RAMA - a Low-Cost Modular Control System for Unmanned Aerial Vehicles OndrejˇSpinka

141 Pages·2010·3.53 MB·English

CzechTechnicalUniversity inPrague
FacultyofElectricalEngineering
DepartmentofControlEngineering
RAMA - a Low-Cost Modular Control System for
Unmanned Aerial Vehicles
Doctoral Thesis
ˇ
Ondrˇej Spinka
Prague,December2009
Ph.D.Programme: ElectricalEngineeringandInformation Technology
Branchofstudy: Control EngineeringandRobotics
Supervisor: Doc. Dr. Ing. ZdeneˇkHanza´lek
Copyright
by
OndˇrejSˇpinka
2009
Anysufficientlyadvancedtechnologyisindistinguishable from magic.
ArthurCharlesClarke
Acknowledgements
Inthefirstplace,IwouldliketothankmyadvisorZdeneˇkHanza´lekforhispassionate
support throughout all those years he had to wait for this thesis to materialize (and
for funding me). His patience surely had to endure some rather exacting tests in
the meantime. My big thanks and hughs also belong to my family and friends, for
supporting me in various ways. Namely, I would like to thank Linda Hron´ıkova´ and
MartinMa´dl´ık,forbeingmythesis-matesandmuch,muchmore.
There are many folks that significantly contributed to the RAMA project, and
whosehelphasbeeninvaluable. Namely(inalphabeticalorder),mybigthanksbelong
to: OtaHerm,fordesigningtheServoControlUnit,whichprovedsoreliableoverthe
years; Ondˇrej Holub, for his gratuitous help with the control algorithms and CNC
milling; Sˇteˇpa´n Kroupa, for his passionate support and relentless urge to explore all
the blind paths; Jiˇr´ı Novotny´, for his great diligence and for laying the foundations
oftheMainControlComputer;MarekPeca,fortheSpejblARMmodule,sensordata
fusionalgorithmsandothersupport;PavelP´ısˇa,forhisinspiringingenuity,invaluable
advice and deep knowledge, and for being my mentor; Michal Sojka, for his great
support, patience and wisdom, not only in the Linux-relates causes; Petr Svoboda,
a true genius I had the privilege to supervise during his graduate projects, for the
Ground Station and help with the magnetometer; and Miloslav Zˇizˇka, for his help
withembeddedLinuxandthemotherboardfortheMainControlComputer. Maythe
LordRamablessthem.
IwouldalsoliketothanksirArthurCharlesClarke,avisioneer,philosopherand
writer, and to sir Isambard Kingdom Brunell, an ingenious victorian constructor, for
inspiring me to become an engineer. And last but not least, my big thanks belong to
JorgeChamandhisPh.D.comics[1],forthegreatartofprocrastination.
This work was supported by the Ministry of Education of the Czech Republic
underproject1M0567.
CzechTechnicalUniversityinPrague OndrˇejSˇpinka
December 2009
Abbreviations
ACB ActuatorBattery
ACL AttitudeControlLayer
ACM AutomaticControlMode
AP AirbornePart
ARCL AngularRateControlLayer
AVB AvionicsBattery
CFM CriticalFailureMode
CRC CyclicRedundancyCheck
DAM DataAcquisitionModule
DU DecouplingUnit
EC ElectronicContainer
EMC ElectromagneticCompatibility
FOD ForeignObjectDebris
GPS GlobalPositioningSystem
GS GroundStation
IMU InertialMeasurementUnit
IPS InternalPowerSupply
MCC MainControlComputer
MCM ManualControlMode
MCU MicroControllerUnit
NU NavigationUnit
PCB PrintedCircuitBoard
PCL PositionControlLayer
PIO ParallelInput-Output
RC RadioControl
RPM RevolutionsPerMinute
SACM Semi-AutomaticControlMode
SCU ServoControlUnit
TAM Three-AxisMagnetometer
TCAS TrafficCollisionAvoidanceSystem
TDCE TelemetryDataCompositionError
TMM TelemetryMeasurementMessage
TSM TimeSynchronizationMessage
TTL TrajectoryTrackingLayer
vi
VB VehicleBus
VCL VelocityControlLayer
VIC VectorInterruptController
WCU WirelessControlUnit
WDCU WirelessDataCommunicationUnit
YPR Yaw,PitchandRoll
RAMA - a Low-Cost Modular Control System for
Unmanned Aerial Vehicles
Ing. OndˇrejSˇpinka
CzechTechnicalUniversityinPrague,2009
ThesisAdvisor: Doc. Dr. Ing. ZdeneˇkHanza´lek
This thesis presents a modular control system for Unmanned Aerial Vehicles
(UAVs), the RAMA control system. RAMA is a universal, lightweight and compact
autopilotforsmallUAVs,designedandbuiltattheDepartmentofControlEngineer-
ing, Faculty of Electrical Engineering of the Czech Technical University in Prague.
RAMAisdesignedasamodular,distributed,hierarchicalsystem,designedwithem-
phasisonreliabilityandsafety. Itisfault-tolerant,implementinganovelarchitecture,
utilizingthegracefuldegradationandasimplereconfigurationtechniquestomaintain
themostcriticalfunctions. RAMAservesasarelativelycheap,openandmodularre-
searchplatform,allowingtotestvarioushardwareandsoftwaresolutionsanddataac-
quisitionandcontrolalgorithms. Thedataandtechnicalexpertiseispubliclyshared,
allowing other researchers, interested in the field, to participate on the project, or to
useourresultstosupporttheirownwork. RAMAisanexcellentplatformforstudent
work,mainlyintheformofsemestralorgraduationprojects. Itisalsoanoutstanding
toolforthePR(PublicRelations)andadvertisingpurposes,attractingattentionoffu-
ture students. The design and construction, both hardware and software wise, along
withthecontrolalgorithmsandtestingresults,areshowninthisdocument.
Goals and Objectives
Thegoalsofthisworkweresetasfollows:
1. Todesignanddeveloparotorcraft-basedUAV(UnmannedAerialVehicle)with
necessaryon-boardavionics(bothhardwareandsoftware).
2. Todevelopthebasiccontrolschemeandthebasiccontrollaws.
3. Perform flight experiments and acquire flight data, in order to prove the feasi-
bilityoftheproposedsolutions.
4. Thoroughly document the whole project and make the technology and results
publiclyavailableattheInternet.
Contents
1 Introduction 1
1.1 Motivation . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 1
1.2 OutlineandContribution . . . . . . . . . . . . . . . . . . . . . . . . 2
1.3 RelatedWork . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 4
2 FlightMechanicsandMathematicalModelingofaRotorcraft 7
2.1 DefinitionoftheCoordinateSystem . . . . . . . . . . . . . . . . . . 7
2.2 FlightMechanicsofaRotorcraft . . . . . . . . . . . . . . . . . . . . 9
2.2.1 BasicAerodynamics . . . . . . . . . . . . . . . . . . . . . . 9
2.2.2 RotorBladeDynamics . . . . . . . . . . . . . . . . . . . . . 13
2.2.3 HelicopterControlFundamentals . . . . . . . . . . . . . . . 15
2.2.3.1 CollectiveandCyclicControls . . . . . . . . . . . 16
2.2.3.2 TailRotorControl . . . . . . . . . . . . . . . . . . 20
2.2.4 EffectsoftheRotorSpeed . . . . . . . . . . . . . . . . . . . 20
2.2.5 CentreofGravity . . . . . . . . . . . . . . . . . . . . . . . . 21
2.3 MathematicalModelofaRotorcraft . . . . . . . . . . . . . . . . . . 21
2.3.1 HelicopterParameters . . . . . . . . . . . . . . . . . . . . . 23
2.3.2 RigidBodyDynamics . . . . . . . . . . . . . . . . . . . . . 25
2.3.3 MainRotorForcesandMoments . . . . . . . . . . . . . . . 26
2.3.3.1 Thrust . . . . . . . . . . . . . . . . . . . . . . . . 26
2.3.3.2 Torque . . . . . . . . . . . . . . . . . . . . . . . . 27
2.3.3.3 BladeFlappingDynamicsandtheMainRotorMo-
mentsandForces . . . . . . . . . . . . . . . . . . 27
2.3.4 EngineandRotorSpeedModel . . . . . . . . . . . . . . . . 28
2.3.5 FuselageForces . . . . . . . . . . . . . . . . . . . . . . . . . 29
2.3.6 TailSurfacesForcesandMoments . . . . . . . . . . . . . . . 29
2.3.6.1 VerticalFin . . . . . . . . . . . . . . . . . . . . . 29
2.3.6.2 HorizontalFin . . . . . . . . . . . . . . . . . . . . 30
2.3.7 TailRotorForcesandMoments . . . . . . . . . . . . . . . . 31
ix
x CONTENTS
3 ControlSystemHardwareArchitecture 35
3.1 Requirements . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 35
3.2 Overview . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 36
3.3 Components . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 39
3.3.1 MainControlComputer . . . . . . . . . . . . . . . . . . . . 39
3.3.2 NavigationUnit . . . . . . . . . . . . . . . . . . . . . . . . . 39
3.3.3 ServoControlUnit . . . . . . . . . . . . . . . . . . . . . . . 42
3.3.4 WirelessDataCommunicationUnit . . . . . . . . . . . . . . 43
3.3.5 WirelessControlUnit . . . . . . . . . . . . . . . . . . . . . 44
3.4 MechanicalOutfitandHousing . . . . . . . . . . . . . . . . . . . . . 45
3.5 ProblemsandSolutions . . . . . . . . . . . . . . . . . . . . . . . . . 49
3.5.1 InertialMeasurementIssues . . . . . . . . . . . . . . . . . . 49
3.5.2 EMCIssues . . . . . . . . . . . . . . . . . . . . . . . . . . . 52
3.5.3 Three-AxisMagnetometerIssues . . . . . . . . . . . . . . . 53
4 ControlAlgorithms 55
4.1 Overview . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 55
4.2 MeasurementsandSensorDataFusion . . . . . . . . . . . . . . . . . 56
4.3 SISOPIDControllerStructure . . . . . . . . . . . . . . . . . . . . . 59
4.4 Low-LevelControlLoops. . . . . . . . . . . . . . . . . . . . . . . . 61
4.4.1 AngularRateControlLayer . . . . . . . . . . . . . . . . . . 61
4.4.2 AttitudeControlLayer . . . . . . . . . . . . . . . . . . . . . 62
5 SoftwareArchitecture 65
5.1 Overview . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 65
5.2 BasicPrinciplesofFunction . . . . . . . . . . . . . . . . . . . . . . 65
5.3 MainControlComputerSoftwareFramework . . . . . . . . . . . . . 68
5.3.1 ControllerLibrary . . . . . . . . . . . . . . . . . . . . . . . 68
5.3.2 LibraryforCANCommunication . . . . . . . . . . . . . . . 68
5.3.3 LibraryforTCP/IPCommunication . . . . . . . . . . . . . . 68
5.3.4 MainProgram . . . . . . . . . . . . . . . . . . . . . . . . . 69
5.4 DataAcquisitionModuleSoftware . . . . . . . . . . . . . . . . . . . 71
5.5 ServoControlUnitFirmware . . . . . . . . . . . . . . . . . . . . . . 73
5.6 GroundStation . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 74
6 ControlSystemSafety 75
6.1 Overview . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 75
6.2 ControlSystemFailureModes . . . . . . . . . . . . . . . . . . . . . 76
6.2.1 MainControlComputerFailureModes . . . . . . . . . . . . 76
6.2.2 NavigationUnitFailureModes. . . . . . . . . . . . . . . . . 78
6.2.3 ServoControlUnitFailureModes . . . . . . . . . . . . . . . 79
6.2.4 CommunicationFailureModes. . . . . . . . . . . . . . . . . 79