Delft University of Technology Autonomous Conflict Detection and Resolution for Unmanned Aerial ...

143 Pages·2017·11.05 MB·English

Delft University of Technology

Autonomous Conflict Detection and Resolution for Unmanned Aerial Vehicles
On integration into the Airspace System
Jenie, Yazdi
DOI
10.4233/uuid:02965443-f1e5-440c-b9af-0e0648be9552
Publication date
2017
Document Version
Final published version
Citation (APA)
Jenie, Y. (2017). Autonomous Conflict Detection and Resolution for Unmanned Aerial Vehicles: On
integration into the Airspace System. https://doi.org/10.4233/uuid:02965443-f1e5-440c-b9af-0e0648be9552
Important note
To cite this publication, please use the final published version (if applicable).
Please check the document version above.
Copyright
Other than for strictly personal use, it is not permitted to download, forward or distribute the text or part of it, without the consent
of the author(s) and/or copyright holder(s), unless the work is under an open content license such as Creative Commons.
Takedown policy
Please contact us and provide details if you believe this document breaches copyrights.
We will remove access to the work immediately and investigate your claim.
This work is downloaded from Delft University of Technology.
For technical reasons the number of authors shown on this cover page is limited to a maximum of 10.
AUTONOMOUS CONFLICT DETECTION AND
RESOLUTION FOR UNMANNED AERIAL VEHICLES
ON INTEGRATION INTO THE AIRSPACE SYSTEM
Proefschrift
terverkrijgingvandegraadvandoctor
aandeTechnischeUniversiteitDelft,
opgezagvandeRectorMagnificusprof.ir.K.C.A.M.Luyben,
voorzittervanhetCollegevoorPromoties,
inhetopenbaarteverdedigenopmaandag23januari2017om10:00uur
door
YazdiIbrahim JENIE
MagisterTeknikinAeronauticsandAstronautics,
InstitutTeknologiBandung,Indonesia
geborenteSurakarta,Indonesia
Ditproefschriftisgoedgekeurddoorde
promotor:Prof.dr. ir.J.M.Hoekstra
copromotor:Dr.ir.E.vanKampen
Samenstellingpromotiecommissie:
RectorMagnificus, voorzitter
Prof.dr.ir.J.M.Hoekstra, TechnischeUniversiteitDelft,promotor
Dr.ir.E.vanKampen, TechnischeUniversiteitDelft,copromotor
Prof.dr.ir.J.A.Mulder, TechnischeUniversiteitDelft
iOnafhankelijkeleden:
Prof. dr. H. Muhammad, InstitutTeknologiBandung
Prof. dr. D. Delahaye, ÉcoleNationaledel’AviationCivile
F. J. L. Bussink,B.Sc. NederlandsLucht-enRuimtevaartcentrum
Prof. dr. R. Curran, TechnischeUniversiteitDelft
iReservelid:
Prof.dr.D. G.Simons,ko TechnischeUniversiteitDelft
Keywords: Airspace Management; Airspace Integration; Autonomous Collision
Avoidance; Conflict Detection and Resolution; Monte Carlo Simu-
lation; Safety Analysis; Unmanned Aerial Vehicle; Velocity Obstacle
Method;
Printedby: Proefschriftmaken,Vianen,TheNetherlands
CoverdesignbyYazdiIbrahimJenie
ISBN978-94-6186-779-7
Anelectronicversionofthisdissertationisavailableat
http://repository.tudelft.nl/.
Copyright©2017byYazdiIbrahimJenie.Allrightsreserved.Nopartofthispublication
maybereproduced,storedinaretrievalsystem,ortransmitted,inanyformorbyany
means, electronics, mechanical, photocopying, recording, orotherwise, withoutprior
permissioninwritingfromtheproprietor.
S
UMMARY
AUTONOMOUSCONFLICTDETECTIONANDRESOLUTIONFORUNMANNED
AERIALVEHICLES
ONINTEGRATIONINTOTHEAIRSPACESYSTEM
YazdiIbrahimJENIE
Inthelastdecade, thecommercialvaluesofUnmannedAerialVehicles(UAV),de-
fined as devices that are capable of sustainable flights in the atmosphere that do not
requiretohaveahuman(pilot)on-board,becomewidelyrecognizedthankstothead-
vancementoftechnologyinmaterials, sensors, computation, andtelemetry. AsUAVs
are becoming cheaper and more user-friendly, many companies are motivated to in-
corporatethemintheireverydaybusiness,suchasfordeliveryservices,journalisms,or
providingInternetservices.
AllofcommercialprospectiveapplicationsforUAVs,however,canonlybeachieved
oncethevehiclesarefullyintegratedintotheairspacesystem. Thisisnotthecaseyet,
sinceUAVoperations,inmostpartoftheworld,arestrictlyregulatedtoflyonlywithin
thevisuallineofsight(VLOS)ofthegroundpilot,forbiddingtheotherwisebeyondvisual
lineofsight(BVLOS)flight.Onemainreasonforsuchstrictregulationsistheapprehen-
sionaboutthesafetyofUAVoperations,whicharelikelytobeheterogeneousduetothe
possiblelargevariationofUAVsintheairspace,eachwiththeirownpreferenceonhow
tointeractwithotherUAVsandwiththecurrent(manned)airtraffic. Hence,airspace
management,especiallyinthemitigationofmid-airconflictsandcollisions,isexpected
tobecomemuchmorecomplex,compromisingtheoverallsafety.
Therefore,theproblemofsafeUAVintegrationintotheairspaceistheselectedtopic
for this research, especially in the development of Conflict Detection and Resolution
(CD&R)systems. Theparticularsystemdescribesanyproceduresanddevicesforvehi-
clestomitigatepotentialmid-airconflictsandcollisions. ForaUAV,thissystemneeds
toconsiderawiderangeofobstaclesitmightencounter,fromastaticunmovingobject
toothervehicleswithcompletelydifferentcharacteristics.Moreover,therecanbeinter-
actionsbetweentwoUAVswithdifferentlevelsofCD&Rsystemawareness. Onlywhen
theirCD&Rsystemsarefullydefinedandregulatedtohandlesuchdiversescenarios,can
UAVsbefullyintegratedintotheairspace.
iii
iv SUMMARY
Themaingoalofthisresearchistodefineandevaluatesystemsfordetectingand
resolving possible mid-air conflicts of Unmanned Aerial Vehicles, specifically to sup-
portsafebeyondvisualline-of-sightoperationsinanintegratedairspace. Thisgoalis
achievedbyaddressingthefourresearchproblems,i.e.theairspaceincompatibility,the
CD&Rdiversity,thedoubtonUAVsafety,andtheUAVautonomousCD&Rinadequacy.
Directlyfromthoseproblems,fourresearchquestionsareformulatedasfollows:
1. WhatstructurecanbedefinedtomanagetheCD&RsystemforUAVsoperatingin
anintegratedairspace?
2. How can the diverse UAV CD&R approaches be classified into a comprehensive
taxonomythatiscompatiblewiththecurrentairspace?
3. How can the safety parameters of the integrated airspace, under influence of a
heterogeneousCD&Rapproaches,canbedetermined?
4. HowcananautonomousCD&RsystemforUAVsbedefinedtohandlepotential
conflicts,seeingthevehicleaspartoftheintegratedtrafficintheairspace?
Toaddressthefirstquestion,thisresearchproposesataxonomyofCD&Rapproaches
forUAVoperatinginanintegratedairspace. PossibleapproachesforUAVsaresurveyed
andbrokendownbasedontheirtypesofsurveillance,coordination,maneuver,andau-
tonomy. Thefactorsarecombinedbackintoseveral‘genericapproaches’,forexample,
theTrafficWarningandCollisionAvoidanceSystem(TCAS)inmannedflightcanbeseen
asCD&Rthatusescombinationofadistributeddependentsurveillance,anexplicitco-
ordination,anescapemaneuver,andconductedmanually. Theapproachesthatfitsthe
schemeofUAVintegrationarethenselectedmethodically,resultinginanoveltaxonomy
ofUAVCD&Rapproaches.
Fromthegenericapproachesinthetaxonomy,amulti-layeredarchitectureisdevel-
opedinthisresearch,managingCD&Rproceduresintheairspacethatarecompatible
withthemannedflights,whilealsoembracingthosethatareuniquetoUAVs’.Themulti-
layeredfeaturemeansthatinsteadofrelyingononlyoneCD&Rapproach,UAVscanim-
plementmultipleapproachinafail-safeconcept,ensuringthateveninacasewhenone
approachfails,therearestillavailablelayersthatcanpreventdirectcollisions.SixCD&R
approachesfromthetaxonomyarefurtherselectedasthesafetylayers,whichincluded
thelayerof(1)Procedural,(2)Manual,(3)Cooperative,(4)Non-cooperative(5)Escape,
and(6)Emergencyapproaches.
Abriefimplementationofthemulti-layeredCD&Rarchitecturesuggestingthatitus-
agedependscloselyonthetypeofmission: inaparticularmissionsomelayersmight
becomelessnecessary,whileinotherstheymightbeimportant.Theproposedarchitec-
ture,however,islackingdefinitionsofphysicalthresholdsbetweenlayers,suchasthe
distanceortime-to-collision,whichneedtobedefinedspecificallyforeachtypeofUAV.
ThisiswarrantedforthefutureworkforUAVsairtrafficmanagement,butmightonlybe
trulybedefinedoncetheBVLOSflightsofUAVsareallowedintheairspace.
Answeringthesecondresearchquestion, thepreviouslyproposedtaxonomyisat-
tributedtoavailableCD&Rmethodsintheliterature,inordertodeterminetheirfitness
andwhethertheyarecomplementaryorinterchangeablefromonetoanother. Atotal
of64CD&Rmethodsareevaluated,rangingfrompreflightcalculationsondeterminis-
SUMMARY v
ticmaps,suchasaGlobalPathPlanning,toreactiveavoidanceswithon-boardsensors,
suchasbyusingtheVelocityObstaclemethod.Usingthetaxonomy,thepositionofeach
approachesintheoverallsafetymanagementscheme,suchasbyusingamulti-layered
architecture,canbedefined.
The taxonomy attribution has shown that many of the available methods fall out-
sidethetaxonomy,andsuggeststheneedtoconcentrateresearchmoretopartswhere
representative methods are lacking. On further evaluation, it also becomes apparent
thatthediversityofCD&Rpreferencesonlyexistedwithinthewallsoflaboratories,due
to the current UAV flight limitation to only within VLOS. Nevertheless, the taxonomy
potentiallycanaidbothdevelopersandauthoritiesindecidinganadequateCD&Rap-
proach(es)toensuresafetyofanupcomingBVLOSflightinanintegratedairspace.
ThethirdquestionisaddressedbysettingupaseriesofMonteCarlosimulationto
derive two safety parameters, i.e. the frequencies of near mid-air collisions (NMAC),
andofmid-aircollisions(MAC).TheformerrepresentshowoftentwoUAVsflycloser
toeachotherthanacertainthresholds,whichissettobe50metersinmostofthedis-
cussioninthisdissertation, whilethelaterdescribetheactualbody-to-bodycollision
between vehicles. The use of the Monte Carlo simulations is meant to overcome the
limitationofavailableanalyticalmethodsinliterature,byincorporatingtheeffectofdis-
tributedCD&Rsystem, aswellastheheterogeneousconditionsetupfortheairspace.
Themethod,however,hasrarelybeenpreferredinthesafetyparameterderivation,due
toitssignificantlytime-consumingprocesstoobtainanymeaningfulresults.Thisprob-
lemisaddressedinthisresearchbysimulatinginhigh-densitysetups,ofwhichresults
arescaleddownlatteron,tomorerealisticdensitiesofanairspace.
TwoCD&Rprotocolsaremodeledinthesimulations,firstoneisthecooperativepro-
tocol,whereeachvehicleconductavoidancethatisimplicitlycoordinatedbycommon
rules-of-the-air,andthesecondoneisthenon-cooperativeprotocol,whereeachvehicle
avoidswithpreferencesthatarerandomlygiven. Acertaintargetlevelofsafety(TLS)is
definedaswellinresearch, tomeasuredthecollectiveperformanceoftheCD&Rsys-
tems,inwhichthefrequencyofNMACsandMACsshouldbelowerthan10−2and10−7
perhour,respectively. ThosevaluesofTLSareproposedonthebasisoftheequivalent
valuesinmanned-flighthistoryforthelastdecade.
Astheresults,whilemaintainingtheTLSoftheairspace,thedistributedcooperative
CD&RprotocolisabletoincreasethemaximumnumberofoperatingUAVinoneflight
leveltoalmosttentimesthenumberwhennoCD&Risapplied. Thiswouldmeanthat
foracitylikeChicagothathasanareaofmorethanfive-thousandkilometer-square,a
totalof45UAVscanoperateindependentlyinonealtitude. Itisalsoconcludedthata
muchbetterresultsareobtainedwhileusingthecooperativeprotocol, whichjustifies
thenecessityoforderintheairspace, whichinthiscaseistheimplementationofthe
Right-of-wayrules.
TheusefulnessofMonteCarlosimulationsmethodisdemonstratedinthisresearch,
testingvariousCD&Ralgorithmsandprotocolsinavastnumberofpossibleconditions,
includingthosethatarepreviouslyunpredicted. Thedownsideofthemethodstillap-
pears, however, in which it cannot derive any meaningful results for the frequency of
MACswithinthenumberofsamplestested,duetotherarenessofMACseveninahigh-
vi SUMMARY
densitysetups. Hence,moresamplesarerecommendedforthefuturework,alongwith
furtherextensiontoincludeaircraftdynamicmodelinsidethesimulations.
ThefourthquestionisaddressedinthisresearchbyintroducingtwonovelCD&Ral-
gorithmswhichareadequatetofillinspecificlayersintheCD&Rarchitectureexplained
before. ThefirstalgorithmistheSelectiveVelocityObstacle(SVO)method, anexten-
sionoftheVelocityObstaclemethod(VO-method)withadditionalcriteriaforimplicit
coordination. ThisCD&RmethodisdevelopedspecificallyfortheCooperativelayerin
theCD&Rarchitecture,whichisbasedontheunlikelinessofthefutureairspacetoex-
istwithoutsomesortoforderorcoordination,suchastheRight-of-wayrules. TheSVO
isalsousedasthebasisofthecooperativeCD&Rprotocolinthepreviouslyexplained
NMACfrequencyderivationusingMonteCarlosimulations.
The second algorithm is the Three-dimensional Velocity Obstacle (3DVO) method
thatrepresenttheVO-methodinthree-dimensionalspace,obtainingamuchwiderrange
ofresolutionpossibilities. Thethree-dimensionalresolutionisperformedinarbitrary
avoidanceplanes,whichnumberanddirectioncanbesetaccordingtotheUAVmaneu-
verability.Furthermore,sinceitisdesignedtofilltheEscapelayerfromthearchitecture,
the3DVOisequippedwithBufferVelocityZones,anadditionalalgorithmtoanticipate
adversemovementsofuncoordinatedobstacles.Itisdiscovered,however,thattheaddi-
tionoftheBufferVelocityzonesincreasesthealgorithmperformancemoresignificantly
thanthenumberofAvoidancePlanesavailable.
BoththeSVOand3DVOmethodhavebeenvalidatedbyseriesofMonteCarlosim-
ulationsinastressfulheterogeneousairspacesetup,inwhichtheywereabletosignifi-
cantlyreducethefrequenciesofNMACsandMACs,andhencearepromisingtosupport
BVLOSoperationinanintegratedairspace. Bothmethod,however,arelackingofvehi-
cledynamicmodel,whichcansignificantlychangetheresult,especiallyintheEscape
layer,inwhichavoidancehappeninacloserange.Moreover,experimentstoproofboth
conceptsisalsowarrantedforfutureworks,especiallyintestinganactualBVLOSflight
wheretheUAVsautonomouslyinteractwiththeheterogeneousairspace. Furthermore,
adequatealgorithmtofillotherlayersinthearchitectureisalsomandatorytosupporta
completeBVLOSflight.ThiswillfurtherenrichtheavailableCD&Rapproachesthatcan
beselectedforUAVoperationinanintegratedairspace.
Therefore,onthebasisoftheresearchperformedinthisdissertation,itisconcluded
thatsafeintegrationofUAVsintotheairspaceisverymuchfeasible. Theconclusionis
supportedbynumeroussimulationsthathavebeenconducted,demonstratingthepos-
sibilitytoreachtheairspaceTLSbyresortingtoanautonomousCD&Rsystem,which
is distributed and works independently in each vehicles. The low risk of UAV opera-
tions, eveninaheterogeneousairspaceconditions, isvalidatedevenmorebytherar-
ityofNMACsandMACsoccurrencestothepointthatanartificiallyexaggeratedsetup,
suchasasuperconflictorahigh-densityairspace,isrequiredtomeasuretheoperational
safety.
WhilemanyCD&RapproachesforUAVsinliteraturehavenotbeendesignedfora
BVLOSflightinanintegratedairspace,theiralgorithmcanbeadjustedtoconformthe
proposedtaxonomy.Anexampleofsuchadjustmentispresentedinthisdissertationby
theextensionoftheVO-methodintoSVOmethodthatfitstheCooperativeapproach,
SUMMARY vii
and3DVOthatisdesignedfortheEscapeapproach. WiththelargediversityofCD&R
approachinliterature,validationinaheterogeneoussetupisanecessity,eitherbysim-
ulationsorbyactualflightexperiments.
Comparedtobackinmid2011whenthisresearchwasinitiated,inthis2016com-
mercialuseofUAVsareincreasinglygettingexposedtothegeneralpublic. Regulations
are being updated to define UAVs’ airworthiness and widens their area of operations.
Operatorawarenessoftheregulationsisalsoincreasingasitisshownbythebooming
ofregisterednumberofdroneowners.Atthesametime,droneadvocacygroupsareas-
sembledtopushregulatorypoliciestoallowUAVoperations,especiallyforBVLOSflight.
TheseindicatesthatUAVintegrationintotheairspaceisinevitable,andthatCD&Rsys-
temstosupportsafetyinsuchairspaceisurgentlyneeded. Therefore,atonepointper-
haps it is best for the authorities to simply start to accommodate the BVLOS flight in
theairspace,allowingbothUAVsandtheirCD&Rsystemtomaturebasedonexperience
theycangaininarealsituation. Asithasbeenshowninthehistoryofmanned-flight
deregulation,thiscancreateacompetitiveenvironmentthatpushesbothmanufacturer
andoperatortocontinuouslystriveforsafetyimprovementsinanintegratedairspace
system.

C
ONTENTS
Summary iii
1 Introduction 1
1.1 UnmannedAerialVehiclesandtheAirspaceSystem . . . . . . . . . . . . 1
1.2 ProblemDefinition . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 4
1.2.1 CurrentAirspaceIncompatibility . . . . . . . . . . . . . . . . . . 4
1.2.2 CD&RSystemDiversity . . . . . . . . . . . . . . . . . . . . . . . 5
1.2.3 UAVCD&RSystemSafety . . . . . . . . . . . . . . . . . . . . . . 6
1.2.4 UAVAutonomousCD&RSystemInadequacy . . . . . . . . . . . . 7
1.3 ResearchObjective . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 7
1.4 ResearchScopeandLimitations . . . . . . . . . . . . . . . . . . . . . . 8
1.5 MethodologyandDissertationOutline . . . . . . . . . . . . . . . . . . . 10
2 TaxonomyandArchitectureofCD&RApproaches 13
2.1 Introduction . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 14
2.2 InventoryofApproachesforUAVCD&RSystem. . . . . . . . . . . . . . . 16
2.2.1 TypesofAirspaceSurveillance. . . . . . . . . . . . . . . . . . . . 16
2.2.2 TypesofCoordination . . . . . . . . . . . . . . . . . . . . . . . . 18
2.2.3 TypesofAvoidanceManeuver . . . . . . . . . . . . . . . . . . . . 19
2.2.4 TypesofAutonomy . . . . . . . . . . . . . . . . . . . . . . . . . 20
2.3 TaxonomyofConflictDetectionandResolutionApproachesforUAV. . . . 20
2.3.1 UAVFlightintheFutureIntegratedAirspace. . . . . . . . . . . . . 21
2.3.2 CombinationProcessofCD&RMethods. . . . . . . . . . . . . . . 23
2.3.3 ApproachesAvailability . . . . . . . . . . . . . . . . . . . . . . . 24
2.4 AMulti-layeredArchitecture . . . . . . . . . . . . . . . . . . . . . . . . 26
2.4.1 GenericApproachesArrangement. . . . . . . . . . . . . . . . . . 26
2.4.2 GeneralImplementation. . . . . . . . . . . . . . . . . . . . . . . 27
2.5 Conclusion . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 28
3 SafetyAssessmentofUAVCD&RSystem 31
3.1 Introduction . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 32
3.2 HeterogeneousAirspaceModel. . . . . . . . . . . . . . . . . . . . . . . 33
3.2.1 HighDensityAirspacewithPeriodicBoundaryCondition . . . . . . 34
3.2.2 TheUncertaintyofConflictDetection . . . . . . . . . . . . . . . . 36
3.2.3 TheVariationofConflictResolution . . . . . . . . . . . . . . . . . 36
3.2.4 OrderintheHeterogeneousAirspace . . . . . . . . . . . . . . . . 38
3.3 MonteCarloSimulations . . . . . . . . . . . . . . . . . . . . . . . . . . 40
3.3.1 GeneralSetup . . . . . . . . . . . . . . . . . . . . . . . . . . . . 40
3.3.2 Output. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 41
3.3.3 Convergence. . . . . . . . . . . . . . . . . . . . . . . . . . . . . 42
ix