A Project report on

DESIGN AND FABRICATION OF QUADCOPTER

Submitted in partial fulfillment of the requirement for the award of degree of

BACHELOR OF TECHNOLOGYin

Mechanical Engineering

Submitted By

ROHIT SAI RAJ. S

LAXMI SAI SHANKAR. C

10D41A03C0

10D41A0398

Under the Guidance ofDr. P. Mallesham

PrincipalB.E., M.E., Ph.D., ISTE(LM)., AMIE (India), IWS, IFS, CSI

Department of Mechanical Engineering

SRI INDU COLLEGE OF ENGINEERING AND TECHNOLOGY(Affiliated to Jawaharlal Nehru Technological University)

2014

Accredited by NBA

CERTIFICATE

This is to certify that the project work entitled “DESIGN AND

FABRICATION OF QUADCOPTER” is the bonafide work done by,

ROHIT SAI RAJ. S 10D41A03C0

LAXMI SAI SHANKAR. C 10D41A0398

The students of Department of Mechanical Engineering in SRI INDU COLLEGE OF

ENGINEERING & TECHNOLOGY submitted this project to JNTU, Hyderabad

in partial fulfillment of the requirements for the award of B.Tech degree in Mechanical

Engineering. This work has been carried out under my guidance and has not been

submitted the same for any university/institution for the award of any degree/diploma.

Internal Examiner HOD

Principal External Examiner

DECLARATION

We hereby declare that the entire work embodied in this project entitled

“DESIGN AND FABRICATION OF A QUADCOPTER” has been carried out

by us.

No part of it has been submitted for the award of any Degree or Diploma at any

other University or Institution.

S. ROHIT SAI RAJ (10D41A03C0)

C. LAXMI SAI SHANKAR(10D41A0398)

ACKNOWLEDGEMENT

I have taken efforts in this project. However, it would not have been

possible without the kind support and help of many individuals and organizations.

I would like to extend my sincere thanks to all of them.

My deep thanks to the Principal, Dr. P. Mallesham, the Guide of the

project, for guiding and correcting various documents of mine with attention and

care. He has taken pain to go through the project and make necessary correction

when needed.

I express my thanks to the Head of Department, M. Srinivas Rao,

Mechanical Engineering of Sri Indu College of Engineering and Technology, for

extending his support.

I would also thank my Institution and my faculty members and technicians

without whom this project would have been a distant reality.

Finally, I take this opportunity to extend my deep appreciation to my family

and friends, for all that they meant to me during the crucial times of the

completion of my project.

ABSTRACT

An unmanned aerial vehicle (UAV) is an aircraft capable of flying without a pilot

or crew on-board. UAV's can be piloted remotely via a remote-control (RC), though

controlling the aircraft autonomously or semi-autonomously is constantly noted. This can

be achieved through a pre-programmed flight. Military applications benefited, still

benefiting, the most since UAV's come in different sizes and shapes, but UAV's can also

be used in other variety of applications such as aerial photography, scientific exploration,

and small-sized items transportation.

Potential applications of autonomous vehicles range from unmanned surveillance to

search and rescue applications dangerous to human beings. Vehicles specifically designed for

hover flight have their own possible applications, including the formation of high gain airborne

phased antenna arrays. With this specific application in mind, our team sought to produce a

four rotor hovering vehicle (Quadcopter) capable of eventual untethered acrobatic autonomous

flights. The modelling is done in PRO-E wildfire 5.0 software and the mechanical design of the

AFV included both the selection of a battery-motor-prop combination for efficient thrust

production and the design of a lightweight yet sufficiently stiff vehicle structure. The

components chosen were selected from the variety of brushless motors, battery technologies

and cell configurations, and fixed pitch propellers suited to use in a four rotor hovering vehicle.

The vehicle structure settled upon achieved a high degree of stiffness with minimal weight

through the use of thin walled aluminum compression members supported by stranded steel

cable.

While a hardware failure prevented the completion of a full range of tests, the team was

able to complete a hands-free hover test that demonstrated the capabilities of the vehicle.

Supplemented with various other final hardware tests, the vehicle demonstrated stable hover

flight, potential vehicle endurance in the range of 6-8 minutes, and possible vertical acceleration

beyond the hover thrust. The final vehicle represented a significant achievement in terms of

overall design and vehicle capability while future improvements will demonstrate more

advanced nonlinear control algorithms and acrobatic flight maneuvers.

[6]

TABLE OF CONTENTS

CHAPTER PAGE NO

1. INTRODUCTION 1

2. LITERATURE REVIEW OF UAV QUADCOPTER 6

2.1 Quad rotor 6

2.2 Background 7

3. MODELLING IN Pro-E WILDFIRE 5.0 12

3.1 About Pro-E 12

3.2 Modeling components individually 12

3.2.1 Rod 12

3.2.2 Plate 15

3.2.3 Motor 15

3.2.4 Propeller 16

3.3 Sub Assembly 16

3.4 Final assembly 17

4. HARDWARE CHARACTERISTICS & SOFTWARE DESIGN 19

4.1 Block Diagram 19

4.2 Mechanical Components Characteristics 20

4.2.1 Frame Characteristics 20

4.2.2 Propellers Characteristics 22

4.3 Electrical & Electronic Characteristics 22

4.3.1 Actuator Characteristics 23

4.3.1.1 Motors Characteristics 23

4.3.1.2 Electronic Speed Controller (ESC) 24

[7]

CHAPTER PAGE NO

4.3.2 Sensors Characteristics 25

4.3.2.1 Gyroscopes Characteristics 25

4.3.2.2 Accelerometer Characteristics 25

4.3.3 Transmitter & Receiver Characteristics 26

4.3.4 Microcontroller Unit (MCU) Characteristics 26

4.3.5 Battery Characteristics 28

4.4 Software & Control Design 29

5. SELECTED COMPONENTS SPECIFICATIONS 30

5.1 Selected Mechanical Components. 30

5.1.1 Selected Frame 30

5.1.2 Selected Propellers 31

5.2 Selected Electrical & Electronic Component 31

5.2.1 Selected Actuators 31

5.2.1.1 Selected Motors 31

5.2.1.2 Selected Electronic Speed Controller 32

5.2.3 Selected Transmitter 33

5.2.4 Selected Receiver 33

5.2.5 Selected Microcontroller Unit (MCU) 34

5.2.6 Selected Battery 35

6. MECHANICAL DESIGN 37

6.1 Quadcopter Modeling 37

6.2 System dynamics 37

6.3 Kinematic Equations and Euler’s angles 41

6.4 Motor alignment 43

6.2 Propeller balancing 43

6.5 Total balancing 44

[8]

CHAPTER PAGE NO

7. OPERATION AND CONTROL THEROY 45

7.1 Forces acting on quadcopter 41

7.2 Quadcopter operation 46

7.3 PID control 48

7.3.1 PID controller 48

7.4 Inertial measurements 49

7.5 Control inputs 49

7.5.1 Roll control 50

7.5.2 Pitch control 51

7.5.3 Yaw control 52

8. IMPLEMENTATION & RESULTS 53

8.1 Assembly 53

8.2 Software and control algorithm 54

8.3 Flight Testing & Results 54

8.3.1 Preflight testing 54

8.3.2 Flight attempts 55

8.4 Future and work development 56

9. CONLUSION 56

10. BIBLOGRAPHY 58

[9]

LIST OF FIGURSS PAGE NO

1. Schematic diagram of a Quadcopter 6

2. Tyes of motions 7

3. Breguet- Richet gyroplane 8

4. Oehmichen Quadcopter 9

5. Dragonfler x4 10

6. Hexakopter 11

7. Starting pro-E 13

8. Selection of planes 13

9. Sketch and extrude 14

10. Plate 15

11. Motor 15

12. Propeller 16

13. Nut 16

14. Assembly of rod and plate 17

15. Assembly of motor and propeller 17

16. Final assembly 18

17. Block diagram of a Quadcopter 19

18. Brushless DC motors 24

19. Micro control unit 26

20. Software and control design 29

21. Frame set used 30

22. Pair of selected SF 1045 propellers 31

[10]

23. ESCs (Electronic speed controller) picked 32

24. Fly Sky FS-CT 6B Transmitter (6 channel) 33

25. Fly Sky Receiver FS-R 6B 33

26. Multiwii SE V2.0 34

27. NED & ABC Reference Frames 38

28. Forces Acting on a Quadcopter 45

29. Yaw,Pitch,Roll 47

30. Illustration of Various Moments of a quadcopter 47

31. Controls in accordance with the transmitter 50

32. Roll Control 51

33. Pitch Control 51

34. Yaw Control 52

[11]

CHAPTER-1

INTRODUCTION1.1 Overview

The popularity of UAV Quadcopter has been only among military applications till

1996. However, with the development of complex and capable electronics ranging from

more powerful, light-weight microcontrollers to even smaller sensors with better

accuracy and precision, it's possible to build Quadcopter with variety of sizes for

different applications.

Quadcopter particularly have been getting quite a lot of attention lately due to

several reasons. One of these reasons is the fact that a Quadcopter is relatively easy

to build and assemble, having less mechanical complexities than other aircraft such as

helicopters, in most cases no gearing between the rotor and the motor is required.

Another reason is the fact that the design of a Quadcopter is depending on four propellers

instead of one big rotor, which is great due to the less kinetic energy generated, and so in

a case of crash the damage would be less catastrophic and easier to fix and maintain. Also

the relative small size of a Quadcopter, which could also be big in several applications,

makes it suitable for surveillance and other tasks where small size is critical. The ability

to control and hover a Quadcopter in low-speeds and its outstanding maneuverability

makes it perform in an excellent manner in aerial photography, scientific exploration, and

small-sized items transportation. Search & Rescue in places that are dangerous or

unreachable for humans, Quadcopter can do the job in searching and stream live images

of the scene.

The most difficult part about a Quadcopter isn't lying in the building phase, but in

the software/programming phase. The success of a Quadcopter depends mainly on how

[12]

good the control algorithm is, the control loop should be able to compensate any errors

during flight with the help of the sensory feedback. The compensation of error shouldn't

be too aggressive, at the same time not painfully slow. It's crucial to reach the balance

between these two, and reaching this state of balance isn't simple nor trivial by any

means. Every millisecond in execution process counts and could be the deciding factor.

Integrating a control theory (approach) in the code is essential to reach this state, with the

Proportional-Integral-Derivative (PID) being most commonly used in such projects.

Since the Quadcopter depends on analog sensors to act as the “eyes”, it's vital to have

precise and accurate feedback from the gyroscope and the accelerometer. In most cases

where analog sensors are integrated, the readings of such sensors are filled with noise.

With Quadcopter in particular, it's quite important not to have “blurry eyes”, and so the

noise must be filtered. Implementing a filter in the algorithm to accomplish such a job is

also quite tricky. Despite the fact that Kalman filter is popular in such projects, another

type has been integrated in the code, that is a complementary filter. This filter is suitable

for the Quadcopter being not processor (microcontroller-wise) intensive and with the

least amount of lag, which is also crucial in stability projects.

1.2 Scope

In the Hashemite Kingdom of Jordan, where natural resources are scarce,

accomplishing the Quadcopter Project with the title Search & Rescue as its main theme is

quite promising and unique. Deserts dominating a large scale of the whole country, in

addition to distant villages and territories inhabited by citizens are all motivating reasons

to have such a project. In a case of emergency, the Quadcopter could be a great, fast, and

economical solution, in which it would be sent to sweep the desired area and provide live

and valid information about the situation. The Quadcopter could also provide emergency

kits and drugs to those camping in the desert or exploring distant areas, when time is

virtue and instant actions are needed. Having the Quadcopter as the "eyes in the sky" is

the driving element in this project. Having mobile senses that could save others and

[13]

eliminate certain dangers can be faster, safer and more efficient than moving a rescue

crew themselves, and that is the utmost desire.

Furthermore, the uniqueness of the Quadcopter to its core provide an interesting

material subject for scientific publications and researches. It's also an initiative to do

similar kind of projects for fellow students and enthusiasts

1.3 Applications

Areas where Quadcopter can be utilized and also their potential applications are

summarized as follows:

• Search & Rescue: In places that are dangerous or unreachable for normal humans,

Quadcopter can do the job in searching and showing live images of the scene. With the

addition of a GPS geotagging and navigation, exceptional results are expected.

• Commercial use: without the need to rent a helicopter for thousands of dollars, aerial

photos and videos can be taken for many different needs; from cinematic, media and

news coverage to photographing professionals and hobbyists whom like to capture great

photos and videos from high altitudes.

• Transporting objects: A Quadcopter can easily transport small objects, which makes it

a great tool for wide variety of needs, for example; transporting medical supplies in

places where sudden catastrophes occur and rapid medical support is needed.

• Educational use: for a project to build or upgrade one, great amount of knowledge and

benefits can be gained and the eager need to make it fly with great stability makes this

project one of the most exciting ways to learn and understand the true meaning of

engineering and how an engineer should think.

[14]

• RC hobbyists: it is considered one of the most amazing toys to be flown and enjoyed,

with its great maneuverability and high speed. In countries like Germany and USA

people are spending a lot of money to experience flying Quadcopter.

• About any sensor can be added to it: which makes the areas for it to be used simply

diverse and variant; like adding a temperature sensor or gas sensor makes it a very

efficient, fast and safe method for taking different measurements in places like chemical

or nuclear reactors, where dangerous materials can be found and them being unsafe for

humans to stay for long periods.

1.4 Current Aims & ObjectivesWith the given time frame and some other limitations, it has been an important step to

declare the base goals and aims in this project. These targets are summarized as

following:

• Building a light-weight, yet sturdy Quadcopter that could take crashes with less

damage with the help of custom-made protective edges and suitable landing gears.

• Building the base of a project that is surely to be upgraded and developed in all

aspects.

• Achieving a stable flight in the present time.

1.5 OutlineThe upcoming chapters is going to provide further details about the Quadcopter and how

it has been accomplished.

Chapter 2 will discuss some theoretical aspects concerning the Quadcopter, as well as the

previous work that has been done related to it.

[15]

Chapter 3 is all about covering the hardware characteristics and the software design, also

presenting a block diagram of the Quadcopter and the architecture of its control algorithm

illustrated in a flow chart.

The selection of components used in the Quadcopter and also the reasons behind the

decisions that have been made is explained in chapter 4.

Finally in chapter 5, the implementation and integration of both the hardware and

software is discussed, in addition to the achieved results and the future plans.

[16]

CHAPTER- 2

LITERATURE REVIEW OF UAV QUADCOPTER

2.1 Quadcopter

A Quadcopter is an aircraft that consists of four-fixed rotors placed at the ends of a cross-

shaped frame.

Figure 1 shows a schematic of a Quadcopter helping to understand how it works. Both

rotor 1 and 3 (front and back) rotate clockwise (CW) producing a torque, while rotors 2

and 4 (right and left) rotate counter clockwise (CCW) producing an opposite torque

resulting in a balanced torque across the aircraft. The four rotors would produce equal

thrust when rotating in the same speed lifting the Quadcopter in the upward direction.

Figure 1. Schematic diagram of the four rotors on a Quadcopter.

[17]

For a better understanding of the dynamics scheme of controlling a Quadcopter, figure 2

shows the degrees of freedom associated with a Quadcopter. In order to control the pitch,

the relative speed of the front and back rotors are changed, while maintaining the same

thrust on the other rotors (right and left). In the same manner, the roll is controlled by

changing the relative speed of the right and left rotors, while maintaining the same thrust

on the other rotors (front and back). Finally the control of yaw, whether clockwise or

counter clockwise, is achieved by varying the speed of the right and left rotors relative to

the speed of the front and back rotors.

Figure 2 .Types of motion.

2.2 Background:

Attempts to build a Quadcopter go back to the early 1900's, it was more of an

experimental rotary-wing plane but very similar to the concept of a Quadcopter. Such

aircraft was built by the Breguet brothers and the assistance of a professor called Charles

Richet, it flew for the first time in 1907. They called it the “Breguet-Richet Gyroplane

No.1”, and there was only one pilot on-board. The frame (chassis) of this gyroplane at the

center of it was a rectangular-shaped tubing steel to support the pilot and the engine (it

was called a powerplant at that time), from that center four arms are projected, also made

from steel, at their end were a 4-blade biplane rotor. Two sets of these rotors would rotate

clockwise and the other two would rotate counter clockwise in order to generate a

[18]

balanced torque around the frame making the aircraft vertically take off. The powerplant

of the gyroplane was Antoinette piston engine rated at 40-hp and the weight of the

aircraft was about 500 kg without the pilot. But their experimental aircraft didn't flew

well and wasn't steerable nor controllable by any means. Figure 3 shows a photo of this

aircraft.

Figure 3. Breguet-Richet Gyroplane Quadcopter

A French scientist and an engineer called Etienne Oehmichen was more successful when

he built the “Oehmichen No.2” in 1922. This aircraft was reliable and capable of lifting

an individual person with ease. This aircraft possessed four rotors and eight auxiliary

propellers (for a better directional control), powered by a 120-hp Le Rhone rotary engine.

Figure 4 shows this amazing machine showing the main components. The frame of this

aircraft is an x-shaped steel-tube with a 2-blade paddle-shaped rotors at the end of each

arm. The eight auxiliary propellers were used for various directional tasks such as; one is

mounted on the nose for steering, two are used to push the aircraft forward, and rest are

mounted horizontally for stability purposes.

[19]

At the beginning of the 1980's, Quadcopter have been getting a lot of attention as

alternatives for mini UAV applications, together with the introduction of smart

electronics, more research and development have been conducted in that area.

Figure 4. Oehmichen Quadcopter

The Draganflyer X4 is an impressive commercial Quadcopter, yet also suitable for

governmental and military usages. The frame is made from carbon fiber and so are the

rotors. This Quadcopter weighs about 680 g and has a payload capacity of 250 g. The

rotors are driven by brushless Direct Drive motors, with stall protection as a safety

feature. The X4 is packed with a total of seven sensors; three gyroscopes, three

accelerometers, and one barometric pressure sensor. The X4 has also an intuitive easy-to-

use controller, with an OLED touch screen and simple interface, which makes the

experience smooth and easy-to-grab for beginners. The mounting for the camera or any

capturing device installed features an anti-vibration design, resulting in a clear,

professional shoots and videos. A user-friendly software to show basic and advanced

[20]

real-time information monitoring, including of course a live stream of the video being

captured, is also available. Figure 5 shows the Draganflyer X4

Figure 5. Draganflyer X4 .

The Quadcopter project was inspired by the two individuals from de Holger Buss and

Ingo Busker. These two initiated their own project in 2006 and never stopped

since, building outstanding aerial platforms suitable for aerial photography, universities

(for educational and scientific purposes), and also as a hobby for enthusiasts. Their latest

aircraft is the Hexakopter featuring six rotors and a flight time up to 36 minutes with a

small payload (capable of a maximum of 1 kg payload), it weighs about 1.2 kg without

the camera. Figure 7 demonstrates the Hexakopter.

[21]

Figure 6. Hexakopter

[22]

CHAPTER-3

MODELLING OF QUADCOPTER IN PRO-E WILDFIRE 5.0

3.1 ABOUT Pro-E

Pro/ENGINEER is a computer graphics system for modelling various mechanical designs and for performing related design and manufacturing operations. The system uses a 3D solid modelling system as the core, and applies the feature-based, parametric modelling method.

Pro/ENGINEER is a feature-based, parametric solid modelling system with many extended design and manufacturing applications. Assembly, processing, manufacturing and other disciplines are using the unique characteristics of these areas. To these features by setting parameters (including not only geometry, but also non-geometric properties), and then modify the parameters are easy to design iterations many times, to achieve product development

.

3.2 Modeling components individually

3.2.1 ROD

First model a spar with appropriate dimensions i.e., 25* 25 cms.

Steps:

Starting Pro/E and Creating new Part:

1. Start Pro/E Wildfire 5.0.

2. Click menu: File > New. A dialogue box will pop up as shown in Figure 7.

3. Give a new name and/or description if desired.

4. Click OK button and Pro/E will create an empty solid part as shown in Figure 7.

5. You may want to take a look of the coordinate system in Pro/E

[23]

Fig. 7 Starting Pro-E

Selection of the planes :

1. Select the desired plane and its reference plane.

2. Here, we have selected front plane as the sketching plane.

Fig.8 Selection of planes

[24]

Sketch and Extrude :

To make a part, the first step is to draw a sketch, then extrude it to form a solid part. Remember, there are number of ways to do one thing in Pro/E.

As shown in Figure :

1. Click the “Front” Reference plan. This is where you draw a sketch. You can also go to step 2 first, then chose the reference plane.

2. Then click the Sketch tool . All the information should be filled up (Figure 3) 3. Click Sketch button in Figure if you want to accept all the inputs. 4. Now Pro/E is in the Sketch mode. This will allow you to sketch in the XY plane and

extrude in the Z direction. 5. You can close the References window by click close button.

Figure no. 9 Extrude (Rod)

[25]

3.2.2 PLATE:

Model a plate with 10 * 10 cms dimensions.

Figure no.10 Plate

3.2.3 MOTOR:

Similarly, model a motor with appropriate dimensions.

Figure no.11 Motor

[26]

3.2.4 PROPELLER:

Model a propeller of 10*4.5 size.

Figure no.12 propeller

3.3 Sub-assembly 1. Place components in sub-assemblies using commands like MATE, ALIGN and

INSERT to create full product assemblies.

2. Modify assembly placement offsets

3. Create and modify assembly datum planes, coordinate systems and cross-sections.

[27]

Figure no.14 Sub-assembly of rods and plates.

Figure no.15 Subassembly of motor and propeller

3.4 FINAL ASSEMBLY:

[28]

Figure no. 16 Final Assembly

[29]

CHAPTER-4

HARDWARE CHARACTERISTICS & SOFTWARE

DESIGN

4.1 Block DiagramThe best way to start the design phase is by drawing a block diagram, which does a

great job explaining the whole system layout in short. The block diagram in figure

demonstrates the main components of the Quadcopter, in addition it also clarifies how

each component is interfaced and coupled with the other parts.

Figure no.17 Block diagram of a Quadcopter control

[30]

4.2 Mechanical Components Characteristics

In this section, the desired characteristics of the mechanical components will be

discussed. Mainly what are the characteristics and features that have been considered

while designing the Quadcopter. Of course also some technical aspects will be

mentioned.

4.2.1 Frame Characteristics

The most suitable way is to begin with is the skeleton of the Quadcopter, the frame. The

frame is

considered the largest (in volume) component used in the Quadcopter and a very

important one. Choosing a frame to fulfill the required need is essential, critical, and also

not simple. The frame should be light-weight yet strong to tolerate possible accidents and

crashes, it has also to be thin.

Light: a feature that is quite important in aircraft and vehicles, and in Quadcopter it is no

exception. Ultimately the goal is to reach the best possible flight time, and to do so the

weight of the frame should be minimal. This also would assure a better stability and

controllability of the Quadcopter.

Strength: having a frame that is sturdy and strong is vital, as the Quadcopter could crash,

or have an accident due to a wrong landing.

Thin: it is quite critical to have a frame that is thin due to several issues; since the

Quadcopter has four motors spinning at a very high speed, consequently during the flight

those motors will eventually get very hot (depending on flight conditions). Hence, having

a proper air flow is a must to cool down the inner components of the motors and prevent

any damage due to overheating. Another upside of a thin frame is that the vertical air

flow generated by the propellers won't be hindered by a wide frame, contributing in a

better flight stability.

[31]

Length: Another issue that should be discussed about the frame, is its length. The focus

in this case is the distance between the middle point of each opposite motor. It's preferred

to cut down this distance as much as possible due to several reasons; it's a good way to

make the power needed from each motor to stabilize and/or fly the Quadcopter around.

Another good side is that it would enhance the controllability, maneuverability, and also

contribute in reducing the overall frame weight.

Now since the design of the Quadcopter would be an x-shaped, at the center of the shape

should exist a plate (bed) where the on-board controller would rest on it and then covered

to ensure protection of anything resting there, from cables to the controller itself. This

plate should also be sturdy and at the same time light-weight.

To ensure safety and avoid severe damage of the Quadcopter, it has been a priority to

also design some safety features. First off a proper landing gear is important to be

installed. In case of a faulty landing or an error during flight time, the landing gear should

be able, or at least, minimize the damage and impact on the whole Quadcopter. A flexible

landing gear would be a good way to assure this.

Landing Gear: Next is the fact that the exposed propellers are absolutely dangerous for

the Quadcopter itself and the humans around it. Those propellers are, as said before,

spinning at very high speeds during flight and would certainly and seriously hurt

someone badly if something went wrong. The damage could affect the Quadcopter itself,

say the Quadcopter hit a wall, an object, or an obstacle, the propellers would break and be

shattered. The motors could take damage and become unusable. Plus also the shattered

pieces could hurt anyone around them. Such reasons are quite persuasive to consider

designing protection around the propellers, at least during flight time and the testing

phase. And could be removed when the Quadcopter is ready and reliable.

[32]

4.2.2 Propellers Characteristics

The mechanical lifting element of the Quadcopter are the propellers. They do come in

different sizes, shapes, and materials; which makes the decision somehow flexible in

choosing one. High quality propellers are made by different manufacturers to deliver

great performance of lifting power at a very small weight; to minimize the torque needed

for spinning them by the motor's rotor.

As mentioned propellers are manufactured from a variety of materials such as; plastic,

which is cheap, available, and light, but is by nature fragile meaning it could be damaged

or broken easily. Wood is another example, it is tough and mid-priced but is certainly

heavier than plastic. Lastly is the carbon fiber which is tough and light-weight but more

expensive than the previous two types.

Choosing a suitable size is quite crucial in the design of the Quadcopter, since it affects

the power consumption, the overall weight, and how sturdy and reliable (stable-wise) the

Quadcopter is. Increasing the size of the propellers means higher thrust delivered, but that

comes at the cost of more torque required to spin them by the motors. Having that in

mind, the criterion for choosing the propellers is mainly dependent on the model that is

being built and its overall weight. As the goal states, the Quadcopter should be about 1.4

kg and propellers with the size 10 inches are appropriate.

Importantly is the fact that four propellers are needed, but with a pair being oriented for

clockwise (CW) direction and the other pair for the counter-clockwise (CCW) direction.

4.3 Electrical & Electronic Characteristics

The design of electrical and electronic components is absolutely an exhausting

phase, picking components and parts that will cooperate and be interfaced together to

make the Quadcopter successful was filled with hardships. As each of these components

would be synchronized and affected by the others, in addition to the fact that each

[33]

component is a main player in the design process, care and precision are a must. In this

section a thorough discussion about this phase will be mentioned.

4.3.1.1 Motors Characteristics

The motors are no doubt one of the most important elements in the Quadcopter, they are

the “muscles” of it. With that in mind it's quite important to choose the right motors to

do the job, as the impact of those is huge on how satisfying and good the final outcome

is.

Brushless DC (BLDC) motors have several advantages over brushed motors and are a

superior choice; due to the lack of mechanical parts and the absence of brushes, as

mentioned before, the BLDC motors are more efficient (converting electrical to

mechanical energy) than brushed DC motors since there are no friction losses due to the

brushes. The BLDC motors are also less subjected to service and maintenance, again

because of no friction, the mechanical wear is eliminated which guarantees a longer life-

time and better reliability. Less noise generated when operating and since the motor

would be covered in a housing, any cooling issues are almost solved. A BLDC motor's

only disadvantage is its high cost in comparison with a brushed DC motor, as it would

require a sophisticated electronic speed controller (ESC) to run it and control its speed.

Also the manufacturing of a BLDC motor isn't as simple as the brushed DC motor. On

the long run though, the cost of a BLDC is theoretically lower keeping in mind that it has

a longer life-time than a brushed one which would compensate its higher cost.

For the Quadcopter, choosing a BLDC motor is definitely a righteous call, but that's not

everything. Since the Quadcopter is a remote-controlled (RC) propelled aircraft project, a

specific type of a BLDC motor called out runner (the outer shell spins around the

windings) is very suitable to operate the Quadcopter with ease due to several factors;

despite the fact that this type is slower than in runners BLDC motors (the rotational core

is housed in the motor's can) but that means that the torque produced is much higher,

this exactly is the selling point why out runners are a perfect choice to run the

propellers. It's also quite efficient from a weight point of view, because there is no need

[34]

for a gearbox, ridding the Quadcopter from it's complexity, noise, inefficiency, and extra

weight.

Figure no 20. A Brushless DC outrunner motor.

4.3.1.2 Electronic Speed Controller (ESC) Characteristics

ECS's are required to run the BLDC motors in the Quadcopter. The ESC is a standalone

chip that's connected to the receiver's control channels and then coupled with the BLDC

motor.

For a better understanding of the ESC, it's more conventional to consider it as a pulse-

width modulation (PWM) controller for the BLDC motors. PWM in short is a great way

of controlling some modern electronics such as a BLDC motor, a fast variation between

the motor being fully off and fully on powered, more conveniently described as a

[35]

percentage called the duty cycle. Controlling the duty cycle means controlling the speed

of the BLDC motor without any losses and also without affecting the load.

4.3.2 Sensors Characteristics

4.3.2.1 Gyroscope Characteristics

At the beginning of the project, the aim was to achieve a self-stabilized Quadcopter, in

order to achieve that there has to be a kind of feedback that tells the microcontroller that

the Quadcopter is tilting or leaning. This special feedback is achieved through a

gyroscope. A gyroscope is a sensor that measures the angular rate or velocity (speed of

rotation). When rotating it also gives a positive or negative readings, and while stationary

gives a constant value.

Choosing an appropriate gyroscope is dependent on a number of factors; the gyroscope

should be fast and responsive, in other words it should be able to detect minimal changes

in the angular velocity in order to compensate the errors faster which would guarantee the

prevention of the accumulation of errors. It should also be small, and light-weight,

usually Micro Electro-Mechanical Systems (MEMS) manufactured sensors do a great job

featuring these two aspects. And because of the existence of noise, a built-in filter is also

a plus, in addition to a conditioning circuit embedded on the chip that would help a lot in

cutting extra parts and complexities.

Since the Quadcopter is governed by three degrees of freedom (pitch, roll, and yaw), a 3-

axis gyroscope is needed.

4.3.2.2 Accelerometer Characteristics

An accelerometer is a sensor capable of measuring the amount of acceleration, also could

measure the tilt. Implementing the accelerometer and the 3-axis gyroscope together on a

single chip yield the inertial measurement unit (IMU). This unit utilizes both sensors to

do an outstanding job in keeping the Quadcopter as much stable and level as possible,

plus having two sensors on one chip reduces any extra space needed.

[36]

Knowing that the implementation (from a code point of view) isn't anything but hard and

complex, nevertheless utilizing some of the true potential of the accelerometer would

affect the final outcome and results. A 3-axis accelerometer would seem to do that job.

4.3.3 Transmitter & Receiver Characteristics

For the pilot to command the Quadcopter from the ground, a transmitter or a remote-

control (RC) is needed. This should have a good range and both a pre-programmed and

user-programmed channel mixing for a better flexibility and usage. The number of

channels is also an aspect that should not be left out, having a proper amount of channels

is always a plus, as it would greatly enhance the features and tweaks that could be

utilized and later on added to the Quadcopter.

The receiver, which is used to get the commands sent from the transmitter by the pilot,

would be directly coupled with the microcontroller through the PWM I/O pins. Having a

receiver with auto channel and frequency selection seems suitable, offering a user-

friendly solution.

4.3.4 Microcontroller Unit (MCU) Characteristics

Figure no.21 Microcontroller

[37]

The on-board controller is without a doubt a vital component in the Quadcopter. The fact

that the on-board controller will be the one responsible for dispatching a variety of

instructions to the other components, yet also receive certain commands from the pilot

and the feedback coming from the sensors. A proper microcontroller would accomplish

such tasks if properly selected. Definitely a microcontroller is the way to go, because of

its capabilities despite its weight and size.

With that in mind, the selection of a proper microcontroller is critical and should be based

on a specific criteria, summarized as follows:

• Speed of operation; in other words how fast and agile is the processing power? Having

a suitable computational power in the Quadcopter is a must, because during flight time,

the controller should be very responsive and quick to guarantee a stable and a well-

behaving flight.

• Cost; both the hardware and the software to run it. Sometimes the cost of these could

and will eventually mean the need to compromise.

• Power needed to run it; yet another reason to maximize the flight time, the

power consumption of the controller should be as minimal as possible.

• Data storage; i.e. Memory. The controller should provide enough memory to handle

the program and code embedded. A project could fail because of the lack of memory.

• Number of I/O ports; when designing the system, one should possess the knowledge of

how many inputs and outputs are needed. Selecting a controller that shorts in input or

output ports could cause unneeded troubles.

[38]

• Analog capabilities; some controllers lack these such as; ADC, DAC, or a comparator.

In such case this would require to have extra few components and undesired clutter.

• Serial communication; which communication protocol is used to interface the

microcontroller? USB would be a great solution, since it's an industry standard and

readily available.

• Development tools; extra tools and programs that might be needed to fully utilize the

microcontroller. Again it could be a cost point of view, or its availability.

• Environmental conditions; where would it be mounted? Temperature and humidity

issues should also be considered.

With the help of these guidelines, the selection of the microcontroller is clearer and more

convenient. Importantly in the case of the Quadcopter that the microcontroller selected

should be powerful, light- weight, easy to interface with a computer and prototype which,

has enough I/O ports, and easy on the pocket.

4.3.5 Battery Characteristics

Having four motors in a Quadcopter that produce high thrust power, that means

high current consumption is required. So a battery with high current capacity and

discharging rate is needed. Such batteries are available in the market but with much

larger scale and weight than normal batteries, and minimizing the weight of components

on a Quadcopter is a very crucial matter to consider so that an efficient stable flying

system can be achieved. Also it shouldn't be missed that the wires used in the connections

between motors, ESC's, and batteries are able to withstand high current discharge.

[39]

4.4 Software & Control DesignAfter selecting the right hardware components, the next step is to have a proper design

for the code that will run on the Quadcopter. This phase is the hardest of all and needs so

much patience and constant tuning and monitoring. Having a snappy control loop is

essential as the Quadcopter tries to self-stabilize itself, without such a loop, the flight

could be sluggish with a huge amount of errors, which will be also accumulative and

eventually would result in a crash with unexpected consequences.

Starting off with a simple, yet very enriched flow chart of how should the program

embedded in the micro controller look like and behave. A flow chart is very similar to the

block diagram; brief and comprehensive. In figure 11 the flow chart shows the basic steps

and processes needed in the main code.

Figure no 22 Control algorithm flow chart.

To summarize the flow chart, it begins with providing the power through the battery, at

this instance hardware components will initialize and boot. After that the sensors will be

calibrated, taking the nominal value that they “see” and consider it as the reference. The

next two steps are mainly getting the values that the sensors read and then sending those

values to the proportional-Integral (PD) which will get the error and output the final

values with the help of the desired values from the transmitter and receiver. To conclude,

mixing is the process of sending the commands to the motors based on the desired input

plus the output value generated from PD.

[40]

CHAPTER- 5

SELECTED COMPONENTS’ SPECIFICATIONS

In this chapter reasons and justifications to the chosen parts and components will be

made.

5.1 Selected Mechanical Components

5.1.1 Frame

The frame used in the Quadcopter, is made of four aluminum drilled rods with square

cross-section and two center wooden plates. The frame weighs about 150 g, depending

also on the type and number of screws used. The distance between the centers of two

aligned motors is 50 cm and from the center of gravity is 25cm. To mount the

microcontroller and the other components that will be interfaced with it, a custom-made

wood plate is used.

[41]

Figure no.23 the frame set used

5.1.2 Selected Propellers

As for the propellers used, they are slow fly (SF) 1045 i.e., 10*4.5 units for clockwise

and counter clockwise rotation. Figure 13 shows a pair of them.

Figure no.24 A pair of the SF 1045 propellers.

5.2 Selected Electrical & Electronic Components

5.2.1 Selected Actuators

5.2.1.1 Selected Motors

The motors selected to actuate the Quadcopter are the BLDC out runners type 750 KV.

Weighing each 78 g, these motors are capable of 750 rpm/Volt, maximum efficiency of

80%, and a maximum current of 18A. Each motor can produce a maximum thrust up to

1000 g +.

Considering the 2:1 ratio between motors thrust power to Quad copter’s weight is

important. Having a light-weight Quadcopter and relatively strong motors implies the fact

that the control of it would be harder since the overrated power of the motors ratio to the

Quadcopter weight would easily produce an unstable flight, and therefore the control

[42]

algorithm has to be accurate. No compromise. The amount of rpm/Volt is mainly

dependent on the Quadcopter's weight and size, as for bigger sizes low rpm/Volt is better

(higher torque) and for small sizes the opposite.

5.2.1.2 Selected Electronic Speed Control (ESC)

The required ESC needed to run the motor is 20 A, the Mystery cloud are capable to

deliver upto 20 A, which is quite enough and safe. Weighing about 25 g and with a lot of

features such as; superior current endurance, protection features, different operating

modes depending on the aerial platform used, and a throttle range that can be

programmed and compatible with all transmitters available in the market.

Figure no.25 the ESC picked

[43]

5.2.3 Selected TransmitterThe transmitter used in the Quadcopter is the same one used in most remote-control (RC)

toys. Having multiple channels and user-defined channel mixing makes it a suitable

choice.

Figure no.26 Fly sky FS-CT6B 6-channel Transmitter

5.2.4 Selected Receiver

As for the receiver, the R16SCAN is selected. Featuring SCAN technology which

enables the receiver to auto-detect the optimum frequency needed without any extra

steps. It weighs only 17g.

[44]

Figure no.27 Fly-sky FS-R6B Receiver

5.2.5 Selected Microcontroller Unit (MCU)

The Multiwii SE V2.0 is a gyro/accelerometer based flight controller that is loaded

with features. With expandability options and full programmability, this device can

control just about any type of aircraft. This is the ideal flight controller for your multi-

rotor aircraft.

Figure no.28 Multiwii SE V2.0 MCU

Features:

 • Small size, 35x35mm mounting holes

 • 6 input channels for standard receiver and PPM SUM receiver

 • Up to 8-axis motor output

 • 2 servos output for PITCH and ROLL gimbal system

 • Can utilize a servo's output to trigger a camera button

 • FTDI/UART TTL socket for debug, upload firmware or LCD display

[45]

 • I2C socket for extend sensor, I2C LCD/OLED display or CRIUS I2c-GPS NAV

board

 • Separate 3.3V and 5V LDO voltage regulator

 • ATMega 328P Microcontroller

 • MPU6050 6 axis gyro/accelerometer with Motion Processing Unit

 • HMC5883L 3-axis digital magnetometer

 • BMP085 digital pressure sensor

 • On board logic level converter

Flight mode:

 • One of the following basic mode

  - Acro

  - Level

  - Alt Hold

  - Head Lock

 • Optional mode

  - HeadFree (CareFree)

  - GPS Hold (Need GPS receiver + I2C-GPS NAV Board)

  - GPS Return to home position (Need GPS receiver + I2C-GPS NAV Board)

Specs:  

Dimension: 40x12x40mm

Weight: 9.6g

Fixing hole spacing: 35mm (It can be changed to 45mm by CRIUS Distribution

Board)

Hole diameter: 3mm

5.2.6 Selected Battery

LiPo (or Lithium Polymer) batteries are rechargeable batteries, normally are composed of

several identical secondary cells in parallel addition to increase the discharge current

capability. They provide high current capacity and discharge rate to weight ratio. They

have also great life cycle degradation rate.

[46]

A LiPo battery package can have more than 1 cell, the voltage of a LiPo cell varies from

about 2.7V (discharged) to about 4.23V (fully charged). The battery or cell

capacities are rated in ampere hours(Ah) or mill ampere hours(mAh). And they are

also rated in C which is the maximum discharge rate.

The BLDC motors have a continuous current discharge ranging between 4–10 A per

motor, so maximum discharge is (10 A*4) = 40 A. And the average current drain during

the flight is 5.5 A per motor (5.5 A * 4) = 22 A. A 2200 mAh 20C battery was chosen for

testing the Quadcopter and it weighs

180 g.

• The battery has maximum discharge of (2.2 Ah * 20) = 44 A, and can run the

Quadcopter for

(2.2 Ah * 60) / 22 A = 6 minutes (theoretically). This battery is illustrated in figure

[47]

CHAPTER 6

MECHANICAL DESIGN

6.1 Quadrotor modelling

The first step before the control stage is the adequate modeling of the system dynamics. This

phase will hopefully facilitate the control of the aircraft as it will provide us with a better

understanding of the overall system capabilities and limitations. The current chapter will guide

us through the equations and techniques used to model our quadrotor and its sensors,

providing the mathematical basis for the application of the system dynamics in a simulation

environment.

6.2 System dynamics

Writing the equations that portray the complex dynamics of an aircraft implies first defining the

system of coordinates to use. Only two reference frames are required, an earth fixed frame and

a mobile frame whose dynamic behavior can be described relative to the fixed frame. The earth

fixed axis system will be regarded as an inertial reference frame: one in which the first law of

Newton1 is valid. Experience indicates this to be acceptable even for supersonic airplanes but

not for hypersonic vehicles. We shall designate this reference frame by ON ED (North-East-

Down) because two of its axis (ux and uy ) are aligned respectively with the North and East

direction, and the third axis (uz ) is directed down, aligned towards the center of the Earth

(Figure 3.1.1). The mobile frame is designated by OABC, or Aircraft- Body-Centered, and has its

origin coincident with the quadrotor’s center of gravity.

An object that is not moving will not move until a net force acts upon it. An object that is moving

will not change its velocity (accelerate) until a net force acts upon it.

The rotational velocity of Earth must not be neglected for hypersonic flight.

[48]

Figure no.30 NED and ABC reference frames

In control theory, knowledge about the dynamic behavior of a given system can be acquired

through its states. For a quadrotor, its attitude about all 3 axis of rotation is known with 6 states:

The Euler angles [φ θ ψ] (Roll – Pitch – Yaw as seen before in Figure (1.2.1)) and the angular

velocities around each axis of the OABC frame [P Q R].

Yet another 6 states are necessary: the position of the center of gravity (or COG) [X Y Z ]

and respective linear velocity components [U V W ] relative to the fixed frame. In sum, the

quadrotor has 12 states that describe 6 degrees of freedom.

Unsurprisingly, we must deduce the equations describing the orientation of the mobile frame

relative to the fixed one, which can be achieved by using a rotation matrix. This matrix results of

the product between three other matrices (R0 (φ), R0 (θ) and R0 (ψ)), each of them

representing the rotation of the ABC frame around each one of the ON ED axis [22]:

[49]

( ; ( ; (

S ( ( (

S =

Where S is the rotation matrix that expresses the orientation of the coordinate frame OABC

relative to the reference frame ON ED. To mathematically write the movement of an aircraft we

must employ Newton’s second law of motion. As such, the equations of the net force and

moment acting on the quadrotor’s body (respectively Fnet and Mnet) are provided:

+

[ +w’

where I is the inertia matrix of the quadrotor, v is the vector of linear velocities and ω0

the vector of angular velocities. If the equation of Newton’s second law is to be as complete

as possible, we should add extra terms such as the Coriolis, Euler and aerodynamic forces (e.g.

wind), but to keep the model simple, and also because the quadrotor is not supposed, at this

stage, to go very far away from the ground station, these forces will not be incorporated in

the modeling process. The force of gravity (Fg) is too significative to be neglected, thus it is

defined by:

[50]

= [ mg [

The force of gravity together with the total thrust generated by the propellers (FP) have

therefore to be equal to the sum of forces acting on the quadrotor:

Fg+ =Fnet

(3.7) Combining equations (3.4), (3.6) and (3.7) we can write the vector of linear

accelerations acting on the vehicle’s body:

+ g

where [FP x FP y FP z ] are the vector elements of FP . Assuming the aircraft is in a

hovered flight, in such a scenario there are forces acting only in the z axis of quadrotor,

corresponding to the situation we have the engines trying to overcome the force of

gravity to keep the aircraft stable at a given altitude:

FPz = T1+T2 + T3 + T4)

(3.9) Note that the minus sign means the lifting force is acting upwards, away from the

surface (note that the positive axis of the ON ED is point downwards)

Working now on Newton’s second law for rotation, the inertia matrix is given by:

I

[51]

Assuming the quadrotor is a rigid body with constant mass and axis aligned with the

principal axis of inertia, then the tensor I becomes a diagonal matrix containing only the

principle moments of inertia.

I

Joining 3.1 and 3.5 we get,

+

Consequently we will have,

+

Information on the moments acting on the aircraft cab be provided by,

= (

= ( )

= ( + )

[52]

Where, is the distance of cog of aircrafts and is constant that relates

thrust and propeller.

6.3 Kinematic equations and Euler angles

In this section we will study the kinematics of the quadrotor. The first stage of kinematics

analysis consists of deriving position to obtain velocity. Let us then consider the position vector

→ −r , which indicates the position of the origin of the OABC frame relative to ON ED :

X + Y

If we derive each component in we can onbtain the instantaneous velocity of relative

to .

+ +

To find out the aircrafts linear velocity v’ in the fixed frame we can use:

Where we can take full advantage of orthogonality of S, meaning its inverse is equal to its

transpose:

[53]

The flight path of the quadrotor in terms of [X Y Z] can be found by integration of equation 3.22. To per- form this integration, the Euler angles φ, θ and ψ must be known. However, the Euler angles themselves are functions of time: the Euler rates φ˙, θ˙, and ψ˙ depend on the body axis angular rates P, Q and R. To establish the relationship between [φ˙ θ˙ ψ˙ ] and [P Q R] the following equality must be satisfied:

+ Q φ˙ + θ˙ + ψ˙

Note that although it may appear that the Euler rates are the same as angular velocities, this is not the case. If a solid object is rotating at a constant rate, then its angular velocity →−ω will be constant, however the Euler rates will be varying because they depend on the instantaneous angles between the coordinate frame of the body and the inertial reference system (e.g. between OABC and ON ED ). The Euler angle sequence is made up of three successive rotations: Roll, Pitch and Yaw. In other words, the angular rate φ˙ needs one rotation, θ˙ needs two and ψ˙ needs +three:

R ( + R ( ) R ( + R( )

Therefore,

Solving for the euler angle rates yields the desired differential equations:

[54]

T

T

where T is the matrix that relates the body-fixed angular velocity vector →−ω and the rate of change of the Euler angles.

6.4 Motor AlignmentAs previously mentioned, the act of mounting the motor mounts to the frame was

extremely difficult due to the fact that the holes needed to be drilled to within +/- .1o of

each other. Any successful flying device must be perfectly balanced, and this is very

prevalent when dealing with a quad rotor. In order to achieve a balanced vertical flight,

the group needed to be certain that the motors were perfectly straight. If the motors were

not perfectly aligned, achieving a balanced, smooth flight would be nearly impossible.

With this in mind, the group devised a way to be sure that all the motor mounts were

aligned correctly. By setting the frame of the quad rotor on a flat surface, the group used

a T-square held against the motor mounts. If the mounts were directly against the edge of

the square, then the mount would be aligned in a right angle.

6.5 PROPELLER BALANCING

Due to the fact that the propellers are operating at such a high RPM, it is crucial to the quad

rotors performance that the propellers are balanced. Although theoretically the propellers are

designed to have symmetric blades, in reality there are slight imperfections. These

[55]

imperfections cause the propellers to vibrate uncontrollably, making smooth flight almost

impossible. By balancing the propellers, vibrations can be significantly reduced.

The group balanced the propellers by examining the relative weight distribution of each

propeller. There are several types of commercially available propeller balancing devices, but a

similarly effective device was made. The method used consisted of attaching the propeller to a

spindle held up between two blocks, allowing the propellers to rotate freely. If one of the blades

is heavier than the other, then the propeller will rotate towards the heavier blade. In such a case

the blades trailing edge was sanded down to compensate for the mass difference. Once the

blades weights were evenly distributed, the propeller balanced horizontally.

6.6 Total Balancing

The quad rotor, which includes the hub, spars, and motor mounts, was carefully designed and

assembled with the idea of having a helicopter which is as close to perfect in terms of its weight

distribution throughout the entire aircraft. As previously mentioned, achieving a steady and

controllable flight is almost impossible to achieve unless the aircraft is as close to perfect

balance. The addition of the electronic components and battery onto the frame of the quad

rotor leaves its weight distribution inconsistent throughout. As a result, the group has devised a

way to make sure that the frame is as balanced as possible.

The way to do this is by attaching a piece of string to the center of the hub and allowing the

quad rotor to float freely. If the weight is not evenly distributed, then the quad rotor will lean

towards the heaviest part. The battery packs, which are mounted below the central hub by

rubber bands, were then adjusted to ensure the quadrotor was balanced in the x and y axes.

[56]

CHAPTER 7

OPERATION AND CONTROL THEORY

7.1 Forces acting on a Quadcopter

Effect

Source

Aerodynamic effects - Propeller rotation

 

Inertial counter torques - Change in propeller

  rotation speed

Gravity effect - Center of mass position

Gyroscopic effects - Change in orientation

  of the rigid body

[57]

  - Change in orientation

of the propeller plane

Friction - All helicopter motion

Figure no.32 Forces acting on a quadcopter

7.2 Quadrotor operation

Each rotor in a quadrotor is responsible for a certain amount of thrust and torque about its

center of rotation, as well as for a drag force opposite to the rotorcraft’s direction of

flight. The quadrotor’s propellers are not all alike. In fact, they are divided in two pairs,

two pusher and two puller blades that work in contra-rotation. As a consequence, the

resulting net torque can be null if all propellers turn with the same angular velocity,

thus allowing for the aircraft to remain still around its center of gravity.

In order to define an aircraft’s orientation (or attitude) around its center of mass,

aerospace engineers usually define three dynamic parameters, the angles of yaw, pitch

and roll. This is very useful because the forces used to control the aircraft act around its

center of mass, causing it to pitch, roll or yaw. Changes in the pitch angle are induced by

contrary variation of speeds in propellers 1 and 3, resulting in forward or backwards

translation. If we do this same action for propellers, we can produce a change in the roll

angle and we will get lateral translation. Yaw is induced by mismatching the balance in

aerodynamic torques (i.e. by offsetting the cumulative thrust between the counter-rotating

blade pairs). So, by changing these three angles in a quadrotor we are able to make it

maneuver in any direction.

[58]

Figure no.33 Yaw, pitch and roll rotations of a common quadrotor.

Figure no 34 Illustration of the various movements of a quadrotor.

[59]

7.3 P.I.D control

The quad rotor will use a Proportional-Integral-Derivative control system, which will be tuned to

determine the optimum response and settling time. The PID controller Eq. (4.9) is a closed-loop

feedback system which will output a control signal u and receive feedback from the inertial

sensors. The controller then calculated the difference between the desired position and

orientation and the current position and orientation and adjusts u accordingly. The equation for

a PID controller is as follows:

U = 𝑃 + I + D

7.3.1 Proportional, Integral, Derivative (PID) Controller

PID, or proportional-integral-derivative controllers are loop feedback controls that aim to

correct for a given error. Often, the effect of a PID is modeled as a step response. One PID

control is needed for each parameter to be corrected. In our case, we need a PID loop for yaw,

pitch, and roll. Future designs might implement PID for altitude and x/y position as well. In the

embedded environment, the proportional, integral, and derivative terms are calculated as

follow:

P = desired – actual

I = I + actual

D = current error – past error

Note that the derivative term can also be determined by accessing the direct ADC values from

the rate gyroscopes for a given axis of rotation.

Each of the three terms has a gain KP, KI, or KD that is tuned to minimize rise time to the step

input and to minimize oscillation and overshoot. For each of the three Euler angles, we

compute a sum comprised of the gains and their corresponding terms, e.g.

Pitch sum = KP*P + Ki*I + KD*D

[60]

At the end of the PID loop, the appropriate summations were added and subtracted from each

of the four motors as seen in the code snippet below. The thrust Floor term corresponds to the

thrust that the user commands on the joystick.

PWM_MOT1 = thrust Floor – roll sum + yaw sum;

PWM_MOT2 = thrust Floor + pitch sum – yaw sum;

PWM_MOT3 = thrust Floor + roll sum + yaw sum;

PWM_MOT4 = thrust Floor – pitch sum – yaw sum;

The entire PID loop must be completed at a relatively high frequency to ensure fast motor

response. Without a fast PID response the quadrotor will not properly stabilize.

7.4 Inertial Measurement

Inertial Measurement Systems sense inertial forces on a body and from those forces linear and angular position and velocity can be calculated. There are two types of INS: initially stabilized and strap down system. The difference comes from the frame of reference the unit is aligned to. In an inertially stabilized unit the gyroscopes remain fixed in reference to an inertial (navigation) reference frame (Fig. 2) and do not rotate with the vehicle which allow it to rotate on all three axes; The gyroscopes do not measure angles directly, they are only used to keep the unit aligned with the reference frame. In a strapped-down system the gyroscopes rotate with the body, and by integrating angular velocities from an initial position the orientation and position of the vehicle can be determined.

7.5 Control inputs

The Quadcopter is an aerial system that uses four propellers to generate lift. Quadcopter that

can be classified as a type of helicopter. Most Quad-Rotors use fixed-pitch blades as opposed to

[61]

most commercial helicopters. The system is controlled by varying the rotational velocity of each

of the rotors and thereby changing the thrust and torque produced.

Figure no.35 Controls in accordance with the transmitter

The Quadcopter is designed for manual control i.e. human control with visual feedback and it is

thus not possible to directly control the rotational velocity of the individual rotors. The

Quadcopter features several different modes of control but in the following only the Heading-

Hold mode will be addressed. For a thorough description of the other modes see G on page 114.

The Quadcopter flown in Heading-Hold mode utilizes a on-board control circuit that manages

the rotational velocity of the four rotors and adjusts the velocity based on on-board sensory

data. The human operator is only able to control the angular velocities of the Quadcopter along

the three body-axis and the generated thrust. This allows a skilled operator to control the

attitude and position of the platform thus enabling the operator to maintain the Quadcopter in

hover.

7.5.1 ROLL:

Roll is when the quadcopter performs a rotation around the x-body axis. This is achieved by changing the angular velocity of the rotors on the y-body axis that is rotor 2 and 4 while maintaining the same angular velocity on rotor 1 and 3. If the desired rotation is positive the roll is performed by increasing the angular velocity of rotor 2 and decreasing the angular velocity of

[62]

rotor 4. This results in a positive roll or rotation around the x-body axis. The rotor velocities related to this maneuvers are illustrated in figure

Figure no.36 Roll control

7.5.2 PITCH:

Pitch is when the QUADCOPTER performs a rotation around the y-body axis. This is achieved by

changing the angular velocity of the rotors on the x-body axis that is rotor 1 and 3 while

maintaining the same angular velocity on rotor 2 and 4. If the desired rotation is positive the

pitch is performed.by increasing the angular velocity of rotor 1 and decreasing the angular

velocity of rotor 3. This results in positive pitch or rotation around y-axis body.

Figure no.37 Pitch Control

[63]

7.5.3 YAW:

Yaw is when the Quadcopter performs a rotation around the z-body axis. This is achieved

mismatching the torque generated by the Quadcopter rotors. During normal flight the net

torque acting on the plat- form body is zero as the rotors along the x-body axis and y-body axis

apply the same amount of torque to the platform. If the torques applied along the axis are

mismatched the platform will perform a rotation around the z-body axis. If the desired rotation

is positive the yaw is performed by increasing the angular velocity of rotor 2 and 4 while

decreasing angular velocity of rotor 1 and 3. This results in a positive yaw or rotation around the

z-body axis. The rotor velocities related to this maneuver are illustrated in figure.

Figure no.38 Yaw Control.

[64]

CHAPTER-8

IMPLEMENTATION & RESULTS

8.1 AssemblyAssembling and connecting all the components of the Quadcopter is a process that needs

extra attention.

Starting with the frame which consists of four Aluminum parts all screwed and tightened

up with the center plate.

After that comes the soldering part; where all the needed soldering was made for the

electronic parts to be connected properly; For the PCB where the sensors will be

mounted, wires which are divided to connect the ESC’s with the battery.

When connecting the Motors and ESC’s together, the direction of rotation of each motor

should be considered.

A custom-made base platform was made to hold the controller on the center plate.

All connections were made between the electronic components and the controller. Then

the

Components were mounted together on the center plate of the frame. An empty CD-ROM

holder is used to protect all the sensitive electrical components of the Quadcopter.

The plastic door stoppers were used as landing gears and attached to the Quadcopter

frame.

[65]

8.2 Software & Control AlgorithmThis section includes a brief information since the development of the project will

continue and further additions will be made, which obliged the investigators to keep the

main controlling algorithm and software confidential.

The Quadcopter controller was programmed using in built program. Multiple classes

were created to divide the work of each part of the program to keep everything neat and

simple, and to improve its functionality.

When the battery is connected to the system, the controller starts as follows:

• The process starts by initializing all the hardware, variables, classes & subclasses

needed in the system.

• The sensors are calibrated by reading their values at standstill position. These values

are considered as the zero values to be compared with any new values.

• PWM signals are read by the receiver.

• The pilot activates the motors by a specific combination of signals sent to the

controller from the transmitter.

• New values of sensors readings are compared to the original values to calculate error.

• The PID controller receives the error and produces an actuationg signal for the degrees

of freedom.

• The mixing formula is executed to adjust the motors speed in order to give the

Quadcopter, the required direction,

8.3 Flight Testing & Results

8.3.1 Preflight Testing

Before the Quadcopter could be tested in free flight, it had to be determined that it would

not respond in a way which would damage itself. First, all of the sensors were connected

to the quadcopter, but not actually mounted on it. This allowed manipulation of the

[66]

sensors while allowing the motors to run, but prevented the Quadcopter from actually

moving. This was a

qualitative test simply to ensure that the motors were responding quickly to variations in

attitude and altitude.

The second test calibrated the hover thrust. The helicopter was attached to a scale and

thrust was increased until the thrust canceled out the weight.

8.3.2 Flight Attempts

The Quadcopter is still going through flight testing which includes tuning of the damping

constants and tweaking of the code to get the most accurate data out of the sensors. The

rangefinder seems to have problems where certain distances are accurate to within a few

millimeters while others can be off by more than a centimeter.

8.4 Our Future Work & Development

• Implementing a better control algorithm using accelerometers to achieve better

stability results.

• Live feedback using wireless technology for various applications; real time aerial

video, image processing, reading different sensors data & battery capacity monitoring.

• Using image processing as an extra sensor to control the movement of the Quadcopter

and minimize the drifting.

• Minimizing the cost of building one by using cheaper components.

• Adding GPS which will make a great method in holding a current position, setting a

destination point or a way point for the Quadcopter to follow. Including using geo

tagging for different applications.

Additional sensors can be added beside the main sensors like pressure & magnetometer

sensors to control the heading and altitude of the Quadcopter, which will result in a

superior stable flight.

[67]

8. CONCLUSION

We have successfully met our design goals and demonstrated autonomous flight. The

main objective of this was to model and control a quadrotor prototype, having a tri-

axis accelerometer and a compass as its sensors.

In the first phase of this, objectives were defined for the quadrotor design, and based on

them a study was carried out on the electronics that would be part of the aircraft. This

analysis resulted in the construction of a quadrotor capable of achieving a flight.

Knowing the characteristics of our quadrotor, we proceeded to the modeling of the

aircraft’s dynamics for implementation of the resulting equations in a computer

simulation environment. Thus, we found that the system is completely controllable

when all states are available.

Joystick and the quadrotor’s control unit, the Arduino. Unfortunately, the quadrotor

displayed an unstable behavior. It was assumed that the lack of inclusion of the Pulse-

Width Modulation signal resolution in the simulations could be the reason why this

instability had not been foreseen. After introducing this new element in the simulation,

we found nevertheless that the controller could still drive the system to the intended

reference, although with a little more difficulty. This information led us to analyze the

noise coming from the sensors with the motors running, which proved to be the

source of the problem.

All the work done so far shows only that there are several aspects of the control process

that need to be corrected/improved in order to make a controlled flight for this prototype

possible. In particular, the inclusion of 3 gyroscopes (one for each axis of rotation)

should be considered, which together with the tri-axis accelerometer, form a

combination of sensors that has already been tested in quad rotors, allowing for very

good control over its pitch and roll angles. The idea is that with gyroscopes we can

determine orientation, but they drift over time (long-term errors), which is something we

can correct with accelerometers (short-term errors, i.e. They are very noisy). But even

then, we would need something else to correct the drifting yaw angle from the gyroscope,

which could be done with a magnetic compass. The long-term idea is that adding a

[68]

greater number of sensors, in addition to those suggested, can only improve the quality

and quantity.

It would also be interesting to develop the simulations further by including new

elements such as aerodynamic forces (i.e. Wind), collisions and other types of control

methods, such as Proportional Derivative controllers. The quadrotor prototype should

also be taken to an outside environment to see its performance tested under more extreme

conditions.

[69]

BIBLIOGRAPGHY

[1] URL: http://en.wikipedia.org

[2] URL: http://3dgameprogramming.net

[3] URL: http://aviastar.org

[4] URL: http://draganfly.com

[5] URL: http://mikrokopter.de

[6] URL: http://www.q4systems.de

[7] URL: http://blogspot.com

[8] URL: http://microcontroller.com

[9] URL: http://pics.towerhobbies.com

[10] URL: http://hobbycity.com

[11] URL: http://xoarintl.com

[12] URL: http://youtube.com

[13] IDG500 Datasheet from URL: http://invensense.com

[14] ADXL335 Datasheet from URL: http://analog.com

[15] http://sparkfun.comhttp://shop.graupner.dehttp://arduino.cc

[70]

[71]