Vision-Based Guidance for Air-to-Air Tracking and Rendezvous of Unmanned Aircraft Systems

146 Pages·2016·7.75 MB·English

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Theses and Dissertations
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Joseph Walter Nichols
Brigham Young University - Provo
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Nichols, Joseph Walter, "Vision-Based Guidance for Air-to-Air Tracking and Rendezvous of Unmanned
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Vision-BasedGuidanceforAir-to-AirTrackingandRendezvous
ofUnmannedAircraftSystems
JosephW.Nichols
Adissertationsubmittedtothefacultyof
BrighamYoungUniversity
inpartialfulfillmentoftherequirementsforthedegreeof
DoctorofPhilosophy
TimothyW.McLain,Chair
RandalW.Beard
MarkB.Colton
ChristopherA.Mattson
BryanS.Morse
DepartmentofMechanicalEngineering
BrighamYoungUniversity
August2013
Copyright©2013JosephW.Nichols
AllRightsReserved
ABSTRACT
Vision-BasedGuidanceforAir-to-AirTrackingandRendezvous
ofUnmannedAircraftSystems
JosephW.Nichols
DepartmentofMechanicalEngineering,BYU
DoctorofPhilosophy
This dissertation develops the visual pursuit method for air-to-air tracking and rendezvous
of unmanned aircraft systems. It also shows the development of vector-field and proportional-
integral methods for controlling UAS flight in formation with other aircraft. The visual pursuit
method is a nonlinear guidance method that uses vision-based line of sight angles as inputs to the
algorithm that produces pitch rate, bank angle and airspeed commands for the autopilot to use in
aircraftcontrol. Themethodisshowntobeconvergentaboutthecenterofthecameraimageframe
andtobestableinthesenseofLyapunov. Inthelateraldirection,theguidancemethodisoptimized
to balance the pursuit heading with respect to the prevailing wind and the location of the target on
the image plane to improve tracking performance in high winds and reduce bank angle effort. In
both simulation and flight experimentation, visual pursuit is shown to be effective in providing
flightguidanceinstrongwinds.
Visual pursuit is also shown to be effective in guiding the seeker while performing aerial
docking with a towed aerial drogue. Flight trials demonstrated the ability to guide to within a few
meters of the drogue. Further research developed a method to improve docking performance by
artificially increasing the length of the line of sight vector at close range to the target to prevent
flight control saturation. This improvement to visual pursuit was shown to be an effective method
forprovidingguidanceduringaerialdockingsimulations.
Ananalysisofthevisualpursuitmethodisprovidedusingthemethodofadjointstoevalu-
ate the effects of airspeed, closing velocity, system time constant, sensor delay and target motion
ondockingperformance. Amethodforpredictingdockingaccuracyisdevelopedandshowntobe
usefulforpredictingdockingperformanceforsmallandlargeunmannedaircraftsystems.
Keywords: aerial docking, aerial recovery, aerial rendezvous, air-to-air tracking, autonomous for-
mationflight,Lyapunovstability,nonlinearcontrol,unmannedaircraftsystem,UAS,UAV,vector-
fieldguidance,vision-basedguidance
ACKNOWLEDGMENTS
I am extremely blessed to have had the opportunity to once again study at Brigham Young
University. I have loved being on campus and associating with the professors and students that
makethisuniversitytrulyuniqueamongthegreatinstitutionsoflearning.
IappreciateDr. TimMcLainfortakingmeonasoneofhisgraduatestudentsandproviding
the mentoring and guidance that were essential to completing this work. Dr. Randy Beard has
been a source of ideas and encouragement to solve the technical challenges associated with this
research. I want to acknowledge the help of Dr. Mark Colton for his collaboration on vector-field
methods. Dr. Bryan Morse provided consultations on computer vision and statistical processes at
keypointsinmyresearch,andIthankDr. ChrisMattsonforhistimelyadviceandencouragement.
IappreciatethefriendshipandconcernshownbyMiriamBusch,thedepartmentgraduateadvisor,
throughoutmytimeatBYU.
IamgratefulformyfriendsintheMAGICCLabfortheirassistanceandcompanionship. In
particularIwanttoacknowledgetheotherstudentsontheaerialrecoveryproject: DanielCarlson,
MarkOwen,JeffFerrin,DallinBriggs,andLiangSun;andthankthemfortheirhelpasweworked
through the many hardware challenges associated with flying two unmanned aircraft and a towed
drogue in formation. I also want to thank my lab colleagues, Rob Leishman, Peter Neidfeldt,
and Robert Klaus for being willing to drop whatever they were doing to consult and help me in
numerousways.
Most importantly, I would like to thank my wife, Diane, for her encouragement and pa-
tience as I have pursued this educational opportunity at this late date in my working career. I also
thank my children and father for their interest and continuous displays of support throughout my
studies.
IappreciatetheDepartmentofMechanicalEngineeringforprovidingaresearchfellowship
and the Department of Veterans Affairs for their financial support through the GI Bill. Research
funding for part of this work was provided by the Air Force Office of Scientific Research through
theSmallBusinessTechnologyTransferProgram,contractnumberFA9550-10-C-0041,andinco-
operationwithLockheedMartinProcerusTechnologies. Thissupportisgratefullyacknowledged.
In addition, I want to thank Mr. Neil Johnson from Lockheed Martin Procerus Technologies for
his assistance in coding the methods developed in the paper for implementation on the Vision
ProcessingUnit,andforassistingintheflighttrials.
TABLEOFCONTENTS
LISTOFTABLES . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . viii
LISTOFFIGURES . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . ix
NOMENCLATURE . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . xi
Chapter1 Introduction . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 1
1.1 Motivation . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 1
1.2 ProblemStatement . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 2
1.3 Definitions . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 4
1.4 LiteratureReview . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 4
1.4.1 VectorFieldFollowing . . . . . . . . . . . . . . . . . . . . . . . . . . . . 4
1.4.2 GuidanceforAir-to-AirTracking . . . . . . . . . . . . . . . . . . . . . . 5
1.4.3 AerialRendezvous . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 6
1.5 Contributions . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 7
1.5.1 EnhancedVectorFieldTracking . . . . . . . . . . . . . . . . . . . . . . . 7
1.5.2 VisualPursuit . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 8
1.5.3 AerialDocking . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 9
1.6 Organization . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 9
Chapter2 SimulationToolsandExperimentalHardware . . . . . . . . . . . . . . . 11
2.1 Simulation . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 11
2.2 Hardware . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 12
2.2.1 Seeker . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 12
2.2.2 Mothership . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 13
2.2.3 Drogue . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 15
2.2.4 GroundStation . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 15
Chapter3 Air-to-AirRendezvoususingVectorFieldMethods . . . . . . . . . . . . . 19
3.1 Introduction . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 19
3.2 OrbitTrackingUsingVectorFields . . . . . . . . . . . . . . . . . . . . . . . . . . 20
3.3 Vision-basedEnhancementstoOrbitTrackingUsingVectorFields . . . . . . . . . 25
3.3.1 InteriorOrbitFollowingforImprovedVehicleTracking . . . . . . . . . . 25
3.3.2 AltitudeBiasCorrectionUsingVision . . . . . . . . . . . . . . . . . . . . 27
3.4 ExperimentalResults . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 30
3.5 ChapterSummary . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 33
Chapter4 VisualPursuit . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 34
4.1 Introduction . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 34
4.2 ModelDevelopment . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 36
4.2.1 CoordinateFrames . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 36
4.2.2 CameraGeometry . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 37
v
4.2.3 SystemDynamics . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 38
4.3 GuidanceMethods . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 42
4.3.1 Proportional-IntegralPursuit . . . . . . . . . . . . . . . . . . . . . . . . . 42
4.3.2 VisualPursuit . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 43
4.3.3 Limitations . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 52
4.4 GuidanceLawsfromDecoupledDynamics . . . . . . . . . . . . . . . . . . . . . 55
4.5 SimulationResults . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 56
4.6 ExperimentalResults . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 60
4.6.1 TrackingAlgorithmPerformance . . . . . . . . . . . . . . . . . . . . . . 60
4.6.2 VisionSensorPerformance . . . . . . . . . . . . . . . . . . . . . . . . . . 61
4.7 ChapterSummary . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 64
Chapter5 AerialDockingUsingaPassiveTowedCableSystem . . . . . . . . . . . . 66
5.1 Introduction . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 66
5.2 SeekerGuidance . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 67
5.3 ExperimentalResults . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 68
5.4 ModifiedVisualPursuitforNear-targetManeuvering . . . . . . . . . . . . . . . . 71
5.4.1 Minimum-distanceContactFactor . . . . . . . . . . . . . . . . . . . . . . 73
5.4.2 Fixed-lengthContactFactor . . . . . . . . . . . . . . . . . . . . . . . . . 74
5.4.3 ComparisonofMethods . . . . . . . . . . . . . . . . . . . . . . . . . . . 75
5.5 ChapterSummary . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 78
Chapter6 AdjointAnalysisofAerialDockingSystem . . . . . . . . . . . . . . . . . 79
6.1 Introduction . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 79
6.2 LinearizationandModelSimplification . . . . . . . . . . . . . . . . . . . . . . . 79
6.2.1 LinearLongitudinalGuidanceModel . . . . . . . . . . . . . . . . . . . . 81
6.2.2 LinearLateralGuidanceModel . . . . . . . . . . . . . . . . . . . . . . . 83
6.2.3 ModelStability . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 85
6.3 MethodofAdjoints . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 87
6.4 TargetMotion . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 89
6.5 SeekerManeuverability . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 97
6.6 VelocityEffects . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 101
6.7 SensorEffects . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 102
6.8 ComparisonofLargeandSmallUASPerformanceUsingVisualPursuit . . . . . . 107
6.9 ChapterSummary . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 109
Chapter7 ConclusionsandFutureWork . . . . . . . . . . . . . . . . . . . . . . . . . 110
7.1 SummaryofMainResults . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 110
7.2 FutureWork . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 110
7.3 Conclusions . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 111
REFERENCES . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 114
AppendixA GuidanceLawsfromDecoupledDynamics . . . . . . . . . . . . . . . . . 118
A.1 LongitudinalDynamics . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 118
vi
A.2 LateralDynamics . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 120
A.3 VisualPursuitinTwoDimensions . . . . . . . . . . . . . . . . . . . . . . . . . . 123
A.4 SimulationResults . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 129
vii
LISTOFTABLES
4.1 SimulationLOSanglecomparison . . . . . . . . . . . . . . . . . . . . . . . . . . 59
4.2 FlighttrialLOSanglecomparison . . . . . . . . . . . . . . . . . . . . . . . . . . 65
5.1 Comparisonofminimum-distanceandfixed-lengthcontactfactorperformance . . 76
6.1 Nominalsystemvariables . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 85
6.2 Nominalsystemvariables . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 95
6.3 Nominalsystemvariables . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 97
6.4 SmallandlargeUASsystemcharacteristics . . . . . . . . . . . . . . . . . . . . . 108
6.5 Dockingsimulationresults . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 108
A.1 Comparisonofcoupledanddecoupledguidancelawsduringdocking . . . . . . . 129
A.2 Comparisonofcoupledanddecoupledguidancelawsduringtracking . . . . . . . 131
viii
LISTOFFIGURES
1.1 Aerialrecoveryconcept. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 1
2.1 Systemarchitecture. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 12
2.2 Internalcommunicationblockdiagram. . . . . . . . . . . . . . . . . . . . . . . . 13
2.3 Seekeraircraft. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 14
2.4 Mothershippreparingfortakeoff. . . . . . . . . . . . . . . . . . . . . . . . . . . . 15
2.5 Droguesystem. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 16
2.6 Droguelaunchprocedure. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 16
2.7 Groundstationdisplay. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 17
3.1 Flightpathdefinedbyintersectingsurfaces. . . . . . . . . . . . . . . . . . . . . . 20
3.2 SeekerorbitmodificationforimprovedLOS . . . . . . . . . . . . . . . . . . . . . 26
3.3 Cameraimageframe. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 28
3.4 Vectorfieldfollowingdistancetestresults. . . . . . . . . . . . . . . . . . . . . . . 30
3.5 Videoframefromseekercamera . . . . . . . . . . . . . . . . . . . . . . . . . . . 31
3.6 Enhancedvectorfieldfollowingtestresults. . . . . . . . . . . . . . . . . . . . . . 32
4.1 Proportionalnavigationandpursuitguidancemethods . . . . . . . . . . . . . . . . 35
4.2 Seekerandtargetinformationflight . . . . . . . . . . . . . . . . . . . . . . . . . 36
4.3 Seekercameraframe. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 37
4.4 Longitudinaldynamics . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 38
4.5 Lateraldynamics . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 39
4.6 Controlsystemblockdiagram . . . . . . . . . . . . . . . . . . . . . . . . . . . . 44
4.7 Comparisonofguidancecommandsanddynamicresponse . . . . . . . . . . . . . 51
4.8 Hiddendynamicresponse . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 53
4.9 Flightcontrolsaturationlimits . . . . . . . . . . . . . . . . . . . . . . . . . . . . 55
4.10 Wagglemaneuver . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 57
4.11 ComparisonofPIandvisualpursuittracking . . . . . . . . . . . . . . . . . . . . 58
4.12 ComparisonofPIandvisualpursuittrackingincrosswind . . . . . . . . . . . . . 60
4.13 Guidancemethodresults . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 62
4.14 Seekervideoframewithtrackenabled . . . . . . . . . . . . . . . . . . . . . . . . 63
4.15 Vision-basedresults . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 64
5.1 Droguealtitudedeviationinthepresenceofwind . . . . . . . . . . . . . . . . . . 66
5.2 Drogueinseekerimage . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 69
5.3 Flighttestresults. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 70
5.4 Lateraldynamicsforfixedcontactfactor. . . . . . . . . . . . . . . . . . . . . . . 72
5.5 Fixed-lengthandminimum-distancecontactfactorcomparison . . . . . . . . . . . 75
5.6 ContactfactorLOSdistanceerrorcomparison. . . . . . . . . . . . . . . . . . . . 77
5.7 Dockingperformancecomparisonusingthecontactfactor . . . . . . . . . . . . . 78
6.1 Comparisonoflinearandnonlinearguidancemodels . . . . . . . . . . . . . . . . 81
6.2 Linearizedlongitudinalguidancesystem . . . . . . . . . . . . . . . . . . . . . . . 82
6.3 Linearizedlateralguidancesystem . . . . . . . . . . . . . . . . . . . . . . . . . . 84
ix