along with the potentiometer is Microcontroller 16F877A process all data
using C programming language.
The pole balancing robot has been successfully developed and actually has
trained me to learn many skills; hardware and software skills besides soft skill. In
this learning process, the researcher gain many knowledge and experience in making
a robot before jump into the industry one day. It is hoping that this project will
contribute something in balancing mobile robot system and will be able to compete
with another balancing robot whenever it is equipped with many features and
functionality. In addition, not much advanced technology can be applied since the
duration time to complete it only one year. However, it can be proceed later with
much more additional intelligences and advanced approach as collections or even to
commercialize after this.
58
7.2
RECOMMENDATIONS
There are a few recommendations for the future research for this robot.
•
Firstly, the system must have encoder. More accurate to calibrate the data.
•
Secondly must do state space or fuzzy logic controller after doing the
mechanical hardware and experiment. It will make the system in a balance
condition.
•
Use other sensor such as accelerometer or gyroscope that is much better
compare to potentiometer.
•
Must calibrate the weight of the base, pole and any other material so that we
know our systems are in incredibly stable in weight.
•
Use a stepper motor. More accurate and steady compare to Racing car motor
•
Focusing more on the programming and the mechanical structure of the
robot
•
Must find the right way to mount the pole into the potentiometer.
As for future enhancement, more features can be added to the mobile robot
using others balancing sensor such as encoder and accelerometer or maybe
gyroscope. This will help the system to be more balance and stable all the time.
59
REFERENCES
[1]
Meng Joo Er, Bak Heng Kee and Chee Chong Tan, “Design and
Development of an Intelligent Controller for a Pole-Balancing Robot”,
thesis.School of Electrical and Electronic Engineering, Nanyang
Technological University,Singapore,2001
[2]
H.Hemami,C.L Golliday Jr., ‘The Inverted Pendulum and Biped Stability,
Mathematical Biosciences 34”,pp 95-110,1977
[3]
K. Yamazaki, The Design and Control of SCOUT I, M. Eng. thesis, McGill
University, 1997
[4]
Rich Chi Ooi, “Balancing a Two-Wheeled Autonomous Robot”, thesis,The
University of Western Australia,School of Mechanical Engineering.
[5]
[6]
[7]
[8]
[9]
[10]
[11]
[12]
[13]
[14]
[15]
Grasser, Felix, Alonso D’Arrigo, Silvio Colombi & Alfred C. Rufer. “JOE: A
Mobile, Inverted Pendulum”, IEEE Transactions on Industrial Electronics, Vol
49. 2002
Herdawatie Binti Abdul Kadir, “Modelling And Control Of A Balancing
Robot Using Digital State Space Approach”,thesis,Faculty of Electrical
Engineering, University of Technology Malaysia,2005.
Mori,S.,Nishira,H.,and Furuta,K, “Control Of Unstable Mechanical System
CONTROL OF PENDULUM”,Int.J.Contr.,Vol 23:pp 673-692,1976.
http://www.robotstoreuk.com/
http://www.nexrobotics.com/products/motor-controllers /
http://en.wikipedia.org/
www.bossbi.com/scooter/segway/iseries.php
http://www.iiisci.org/Journal/CV$/sci/pdfs/S406IQ.pdf
http://www.geology.smu.edu/~dpa-www/robo/nbot/
http://www.microchip.com
www.cytron.com
60
APPENDIX
SOURCE CODE OF DEVELOPMENT OF POLE BALANCING MOBILE
ROBOT
61
Source Code
signed double angle;
unsigned data;
//-------------------------------------------------------------------------void kiri1()
{
portd.f0=0;
portd.f1=1;
Pwm1_Change_Duty(250);
delay_ms(1000);
portd.f1=1;
portd.f0=0;
Pwm1_Change_Duty(200);
}
void kiri2()
{
portd.f0=0;
portd.f1=1;
Pwm1_Change_Duty(250);
delay_ms(1000);
portd.f1=1;
portd.f0=0;
Pwm1_Change_Duty(200);
}
62
void kiri3()
{
portd.f0=0;
portd.f1=1;
Pwm1_Change_Duty(250);
delay_ms(1000);
portd.f1=1;
portd.f0=0;
Pwm1_Change_Duty(200);
}
void kiri4()
{
portd.f0=0;
portd.f1=1;
Pwm1_Change_Duty(180);
delay_ms(1000);
portd.f1=1;
portd.f0=0;
Pwm1_Change_Duty(150);
}
void stay()
{
portd.f0=0;
portd.f1=0;
Pwm1_Change_Duty(0);
}
63
void kanan1()
{
portd.f0=1;
portd.f1=0;
Pwm1_Change_Duty(180);
delay_ms(1000);
portd.f1=0;
portd.f0=1;
Pwm1_Change_Duty(150);
}
void kanan2()
{
portd.f0=1;
portd.f1=0;
Pwm1_Change_Duty(180);
delay_ms(1000);
portd.f1=0;
portd.f0=1;
Pwm1_Change_Duty(150);
}
void kanan3()
{
portd.f0=1;
portd.f1=0;
Pwm1_Change_Duty(180);
delay_ms(1000);
64
portd.f1=0;
portd.f0=1;
Pwm1_Change_Duty(150);
}
void kanan4()
{
portd.f0=1;
portd.f1=0;
Pwm1_Change_Duty(180);
delay_ms(1000);
portd.f1=0;
portd.f0=1;
Pwm1_Change_Duty(150);
}
void terus()
{
portd.f0=1;
portd.f1=0;
Pwm1_Change_Duty(180);
delay_us(1000);
}
void main()
{
65
TRISC=0;
TRISD=0;
TRISA=0xFF;
ADCON1=0;
PORTD=0;
Pwm_Init(5000);
Pwm_Start();
while(1)
{
delay_us(100);
data=Adc_Read(0);
angle=0.273*data-143.7;
if((angle>-20)&&(angle<-15))
kiri1();
else if((angle>-15)&&(angle<-10))
{ kiri2();
}
else if((angle>-10)&&(angle<-5))
{ kiri3();
}
else if((angle>-5)&&(angle<0))
{ kiri4();
}
else if(angle<0.1)
{ stay();
}
else if((angle>0)&&(angle<5))
{ kanan1();
66
}
else if((angle>5)&&(angle<10))
{ kanan2();
}
else if((angle>10)&&(angle<15))
{ kanan3();
}
else if((angle>15)&&(angle<20))
{ kanan4();
}
else if(angle>20)
{ terus();
}
}
}