Optimizing small multi-rotor unmanned aircraft: a practical design guide

146 Pages·2019·3.71 MB·English

by  Prior

Optimizing Small Multi-Rotor
Unmanned Aircraft
Team Gryphon’s X8 CAD design for the IMechE UAS Challenge 2016.

Optimizing Small
Multi-Rotor Unmanned
Aircraft
A Practical Design Guide
Stephen D. Prior
Faculty of Engineering and Physical Sciences, The
University of Southampton, Southampton, UK
CRC Press/Balkema is an imprint of the Taylor & Francis Group,
an informa business
© 2019 Taylor & Francis Group, London, UK
Typeset by Apex CoVantage, LLC
All rights reserved. No part of this publication or the information
contained herein may be reproduced, stored in a retrieval system,
or transmitted in any form or by any means, electronic, mechanical,
by photocopying, recording or otherwise, without written prior
permission from the publishers.
Although all care is taken to ensure integrity and the quality of
this publication and the information herein, no responsibility
is assumed by the publishers nor the author for any damage
to property or persons as a result of operation or use of this
publication and/or the information contained herein.
Library of Congress Cataloging-in-Publication Data
Names: Prior, Stephen D. (Mechanical engineer), author.
Title: Optimizing small multi-rotor unmanned aircraft : a practical
design guide / Stephen Prior, the University of Southampton, UK.
Description: London ; Boca Raton : CRC Press/Balkema is an imprint
of the Taylor & Francis Group, an Informa Business, [2019] |
Includes bibliographical references and index.
Identifiers: LCCN 2018035139 (print) | LCCN 2018036464 (ebook) |
ISBN 9780429428364 (ebook) | ISBN 9781138369887 (hbk : alk. paper)
Subjects: LCSH: Drone aircraft—Design and construction.
Classification: LCC TL685.35 (ebook) | LCC TL685.35 .P75 2019 (print) |
DDC 629.133/39—dc23
LC record available at https://lccn.loc.gov/2018035139
Published by: CRC Press/Balkema
Schipholweg 107c, 2316 XC Leiden, The Netherlands
e-mail: [email protected]
www.crcpress.com – www.taylorandfrancis.com
ISBN: 978-1-138-36988-7 (hbk)
ISBN: 978-0-429-42836-4 (eBook)
This book is dedicated to the memory of my father,
Robert Charles Henry Prior (1928–2008).

Table of Contents
List of tables xi
List of figures xiii
List of abbreviations xvii
General assumptions xix
Design constraints xxi
Preface xxiii
Acknowledgements xxv
1 Introduction 1
2 Lithium Polymer battery (power supply) 5
2.1 Safety considerations 9
2.2 Lithium Polymer discharge characteristics 9
3 Electronic Speed Controller (ESC) 11
3.1 Timing 13
3.2 Cut-off voltage 14
3.3 Switching frequency 15
4 The Brushless DC (BLDC) motor (outrunner) 17
4.1 BLDC motor construction and theory 20
4.2 Equivalent brushed DC motor equations 21
4.3 Comparing theoretical and empirical data 26
4.3.1 Analysis of motor torque equations 27
4.3.2 Analysis of motor speed equations 28
4.3.3 Test measurements 29
4.3.4 Online design tools 30
viii Table of Contents
5 The propeller (rotor) 33
5.1 Propeller or rotor? 35
5.2 Propeller variables 35
5.3 Propeller geometry 39
5.4 Simple momentum theory 41
5.5 Non-dimensional rotor (propeller) coefficients 43
5.6 Figure of Merit (FM) 44
5.7 Propeller efficiency (η ) 46
p
5.8 Co-axial and overlapping rotor designs 48
5.8.1 Different upper and lower rotors 53
5.9 Reynolds number, Re 53
5.10 Airfoil geometry 57
5.11 Airfoil theory – Blade Element Theory (BET) 59
5.12 Online airfoil resources 60
6 The system solution 65
6.1 IMechE UAS challenge – a worked multi-rotor example 67
6.2 Measuring the propulsive efficiency 71
6.3 Forward flight 74
6.4 Dihedral and cant angles 76
6.5 Active thrust vectoring 78
7 Conclusion 79
7.1 Economic and societal impact 79
7.2 Future directions, opportunities and threats 80
Appendices
Appendix A1 Li-Po batteries ready reckoner (6S) 83
Appendix A2 A range of 6S Li-Po batteries with high
specific energy (Wh/kg) (June 2018) 84
Appendix B Guidance on the safe use, handling, storage
and disposal of Lithium Polymer batteries 87
Appendix C T-Motor BLDC motor selection tool 93
Appendix D Overall system selection spreadsheet 95
Appendix E Examples of multi-rotor systems built at
the ASL 97
Appendix F Drone radio frequency legal requirements
in the UK 113
Table of Contents ix
Appendix G Example Pixhawk flight controller wiring
diagram and mission planner set-up
(PID tuning) 115
References 117
Index 119