Integrated Approaches to handle UAV actuator fault

171 Pages·2015·2.06 MB·English

CRANFIELD UNIVERSITY
Chang How Lo
Integrated Approaches to handle UAV
actuator fault
chool of erospace ransport and anufacturing
S A , T M
PhD
Academic year 2015
Supervisors: Dr Hyo-Sang Shin, Professor Antonios Tsourdos
August 2015
ThisthesisissubmittedinpartialfulfillmentoftherequirementsfortheDegreeofPhD.
(cid:13)c CranfieldUniversity, 2015. Allrightsreserved. Nopart ofthispublicationmaybe
reproducedwithoutthepriorwrittenpermissionofthecopyrightowner.

Abstract
UnmannedAerialVehicles(UAV)hashistoricallyshowntobeunreliablewhen
compared to their manned counterparts. Part of the reason is they may not be
ff
able to a ord the redundancies required to handle faults from system or cost
constraints. This research explores instances when actuator fault handling may
be improved with integrated approaches for small UAVs which have limited
actuatorredundancy.
Theresearchstartedwithexaminingthepossibilityofhandlingthecasewhere
noactuatorredundancyremainspostfault. Twofaultrecoveryschemes,combing
control allocation and hardware means, for a Quad Rotor UAV with no redun-
dancyuponfaulteventaredevelopedtoenablesafeemergencylanding.
Inspired by the integrated approach, a proposed integrated actuator control
scheme is developed, and shown to reduce the magnitude of the error dynamics
wheninputsaturationfaultsoccur. Geometricalinsightstotheproposedactuator
scheme are obtained. Simulations using an Aerosonde UAV model with the
proposed scheme showed significant improvements to the fault tolerant stuck
faultrangeandimprovedguidancetrackingperformance.
While much research literature has previously been focused on the controller
to handleactuator faults,fault tolerant guidance schemes mayalso beutilized to
accommodate the fault. One possible advantage of using fault tolerant guidance
ff
isthatitmayconsiderthefaultdegradatione ectsontheoverallmission.
A fault tolerant guidance reconfiguration method is developed for a path fol-
lowingmission. Themethodprovidesanadditionaldegreeoffreedomindesign,
whichallowsmoreflexibilitytothedesignertomeetmissionrequirements.
This research has provided fresh insights into the handling UAV extremal
actuator faults through integrated approaches. The impact of this work is to ex-
pandonthepossibilitiesapractitionermayhaveforimprovingthefaulthandling
capabilitiesofaUAV.
Tomyfamily
ii
Contents
Abstract i
1 Introduction 1
1.1 Background . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 1
1.2 Motivation . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 3
1.3 Researchaimandapproach . . . . . . . . . . . . . . . . . . . . . . . 6
1.4 Contributions . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 7
1.5 Researchpublications . . . . . . . . . . . . . . . . . . . . . . . . . . . 8
1.6 Organizationofthesis . . . . . . . . . . . . . . . . . . . . . . . . . . 8
2 LiteratureReview 10
2.1 Introduction . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 10
2.2 ModelBasedFaultTolerantControlOverview . . . . . . . . . . . . 11
2.2.1 FaultTolerantControlObjective . . . . . . . . . . . . . . . . 12
2.2.2 RedundancyisKeytoFaultTolerantControl . . . . . . . . . 12
2.3 FaultTolerantControlTypes . . . . . . . . . . . . . . . . . . . . . . . 14
2.3.1 PassiveFaultTolerantControl . . . . . . . . . . . . . . . . . 14
2.3.2 ActiveFaultTolerantControl . . . . . . . . . . . . . . . . . . 14
2.4 FaultDetectionandDiagnosisMethods . . . . . . . . . . . . . . . . 17
2.4.1 ResidualGeneration . . . . . . . . . . . . . . . . . . . . . . . 17
2.4.1.1 ObserverBased . . . . . . . . . . . . . . . . . . . . 17
2.4.1.2 ParityRelations . . . . . . . . . . . . . . . . . . . . 18
2.4.1.3 ParameterEstimation . . . . . . . . . . . . . . . . . 21
2.4.1.4 CombinationsofMethods . . . . . . . . . . . . . . 21
2.4.2 ResidualEvaluation . . . . . . . . . . . . . . . . . . . . . . . 21
iii
Contents
2.5 ReconfigurableControlMethods . . . . . . . . . . . . . . . . . . . . 22
2.5.1 ControlAllocation . . . . . . . . . . . . . . . . . . . . . . . . 22
2.5.2 FaultToleranceGuidance . . . . . . . . . . . . . . . . . . . . 24
2.6 Discussion . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 24
2.7 Conclusion . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 25
3 Improving the performance of an actuation system when subjected to
saturationfault 27
3.1 Introduction . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 27
3.2 DescriptionofControlScheme . . . . . . . . . . . . . . . . . . . . . 29
3.2.1 ConventionalActuatorControlScheme . . . . . . . . . . . . 29
3.2.2 IntegratedActuatorControlScheme . . . . . . . . . . . . . . 31
3.2.3 ComparisonofControlSchemes . . . . . . . . . . . . . . . . 31
3.2.3.1 Nonsaturationcase . . . . . . . . . . . . . . . . . . 32
3.2.3.2 Oneactuatorsaturationfaultcase . . . . . . . . . . 33
3.2.4 Twoactuatorssaturation . . . . . . . . . . . . . . . . . . . . . 35
3.3 Simulation . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 39
3.3.1 SimulationModel . . . . . . . . . . . . . . . . . . . . . . . . . 39
3.3.2 SimulationResults . . . . . . . . . . . . . . . . . . . . . . . . 39
3.4 Conclusion . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 46
4 Discretedomainanalysisontheintegratedactuatorcontrolscheme 47
4.1 Introduction . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 47
4.2 Conventionalcontrolscheme . . . . . . . . . . . . . . . . . . . . . . 47
4.3 Integratedactuatorcontrolscheme . . . . . . . . . . . . . . . . . . . 50
4.4 Propertiesoftheintegratedactuatorcontrolscheme . . . . . . . . . 52
4.4.1 LinearEquivalenceintheVirtualDemandspace . . . . . . . 52
4.4.2 OrthogonalControlUpdatedirection . . . . . . . . . . . . . 55
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Contents
4.4.3 Outputstuckfaultbehaviour . . . . . . . . . . . . . . . . . . 58
4.4.3.1 Possibledrawbackandpossiblesolutions . . . . . 60
4.4.4 SimulationsandDiscussion . . . . . . . . . . . . . . . . . . . 63
4.4.4.1 Unconstrainedsimulations . . . . . . . . . . . . . . 65
4.4.4.2 Inputsaturationsimulations . . . . . . . . . . . . . 72
4.4.4.3 Weightedcontrolschemesimulations . . . . . . . . 76
4.4.4.4 Twostepcontrolschemesimulations . . . . . . . . 80
4.4.4.5 AntailfincontrolledUAVexample . . . . . . . . . 84
4.5 Conclusion . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 91
5 Application of an integrated actuator control scheme to improve the
AerosondeUAV’sfaulttolerance 92
5.1 Introduction . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 92
5.2 Demonstrationwithflightcontrol . . . . . . . . . . . . . . . . . . . . 93
5.2.1 SimulationsResults . . . . . . . . . . . . . . . . . . . . . . . . 95
5.2.1.1 Aileronfault . . . . . . . . . . . . . . . . . . . . . . 95
5.2.1.2 Ruddervatorfault . . . . . . . . . . . . . . . . . . . 101
5.2.1.3 Ruddervatorfault . . . . . . . . . . . . . . . . . . . 107
5.2.2 Comparisonsonfaulttolerantrange . . . . . . . . . . . . . . 112
5.3 Demonstrationwithguidanceincluded . . . . . . . . . . . . . . . . 116
5.4 Conclusion . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 120
6 Aguidancereconfigurationstrategy 122
6.1 Introduction . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 122
6.2 GuidanceScheme . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 123
6.3 Aileronactuatorfault . . . . . . . . . . . . . . . . . . . . . . . . . . . 125
6.3.1 Rollperformancedegradationduestuckaileronfault . . . . 126
6.4 Proposedmethod . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 127
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Contents
6.4.1 Reconfigurationofpathfollowingalgorithm . . . . . . . . . 127
6.4.2 Impact of path following ability of the guidance scheme
withchange . . . . . . . . . . . . . . . . . . . . . . . . . . . . 129
6.4.3 Changingpathradiustomitigatefault . . . . . . . . . . . . 131
6.5 Simulationresults . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 132
6.6 Conclusions . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 144
7 Conclusions 145
8 FutureWork 147
References 148
vi
List of Tables
4.1 Actuatorplantparametersusedinthesimulation . . . . . . . . . . 64
vii
List of Figures
1.1 UAV failure rates illustrating the high mishap rates of UAVs com-
paredtogeneralaviationaircraft,takenfromRef.[1] . . . . . . . . 2
1.2 AveragedcausesofUAVsystemfailurescauses . . . . . . . . . . . 4
2.1 FlightEnvelopeProtectionusingFaultTolerantControl . . . . . . . 13
2.2 ActiveFaultTolerantControlSystemblockdiagram . . . . . . . . . 15
2.3 ModelBasedFaultDiagnosis . . . . . . . . . . . . . . . . . . . . . . 16
2.4 SomeReconfigurablecontrolmethods . . . . . . . . . . . . . . . . . 23
3.1 Atypicalvehicleautopilotschemewiththeactuationsystemblock. 29
3.2 ConventionalActuatorControlArchitecture . . . . . . . . . . . . . 29
3.3 IntegratedActuatorControlArchitecture . . . . . . . . . . . . . . . 31
3.4 Integratedactuatorcontrolscheme . . . . . . . . . . . . . . . . . . . 32
3.5 Simulation results showing the 2 control schemes having exact
responseswhenthereisnoactuatorsaturationevents. . . . . . . . . 41
3.6 Simulationresultsfor1actuatorsaturationcase. . . . . . . . . . . . 42
3.7 Individualactuatorresponsesfor1actuatorsaturationcase. . . . . 43
3.8 SimulationresultsforActuator1and2saturationcase. . . . . . . . 44
3.9 IndividualactuatorresponseforActuator1and2saturationcase. . 45
4.1 Atypicalvehicleautopilotschemewiththeactuationsystemblock. 48
4.2 Aconventionalactuatorcontrolscheme. . . . . . . . . . . . . . . . . 49
4.3 IntegratedActuatorControlArchitecture . . . . . . . . . . . . . . . 50
4.4 IntegratedActuatorControlArchitectureindetail . . . . . . . . . . 51
ff
4.5 Di erences in control signal update direction between the inte-
gratedandconventionalactuatorcontrolschemes. . . . . . . . . . . 58