Safety and Reliability in Cooperating Unmanned Aerial Systems

234 Pages·2010·1.5 MB·English

by  Camille Alain Rabbath

7108tp.indd 1 3/12/09 9:38:38 AM
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Camille Alain Rabbath
Nicolas Léchevin
Defence R&D Canada - Valcartier
World Scientific
NEW JERSEY • LONDON • SINGAPORE • BEIJING • SHANGHAI • HONG KONG • TAIPEI • CHENNAI
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Published by
World Scientific Publishing Co. Pte. Ltd.
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British Library Cataloguing-in-Publication Data
A catalogue record for this book is available from the British Library.
SAFETY AND RELIABILITY IN COOPERATING UNMANNED AERIAL SYSTEMS
Copyright © 2010 by World Scientific Publishing Co. Pte. Ltd.
All rights reserved. This book, or parts thereof, may not be reproduced in any form or by any means,
electronic or mechanical, including photocopying, recording or any information storage and retrieval
system now known or to be invented, without written permission from the Publisher.
For photocopying of material in this volume, please pay a copying fee through the Copyright
Clearance Center, Inc., 222 Rosewood Drive, Danvers, MA 01923, USA. In this case permission to
photocopy is not required from the publisher.
ISBN-13 978-981-283-699-1
ISBN-10 981-283-699-3
Printed in Singapore.
Kim Lee - Safety and Reliability.pmd 1 9/16/2009, 10:46 AM
September2,2009 17:39 WorldScienti(cid:12)cBook-9inx6in ws-book9x6CAR
Preface
The vision is clear: severalunmanned aerial vehicles collaborate and coor-
dinatetheir(cid:13)ightandactionstoachieveamission,whilehumanoperators,
barely involved, monitor the progress of the vehicles. This vision is not
yet a reality. Before multiple unmanned aerial vehicles are deployed in a
coordinated fashion, novel systems must be devised. Among those, sys-
tems that ensure safe and reliable operations. Currently, a great many
researchersaredeployingeverye(cid:11)orttodesignmoree(cid:11)ectivemulti-vehicle
control concepts and algorithms. Furthermore, there exists a vast body of
knowledge in fault-tolerant control, and in fault detection and fault recov-
ery techniques for the individual aerial platform. Yet, very little has been
said to date about how to perform reliable and safe autonomous multi-
vehicle operations. Indeed, ensuring mission success despite o(cid:11)-nominal,
or degraded, operations of mission-critical vehicle components is an open
problem which has drawn attention only recently. Despite fault-tolerant
controlsoftwareand hardwareembedded onboardairvehicles, overall(cid:13)eet
performancemaystillbedegradedaftertheoccurrenceofanomalousevents,
suchassystemsmalfunctions,damageandfailures. Asfarasweareaware,
this book is the (cid:12)rst of its kind in presenting a set of basic principles and
algorithms for the analysis and design of health management systems for
cooperating unmanned aerial vehicles. Such systems rely upon monitoring
and fault adaptation schemes. Cooperative health management systems
seek to provide adaptation to the presence of faults, from a team per-
spective, by capitalizing on the availability of interconnected computing,
sensing, and actuation resources. There is currently little literature on the
safety and reliability for cooperating unmanned aerial systems, although
the topic of cooperation for e(cid:11)ective (cid:13)eet monitoring and fault-adaptation
purposes is emerging.
v
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vi Safetyand ReliabilityinCooperating Unmanned Aerial Systems
This monograph is the culmination of several years of research, and as
such is biased with previous results obtained by the authors. We have our
own view on the problem of health management, and have addressed a
limited number of scenarios. This monograph presents the concepts in the
form of theorems, lemmas, propositions, and step-by-step procedures. The
health management concepts are illustrated by means of simple examples
and numerical simulations of practical UAS operations. Cases of tight
formation control and coordinated rendezvous for a network of formations
are addressed in this book. Therefore, researchers, academics, graduate
students and aerospaceengineers, we hope, will appreciate the content.
WewishtothankDefence R&DCanada,andinparticularDr. Alexan-
dre Jouan for his support of this initiative. The (cid:12)rst author acknowledges
the support of the Natural Sciences and Engineering Research Council of
Canada(NSERC). The secondauthorgratefullyacknowledgesthe support
of NSERCandthe Department ofNationalDefence ofCanadainthe form
ofaVisitingFellowship. WewouldliketothankQuanserInc. forproviding
experimentaldatatosupportthemodelingoftheALTAV,inparticularDrs
JacobApkarianandErnestEaronwhohaveshownconstantsupportofour
ideas. Wehaveindeedlearnedquitealotfromtheirvastknowledgeofreal-
timecontrolsystems. Wealsohadthepleasureofcollaboratingwithseveral
academic researchers in the areas of unmanned systems control and fault
tolerance. In particular, we would like to thank Professor Youmin Zhang
of Concordia University for the many discussions we had on the area of
individual vehiclefault-tolerantcontrol,thus improvingourunderstanding
of the issues and challenges in such (cid:12)eld. We would like to thank Dr. An-
tonios Tsourdos and his team at Cran(cid:12)eld University (UK). We have had
thehonorofcollaboratingwithAntoniosforseveralyears,whichhelpedus
learn more e(cid:11)ective techniques of cooperative control, path planning, and
guidance. The generous advices of Mr. Jean B(cid:19)elanger, Dr. Dany Dionne
and Professor Pierre Sicard of University of Qu(cid:19)ebec at Trois-Rivi(cid:18)eres are
also gratefully acknowledged. This book was written over a period of one
year after working hours and during weekends. Hence, we would like to
expressour most sinceregratitude and warmful thanks to our families and
friends for their support during this intense period of our lives.
C.A. Rabbath and N. L(cid:19)echevin
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Contents
Preface v
1. Introduction 1
1.1 Unmanned Aerial Systems . . . . . . . . . . . . . . . . . . 2
1.2 Cooperative Control . . . . . . . . . . . . . . . . . . . . . 3
1.3 Contingencies . . . . . . . . . . . . . . . . . . . . . . . . . 6
1.3.1 Faults and failures of UAV components . . . . . . 7
1.3.2 Vehicle damage . . . . . . . . . . . . . . . . . . . 8
1.3.3 Information (cid:13)ow faults . . . . . . . . . . . . . . . 8
1.3.4 Team anomalies and collisions . . . . . . . . . . . 9
1.3.5 Environmental e(cid:11)ects . . . . . . . . . . . . . . . . 10
1.3.6 Book overview . . . . . . . . . . . . . . . . . . . . 11
2. Health Management for the Individual Vehicle: A Review 13
2.1 Passiveand Active Fault-Tolerant Control Systems . . . . 14
2.2 Fault/Failure Detection and Diagnosis . . . . . . . . . . . 16
2.3 Control Recon(cid:12)guration . . . . . . . . . . . . . . . . . . . 17
2.4 FTC and FDD Techniques for MAV and SUAV . . . . . . 19
3. Health Monitoring and Adaptation for UAS Formations 21
3.1 Models of Vehicle Dynamics, Flight Control, and Faults . 25
3.1.1 ALTAV dynamics and control . . . . . . . . . . . 26
3.1.2 Quadrotor dynamics and control . . . . . . . . . . 29
3.1.3 Actuator faults. . . . . . . . . . . . . . . . . . . . 31
3.2 Formation Control . . . . . . . . . . . . . . . . . . . . . . 33
3.2.1 Elements of contraction theory . . . . . . . . . . . 35
vii
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viii Safetyand Reliabilityin Cooperating Unmanned Aerial Systems
3.2.2 Simpli(cid:12)ed modeling for the purpose of formation
control synthesis . . . . . . . . . . . . . . . . . . . 37
3.2.3 Formation control objective . . . . . . . . . . . . 42
3.2.4 Closed-loop representation of the formation. . . . 43
3.2.5 Convergence analysis of state trajectories . . . . . 48
3.2.6 Modeling a formation of UAVs with realistic
nonlinear dynamics . . . . . . . . . . . . . . . . . 57
3.2.7 Trajectory of the leader and obstacle/threat
avoidance . . . . . . . . . . . . . . . . . . . . . . . 58
3.2.8 Formation control design algorithm . . . . . . . . 60
3.3 Observer-BasedDecentralized Abrupt Fault Detector . . . 61
3.3.1 Context . . . . . . . . . . . . . . . . . . . . . . . . 61
3.3.2 Simpli(cid:12)ed model of vehicle closed-loop dynamics . 62
3.3.3 Concept of observerwith disturbance attenuation 65
3.3.4 Synthesis of DAFD . . . . . . . . . . . . . . . . . 69
3.3.5 Threshold selection . . . . . . . . . . . . . . . . . 77
3.3.6 DAFD design algorithm. . . . . . . . . . . . . . . 79
3.4 Signal-Based Decentralized Non-Abrupt Fault Detector . 80
3.4.1 Context . . . . . . . . . . . . . . . . . . . . . . . . 80
3.4.2 Networked information and coupling e(cid:11)ects . . . . 81
3.4.3 Estimator of heading angle . . . . . . . . . . . . . 85
3.4.4 Statistical test for DNaFD . . . . . . . . . . . . . 86
3.4.5 DNaFD design algorithm . . . . . . . . . . . . . . 89
3.5 UAV Command Adaptation . . . . . . . . . . . . . . . . . 90
3.6 Simulations and Experiments . . . . . . . . . . . . . . . . 93
3.6.1 Formation control of unicycles . . . . . . . . . . . 94
3.6.2 Formation control of quadrotor aircraft . . . . . . 102
3.6.3 DAFD and formation control of ALTAVs . . . . . 104
3.6.4 DAFD and quadrotorformation control . . . . . . 112
3.6.5 DNaFD and formation control of ALTAVs . . . . 115
3.6.6 Decentralized fault detection for mixed-type,
concurrent actuator faults . . . . . . . . . . . . . 123
3.6.7 DAFD/DNaFD in closed loop with individual
vehicle FDD system . . . . . . . . . . . . . . . . . 126
3.6.8 A note on the digital implementation . . . . . . . 129
4. Decision Making and Health Management for
Cooperating UAS 131
4.1 Coordinated Rendezvous of UAS Formations . . . . . . . 134
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Contents ix
4.1.1 Context . . . . . . . . . . . . . . . . . . . . . . . . 134
4.1.2 Related work . . . . . . . . . . . . . . . . . . . . . 137
4.1.3 Multi-formations. . . . . . . . . . . . . . . . . . . 138
4.1.4 Models . . . . . . . . . . . . . . . . . . . . . . . . 140
4.1.5 UAS-threat encounters modeled as Markov
decision processes . . . . . . . . . . . . . . . . . . 152
4.1.6 Problem formulation . . . . . . . . . . . . . . . . 156
4.1.7 Decision policies: perfect information . . . . . . . 160
4.1.8 Decision policies: partially known environment . . 164
4.1.9 Design of CHM and decision making system . . . 173
4.2 Cooperation Despite Information Flow Faults . . . . . . . 174
4.2.1 Context . . . . . . . . . . . . . . . . . . . . . . . . 174
4.2.2 Impact of information (cid:13)ow fault on UAS decision
policies . . . . . . . . . . . . . . . . . . . . . . . . 175
4.2.3 Health state estimation . . . . . . . . . . . . . . . 177
4.2.4 Distributed computations of W0 . . . . . 182
k;Pi;(cid:13)E;(cid:23)j
4.3 Numerical Simulations . . . . . . . . . . . . . . . . . . . . 184
4.3.1 Single target area and perfectlfy known
environment . . . . . . . . . . . . . . . . . . . . . 184
4.3.2 Sequence of targets and perfect knowledge of
environment . . . . . . . . . . . . . . . . . . . . . 191
4.3.3 The case of perturbed MDPs . . . . . . . . . . . . 193
4.3.4 Successivezonesofsurveillancein partiallyknown
environment . . . . . . . . . . . . . . . . . . . . . 197
4.3.5 Information (cid:13)ow faults . . . . . . . . . . . . . . . 199
4.4 Distributed and Parallel Implementation of Optimization
Algorithms . . . . . . . . . . . . . . . . . . . . . . . . . . 200
4.4.1 Context . . . . . . . . . . . . . . . . . . . . . . . . 200
4.4.2 Architecture . . . . . . . . . . . . . . . . . . . . . 201
4.4.3 Distributed and parallel simulation environment . 202
4.4.4 Experiments . . . . . . . . . . . . . . . . . . . . . 204
Bibliography 207
Index 221