Characterization and Control of a Saab Seaeye Thruster by M. Amos Buchanan BA, Reed College ...

137 Pages·2015·30.81 MB·English

CharacterizationandControlofaSaabSeaeyeThruster
by
M.AmosBuchanan
B.A.,ReedCollege,2002
AThesisSubmittedinPartialFulfillmentofthe
RequirementsfortheDegreeof
MasterofScience
intheDepartmentofMechanicalEngineering
©M.AmosBuchanan,2015
UniversityofVictoria
Allrightsreserved. Thisthesismaynotbereproducedinwholeorinpart,by
photocopyingorothermeans,withoutthepermissionoftheauthor.
ii
CharacterizationandControlofaSaabSeaeyeThruster
by
M.AmosBuchanan
B.A.,ReedCollege,2002
SupervisoryCommittee
Dr. BradleyBuckham,Co-Supervisor
(DepartmentofMechanicalEngineering)
Dr. ColinBradley,Co-Supervisor
(DepartmentofMechanicalEnigneering)
iii
SupervisoryCommittee
Dr. BradleyBuckham(DepartmentofMechanicalEngineering)
Co-Supervisor
Dr. ColinBradley(DepartmentofMechanicalEngineering)
Co-Supervisor
ABSTRACT
The use of Remotely Operated Vehicles (ROVs) in exploring and building infrastructure in
the ocean is expanding. ROVs are performing tasks underwater that would be difficult or
impossibletodowithhumandivers. Thesevehiclesarebeingusedinincreasinglycomplicated
anddemandingenvironmentsthatrequireimprovementsinthemethodsforcontrollingthese
vehicles. Currently, research into semi-autonomous control is being conducted to aide ROV
pilotsincompensatingforenvironmentaldisturbancesandunknowndynamics. Toeffectively
implementsemi-autonomouscontrol,precisethrustforcesmustbeelicitedfromthethrusters.
This work discusses a low-level thruster controller that can be used as part of a semi-
autonomous guidance, navigation and control system for a ROV. A thruster dynamics model
describing the thrust force of a propeller-type underwater thruster was derived and imple-
mented for the thruster on the Saab Seaeye Falcon ROV. The thruster dynamics model de-
scribed is a quadratic equation that uses the propeller velocity to determine thrust force. This
model includes a mechanism for compensation against the external motion of the thruster,
suchasoccurswhentheROVmovesthroughthewater.
Several experiments were performed to fully characterize the quadratic thruster dynamics
model and test its ability to accurately predict thrust force based on a known ambient water
velocity and propeller angular velocity. The drag force was calculated and removed from the
force measurements to get the thrust force used in the model. The model coefficients were
determinedandthentheresultingmodelwastestedagainstexperimentaldatatodeterminethe
efficacy of the model in the lab environment and compare it to a widely used linear thruster
dynamics model. The results showed the quadratic model improved upon the linear model,
andthequadraticmodelwasvalidoveralargerrangeofambientwatervelocities.
The quadratic model was then inverted to provide a thruster control algorithm that deter-
minesthepropellerangularvelocitynecessarytoproduceadesiredthrustforce. Thisalgorithm
was used to design a low-level thruster controller. This controller was designed to be used on
an existing vehicle where thrust force feedback is not available and difficult or expensive to
add. Thisallowsittobeusedinawiderrangeofapplicationsthancontrollersthatrelyonsuch
feedback to operate. The controller was implemented using a PID control loop to drive the
angular velocity of the propeller to the desired rate. An iso-parametric mapping, which trans-
forms the linear PID output to the non-linear thruster input, was added to provide a faster
response time for the controller over the entire range of the propeller velocity. The perfor-
mance of this low-level thruster controller was demonstrated in the test environment. The
low-level thruster controller followed a desired thrust force under a range of ambient water
velocities.
Thethrustercharacterizationandlow-levelthrustercontrollerwasdesignedtobeusedon
an existing ROV. The motivation behind this work is to build a controller that may be imple-
iv
mented for use by a high-level vehicle controller. The low-level thruster controller presented
here does not depend on sensors or equipment that is largely unavailable on vehicles without
costly retrofits, and the experimental characterization does not require intimate knowledge of
theinnerworkingsofthethruster. Thismakesiteasytoimplementandgeneralizetoavariety
of thrusters. The results of this work show a low-level thruster controller than can be used in
acontrolschemaforexistingROVs.
v
Contents
SupervisoryCommittee ii
Abstract iii
TableofContents v
ListofTables vii
ListofFigures viii
Acknowledgements x
1 Introduction 1
1.1 RemotelyOperatedUnderwaterVehicles . . . . . . . . . . . . . . . . . . . . 2
1.2 ReviewofThrusterDynamicModelsandExperiments . . . . . . . . . . . . . 5
1.3 ApplicationofModelstoThrusterControllers . . . . . . . . . . . . . . . . . 9
1.4 ResearchMotivationandObjectives . . . . . . . . . . . . . . . . . . . . . . . 11
1.5 ThesisOverview . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 12
2 ThrusterDynamicsModelling 14
2.1 PhysicalModelofThrustForce . . . . . . . . . . . . . . . . . . . . . . . . . 14
2.2 ThrusterDynamicsandLinearModelofThrustForce . . . . . . . . . . . . . 18
2.3 QuadraticModelofThrustForce . . . . . . . . . . . . . . . . . . . . . . . . 21
2.4 Three-StateExtensionofQuadraticModel . . . . . . . . . . . . . . . . . . . 23
3 ThrusterTestingSetupandPlan 27
3.1 OverviewofExperiment . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 29
3.2 EquipmentDescriptionandCalibration . . . . . . . . . . . . . . . . . . . . . 31
3.2.1 CommandofThruster . . . . . . . . . . . . . . . . . . . . . . . . . . 34
3.2.2 ForceSensorsandCalibration . . . . . . . . . . . . . . . . . . . . . . 34
3.2.3 PropellerAngularVelocityMeasurements . . . . . . . . . . . . . . . 38
3.2.4 AmbientWaterVelocityMeasurementwithFlowmeter . . . . . . . . 41
3.2.5 FlumeTank . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 43
3.2.6 Free-StandingTank . . . . . . . . . . . . . . . . . . . . . . . . . . . 44
3.3 TestPlan . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 45
vi
4 ResultsandAnalysisofThrusterTests 47
4.1 PropellerVelocityScalingValue . . . . . . . . . . . . . . . . . . . . . . . . . 48
4.2 ThrusterInputCommandandPropellerVelocity . . . . . . . . . . . . . . . . 50
4.3 ThrusterDeadbandMeasurements . . . . . . . . . . . . . . . . . . . . . . . 53
4.4 ChoiceofThrustForceDatum . . . . . . . . . . . . . . . . . . . . . . . . . 54
4.5 DragForceCalculation . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 55
4.6 Near-SurfaceEffectsInTheForceMeasurements . . . . . . . . . . . . . . . 59
4.7 CalculationofThrustCoefficient . . . . . . . . . . . . . . . . . . . . . . . . 62
4.8 ComparisonofThrustModelandActualForce . . . . . . . . . . . . . . . . . 66
4.9 ThrusterCommandResponseTimes . . . . . . . . . . . . . . . . . . . . . . 76
5 DesignofaThrusterController 78
5.1 DeterminingtheDesiredPropellerVelocity . . . . . . . . . . . . . . . . . . . 79
5.2 DeterminingtheThrusterInputCommand . . . . . . . . . . . . . . . . . . . 86
5.3 IntegratingtheController . . . . . . . . . . . . . . . . . . . . . . . . . . . . 94
6 ResultsofThrusterControllerTesting 97
6.1 PIDControllerResponseTestResults . . . . . . . . . . . . . . . . . . . . . . 97
6.2 Iso-ParametricMappingResults . . . . . . . . . . . . . . . . . . . . . . . . . 103
6.3 Steady-StateThrustResults . . . . . . . . . . . . . . . . . . . . . . . . . . . 105
7 Conclusions 119
7.1 SummaryofFindings . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 119
7.2 FutureWork . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 121
A Variables 124
Bibliography 126
vii
List of Tables
Table1.1 ComparisonofObservationandWorkclassROVs. . . . . . . . . . . . 4
Table3.1 Listofphysicalquantitiesrequiredbythemodel. . . . . . . . . . . . . . 30
Table3.2 Listofmeasurementsrequiredbythedesign. . . . . . . . . . . . . . . . 31
Table3.3 Summaryofequipmentusedintheexperiment. . . . . . . . . . . . . . 33
Table3.4 Valuesfortheforcesonthesensors. . . . . . . . . . . . . . . . . . . . 37
Table3.5 Sloperesultsforeachsensor. . . . . . . . . . . . . . . . . . . . . . . . 37
Table4.1 Thrusterspeedscalingfactors. . . . . . . . . . . . . . . . . . . . . . . . 51
Table4.2 Valuesforthedeadbandmeasurements. . . . . . . . . . . . . . . . . . . 53
Table4.3 Resultsofthedragcalculation. . . . . . . . . . . . . . . . . . . . . . . . 59
Table4.4 Valuesforthethrustcoefficientforeachstate. . . . . . . . . . . . . . . 72
Table4.5 Summaryofthrustforceerror. . . . . . . . . . . . . . . . . . . . . . . . 75
Table5.1 Mappingcontrolpointsusedforthethird-orderiso-parametricmap. . . 91
Table5.2 Shiftingcontrolpointsusedforthethird-orderiso-parametricmap. . . . 92
Table6.1 TheresultinggainsfromtuningthePIDcontrollerwithnomappings. . 100
Table6.2 PIDstepresponsedata. . . . . . . . . . . . . . . . . . . . . . . . . . . 100
Table6.3 GainsforthePIDcontrollerwithmappings. . . . . . . . . . . . . . . . 104
Table6.4 PIDandmappingstepresponsedata. . . . . . . . . . . . . . . . . . . . 106
Table6.5 Averagesteady-statethrustforceerrorfordifferentwaterspeeds. . . . . 111
viii
List of Figures
Figure1.1 SizedifferencebetweenObservationandworkclassROVS. . . . . . . 3
Figure1.2 PlacementofthethrustersaroundtheSeaeyeFalcon. . . . . . . . . . . 5
Figure1.3 AutonomousROVcontrolschema. . . . . . . . . . . . . . . . . . . . 6
Figure1.4 Thrusterdynamicsmodelparameters. . . . . . . . . . . . . . . . . . . 7
Figure2.1 Axialwatervelocity,ambientfluidvelocityandvehiclevelocity. . . . . . 15
Figure2.2 Graphshowingthelinearmodelfortheadvanceratio. . . . . . . . . . 20
Figure2.3 Physicalinterpretationoftheaxialwatervelocity. . . . . . . . . . . . . 21
Figure2.4 Graphshowingthequadraticmodelforthethrustcoefficient. . . . . . 23
Figure2.5 Representationofallthreeflowstates. . . . . . . . . . . . . . . . . . . 24
Figure3.1 TheSI-MCT01thrusterfortheSeaeyeFalcon. . . . . . . . . . . . . . . 28
Figure3.2 Thefullsensorframewiththruster. . . . . . . . . . . . . . . . . . . . . 28
Figure3.3 Boxdiagramofthesetup. . . . . . . . . . . . . . . . . . . . . . . . . . 32
Figure3.4 Collarandsensorframeforthethruster. . . . . . . . . . . . . . . . . . 33
Figure3.5 Forcediagramofthesensorframe. . . . . . . . . . . . . . . . . . . . . 35
Figure3.6 Resultsoftheforcesensorcalibration. . . . . . . . . . . . . . . . . . . 38
Figure3.7 Placementofthemagnetsandreedswitch. . . . . . . . . . . . . . . . . 39
Figure3.8 Themagnetsandreedswitchonthethruster. . . . . . . . . . . . . . . 40
Figure3.9 Outputfromthereedswitch. . . . . . . . . . . . . . . . . . . . . . . . 40
Figure3.10 Theflowmeterusedtomeasureambientwatervelocity. . . . . . . . . . 41
Figure3.11 Theflumetank. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 42
Figure3.12 Thefree-standingtankusedinpropellerangularvelocitytests. . . . . . 44
Figure4.1 Outputofthereedswitch. . . . . . . . . . . . . . . . . . . . . . . . . 49
Figure4.2 Thrustermotorvelocitycomparedtopropellerangularvelocity . . . . . 50
Figure4.3 Comparisonofthrusterinputandpropellerangularvelocity. . . . . . . 51
Figure4.4 Comparisonofthrusterinputandcurrent. . . . . . . . . . . . . . . . . 52
Figure4.5 Hysteresiscurveofthethrusterdeadband . . . . . . . . . . . . . . . . 53
Figure4.6 Biasofforcesensorsovertime. . . . . . . . . . . . . . . . . . . . . . . 58
Figure4.7 Forcebiasovertimeforzeropropellerangularvelocity. . . . . . . . . . 60
Figure4.8 Near-surfaceeffectofpropeller. . . . . . . . . . . . . . . . . . . . . . 61
Figure4.9 Exampleofnear-surfaceeffectsonthrust. . . . . . . . . . . . . . . . . 62
Figure4.10 Thrustcoefficientforpositiveandnegativeambientwatervelocities . . 63
Figure4.11 ThrustCoefficientcurveforpositiveambientwatervelocity. . . . . . . 64
Figure4.12 ThrustCoefficientcurvefornegativeambientwatervelocity. . . . . . . 64
ix
Figure4.13 Resultsofthelinearthrustmodel,positivewaterspeed. . . . . . . . . . 67
Figure4.14 Resultsofthelinearthrustmodel,positivewaterspeed. . . . . . . . . . 68
Figure4.15 Resultsofthequadraticthrustmodel,positivewaterspeed. . . . . . . . 69
Figure4.16 Resultsofthequadraticthrustmodel,negativewaterspeed. . . . . . . . 70
Figure4.17 Resultsofthelinearandquadraticmodelsfor𝑢 = 0. . . . . . . . . . . 71
Figure4.18 Comparisonoferrorforlinearandquadraticmodels,positive 𝑢. . . . . 73
Figure4.19 Comparisonoferrorforlinearandquadraticmodels,negative𝑢. . . . . 74
Figure4.20 Comparisonoferrorforlinearandquadraticmodels, 𝑢 = 0. . . . . . . 76
Figure4.21 Thrustercommandresponsetimes. . . . . . . . . . . . . . . . . . . . . 77
Figure5.1 ActualandpredictedΩ fornoambientwatervelocity. . . . . . . . . . 82
𝑑
Figure5.2 ActualandpredictedΩ forspecifiedambientwatervelocities. . . . . . 83
𝑑
Figure5.3 ActualandpredictedΩ forspecifiedambientwatervelocities. . . . . . 84
𝑑
Figure5.4 ActualandpredictedΩ forspecifiedambientwatervelocities. . . . . . 85
𝑑
Figure5.5 Thedifferenceinriseandfalltimesforthepropellerangularvelocity. . 87
Figure5.6 Exampleofaniso-parametricmapping. . . . . . . . . . . . . . . . . . 88
Figure5.7 Iso-parametricmap. . . . . . . . . . . . . . . . . . . . . . . . . . . . . 91
Figure5.8 ShiftingIso-parametricmap. . . . . . . . . . . . . . . . . . . . . . . . 93
Figure5.9 Iso-parametricmapping,𝐶0 continuousB-Spline. . . . . . . . . . . . . 94
Figure5.10 Iso-parametricmapping,𝐶2 continuousB-Spline. . . . . . . . . . . . . 95
Figure5.11 Diagramofthethrustercontroller. . . . . . . . . . . . . . . . . . . . . 95
Figure6.1 PIDControllerresponse,positivepropellerangularvelocity. . . . . . . 101
Figure6.2 PIDControllerresponse,negativepropellerangularvelocity. . . . . . . 102
Figure6.3 Summaryofthrustercontrollerstepresponses,±9rad/s. . . . . . . . . 107
Figure6.4 Summaryofthrustercontrollerstepresponses,±26rad/s. . . . . . . . 108
Figure6.5 Summaryofthrustercontrollerstepresponses,±52rad/s. . . . . . . . 109
Figure6.6 Steady-statethrustanderrorforambientwaterspeed𝑢 = 0.000 m/s. . 112
Figure6.7 Steady-statethrustanderrorforambientwaterspeed𝑢 = −0.805 m/s. 112
Figure6.8 Steady-statethrustanderrorforambientwaterspeed𝑢 = −0.669 m/s. 113
Figure6.9 Steady-statethrustanderrorforambientwaterspeed𝑢 = −0.557 m/s. 113
Figure6.10 Steady-statethrustanderrorforambientwaterspeed𝑢 = −0.376m/s. 114
Figure6.11 Steady-statethrustanderrorforambientwaterspeed𝑢 = −0.285 m/s. 114
Figure6.12 Steady-statethrustanderrorforambientwaterspeed𝑢 = −0.205 m/s. 115
Figure6.13 Steady-statethrustanderrorforambientwaterspeed𝑢 = 0.205 m/s. . 115
Figure6.14 Steady-statethrustanderrorforambientwaterspeed𝑢 = 0.285 m/s. . 116
Figure6.15 Steady-statethrustanderrorforambientwaterspeed𝑢 = 0.376m/s. . 116
Figure6.16 Steady-statethrustanderrorforambientwaterspeed𝑢 = 0.557 m/s. . 117
Figure6.17 Steady-statethrustanderrorforambientwaterspeed𝑢 = 0.669 m/s. . 117
Figure6.18 Steady-statethrustanderrorforambientwaterspeed𝑢 = 0.805 m/s. . 118
x
ACKNOWLEDGEMENTS
I’ve had a good deal of support in the course of this research, and I would not have been
abletofinishwithouttheaideofseveralpeopleinmylife.
I’d like to thank my advisers, Brad Buckham and Colin Bradley. Brad spent many hours
withme,pushingmetothinkcriticallyabouteverychoiceImadeandguidingmyunderstanding
of the analytical tools necessary to finish my research. Colin’s guidance kept me focused and
grounded, necessary to keep this research from ballooning out of control. They provided me
with both the funding and knowledge I needed to realize my work from beginning to end.
TheyalsoprovidedspaceandequipmentIneededtoconductmyresearch.
I’d like to thank Alison Proctor, who took me under her wing and guided me throughout
my time here. With her help I was made the transition into mechanical engineering. I gained
both knowledge and skills under her tutelage, and without her the research presented here
wouldnothavebeenpossible.
I’d like to thank the people at the Ocean Technology Laboratory: Jeff Kennedy, Darryl
Gamroth, Emmett Gamroth and Lori Muck. They gave me the tools I needed to construct a
workingapparatus. JeffKennedyimpartedmuchoftheknowledgeandexpertisethatwentinto
the design of my test apparatus. Emmett Gamroth and Darryl Gamroth provided assistance
in the technical aspects of LabView. Lori Muck provided administrative support, keeping the
wheelsturningforwardwhereit’snotalwaysimmediatelyvisible.
I’dliketothankthepeoplewhosupportedmeinthefluidslab: PeterOshkaiandMostafa
Rahimpour. Theygavemetimeontheirflumetank,whichallowedmetorunmyexperiment.
WithouttheirtrainingandequipmentIwouldnothavebeenabletofinish.
I’d like to thank my parents for their support in my academic endeavours. Without their
assistanceIwouldnothavemadeitthroughthelastfewyearsofschool.
I’d like to thank all of my roller derby family, especially the crew of officials all over Van-
couver Island and the islands nearby. They provided me with an outlet for my frustrations,
and the confidence to keep learning and growing. They accepted me into their community,
and gave me a home in a new place. I’d like to thank all of my blues dance family. They
provided me with an escape and welcomed me into this new home I made for myself in this
country.
Andfinally,I’dliketothankmyfriendsthathavesupportedmeemotionallythroughmany
years,uptoandincludingmyreturntoschool. KathrynBrayandCandyTanhavespentmany
hours getting me through all the difficult times in my life, and without them I wouldn’t have
madeitthisfar.