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Executive Summary

This report outlines the design and manufacture of an Unmanned Aerial Vehicle (UAV)intended for civil and commercial surveillance applications. Particular emphasis isplaced on the search and rescue capabilities of the aircraft, for potential entranceinto the 2009 ARCAA Outback Challenge. The Outback Challenge requires that theaircraft be capable of autonomously searching a remote area for a missing bushwalker,and then dropping emergency supplies.

In 2007, the iSOAR UAV was developed at the University of Adelaide for a similarpurpose. The knowledge and components accumulated throughout the development ofthe iSOAR aircraft provided an extensive resource for the 2009 project. The fuselage,propulsion system, modems and video downlink were retained from the 2007 project,allowing the 2009 project team to focus on additional systems such as the integra-tion of the aircraft autopilot, an emergency recovery system and image processing forautonomous detection of ground targets.

The 2007 iSOAR aircraft demonstrated high takeo and landing speeds, resulting in anumber of crashes. In order to solve this problem, a new pair of wings were designedand manufactured with an increased wing area, aspect ratio, and the addition of flaps.The new wings dramatically reduced takeo and landing speeds while maintaining goodcruise performance.

The aircraft autopilot was not successfully implemented in the 2007 iSOAR UAV, asit resulted in a loss of remote control (RC) communication. This issue was solved in2009, with fully autonomous flight demonstrated in a test aircraft.

The use of a parachute for emergency recovery was deemed infeasible as it would com-pose too high a proportion of the overall aircraft weight. It was therefore decided thatin the event of component or communications failure, the aircraft would be deliberatelycrashed in order to prevent the aircraft drifting into populated areas.

The imaging system was redesigned for autonomous detection of the ARCAA OutbackChallenge target, and consisted of an infrared camera and image processing software.

iii

The completed system was demonstrated to be capable of automatically detecting andtracking a 3W infrared light source from an altitude of 50m.

Future work for the project includes the integration of an improved camera with theability to encompass both visual and infrared imagery, a modified video communi-cations link to reduce interference with the autopilot modem, construction of a newlanding gear to allow for a modular payload system, and re-manufacture of the air-craft fuselage in order to reduce weight through more ecient layup techniques. Theproject team intends to finish these tasks and complete full system integration in orderto successfully compete in the 2010 ARCAA Outback Challenge.

iv

Acknowledgements

The authors would like to acknowledge the contributions made by many people through-out the course of this project.

Firstly, the group would like to thank our project supervisor, Dr. Maziar Arjomandi.Dr Arjomandis guidence, experience and engineering knowledge have been invaluableto the group throughout the year. The group greatly appreciates the time and eortDr Arjomandi has spent in ensuring the success of the project.

The project received financial support from Codan, which was greatly appreciated.Without this support, the goals of the project may not have been realised. The groupwould like to thank Codan for their support of engineering education in Australia.

The group would also like to acknowledge the financial support received from TheSir Ross and Sir Keith Smith Fund, which has contributed greatly to the aerospaceindustry within South Australia. Without the assistance of The Sir Ross and Sir KeithSmith Fund, many aspects of this project would not have been possible.

The assistance of the sta at the School of Mechanical Engineering Workshop is greatlyappreciated. In particular, the assistance provided by Philip Schmidt and Bill Finchwas invaluable, and the group would like to acknowledge their work.

Finally, the authors would like to thank their friends and families for supporting themthroughout the year.

Smith Fund Acknowledgment and Disclaimer

Research undertaken for this report has been assisted with a grant from the SmithFund (www.smithfund.org.au). The Smith Fund by providing funding for this projectdoes not verify the accuracy of any findings or any representation contained in it. TheSmith Fund does not accept any responsibility or liability from any person, companyor entity that may have relied on any written report or representations contained inthis report if that person, company or entity suers any loss (financial or otherwise)as a result.

v

Disclaimer

The authors listed below hereby declare that the contents of this report are their ownoriginal work unless otherwise specified.

Mark Eldridge 1120791 ................................................................

James Harvey 1147525 ................................................................

Todd Sandercock 1132146 ................................................................

Ashleigh Smith 1147261 ................................................................

vii

Contents

Executive Summary . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . iii

Acknowledgements . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . v

Disclaimer . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . vii

Table of Contents . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . xvi

List of Figures . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . xx

List of Tables . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . xxi

Nomenclature . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . xxvi

1 Introduction 1

1.1 Background . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 1

1.2 Aim . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 2

1.3 Project Goals . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 2

1.4 Scope . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 3

1.5 Significance . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 3

1.6 ARCAA UAV Outback Challenge . . . . . . . . . . . . . . . . . . . . . 4

2 Feasibility Study 5

2.1 Mission Requirements . . . . . . . . . . . . . . . . . . . . . . . . . . . 5

2.1.1 Mission Parameters . . . . . . . . . . . . . . . . . . . . . . . . . 5

2.1.2 Search Pattern . . . . . . . . . . . . . . . . . . . . . . . . . . . 7

2.1.3 Optimisation of search pattern . . . . . . . . . . . . . . . . . . . 8

2.2 UAV Market Survey . . . . . . . . . . . . . . . . . . . . . . . . . . . . 10

2.3 Control and Communication Systems . . . . . . . . . . . . . . . . . . . 13

ix

2.4 Imaging Systems . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 15

2.5 Recovery Systems . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 16

2.6 Technical Task . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 19

2.6.1 Technical Level . . . . . . . . . . . . . . . . . . . . . . . . . . . 19

2.6.2 Economic Parameters . . . . . . . . . . . . . . . . . . . . . . . 19

2.6.3 Standard Requirements . . . . . . . . . . . . . . . . . . . . . . 19

2.6.4 Performance Requirements . . . . . . . . . . . . . . . . . . . . 20

2.6.5 System Requirements . . . . . . . . . . . . . . . . . . . . . . . . 21

3 Conceptual Design 23

3.1 Aircraft Configuration . . . . . . . . . . . . . . . . . . . . . . . . . . . 23

3.1.1 Configuration Review . . . . . . . . . . . . . . . . . . . . . . . . 23

3.1.2 Propeller Placement . . . . . . . . . . . . . . . . . . . . . . . . 23

3.1.3 Configuration Selection . . . . . . . . . . . . . . . . . . . . . . . 25

3.2 Aircraft Design Parameters . . . . . . . . . . . . . . . . . . . . . . . . 25

3.3 Aircraft Preliminary Sizing . . . . . . . . . . . . . . . . . . . . . . . . . 26

3.3.1 Stall Requirements . . . . . . . . . . . . . . . . . . . . . . . . . 27

3.3.2 Takeo Distance Requirements . . . . . . . . . . . . . . . . . . 27

3.3.3 Climb Requirements . . . . . . . . . . . . . . . . . . . . . . . . 28

3.3.4 Cruise Requirements . . . . . . . . . . . . . . . . . . . . . . . . 28

3.3.5 Matching Diagram Results . . . . . . . . . . . . . . . . . . . . . 28

3.3.6 Weight Estimation . . . . . . . . . . . . . . . . . . . . . . . . . 30

3.3.7 Final Design Point . . . . . . . . . . . . . . . . . . . . . . . . . 30

3.4 Propulsion System . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 30

3.4.1 Motor Type Selection . . . . . . . . . . . . . . . . . . . . . . . . 30

3.4.2 Electric Motor Selection . . . . . . . . . . . . . . . . . . . . . . 32

3.4.3 Propeller Selection . . . . . . . . . . . . . . . . . . . . . . . . . 32

3.4.4 Electronic Speed Controller (ESC) Selection . . . . . . . . . . . 32

3.4.5 Motor Batteries . . . . . . . . . . . . . . . . . . . . . . . . . . 33

x

3.5 Manufacturing Concepts . . . . . . . . . . . . . . . . . . . . . . . . . . 34

3.5.1 Wing Manufacture Methods . . . . . . . . . . . . . . . . . . . . 34

3.5.2 Selection . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 36

3.6 Control and Communication Systems . . . . . . . . . . . . . . . . . . . 36

3.6.1 Mission Requirements . . . . . . . . . . . . . . . . . . . . . . . 36

3.6.2 Manual Control . . . . . . . . . . . . . . . . . . . . . . . . . . . 38

3.6.3 Autonomous control . . . . . . . . . . . . . . . . . . . . . . . . 40

3.7 Imaging System . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 42

3.7.1 Requirements . . . . . . . . . . . . . . . . . . . . . . . . . . . . 42

3.7.2 Problem Description . . . . . . . . . . . . . . . . . . . . . . . . 43

3.7.3 Camera Selection . . . . . . . . . . . . . . . . . . . . . . . . . . 44

3.7.4 Downlink Selection . . . . . . . . . . . . . . . . . . . . . . . . . 45

3.7.5 Image Processing System . . . . . . . . . . . . . . . . . . . . . . 46

3.7.6 Summary . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 47

3.8 Recovery System . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 48

3.8.1 Comparison of Recovery Methods . . . . . . . . . . . . . . . . . 48

3.8.2 Comparison of Parachute Types . . . . . . . . . . . . . . . . . . 49

3.8.3 Parachute Sizing . . . . . . . . . . . . . . . . . . . . . . . . . . 51

3.8.4 Summary . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 54

3.9 Payload Release Mechanism . . . . . . . . . . . . . . . . . . . . . . . . 55

3.9.1 Concepts . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 55

3.9.2 Summary . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 56

3.10 Final Concept . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 56

4 Detailed Design 59

4.1 Airfoil Selection . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 59

4.1.1 Selection Considerations . . . . . . . . . . . . . . . . . . . . . . 59

4.2 Tailplane Design . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 61

4.2.1 Tailplane sizing . . . . . . . . . . . . . . . . . . . . . . . . . . . 61

xi

4.2.2 Rudder and Elevator Sizing . . . . . . . . . . . . . . . . . . . . 61

4.3 Wing Design . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 62

4.3.1 Design Factors . . . . . . . . . . . . . . . . . . . . . . . . . . . 62

4.3.2 Aerodynamic Design . . . . . . . . . . . . . . . . . . . . . . . . 62

4.3.3 Control Surface Sizing . . . . . . . . . . . . . . . . . . . . . . . 63

4.3.4 Mechanical Design . . . . . . . . . . . . . . . . . . . . . . . . . 64

4.4 Autopilot . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 67

4.4.1 Micropilot 2028g issues . . . . . . . . . . . . . . . . . . . . . . . 68

4.4.2 Paparazzi Hardware . . . . . . . . . . . . . . . . . . . . . . . . 69

4.4.3 Paparazzi Software . . . . . . . . . . . . . . . . . . . . . . . . . 70

4.4.4 Sensor Calibration . . . . . . . . . . . . . . . . . . . . . . . . . 73

4.4.5 Tuning . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 74

4.4.6 Flight Plan . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 74

4.5 Communication Systems Design . . . . . . . . . . . . . . . . . . . . . . 79

4.5.1 Review of 2007 design . . . . . . . . . . . . . . . . . . . . . . . 79

4.5.2 Investigation of possible causes . . . . . . . . . . . . . . . . . . 81

4.5.3 Preliminary Testing . . . . . . . . . . . . . . . . . . . . . . . . . 83

4.5.4 Solution generation . . . . . . . . . . . . . . . . . . . . . . . . . 84

4.5.5 Video Downlink . . . . . . . . . . . . . . . . . . . . . . . . . . . 85

4.5.6 Summary of Design . . . . . . . . . . . . . . . . . . . . . . . . . 85

4.6 Imaging System . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 85

4.6.1 Camera . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 85

4.6.2 Image Processing . . . . . . . . . . . . . . . . . . . . . . . . . . 87

4.6.3 Summary . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 89

4.7 Ground Station . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 89

4.7.1 Aircraft Remote Control Transmitter . . . . . . . . . . . . . . . 89

4.7.2 Paparazzi Ground Control Station . . . . . . . . . . . . . . . . . 90

4.7.3 Imaging System . . . . . . . . . . . . . . . . . . . . . . . . . . . 90

4.7.4 Personnel Requirements . . . . . . . . . . . . . . . . . . . . . . 90


4.9 Final Design . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 92

xii

5 Manufacturing 93

5.1 Wing Construction . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 93

5.1.1 Procedure . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 93

5.1.2 Manufacturing Issues . . . . . . . . . . . . . . . . . . . . . . . . 96

5.2 Fuselage Modification . . . . . . . . . . . . . . . . . . . . . . . . . . . . 96

5.2.1 Wing Attachment . . . . . . . . . . . . . . . . . . . . . . . . . . 96

5.2.2 Battery Location . . . . . . . . . . . . . . . . . . . . . . . . . . 97


5.4 Electronic System Installation . . . . . . . . . . . . . . . . . . . . . . . 98

5.5 Quality Assurance . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 99

5.6 Completed Airframe . . . . . . . . . . . . . . . . . . . . . . . . . . . . 100

6 Testing 101

6.1 Component Testing . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 101

6.1.1 Wing Structural Test . . . . . . . . . . . . . . . . . . . . . . . . 101

6.1.2 Static Propulsion Test . . . . . . . . . . . . . . . . . . . . . . . 103

6.1.3 Communication Range Test . . . . . . . . . . . . . . . . . . . . 104

6.1.4 Imaging System Test . . . . . . . . . . . . . . . . . . . . . . . . 105

6.1.5 Payload Release Mechanism . . . . . . . . . . . . . . . . . . . . 107

6.2 Flight Testing . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 107

6.2.1 Airframe Tests . . . . . . . . . . . . . . . . . . . . . . . . . . . 107

6.2.2 Autopilot Test . . . . . . . . . . . . . . . . . . . . . . . . . . . . 110

6.2.3 Imaging System Test . . . . . . . . . . . . . . . . . . . . . . . . 112

6.2.4 Payload Deployment Test . . . . . . . . . . . . . . . . . . . . . 114

7 Management and Finances 115

7.1 Risk Management . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 115

7.2 Project Management . . . . . . . . . . . . . . . . . . . . . . . . . . . . 115

7.2.1 Management Delegation . . . . . . . . . . . . . . . . . . . . . . 115

7.2.2 Communication . . . . . . . . . . . . . . . . . . . . . . . . . . 116

7.3 Financial Management . . . . . . . . . . . . . . . . . . . . . . . . . . . 117

7.4 Time Management . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 117

xiii

8 Conclusion 119

8.1 Project Goals . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 119

8.2 Future Work and Recommendations . . . . . . . . . . . . . . . . . . . . 122

Bibliography 125

A Airfoil Comparison i

B Matching Diagram Verification v

B.1 Take O Distance Verification . . . . . . . . . . . . . . . . . . . . . . . v

B.1.1 Verification point 1 . . . . . . . . . . . . . . . . . . . . . . . . . v

B.1.2 Verification point 2 . . . . . . . . . . . . . . . . . . . . . . . . . vi

B.2 Climb Performance Verification . . . . . . . . . . . . . . . . . . . . . . vii

B.3 Cruise Performance Verification . . . . . . . . . . . . . . . . . . . . . . viii

C Tailplane Sizing Calculations ix

D Spar Stress Calculations xi

E Test Procedures xiii

E.1 Test aircraft . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . xiii

E.2 Component Testing . . . . . . . . . . . . . . . . . . . . . . . . . . . . xiv

E.2.1 Static Wing Loading . . . . . . . . . . . . . . . . . . . . . . . . xiv

E.2.2 Motor Verification . . . . . . . . . . . . . . . . . . . . . . . . . xv

E.2.3 Preliminary communication field tests . . . . . . . . . . . . . . . xvi

E.2.4 Communication Long Range Verification . . . . . . . . . . . . . xix

E.3 Flight testing . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . xx

E.3.1 Proof of aerodynamic and mechanical design . . . . . . . . . . xx

E.3.2 Flight performance verification . . . . . . . . . . . . . . . . . . xxii

E.3.3 Autopilot . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . xxiii

E.3.4 Imaging System . . . . . . . . . . . . . . . . . . . . . . . . . . xxiv

E.3.5 Payload Deployment . . . . . . . . . . . . . . . . . . . . . . . . xxv

xiv

F Project Scheduling xxvii

G Bill of Materials xxix

H Paparazzi Code xxxiii

H.1 Airframe File . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . xxxiii

H.2 Flightplan File . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . xl

I Image Processing Code xlvii

I.1 Initial Processing . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . xlvii

I.2 Blob Quality Analysis . . . . . . . . . . . . . . . . . . . . . . . . . . . xlix

I.3 Ivy Bus Communication . . . . . . . . . . . . . . . . . . . . . . . . . . l

J Micropilot 2028g Development liii

J.1 Solution to Micropilot issues . . . . . . . . . . . . . . . . . . . . . . . . liii

J.2 Micropilot Configuration . . . . . . . . . . . . . . . . . . . . . . . . . . liii

J.3 Micropilot Flight Plans . . . . . . . . . . . . . . . . . . . . . . . . . . . lv

K Meeting Minutes lix

K.1 Tuesday 3.2.09 . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . lix

K.2 Tuesday 10.2.09 . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . lxii

K.3 Thursday 19.02.09 . . . . . . . . . . . . . . . . . . . . . . . . . . . . . lxiv

K.4 Monday 02.03.09 . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . lxviii

K.5 Monday 16.03.09 . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . lxxi

K.6 Monday 23.03.09 . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . lxxiv

K.7 Monday 30.03.09 . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . lxxvii

K.8 Monday 06/04/09 . . . . . . . . . . . . . . . . . . . . . . . . . . . . . lxxix

K.9 Monday 20/04/09 . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . lxxxi

K.10 Monday 27/04/09 . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . lxxxii

K.11 Monday 04/05/09 . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . lxxxv

K.12 Monday 11/04/09 . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . lxxxvii

xv

K.13 Monday 25/05/09 . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . lxxxix

K.14 Monday 01/06/09 . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . xc

K.15 Monday 15/06/09 . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . xci

K.16 Monday 13/07/09 . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . xciii

K.17 Monday 20/07/09 . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . xcv

K.18 Monday 03/08/09 . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . xcviii

K.19 Monday 03/08/09 . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . ci

K.20 Monday 10/08/09 . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . ciii

K.21 Monday 17/08/09 . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . civ

K.22 Monday 24/08/09 . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . cv

K.23 Monday 31/08/09 . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . cvi

K.24 Monday 07/09/09 . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . cvii

K.25 Monday 07/09/09 . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . cviii

K.26 Monday 28/09/09 . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . cix

K.27 Monday 12/10/09 . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . cx

L CAD Drawings cxiii

xvi

List of Figures

2.1 Search and Rescue Area . . . . . . . . . . . . . . . . . . . . . . . . . . 6

2.2 Search patterns . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 7

2.3 Creeping line search pattern . . . . . . . . . . . . . . . . . . . . . . . . 8

2.4 The iSOAR UAV (Avalakki et al. 2007) . . . . . . . . . . . . . . . . . . 11

2.5 Aerosonde (Corporation 2009) . . . . . . . . . . . . . . . . . . . . . . 11

2.6 The Insitu/Boeing ScanEagle UAV (CNet 2007). . . . . . . . . . . . . . 12

2.7 Silver Fox (Sadaghiani 2007) . . . . . . . . . . . . . . . . . . . . . . . 12

2.8 CryoWing (Norut 2008) . . . . . . . . . . . . . . . . . . . . . . . . . . 13

2.9 The Boeing/Insitu ScanEagle UAV, showing the imaging compartment(CNet 2007). . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 16

2.10 The IAI I-View MK50 UAV, with para-foil recovery system deployed(IAI 2002) . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 17

2.11 The SkyHook capture system used for the Boeing ScanEagle (Insitu2009) . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 18

3.1 Matching Diagram . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 29

3.2 Built up wing construction (Johnson 2007) . . . . . . . . . . . . . . . . 34

3.3 Composite covered foam core construction (Decker 2002) . . . . . . . . 35

3.4 DX7 Spektrum RC system including dual receivers and servos (ModelModelFlight 2009) . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 39

3.5 Micropilot 2028g (MicroPilot 2009) . . . . . . . . . . . . . . . . . . . . 42

3.6 Steady-state descent rate versus nominal parachute diameter . . . . . . 52

3.7 Final concept 3-View of the aircraft . . . . . . . . . . . . . . . . . . . . 57

3.8 A side fiew of the final concept aircraft, showing all major subsystems. 57

xvii

4.1 The performance of the SD7032 airfoil at various Reynolds numbers . . 60

4.2 V-N Diagram including gust loading . . . . . . . . . . . . . . . . . . . 63

4.3 Local Lift Distribution . . . . . . . . . . . . . . . . . . . . . . . . . . . 65

4.5 Wing tongue joiner . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 65

4.4 Bending Moment Distribution . . . . . . . . . . . . . . . . . . . . . . . 66

4.6 Spar design . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 67

4.7 TWOG v1.00 architecture (Paparazzi 2009) . . . . . . . . . . . . . . . 70

4.8 Two IR sensors used to measure aircraft roll (Paparazzi 2009) . . . . . 71

4.9 Autopilot configuration . . . . . . . . . . . . . . . . . . . . . . . . . . . 71

4.10 Arrangement of autopilot components within the UAV . . . . . . . . . 72

4.11 Paparazzi Center . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 72

4.12 Paparazzi GCS . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 73

4.13 Search Pattern . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 75

4.14 Figure 8 loiter pattern . . . . . . . . . . . . . . . . . . . . . . . . . . . 76

4.15 Payload drop routine . . . . . . . . . . . . . . . . . . . . . . . . . . . . 77

4.16 Return to home pattern . . . . . . . . . . . . . . . . . . . . . . . . . . 78

4.17 2007 Communication systems configuration . . . . . . . . . . . . . . . . 80

4.18 Communication systems configuration . . . . . . . . . . . . . . . . . . . 86

4.19 Layout of communication systems within UAV . . . . . . . . . . . . . . 86

4.20 The Image Processing software . . . . . . . . . . . . . . . . . . . . . . 87

4.21 The payload release mechanism design . . . . . . . . . . . . . . . . . . 91

4.22 Final aircraft design, showing all major systems . . . . . . . . . . . . . 92

5.1 Core Cutting . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 94

5.2 Wingbox Core . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 94

5.3 Spar Cap Layup . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 95

5.4 Fibreglass Layup . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 95

5.5 Completed wing with control surfaces removed . . . . . . . . . . . . . . 96

5.6 Wing attachment . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 97

xviii

5.7 Battery installation . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 98

5.8 Removable payload release mechanism . . . . . . . . . . . . . . . . . . 99

5.9 Installed Electronics . . . . . . . . . . . . . . . . . . . . . . . . . . . . 99

5.10 Completed airframe . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 100

6.1 Wing Load Distribution . . . . . . . . . . . . . . . . . . . . . . . . . . 102

6.2 Motor Test Stand . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 103

6.3 Thrust vs Battery Power . . . . . . . . . . . . . . . . . . . . . . . . . . 104

6.4 Autopilot signal strength . . . . . . . . . . . . . . . . . . . . . . . . . . 105

6.5 Initial Testing of the Image Processing Software . . . . . . . . . . . . . 106

6.6 Takeo performance for various flap configurations . . . . . . . . . . . 108

6.7 Increasing proportional gain on navigation loop . . . . . . . . . . . . . 111

6.8 Figure 8 path performed autonomously . . . . . . . . . . . . . . . . . . 112

6.9 System testing of the Image Processing software, showing detection of a3W infrared lamp . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 113

7.1 Management Structure . . . . . . . . . . . . . . . . . . . . . . . . . . . 116

7.2 Number of work hours per month . . . . . . . . . . . . . . . . . . . . . 118

A.1 Polar plot comparison of airfoils for Re = 100,000 . . . . . . . . . . . . ii

A.2 Polar plot comparison of airfoils for Re = 200,000 . . . . . . . . . . . . ii

A.3 Polar plot comparison of airfoils for Re = 300,000 . . . . . . . . . . . . iii

A.4 Polar plot comparison of airfoils for Re = 400,000 . . . . . . . . . . . . iii

A.5 Polar plot comparison of airfoils for Re = 500,000 . . . . . . . . . . . . iv

A.6 Polar plot comparison of airfoils for Re = 600,000 . . . . . . . . . . . . iv

D.1 Spar Dimensions . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . xii

E.1 Test Aircraft . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . xiii

E.2 RC range test . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . xvii

E.3 UAV supported by stand . . . . . . . . . . . . . . . . . . . . . . . . . . xviii

E.4 Accomodation Hill . . . . . . . . . . . . . . . . . . . . . . . . . . . . . xx

xix

F.1 Gantt Chart of Internal and External Deadlines . . . . . . . . . . . . . xxvii

F.2 Gantt Chart of Project Tasks . . . . . . . . . . . . . . . . . . . . . . . xxviii

xx

List of Tables

2.1 Parameters of mission strategy . . . . . . . . . . . . . . . . . . . . . . . 10

3.1 Airframe Configuration Decision Matrix . . . . . . . . . . . . . . . . . 24

3.2 Wing Dihedral . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 26

3.3 Decision matrix for propulsion system selection . . . . . . . . . . . . . 31

3.4 Current Available Brushless Motors . . . . . . . . . . . . . . . . . . . . 32

3.6 Li-Po and Ni-MH Battery Comparison . . . . . . . . . . . . . . . . . . 33

3.8 AXI 4130-20 specifications . . . . . . . . . . . . . . . . . . . . . . . . . 33

3.9 Decision matrix for wing manufacture selection . . . . . . . . . . . . . 36

3.10 Comparison of 2028g with other autopilot systems . . . . . . . . . . . 41

3.11 Decision matrix for payload release system selection . . . . . . . . . . . 56

3.12 Design Specifications . . . . . . . . . . . . . . . . . . . . . . . . . . . . 56

4.1 The airfoils analysed for use on the redesigned wing . . . . . . . . . . . 60

4.2 Tailplane sizing requirements . . . . . . . . . . . . . . . . . . . . . . . 61

4.3 2024-T3 Aluminium Material Properies (Typical) . . . . . . . . . . . . 66

4.4 Pultruded carbon-reinforced epoxy strip (Chen & Lui 2005) . . . . . . 66

4.5 Final Camera Specifications . . . . . . . . . . . . . . . . . . . . . . . . 86

6.1 Aircraft Performance . . . . . . . . . . . . . . . . . . . . . . . . . . . . 110

6.2 Flight path error . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 111

7.1 Breakdown of Finances . . . . . . . . . . . . . . . . . . . . . . . . . . . 117

7.2 Major Milestones . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 118

xxi

Nomenclature

=2(WS )gcCl

Ground roll friction

Air density

ARCAA Australian Research Centre for Aerospace Automation

CASA Civil Aviation Safety Authority

CASRs Civil Aviation Safety Regulations

CCD Charge-Coupled Device

CCTV Closed-Circuit Television

Cdp Coecient of Drag of the parachute

CH Chord length of horizontal stabiliser

cHT Horizontal tail volume coecient

CLmax Maximum lift coecient

CLTO Take o configuration coecient of lift

CNC Computer Numerical Control

CPU Central Processing Unit

Cv Chord length of vertical stabiliser

cV T Vertical tail volume coecient

CW Average wing chord length

Cx Parachute opening force coecient at infinite mass conditions

xxiii

D Drag

Do Distance between opposite sides of a polygonal parachute, assuming the numberof sides is even

Dp Drag generated by the parachute in steady-state descent

DSM2 Second generation spread spectrum modulation

DSSS Direct-Sequence Spread Spectrum

FHSS Frequency Hopping Spread Spectrum

Fo Parachute opening force

g Acceleration due to gravity at sea level

GCS Ground Control Station

GPS Global Positioning System

GUI Graphical User Interface

HFOV Horizontal Field of View

IC Internal Combustion

iSOAR intelligent Surveillance for Outback Aerial Rescue

JVM Java Virtual Machine

K = 1Ae

k = 0.885.3+

KA =

2(WS )(CD0 KC2LTO + CLTO)

KT =TW

LED Light Emitting Diode

LHT Horizontal tail moment arm

LiPo Lithium-Polymer

Ls Length of each side of a polygonal parachute

LV T Vertical tail moment arm

xxiv

ma Mass of the iSOAR aircraft

n Change in load factor due to gust load

n Number of sides in a flat polygonal parachute

Ni-MH Nickel Metal Hydride

OSS Open-Source Software

PFD Primary Flight Display

PID Proportional Integral Derivative

PN Pseudonoise

PWM Pulse Width Modulation

q Dynamic viscosity (12V2)

R Reefing fraction of parachute

RC Remote Control

RF Radio Frequency

RSO Range Safety Ocer

Sg Take o ground roll

SHT Horizontal tailplane area

SOP Safe Operating Procedure

Sp Parachute surface area

SRTM Shuttle Radar Topography Mission

SV T Vertical tailplane area

SW Wing planform area

T Thrust

TWOG Tiny Without GPS

U = kUde

xxv

UAV Unmanned Aerial Vehicle

Vclimb Climb Velocity

Vd Steady-state descent rate of the aircraft

Vi Speed of the aircraft at the point of parachute deployment

Vstall Stall velocity

Wa Weight of the aircraft

W/P Power Loading

W/S Wing Loading

Xi Parachute opening force reduction factor

xxvi

Chapter 1

Introduction

1.1 Background

Unmanned Aerial Vehicles (UAVs) are a rapidly advancing area of technology, withmilitary UAVs having been in use for many years. Unmanned aircraft also have greatpotential for civilian and commercial applications, particularly in situations where amanned aircraft would not be cost eective or where human life may be endangered.Though not as widely publicised as military related UAVs, significant developmentshave been made in the civil domain.

The civil and commercial potential of these systems has resulted in a large amountof research and development towards eective, aordable unmanned aircraft for civiluse. The Aerosonde is one such example - a UAV developed in Australia by AerosondePty Ltd and used by the Bureau of Meteorology and Sencon Environmental Systems.The Aerosonde aircraft is used for meteorological and environmental surveillance overoceanic, remote, and hazardous areas. In addition, many universities across Australia(including the University of Adelaide) have had significant involvement in the researchand development of unmanned aircraft.

In 2007 a team of 8 students from the University of Adelaide School of MechanicalEngineering designed and manufactured a UAV named iSOAR, for intelligent Surveil-lance for Outback Aerial Rescue. The iSOAR aircraft was specifically designed forcivilian applications, such as fire detection and monitoring, shark spotting, and tracsurveillance. It was also intended to enter the aircraft in the 2007 ARCAA OutbackUAV Challenge (described in greater detail in Section 1.6) , a competition focused onthe use of unmanned aircraft for search and rescue.

1

2 CHAPTER 1. INTRODUCTION

1.2 Aim

The aim of the 2009 project was to design, manufacture and test a fixed-wing UAVcapable of performing a variety of civil or commercial tasks which might normally relyon manned aircraft. Using the experience obtained from the 2007 project, the 2009team aims to improve on the design of the iSOAR aircraft with regard to aerodynamicand functional performance during all stages of flight, payload deployment, level ofautonomy, and through the successful implementation of emergency recovery and imageprocessing systems. In addition, the team intends to compete successfully in the 2009ARCAA 2009 UAV Challenge - Outback Rescue.

1.3 Project Goals

A number of goals were specified at the commencement of the project. The goalsmaintain the direction of the project as well as providing a measure of success atits conclusion. The primary goals were essential for the successful completion of theproject, while the extended goals are to be completed if time and resources allow.

Primary Goals

Design and manufacture a new pair of wings with improved performance over the2007 iSOAR aircraft.

Design and implement a reliable payload deployment device capable of deliveringa 500mL bottle of water to within 100 m of a specified target.

Implement an autopilot system capable of controlling the UAV outside of visiblerange. The desired level of autonomy includes maintaining straight and levelflight, negotiating turns, and allowing changes in altitude.

Develop software capable of detecting and tracking an object (representing aperson) from the aircraft camera feed and communicating its location with theaircraft. The aircraft should use this location to drop the payload previouslydescribed.

Extension Goals

Meet the minimum requirements for participation in the ARCAA 2009 UAVChallenge Outback Rescue.

The University of Adelaide

1.4. SCOPE 3

Reduce the takeo weight of the UAV to 9 kg or less.

Develop a system capable of determining the GPS coordinates, within 100maccuracy, of a specified target on the video footage streamed from the UAV.

Improve the quality of the video system, such that it is possible to identify ahuman from cruise altitude.

Design and implement an emergency recovery system, with the primary goal ofensuring safety to people on the ground and secondary goal of minimising damageto the UAV.

1.4 Scope

As a general purpose surveillance UAV, the design has the capacity for a numberof dierent applications in the civil and commercial sphere. The Outback Challengeprovides a means of clearly defining the scope of the project while maintaining thefundamental features of a UAV designed for civil and commercial tasks. Though thecompetition rules define much of the scope of the project, actually competing in thecompetition was not essential to the success of the design.

Success in the Outback Challenge requires the design to be capable of a reasonabledegree of autonomy, in addition to possessing imaging systems capable of identifyinga human target from cruise altitude. Such abilities are also required for many civiland commercial tasks where UAVs might be required to play a role, and so success-fully meeting these requirements would make the aircraft useful for many applicationsoutside of the competition itself.

1.5 Significance

The use of UAVs oers significant benefits in a variety of civil and commercial appli-cations. The lack of a human pilot is a significant advantage as it eliminates the riskto a pilots life, significantly increases endurance time, and allows a greater load factorto be sustained. In addition, UAVs have relatively low manufacturing and operationalcosts, and a high flexibility for adjusting to a customers needs (Sarris 2001).

Some of the applications for which UAVs can be utilised include search and rescue, coastwatch, border patrol, bushfire detection and monitoring, trac monitoring, mapping

Design and Build a Search and Rescue UAV

4 CHAPTER 1. INTRODUCTION

and surveying, surveillance, and media coverage. In each of these applications, replac-ing a manned aircraft with a UAV has the potential to significantly reduce costs. Forthe same expense as a single manned aircraft (generally including a pilot and copilot),multiple UAV platforms could be used to achieve a greater level of coverage.

1.6 ARCAA UAV Outback Challenge

The UAV Outback Challenge is a joint initiative between the Australian ResearchCentre for Aerospace Automation (ARCAA), the Queensland Government, and BoeingAustralia Limited. The competition is designed to promote the development of UAVsfor civil purposes in Australia, and is one of the largest competitions of its kind in theworld (ARCAA 2009).

The scoring system for the competition allocates points based on whether aircraft cansuccessfully complete competition tasks, as well as for safety and design. The 2009competition incorporates three separate challenges:

An Airborne Delivery Challenge, which is restricted to secondary school students.This challenge requires competitors to design, build and fly a remotely controlledaircraft a short distance and then release a payload.

A Robot Airborne Delivery Challenge, which is similar to the Airborne DeliveryChallenge, but requires the aircraft to be autonomous. This challenge is alsorestricted to secondary school students.

A Search and Rescue Challenge, where competitors must design, build and deploya UAV to find a lost bushwalker within a set search area. Once the bushwalkerhas been found the UAV is required to deliver emergency supplies. This challengehas no restriction on entrants.

The aim of the 2009 project is to design and build a UAV suitable for entrance in theSearch and Rescue Challenge.


Chapter 2

Feasibility Study

Although the vehicle was designed with the intention of being suitable for various civiland commercial applications, the design was heavily influenced by the requirements ofthe 2009 ARCAA Outback Challenge. It was believed that the competition provided arealistic scenario to which the UAV could be applied, and required capabilities whichwould be applicable in a variety of other applications. A number of existing UAVsystems were investigated prior to beginning the design. This analysis was used toascertain the feasibility of the intended design and reveal existing technologies. Theresults of the feasibility study were used to generate the technical task for the project.

2.1 Mission Requirements

Initially it was neccessary to determine the optimum search strategy for the mission.This was used to define the aircrafts required cruise speed, which in turn had a sig-nificant impact on other performance and systems requirements. It was assumed thatdesigning the UAVs performance specifically for search and rescue missions would notprevent it from performing other surveillance missions, such as coastwatch, border pa-trol, shark spotting and bushfire monitoring. The optimum strategy was defined as thestrategy which would maximise the probability of finding the subject, while minimisingthe time taken to do so.

2.1.1 Mission Parameters

The primary objective of the Outback Challenge is to search a remote area for amissing bushwalker and deliver an emergency package. This task must be performedwith minimal human input.

5

6 CHAPTER 2. FEASIBILITY STUDY

Mission Boundary Constraints

The Outback Challenge is held at Kingaroy airport in South East Queensland, Aus-tralia. Kingaroy airport is at an elevation of 1472 ft (450m) above sea level and hasa runway of length 5249 ft (1600m). The competition has a flight corridor, missionboundary and search area predefined in the rules of the competition. The flight cor-ridor is approxiamately 0.2 nautical miles (0.3 km) by 1 nautical miles (1.8km), andthe vehicle must stay within this flight corridor on transition from the airport to themission area, and vice versa.

The mission boundary has an approximately rectangular geometry of dimensions 2 nm(3.6km) by 3 nm (5.4km). The target is located in the search area which is defined asbeing 0.5 nm within the mission boundary and hence has a rectangular geometry of1 nm (1.8km) by 2 nm (3.6 km). The vehicle is also limited to flying at an altitudebetween 200ft and 400ft (though permission can be attained from CASA to fly to1500ft), with the exception of take-o and landing. If at any time the vehicle exitsthe mission boundary, the vehicles mission is terminated by the Range Safety Ocer(RSO). Figure 2.1, illustrates the flight corridor, mission boundary and search area.

Figure 2.1: Search and Rescue Area


2.1. MISSION REQUIREMENTS 7

Rescue

The target of the search is Outback Joe, a human dummy wearing light khaki clothesand an Akubra hat. There is a simulated heat signature for the dummy in the formof a 12 volt Videotec IR50 infrared lamp, which emits light at a wavelength of 850nm.The dummy will not be moving and will be positioned in a typical resting pose for atired and lost bushwalker as would be viewed from the air.

Once Outback Joe has been located, GPS coordinates of his detected position must beprovided to the judges. Once the judges deem the UAV to be within close proximityto Outback Joe, the vehicle must deploy a minimum of 500 mL of fluid safely to him.The fluid must be in an unopened vessel, suitable for human consumption, and it mustbe possible to open the vessel so that the contents can be measured by the judges. Thepackage must be dropped within 100m of Outback Joe, without contacting him.

2.1.2 Search Pattern

Possible searh patterns considered most relevant to this mission included creeping line,expanding square, and sector search patterns as shown in Figure 2.2 .

Figure 2.2: Search patterns

The expanding square and sector patterns are advantageous in missions where thereis some prior knowledge of the subjects whereabouts, as the search pattern can beginand be centred around the area of highest probability. In this way the time takento find the subject is minimised. For the Outback Challenge however, there was nodata provided to indicate where Outback Joe was more likely to be situated, eectivelyremoving the advantage of both patterns. Considering this, the sector search was nolonger feasible as it would cover the central area of the pattern multiple times, whichwould be an inecient use of the allowed search time. Furthermore, it is generally



dicult to maintain navigational accuracy for the expanding square approach (Wollan2004), paticularly within the central region of the pattern where there are many turnswithin a small area. This is especially relevant for aircraft, which have a limited turnradius and are aected by cross winds.

The creeping line approach is generally considered advantageous in large search areas(Wollan 2004) where there is no prior knowledge of the subjects position. This isbecause it covers the entire area with consistent detail and can be implemented withreasonably high navigational accuracy due to the low path complexity. Therefore, theuse of a creeping line pattern was considered the most feasible option for this mission.

2.1.3 Optimisation of search pattern

The creeping line pattern was modified such that the path doubles back over the searcharea. This was done such that the required turn radius of the UAV was increased andtherefore the UAV could perform the turns at a greater speed. Figure 2.3 shows theaircraft part way through the creeping line search pattern.

Figure 2.3: Creeping line search pattern

Optimisation of the search pattern involved reducing the total search distance to aminimum, while ensuring the entire area was covered. This was performed using aspreadsheet.

The spreadsheets input parameters included:


2.1. MISSION REQUIREMENTS 9

Cruise altitude: Increasing the cruise altitude increases the sweep width (widthof ground seen in cameras HFOV) and therefore reduces the total search distanceand time taken to cover the entire area. However, increasing altitude also reducesimage detail. Therefore, a cruise altitude of 300 ft (midpoint of allowed range)was selected as it was believed that it provided a balance between image detailand sweep width.

Camera horizontal field of view (HFOV): Coupled with cruise altitude,HFOV determines the UAVs sweep width. At this stage the camera that wouldeventually be used was not known. Therefore, a standard 3.6 mm, 1/3 CCTVcamera was assumed with a HFOV of 67.4.

Track width: Is the distance between the midpoint of each sweep as indicatedin figure 2.2. Therefore, increasing the track width decreases sweep overlap andthe total search distance. Some sweep overlap is required however to avoid gapsin the search area.

Search time: The time allocated for the search phase of the mission was 50minutes, which allowed 10 minutes for setup.

The spreadsheets output parameters included:

Total distance: The optimisation process required the total search distance tobe minimised.

Sweep width: For a cruise altitude of 300 ft (91.4 m) and a HFOV of 67.4,the sweep width was 122 m.

Sweep overlap: It was believed that a sweep overlap of at least 5% (corre-sponding to 6m of overlap on either side of a sweep) was reasonable to accountfor navigational inaccuracies.

Cruise speed: Was calculated from the total search distance and the searchtime of 50 minutes.

While keeping the cruise altitude, camera HFOV and search time fixed as above, thetrack width was increased until the sweep overlap was reduced to approximately 5%.The results of this optimisation are indicated in table 2.1.

It was therefore decided that the design cruise speed would be 25 m/s (90 km/h). Itshould be noted that the above parameters were merely estimates to base the designwork on as futher optimisation would be made through testing.



Table 2.1: Parameters of mission strategyParameter

Cruise altitude 300 ftCamera HFOV 67.4Track width 115 mSearch time 50 minsTotal distance 70643 mSweep width 122 mSweep overlap 5.71%Cruise speed 23.55 m/s

2.2 UAV Market Survey

Before commencing design work, it was necessary to benchmark a number of existingUAV platforms with similar mission profiles. This demonstrated the feasibility ofthe intended design and the expected level of performance. The surveillance UAVsanalysed included the 2007 iSOAR aircraft, Aerosonde, ScanEagle, Silver Fox andCryoWing.

2007 iSOAR Aircraft

The iSOAR UAV, depicted in figure 2.4, was designed and manufactured at the Univer-sity of Adelaide for a variety of surveillance applications, including search and rescue.iSOAR utilises a conventional configuration with a wing span of 1.9 m and a weight ofapproximately 11 kg, and uses an AXI Gold Line electric motor for propulsion.

The iSOAR aircraft is capable of cruising at 25 m/s for over 1 hour and 15 minutesand has a communication range of 10 km. As the autopilot was not successfully imple-mented, the maximum mission range was never realised. In addition, iSOAR requireda runway for take-o and landing.

Aerosonde

The UAV Aersonde, indicated in figure 2.5, was designed by an Australian company ofthe same name, and has been successful around the world. Aerosonde is capable of per-forming a variety of missions including surveillance and meteorological investigations,and has a relatively long endurance of up to 24 hours. It has a wingspan of 3.45 m, amaximum gross take-o weight of 16.8 kg and a cruise speed of 26 m/s (Corporation2009). Propulsion is obtained through the use of a 4-stroke, 24cc single cylinder engine.


2.2. UAV MARKET SURVEY 11

Figure 2.4: The iSOAR UAV (Avalakki et al. 2007)

Figure 2.5: Aerosonde (Corporation 2009)

ScanEagle

ScanEagle is a small UAV with a wing span of 3.1 m and a maximum take-o weightof 18 kg, developed by Insitu and Boeing for military surveillance. The aircraft itselfdoes not incorporate landing gear, with launching being performed using a catapault,and landings accomplished using the SkyHook retrieval system. SkyHook involvesusing a cable to catch the aircraft via hooks mounted on the wingtips. ScanEagle hasan endurance of over 20 hours, a range of over 100 km, and a cruise speed of 25 m/s(Insitu 2009). The aircraft is powered by a propellor in a pusher configuration, and a1.9hp 2-stroke internal combustion engine.



Figure 2.6: The Insitu/Boeing ScanEagle UAV (CNet 2007).

Silver Fox

Silver Fox, indicated in figure 2.7, is a medium range reconnaissance, surveillanceand intelligence UAV, which has been used extensively by the Canadian Army andAmerican Army (Sadaghiani 2007). Silver Fox is launched via a bungee catapult,which allows its use in a variety of terrains. The UAV has a conventional configurationwith a wing span of 2.1 m and a maximum take-o weight of 11.3 kg. It incorporatesa modular design, which can be suited for a number of dierent payloads, and has anendurance of 10 hours, a range of 40 km and a cruise speed of 25 m/s (ONR 2004). A2-stroke engine using a mixture of petrol and oil is used for propulsion.

Figure 2.7: Silver Fox (Sadaghiani 2007)


2.3. CONTROL AND COMMUNICATION SYSTEMS 13

CryoWing

The UAV CryoWing was developed by the Northern Research Institute of Norway andhas been used for a variety of environmental monitoring tasks in the Arctic, includingmapping and meteorological measurements. As depicted in figure 2.8, CryoWing has awing span of 3.8 m, a maximum take-o weight of 30 kg and incorporates a V-tail andpush propeller. In addition, its use in snow conditions requires a catapult launcher andbelly landing. CryoWing has an endurance of 5 hours, range of 500 km and a cruisespeed of 28 to 33 m/s (Norut 2008). The aircraft is powered by a 25cc or 35cc internalcombustion engine, running on standard automotive petrol.

Figure 2.8: CryoWing (Norut 2008)

Summary

The above UAVs demonstrated that the capabilites required of the 2009 UAV wereindeed feasible. This was particularly evident from their endurance and range, whichin general was far superior to that required for the ARCAA Outback Challenge. Inaddition, all the above UAVs had a cruise speed of 25 to 33 m/s, which was similar tothat of the intended design.

2.3 Control and Communication Systems

There are a variety of commercially available autopilot systems designed for the modelflight industry and for research applications. Companies involved in the manufactureof these systems include Micropilot, Cloudcap Technology, Procerus Technologies and



UAV Navigation. In addition to these, an open-source software (OSS) autopilot systemcalled Paparazzi is available, with the hardware either custom built or purchased froma supplier.

The majority of these autopilot systems are capable of controlling a UAV from launch torecovery whilst maintaining communication with a ground station a significant distanceaway. Some examples of the use of these autopilot systems are given below.

CryoWing

Micropilots 2028g autopilot is utilised in the CryoWing UAV, discussed in furtherdetail in Section 2.2. This aircraft can operate autonomously from launch to recovery,and utilises a satellite link which allows a communication range of up to 500 km (Norut2008). Flight plans are pre-programmed in the autopilot, and the UAV navigates viaGPS waypoints.

Silver Fox

A Piccolo autopilot system, developed by Cloudcap Technology, was used in the SilverFox UAV (discussed in Section 2.2). Silver Fox is also capable of fully autonomous flightfrom launch to recovery, whilst maintaining communication with the ground stationup to its full range of 40km (Deagel 2003).

Funjet

A paparazzi autopilot system was successfully implemented in a Multiplex Funjet, forthe purpose of gathering meteorological data in the Arctic for the Geophysical Instituteof the University of Bergen/Norway. The UAV autonomously climbs to 1500m, whereit performs a loiter pattern and then glides back to base. Communication is maintainedwith the ground station throughout the entire flight, with takeo and landing performedunder manual control (Paparazzi 2009).

Summary

The above UAVs represent a few of many examples where commercially purchasedand open source autopilot systems have been successfully implemented for missionssimilar to that of the 2009 Search and Rescue UAV. It therefore appears feasible thatan aircraft can be developed to successfully demonstrate all the capabilities specifiedby the project goals.


2.4. IMAGING SYSTEMS 15

2.4 Imaging Systems

Many modern UAVs have extremely sophisticated imagery systems, capable of record-ing high-resolution footage in both the visible and infrared wavelengths. Due to thecomplexity and cost of these systems they are often made as modular systems, with asingle imaging module used for many UAVs in the same family.

An imaging system for use on an unmanned aircraft has quite dierent requirementscompared to a ground-based system, and the use of image processing tools for au-tomonous identification of objects can restrict the type of imaging systems which canbe used.

2007 iSOAR Aircraft

The 2007 iSOAR aircraft incorporated a lone visual-spectrum analogue camera placedin the belly of the aircraft, angled forwards in order to be useful for aircraft control aswell as ground surveillance.

The project team performed a detailed analysis of all available imaging options whendesigning the iSOAR UAV. As automatic image processing was not considered feasiblein the time given, the group required live video footage from the aircrafts camera formanual identification through the ground station (Avalakki et al. 2007).

The selected imaging system consisted of a high-resolution analogue camera suppliedby WirelessVideoCameras, as part of a package including a transmitter and groundstation receiver. The camera incorporated a colour CCD with a resolution of 450TVLand weighed 70g, while the downlink transmitted in the 2.4 GHz frequency band withan output power of 1W.

Boeing ScanEagle

ScanEagle is a small, long endurance UAV built by Insitu and Boeing. ScanEagleutilises an imaging system consisting of a stabilised camera turret located below theaircraft, which can contain either an electro-optical visual spectrum camera, or aninfrared camera. The turret is designed to track targets for extended periods, andcan resolve objects the size of small vehicles from a range of at least 5 standard miles(Insitu 2009).



Figure 2.9: The Boeing/Insitu ScanEagle UAV, showing the imaging compartment(CNet 2007).

Aerosonde

The Aerosonde UAV has been used for meteorological missions in the Arctic where itsuccessfully carried and operated a Histrionics KTII infrared pyrometer for measuringground temperature and a variety of still and video cameras for surface imaging. Theseinstruments have recorded imagery up to an altitude of 1500m. Integrating an infraredcamera into Aerosonde for search and rescue missions in the Arctic has also beenproposed (Curry et al. 2004).

Summary

Based on the analysis of other UAV systems currently on the market, it was deemedquite feasible that an imaging system could be incorporated into the aircraft, but thatfurther analysis would be required in order to determine the type of imaging methodwhich should be used, as well as the form of image processing for autonomous detectionof ground targets. Additionally, selection of a suitable downlink for providing imageryto ground station controllers was an important consideration which would be conductedduring conceptual design for the overall imaging system.

2.5 Recovery Systems

A large number of modern UAVs employ recovery systems as an alternative or replace-ment to a standard runway landing. These systems vary from simple hemisphericalor cruciform parachute systems, to parafoil systems with complex rigging and steering


2.5. RECOVERY SYSTEMS 17

ability. Some systems do not employ parachutes at all, and instead rely on ground-based systems by which the aircraft is simply flown into a net or cable and caught.

The purpose of such recovery systems can vary. Some systems are simply designed toreduce damage to the UAV in the event of an emergency, while others are intended asreplacements to standard runway landings, even to the point where the aircraft maynot include a landing gear.

IAI I-View

The Israel Aerospace Industries I-View series of UAVs all incorporate a parachuterecovery system for precise landings. The parachute is a parafoil type, with steeringability to allow the pilot to land on a set location. The system is claimed to have anaccuracy of 50m x 50m, with no limitation on crosswinds (IAI 2002).

Figure 2.10: The IAI I-View MK50 UAV, with para-foil recovery system deployed (IAI2002)

Boeing ScanEagle

The ScanEagle UAV implements a novel recovery system which completely replacesa standard landing gear. The aircraft is flown into a vertical wire on the ground,and captured through use of hooks on the aircraft wings (Insitu 2009). This has theadvantage of negating the need for a landing gear to be attached to the aircraft, whichreduces the drag experienced by the aircraft in flight, and can also reduce weight(although the need for strengthened wings can reduce this advantage).



Figure 2.11: The SkyHook capture system used for the Boeing ScanEagle (Insitu2009)

2007 iSOAR Aircraft

The 2007 iSOAR Aircraft incorporated a parachute recovery system consisting of anoctagonal parachute deployed using a spring-loaded drogue parachute (Avalakki et al.2007). The deployment method of the 2007 parachute relied on a series of actuatorswhich would release the top hatch of the aircraft during flight, followed by the releaseof a spring-loaded mechanism which would propel the drogue chute out of the top ofthe aircraft. The force generated by the drogue parachute would then pull the mainparachute from the aircraft. The 2007 recovery system was designed as a completereplacement to standard runway landings, and was also intended for use when theaircraft was being launched from a moving car (without the landing gear attached).

The main parachute had an equivalent surface area of 3.65 m2, which corresponded toa descent rate of 8.02 m/s or an equivalent drop height of 3.28 m. The parachute wasattached to the aircraft at four locations on the wing tongue using 200lbs kite line,however no swivel was incorporated in the design, potentially resulting in problemswith a rotating parachute or aircraft upon descent. Ripstop nylon was home-stitchedinto the required octagon shape, resulting in a total parachute weight, including lines,of 600g.

Summary

From analysis of the systems listed above, it appears feasible that a recovery systemcan be developed in order to improve safety and reduce damage to the aircraft in anemergency situation. However, further analysis is needed to ensure that such a systemdoes not compromise the performance of the aircraft due to the extra weight involved.


2.6. TECHNICAL TASK 19

2.6 Technical Task

The technical task, including the technical level, economic parameters, standard re-quirements and performance requirements, was generated from the results of the fea-siblity study.

2.6.1 Technical Level

The intent of the project is to consider all aspects of a general purpose surveillanceUAV, from concept to implementation. However, as the overall design goals of theproject are similar to those of the 2007 iSOAR aircraft, many of the resources (bothmaterial and academic) left from the 2007 project will be utilised where appropriate.The technical level to be achieved is as below:

Extended design and development of the existing UAV platform manufacturedusing existing techniques and readily available materials.

Integration of existing avionics and improved image analysis equipment.

Configure avionics and image analysis equipment with relatively simple program-ming techniques such that the vehicle can perform missions autonomously.

Flight testing of new structures, avionics and image analysis equipment to demon-strate the vehicles ability to complete autonomous missions successfully.

The vehicle is to have good structural integrity, reliability and appeal for com-mercial sale and use.

2.6.2 Economic Parameters

The aim of the project is to produce a relatively inexpensive UAV. Therefore, whereappropriate, components utilised in the 2007 design will be reused in the 2009 design.The preliminary budget of this project, considering the intended design changes only,is restricted to $5,000. The details of the budget are presented in the Management andFinances section.

2.6.3 Standard Requirements

The vehicle is to be operated within Australia, and therefore it will be required tomeet the Civil Aviation Safety Regulations (CASRs) set out by the Civil Aviation



Safety Authority (CASA), the governing body of Australias Aviation Industry. Inparticular, the design of the aircraft must adhere to UA25 of CASR which is entitledDesign Standards: Unmanned Aerial Vehicles - Aeroplanes. The operation of thisvehicle must be in accordance with Part101 of CASR which is entitled Unmannedrocket and aircraft operation.

2.6.4 Performance Requirements

Altitude

The operational altitude is to be between 200 ft and 400 ft, excluding take-o andlanding. The cruise altitude will be 300 ft as it provides a reasonable balance betweenimage clarity and the sweep width of the UAV.

Cruise Speed

In order to cover the entire search area (total search distance of 70643 m) in 50 minutes,the aircraft requires a cruise speed of 25 m/s.

Operational Range

While remaining within the mission boundary specified in section 2.1.1, the maximumdistance from the ground station is 8.8 km. With the inclusion of a 1.2km safetymargin, the mission range was therefore limited to 10 km.

Takeo and Landing

The takeo and landing distance of the aircraft is limited to the ARCAA OutbackChallenge runway length of 1600m. However, smaller takeo and landing distances aredesirable in order for the UAV to be flexible in a variety of locations. A distance inthe order of 50m appeared reasonable for most applications and the intended size ofthe UAV.

Endurance

The UAVs minimum endurance will be 1 hour and 15 minutes of continuous flight inaccordance with the maximum mission time allowed for the Outback Challenge.


2.6. TECHNICAL TASK 21

Level of Autonomy

In accordance with the Outback Challenge rules, the UAV must be capable of someform of autonomous control. For the purposes of the project it was desired that theaircraft would be capable of fully autonomous flight, excluding takeo and landing.

2.6.5 System Requirements

Airframe

The airframe should be of an appropriate size such that it can safely house all sub-systems and fit in a standard station wagon. This would greatly improve its ease oftransportation and the flexibility of its operations. In addition, the components of theairframe must be capable of withstanding the stresses imposed on them during all flightregimes. The control surfaces must be capable of providing adequate control in pitch,roll and yaw directions.

Propulsion System

The UAV is to be propeller driven and employ a brushless DC motor. The batter-ies should have sucient capacity for at least 1 hour and 15 minutes of continuousoperation.

Control System

A control system capable of both autonomous and manual control is required. Theautopilot should be capable of autonomous navigation in 3 dimensions based on GPSwaypoints, and it should be possible to modify the UAVs flight path mid-flight.

A reliable communication link should be maintained between the UAV and groundstation up to the maximum range of 10 km, and should provide a means of receivingflight data at the ground station and asserting manual commands. Onboard batteriesare required to power the autopilot and modem. Their capacity should be sucientfor 1 hour and 15 minutes of continuous operation.

Imaging System

The camera should be able to distinguish a person from an altitude of 300 ft. Inorder to ensure the entire search area is covered (using the search strategy outlined in



Section 2.1), the camera requires a horizontal field of view (HFOV) of at least 67.3.A downlink is required to stream video footage from the UAV to the ground station,with a minimum range of 10km. The onboard batteries for the camera and downlinkshould be sucient for 1 hour and 15 minutes of continuous operation.

Payload Deployment

The payload is a container capable of holding 500ml of water. The deployment mecha-nism should be capable of jettisoning the rescue package on command, and be reliableup to the maximum operational range of 10 km. The payload is to land within 100m of the target, and no water should be lost from the container on impact with theground.

Emergency Recovery

It must be possible to deploy the recovery system by manual command, where thecommand can be applied up to the maximum operational range, and will be appliedautomatically onboard the aircraft if communication is lost for greater than 5 seconds.The primary requirement of the recovery system is to ensure safety of people on theground. Minimising the damage inflicted on the UAV is a secondary consideration.


Chapter 3

Conceptual Design

The conceptual design of the aircraft and associated systems involved the analysis ofhow each mission requirement would be met, and selection of components and manu-facturing techniques used to create each system.

3.1 Aircraft Configuration

The choice of aircraft configuration is an important decision, and can drastically aectthe performance of the aircraft in a given application. Due to the desire to make useof as many resources from the 2007 iSOAR aircraft as possible, the decision of aircraftconfigration was reasonably restricted.

3.1.1 Configuration Review

A review of possible airframe configurations was performed. Good stability and con-trollability were desirable characteristics for maximising the reliability of autonomousflight, while high eciency and low weight were beneficial for high endurance missions.Furthermore, the manufacture time and cost was also a limiting factor. A decisionmatrix is depicted in Table 3.1, which shows that a conventional configuration was themost beneficial in terms of the chosen criteria.

3.1.2 Propeller Placement

The placement of the aircraft propeller is also an important consideration, and canhave a significant impact on the performance and maintenance requirements of theaircraft.

23

24 CHAPTER 3. CONCEPTUAL DESIGN

Table 3.1: Airframe Configuration Decision MatrixCriteria Conventional Pod & Boom Twin Tail Flying Wing Canard

Controllability 5 5 4 2 3Stability 5 5 5 2 1Eciency 3 3 2 4 3Weight 3 3 2 5 4

Manufacture time 5 2 1 3 2Total 21 18 14 16 13

The two main propellor configurations are:

Tractor or Puller

This configuration is the most common configuration for single-engine air-craft, and has the propellor mounted at the nose of the aircraft.

Advantages

Easy to locate propellor on the aircraft without clearance issues

Well-known configuration

Ideal weight location for aircraft centre of gravity

Disadvantages

Prevents placement of imaging or communications equipment in thenose of the aircraft

Pusher

This configuration has the propellor mounted behind the fuselage, pushingthe aircraft through the air.

Advantages

Improved aerodynamic eciency, as propellor wash does not flowover aircraft wing

Aircraft nose can be used for imaging or communications equipment

Disadvantages

Aircraft take-o can result in propellor impacting the runway unlessclearances are correctly calculated

Aircraft landing gear may pick up rocks or other debris, possiblydamaging the propellor

Large mass at rear of aircraft can have a negative eect on aircraftcentre of gravity


3.2. AIRCRAFT DESIGN PARAMETERS 25

3.1.3 Configuration Selection

One of the major aims of the project was that as many resources possible would beused from the 2007 iSOAR aircraft, in order to minimise project expenses. Changingthe aircraft configuration would preclude the use of many of these components - partic-ularly the aircraft fuselage and empennage, which could not be feasibly redesigned andmanufactured with the resources available to the project group. In addition, a con-ventional configuration was deemed the most eective configuration for the redesignedaircraft, due to its inherent stability and manufacturability advantages over most otherconfigurations.

For these reasons, a conventional aircraft configuration was chosen for use on the 2009Search and Rescue UAV, with the propellor placed in the aircraft nose in a tractorconfiguration.

3.2 Aircraft Design Parameters

In order to accurately generate a preliminary design for the aircraft, several aircraftparameters were determined by considering the class of aircraft being designed, as wellas its likely performance parameters and mode of operation. These parameters, alongwith the decisions made and the reasoning for those decisions, are listed below.

Aspect Ratio

The aspect ratio of the wing is an important consideration, as it determines the liftdistribution of the wing. A high aspect ratio increases the aerodynamic eciency ofthe wing at the expense of higher structural weight, while a lower aspect ratio willconserve structural weight but have a lower aerodynamic eciency (Raymer 2006).

It was decided that an aspect ratio of 10 would be an eective balance between aerody-namic and structural eciency for the 2009 aircraft. This is an increased aspect ratioover the wing used for the 2007 iSOAR aircraft, which used an aspect ratio of 8.

Twist

A wing twist angle of -2 degrees is recommended for general aviation aircraft (2 degreeswashout) (Raymer 2006), and this value was chosen for use on the redesigned aircraftwings.



Sweep Angle

Swept wings are generally used for aircraft travelling at supersonic or high transonicspeeds, where portions of the wing may experience supersonic air flow (Raymer 2006).As the project requirements call for an aircraft with a cruise speed far below the speedof sound, it was decided that it was not necessary to implement a swept wing.

Taper Ratio

For an aircraft with a sweep angle of zero a taper ratio of 0.45 is ideal as stated byRaymer (2006).

Wing Dihedral

From the results of a market survey on UAV wing dihedral (presented in Table 3.2) itcan be seen that the broad range of modern UAVs have a low dihedral angle. Largerdihedral angles are seen on many passenger aircraft in order to increase stability andreduce pilot workload (Raymer 2006), a problem which is less important in the case ofan unmanned aircraft.

Table 3.2: Wing DihedralAircraft Dihedral

Global Hawk 0oScanEagle 0oCryo Wing 1oSilver Fox 0oKnat 750 0oIAI Heron 0oPredator 0o

MQ-9 Reaper 0o

3.3 Aircraft Preliminary Sizing

In order to determine the engine power and wing area required by the aircraft, a match-ing diagram was created. The matching diagram relates the power loading (W/P) andwing loading (W/S) of the aircraft, and contains a line representing each performancerequirement of the aircraft.


3.3. AIRCRAFT PRELIMINARY SIZING 27

3.3.1 Stall Requirements

Given the desired stall speed and a known maximum lift coecient for the aircraft, therequired maximum wing loading was calculated using the following equation:

W/S =1

2V 2stallCLmax (3.1)

The stall speed of the aircraft was chosen to be a maximum of 15m/s at an altitude of1500ft. This is the maximum altitude allowed under the rules of the ARCAA OutbackUAV Challenge, and is also an appropriate altitude for most applications the aircraftis likely to be used. This resulted in a wing loading of:

W/S = 16.0 kg/m2 (3.2)

3.3.2 Takeo Distance Requirements

The takeo distance requirements provide a maximum power loading for the aircraft,given the minimum length of runway the aircraft is designed to take o from. A shorterrunway will require a lower power loading (corresponding to a higher power engine).

The desired maximum takeo distance for the 2009 iSOAR aircraft was chosen to be50m, as this is a common distance for model aircraft runways, and a longer distancewould reduce the aircrafts mission flexibility. This was an important considerationfrom a marketing perspective, but was also essential to allow adequate flight testing ofthe aircraft.

Obstacle clearance was not considered, as any airfield used for takeo would likely beseveral times larger than 50m.

To find takeo length (Sg) the following equation was used:

Sg =

1

2gKA

ln

KT +KAV 2LOF

KT

(3.3)

Where:

KA =

2WS

CD0 KC2LTO + CLTO (3.4)Design and Build a Search and Rescue UAV


KT =T

W (3.5)

3.3.3 Climb Requirements

The climb requirements for the aircraft are specified by CASA, and must be met if theaircraft is to be certified. The required climb gradient is 8.33%, with a safety factor of1.4 (resulting in a desired climb gradient of 11.67%).

The equation for climb requirements with respect to power loading and wing loadingwas derived from fundamental equations for steady climb:

T D W sin() = 0 (3.6)

P

W

=V

sin() +

S

W

q

CD0 +K

W

S

cos()

q

2(3.7)

For safety Vclimb = 1.3Vstall

V = 1.3

2WS

CLmax

(3.8)

3.3.4 Cruise Requirements

The cruise speed was calculated to be 25m/s in Section 2.1.3.

Cruise speed requirements were calculated using the following equation:

P

W=V

qCD0WS

+ WS

K

q

(3.9)

3.3.5 Matching Diagram Results

The matching diagram in Figure (3.1) shows the results of the preliminary sizing of theaircraft. The curves on the graph represent the limitations of wing loading and powerloading in order for the aircraft to meet all performance and regulatory requirements.


3.3. AIRCRAFT PRELIMINARY SIZING 29

The Met Area (area where the power loading and wing loading will both meet allrequirements) is shown. Smaller values on the y-axis correspond to a higher requiredengine power, and smaller values on the x-axis correspond to a higher required wingplanform area.

60!"#$%&'()&"(*"+

50

!"

40

#$%&$!

30%!&'

Stall RequirementsCruise Requirements

()*+

,- Cruise RequirementsClimb Requirements50m Takeoff20

')./0( 50m Takeoff

2007 iSOAR Aircraft123 '4563

10

' 1237827 9::;7,0

0

0 5 10 15 20 25 30

!,-% ()*+,-% !&? #$%&@9"!,-%()*+,-%!&?#$%&@ "

Figure 3.1: Matching Diagram

It can be seen from the matching diagram that the aircraft is mainly limited by thedesired stall speed and take o requirements. Although the desired stall speed is not afixed requirement for this aircraft, keeping the stall speed as low as possible aids withlow speed flying such as on an approach to land. In this important stage of flight it isnecessary to slow the aircraft as much as possible to reduce the landing distance whilekeeping full control of the aircraft and minimising the risk of stalling or spinning.

The preliminary design point for the aircraft, chosen from the matching diagram (Fig-ure 3.1) was chosen as:

W/P = 18 kg/kW

W/S = 16 kg/m2



3.3.6 Weight Estimation

The 2007 iSOAR aircraft had a total takeo weight of 11kg, and this value was usedas an initial estimate of the final weight of the 2009 aircraft. By omitting the weightof the aircraft parachute, rigging and deployment system (further discussed in Section3.8), as well as making the assumption that the redesigned wings would be equivalentor less weight than their 2007 counterparts, it was decided to use a weight estimate of10kg for the 2009 aircraft.

3.3.7 Final Design Point

As explained in further detail in Section 2.6.4, it was decided that the 2009 designwould make use of the AXI 4130-20 electric motor used for the 2007 aircraft. Thismotor has a rated power of 900 watts.

Using the aircraft weight estimate of 10kg from Section 3.3.6, the shifted power loadingfor the aircraft then becomes 11 kg/kw with addition of the 900 watt AXI GoldLinemotor. A 10kg aircraft weight also results in a required wing area of 0.625m2.

The final design point for the aircraft is therefore:

W/P = 11 kg/kW

W/S = 16 kg/m2

3.4 Propulsion System

A propeller driven aircraft was selected given the preference for high engine eciencyover high thrust. This preference was based on the need for high endurance and itwas expected that the aircraft would perform the majority of its missions at cruise.Furthermore, it was decided at the commencement of the project that an o the shelfpropulsion system would be sourced to reduce development time and ensure reliability.

3.4.1 Motor Type Selection

A survey of similar UAVs on the market indicated that the majority use either internalcombustion (IC) or electric power plants.


3.4. PROPULSION SYSTEM 31

IC Engines

Hydrocarbon internal combustion engines, such as glow-plug engines, were common inthe model aircraft industry and in research applications. The glow-plug engine workssimiliar to an automobile engine, however a catalytic reaction between the glow-plugand the fuel (rather than a spark plug) ignites the fuel/air mixture. It was evident thatthe fuel used by these UAVs were common and therefore would be easily accessible. Inaddition, the fuel used by IC engines has a relatively high energy density. IC enginesrequire regular maintenance however, such as the application of lubricants, and areknown to emit pollutants into the atmosphere.

Electric Motors

The popularity of electric motors in the model flight industry and in research ap-plications has increased in recent years due to significant improvements in batterytechnology. The large storage capabilites of lithium polymer (LiPo) batteries have hada significant impact on this increase. Electric motors are noted for their relatively higheciency and low level of maintenance, however the batteries they use have a relativelylow energy density in comparison to fossil fuels.

The use of a brushless DC motor appeared more beneficial than a brushed DC motor,as they experience less frictional losses and are therefore more ecient and have alonger service life (Model ModelFlight 2009).

Summary

A decision matrix was created in order to determine which propulsion system wouldbest meet the project requirements. The selection criteria is outlined in table 3.3 andeach system was given a score out of 5 for each criteria. From this, the decision wasmade to use a brushless DC electric motor.

Table 3.3: Decision matrix for propulsion system selectionSystem IC engine Electric motor

Energy density 4 2Engine eciency 2 4

Level of maintenance 3 5Ease of implementation 3 4Environmental impact 2 5

Total 14 20



3.4.2 Electric Motor Selection

A power of 560 W was required from the motor. Therefore, a market survery wasconducted of electric motors with the capability to provide this as shown in Table 3.4.

Table 3.4: Current Available Brushless Motors

Motor Kv (RPM/V) Weight (g)

MaximumEciencyCurrent(A)

Pmax(W ) Reference

AXI4130-20 305 409 40 1000

ModelMotors(2009)

AXI4130-16 385 409 40 1000

ModelMotors(2009)

Power 46 670 209 40 925 E-Flite(2009)

Power 60 400 380 40 1425 E-Flite(2009)

Purchasing a Power 60 motor would improve the power to weight ratio in comparisonto the AXI 4130-20, which was purchased in 2007. However, the small improvementin weight was not significant enough to justify the incurred expense, therefore the AXI4130-20 was maintained in the design.

3.4.3 Propeller Selection

Overloading electric motors by using an unsuitable propeller can quickly lead to damageof the motor, hence a propeller size of 16x8 was chosen based on the manufacturersrecommendations and confirmed through testing.

3.4.4 Electronic Speed Controller (ESC) Selection

The Electronic Speed Controller used in the 2007 design was chosen based on its weight,cost and its current handling capabilities (Avalakki et al. 2007). The selected ESC wasthe MasterSpin 750 OPTO and at the time was the best option. However, given thebudget and time constraints of the project it was not deemed necessary to select anotherESC.


3.4. PROPULSION SYSTEM 33

3.4.5 Motor Batteries

There were two battery types, which had sucient capacity for the mission, they wereLithium-Polymer and Nickel Metal Hydride (Ni-MH) batteries. A market survey wasconducted to determine which of these batteries would be most feasible. Below is acomparison of the two battery types.

Table 3.6: Li-Po and Ni-MH Battery Comparison

Type ofBattery

Voltage(V)

Charge(Ahr) Weight (g)

Lithium-Polymer 11.1 1.0 85Nickel Metal Hydride 10.8 1.0 175

As shown in Table 3.6 Li-Po batteries are lighter than Ni-MH batteries for the sameamount of charge and similiar voltage. Therefore given that weight was a primaryfactor for selection of the batteries, Li-Po batteries were selected.

The manufacturers recommendations for the AXI 4130-20 are listed in Table 3.8(Model Motors 2009).

Table 3.8: AXI 4130-20 specificationsmotor (%) No. LiPo Cells Vmotor (V)

85 8 29.6

An endurance of 75 min was required where it was assumed that the aircraft wouldcruise at 160 W for 72 min and utilise maximum power of 560 W for 3min. The requiredbattery capacity was therefore calculated to be 8.7Ahr using the equation below.

Cbattery =

Imotort =

tPshaft

motorVmotor

max

+

tPshaft

motorVmotor

cruise

Flight Power EVO20-33004S battery packs were recommended by Model Flight (2009).These had a voltage of 14.8 V and a capacity of 3300 mAhr each. Two packs wereconnected in series to produce a twin pack with the voltage required for the motor,and 3 of these twin packs were connected in parallel to provide the desired capacity.Therefore, 6 battery packs were required in total.



3.5 Manufacturing Concepts

The manufacturing methods selected for all parts of this aircraft are based on cost,required tooling and material availability. Techniques considered are primarily based onmethods used in the model aircraft industry where weight, strength, cost and materialavailability are of upmost importance. The manufacturing methods considered includebuilt up structures, foam core and hollow moulded.

3.5.1 Wing Manufacture Methods

Built up

A built up manufacture method involves the use of materials such as aluminium orwood in order to manufacture spars and ribs for the internal structure of the aircraftwing (see Figure 3.2). Aluminium becomes impractical to use for smaller aircraft,and so materials such as balsawood and plywood are

2009 final report compressed

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