Microcontroller Based Applied Digital Control

313 Pages·2006·5.42 MB·English

JWBK063-FM JWBK063-Ibrahim January4,2006 18:11 CharCount=0
Microcontroller Based
Applied Digital Control
MicrocontrollerBasedAppliedDigitalControl D.Ibrahim
(cid:1)C 2006 John Wiley & Sons, Ltd. ISBN: 0-470-86335-8
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Microcontroller Based
Applied Digital Control
Dogan Ibrahim
Department of Computer Engineering
Near East University, Cyprus
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LibraryofCongressCataloging-in-PublicationData
Ibrahim,Dogan.
Microcontrollerbasedapplieddigitalcontrol/DoganIbrahim.
p. cm.
ISBN0-470-86335-8
1.Processcontrol—Dataprocessing. 2.Digitalcontrolsystems—Designandconstruction. 3.Microprocessors.
I.Title.
TS156.8.I1262006
629.8(cid:2)9—dc22 2005030149
BritishLibraryCataloguinginPublicationData
AcataloguerecordforthisbookisavailablefromtheBritishLibrary
ISBN-13 978-0-470-86335-0(HB)
ISBN-10 0-470-86335-8(HB)
Typesetin10/12ptTimesbyTechBooks,NewDelhi,India
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Contents
Preface xi
1 Introduction 1
1.1 TheIdeaofSystemControl 1
1.2 ComputerintheLoop 2
1.3 CentralizedandDistributedControlSystems 5
1.4 ScadaSystems 6
1.5 HardwareRequirementsforComputerControl 7
1.5.1 GeneralPurposeComputers 7
1.5.2 Microcontrollers 8
1.6 SoftwareRequirementsforComputerControl 9
1.6.1 Polling 11
1.6.2 UsingExternalInterruptsforTiming 11
1.6.3 UsingTimerInterrupts 12
1.6.4 BallastCoding 12
1.6.5 UsinganExternalReal-TimeClock 13
1.7 SensorsUsedinComputerControl 14
1.7.1 TemperatureSensors 15
1.7.2 PositionSensors 17
1.7.3 VelocityandAccelerationSensors 20
1.7.4 ForceSensors 21
1.7.5 PressureSensors 21
1.7.6 LiquidSensors 22
1.7.7 AirFlowSensors 23
1.8 Exercises 24
FurtherReading 25
2 SystemModelling 27
2.1 MechanicalSystems 27
2.1.1 TranslationalMechanicalSystems 28
2.1.2 RotationalMechanicalSystems 32
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vi CONTENTS
2.2 ElectricalSystems 37
2.3 ElectromechanicalSystems 42
2.4 FluidSystems 44
2.4.1 HydraulicSystems 44
2.5 ThermalSystems 49
2.6 Exercises 52
FurtherReading 52
3 ThePICMicrocontroller 57
3.1 ThePICMicrocontrollerFamily 57
3.1.1 The10FXXXFamily 58
3.1.2 The12CXXX/PIC12FXXXFamily 59
3.1.3 The16C5XFamily 59
3.1.4 The16CXXXFamily 59
3.1.5 The17CXXXFamily 60
3.1.6 ThePIC18CXXXFamily 60
3.2 MinimumPICConfiguration 61
3.2.1 ExternalOscillator 63
3.2.2 CrystalOperation 63
3.2.3 ResonatorOperation 63
3.2.4 RCOperation 65
3.2.5 InternalClock 65
3.3 SomePopularPICMicrocontrollers 66
3.3.1 PIC16F84Microcontroller 67
3.3.2 PIC16F877Microcontroller 71
3.4 Exercises 75
FurtherReading 76
4 ProgrammingPICMicrocontrollersinC 77
4.1 PICCLiteVariableTypes 78
4.1.1 Bit 78
4.1.2 UnsignedChar 78
4.1.3 SignedChar 79
4.1.4 UnsignedInt 79
4.1.5 SignedInt 79
4.1.6 Long 79
4.1.7 UnsignedLong 79
4.1.8 Float 80
4.1.9 Double 80
4.2 Variables 80
4.3 CommentsinPrograms 81
4.4 StoringVariablesintheProgramMemory 82
4.5 StaticVariables 82
4.6 VolatileVariables 83
4.7 PersistentVariables 83
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CONTENTS vii
4.8 AbsoluteAddressVariables 83
4.9 Bank1Qualifier 83
4.10 Arrays 84
4.11 ASCIIConstants 86
4.12 ArithmeticandLogicOperators 86
4.13 NumberBases 89
4.14 Structures 89
4.15 ProgramFlowControl 91
4.15.1 If–ElseStatement 91
4.15.2 Switch–CaseStatement 92
4.15.3 ForStatement 94
4.15.4 WhileStatement 95
4.15.5 DoStatement 95
4.15.6 BreakStatement 96
4.15.7 ContinueStatement 96
4.16 FunctionsinC 96
4.16.1 UserFunctions 97
4.16.2 Built-inFunctions 98
4.17 PointersinC 99
4.18 Pre-processorCommands 101
4.18.1 #define 101
4.18.2 #include 103
4.18.3 #asmand#endasm 103
4.19 AccessingtheEEPROMMemory 104
4.20 InteruptsinCPrograms 104
4.21 DelaysinCPrograms 105
4.22 StructureofaCProgram 105
4.23 PICMicrocontrollerInput–OutputInterface 107
4.23.1 ConnectinganLED 107
4.23.2 ConnectingaPush-ButtonSwitch 109
4.23.3 ConnectinganLCD 111
4.24 Exercises 116
FurtherReading 117
5 MicrocontrollerProjectDevelopment 119
5.1 HardwareandSoftwareRequirements 119
5.2 ProgramDevelopmentTools 120
5.2.1 FlowCharts 121
5.2.2 StructureCharts 121
5.2.3 Pseudocode 123
5.3 Exercise 129
FurtherReading 129
6 SampledDataSystemsandthez-Transform 131
6.1 TheSamplingProcess 131
6.2 Thez-Transform 136
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viii CONTENTS
6.2.1 UnitStepFunction 137
6.2.2 UnitRampFunction 137
6.2.3 ExponentialFunction 138
6.2.4 GeneralExponentialFunction 138
6.2.5 SineFunction 139
6.2.6 CosineFunction 139
6.2.7 DiscreteImpulseFunction 140
6.2.8 DelayedDiscreteImpulseFunction 140
6.2.9 Tablesofz-Transforms 140
6.2.10 Thez-TransformofaFunctionExpressedasaLaplaceTransform 140
6.2.11 Propertiesofz-Transforms 143
6.2.12 Inversez-Transforms 145
6.3 PulseTransferFunctionandManipulationofBlockDiagrams 154
6.3.1 Open-LoopSystems 154
6.3.2 Open-LoopTimeResponse 156
6.3.3 Closed-LoopSystems 162
6.3.4 Closed-LoopTimeResponse 166
6.4 Exercises 166
FurtherReading 169
7 SystemTimeResponseCharacteristics 171
7.1 TimeResponseComparison 171
7.2 TimeDomainSpecifications 174
7.3 Mappingthes-Planeintothez-Plane 177
7.4 DampingRatioandUndampedNaturalFrequencyinthez-Plane 178
7.4.1 DampingRatio 178
7.4.2 UndampedNaturalFrequency 179
7.5 DampingRatioandUndampedNaturalFrequencyUsingFormulae 181
7.6 Exercises 183
FurtherReading 184
8 SystemStability 187
8.1 FactorizingtheCharacteristicEquation 187
8.2 Jury’sStabilityTest 189
8.3 Routh–HurwitzCriterion 192
8.4 RootLocus 194
8.5 NyquistCriterion 201
8.6 BodeDiagrams 205
8.7 Exercises 208
FurtherReading 211
9 DiscreteControllerDesign 213
9.1 DigitalControllers 214
9.1.1 Dead-BeatController 215
9.1.2 DahlinController 217
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CONTENTS ix
9.1.3 Pole-PlacementControl–Analytical 219
9.1.4 Pole-PlacementControl–Graphical 222
9.2 PIDController 230
9.2.1 SaturationandIntegralWind-Up 233
9.2.2 DerivativeKick 233
9.2.3 PIDTuning 134
9.3 Exercises 137
FurtherReading 240
10 ControllerRealization 243
10.1 DirectStructure 243
10.1.1 DirectCanonicalStructure 243
10.1.2 DirectNoncanonicalStructure 245
10.2 CascadeRealization 246
10.3 ParallelRealization 249
10.4 PIDControllerImplementations 250
10.5 MicrocontrollerImplementations 253
10.5.1 ImplementingSecond-OrderModules 254
10.5.2 ImplementingFirst-OrderModules 260
10.5.3 ImplementingHigher-OrderModules 263
10.6 ChoiceofSamplingInterval 263
10.7 Exercises 267
FurtherReading 268
11 LiquidLevelDigitalControlSystem:aCaseStudy 269
11.1 TheSystemSchematic 269
11.2 SystemModel 270
11.3 IdentificationoftheSystem 273
11.4 DesigningaController 274
11.5 Conclusions 278
AppendixA Tableofz-Transforms 283
AppendixB MATLABTutorial 285
Index 307
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Preface
Computersnowformanintegralpartofmostreal-timecontrolsystems.Withtheadventofthe
microprocessorsandmicrocontrollersinthelastfewdecadestheuseofcomputersincontrol
applicationshasbeenevergrowing.Microcontrollersaresingle-chipcomputerswhichcanbe
usedtocontrolreal-timesystems.Suchcontrollersarealsoreferredtoasembeddedreal-time
computers.Thesedevicesarelow-cost,single-chipandeasytoprogram.Microcontrollershave
traditionallybeenprogrammedusingtheassemblylanguageofthetargetprocessor.Itisnow
possibletoprogramthesedevicesusinghigh-levellanguagessuchasBASIC,PASCAL,orC.
Asaresultofthis,verycomplexcontrolalgorithmscanbedevelopedandimplementedonthe
microcontrollers.
Thisbookisaboutthetheoryandpracticeofmicrocontrollerbasedautomaticcontrolsystems
engineering.Apreviousknowledgeofmicrocontrollerhardwareorsoftwareisnotrequired,
butthereaderwillfinditusefultohavesomeknowledgeofacomputerprogramminglanguage.
Chapter1ofthebookpresentsabriefintroductiontothecontrolsystemsandtheelementsof
computerbasedcontrolsystems.Somepreviousknowledgeofthetheoryofcontinuous-time
controlsystemsishelpfulinunderstandingthismaterial.
Chapter2isaboutsystemmodelling.Modellingadynamicsystemisthestartingpointin
controlengineering.Modelsofvariousmechanical,electrical,andfluidsystemsareintroduced
inthischapter.
Chapter3isdevotedtothepopularPICmicrocontrollerfamilywhichisdescribedandused
inthisbook.ThePICfamilyisoneofthemostwidelyusedmicrocontrollersincommercialand
industrialapplications.Thechapterdescribesthefeaturesofthisfamily,andbasicapplication
notesarealsogiven.
ThebookisbasedontheCprogramminglanguageknownasPICCLite.Thisisdistributed
freebyHi-TechSoftwareandisusedtoprogramthePICfamilyofmicrocontrollers.Chapter
4givesabriefintroductiontothefeaturesofthislanguage.
ThemicrocontrollerprojectdevelopmentcycleisdescribedinsomedetailinChapter5.The
knowledgeofthemicrocontrollerdevelopmentcycleisimportantasthedevelopedcontroller
algorithmhastobeimplementedonthetargetmicrocontroller.
Chapters6and7aredevotedtotheanalysisofdiscrete-timesystems.Thetermsdiscrete-
timesystem,sampled-datasystemanddigitalcontrolsystemareallusedinterchangeablyinthe
bookandrefertothesametopic.Thesamplingprocess,z-transforms,andthetimeresponse
ofdiscrete-timesystemsareexplainedindetailinthesetwochapters.
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xii PREFACE
Thestabilityofacontrolsystemisoneofthemostimportanttopicsincontrolengineering.
Chapter 8 analyses the stability of digital control systems with examples, using the various
well-establishedanalyticalandgraphicalstabilitytechniques.
The analysis and design of digital controllers are described in Chapter 9, where various
digitalcontrolleralgorithmsaredevelopedwithexamples.
After a digital controller is designed, it has to be implemented on the microcontroller;
this is known as the realization of the controller. Chapter 10 describes various realization
techniques, describing the advantages and disadvantages of each technique. Programming
examplesaregiventoshowhowaparticularrealizationcanbeprogrammedandimplemented
onamicrocontroller.
Finally, Chapter 11 presents a case study. A liquid level control system is modelled and
thenasuitabledigitalcontrolleralgorithmisdeveloped.Thealgorithmisthenimplemented
onaPICmicrocontroller.Thetimeresponseofthesystemisgiven,alongwithafullprogram
listingofthealgorithm.
Many people have assisted in the production and development of this book. In particular,
I wish to acknowledge the contribution of the students and staff members of the Computer
EngineeringDepartmentoftheNearEastUniversity.
DoganIbrahim
NearEastUniversity