MichaelA.Johnson MohammadH.Moradi PIDControl NewIdentificationandDesignMethods Michael A.Johnson and Mohammad H.Moradi (Editors) With J.Crowe,K.K.Tan,T.H.Lee,R.Ferdous,M.R.Katebi,H.-P.Huang, J.-C. Jeng,K.S.Tang,G.R.Chen,K.F.Man,S.Kwong,A.Sánchez, Q.-G. Wang,Yong Zhang,Yu Zhang,P.Martin,M.J.Grimble and D.R. Greenwood PID Control New Identification and Design Methods With285Figures 1 3 MichaelA.Johnson,PhD MohammadH.Moradi,PhD IndustrialControlCentre ElectricalEngineeringGroup UniversityofStrathclyde FacultyofEngineering GrahamHillsBuilding Bu-AliSinaUniversity 50GeorgeStreet Hamadan Glasgow Iran G11QE UK BritishLibraryCataloguinginPublicationData PIDcontrol:newidentificationanddesignmethods 1.PIDcontrollers I.Johnson,MichaelA.,1948- II.Moradi,MohammadH. (MohammadHassan),1967- 629.8 ISBN1852337028 LibraryofCongressCataloginginPublicationData PIDcontrol:newidentificationanddesignmethods/MichaelA.Johnson (editor),MohammedH.Moradi(editor);withJ.Crowe...[etal.] p. cm. Includesbibliographicalreferencesandindex. ISBN1-85233-702-8 1.PIDcontrollers–Designandconstruction.I.Johnson,MichaelA.,1948-II.Moradi, MohammadH.(MohammadHassan),1967-III.Crowe,J. TJ223.P55P532005 629.8--dc22 2004057797 Apartfromanyfairdealingforthepurposesofresearchorprivatestudy,orcriticismorreview,aspermittedunderthe Copyright,DesignsandPatentsAct1988,thispublicationmayonlybereproduced,storedortransmitted,inanyformorbyany means,withthepriorpermissioninwritingofthepublishers,orinthecaseofreprographicreproductioninaccordancewith thetermsoflicencesissuedbytheCopyrightLicensingAgency.Enquiriesconcerningreproductionoutsidethoseterms shouldbesenttothepublishers. ISBN-10:1-85233-702-8 ISBN-13:978-1-85233-702-5 SpringerScience+BusinessMedia springeronline.com ©Springer-VerlagLondonLimited2005 MATLAB®andSIMULINK®areregisteredtrademarksofTheMathworksInc.,3,AppleHillDrive,Natick,MA01760-2098,USA. http://www.mathworks.com/ LabVIEW™isaregisteredtrademarkofNationalInstrumentsCorporation,11500,N.MopacExpwy.,Austin,TX78759-3504, USA. SIMATIC®isaregisteredtrademarkofSiemensAG,Germany. DeltaV™isatrademarkofEmersonProcessManagement. Plantweb®isaregisteredtrademarkofEmersonProcessManagement. Theuseofregisterednames,trademarks,etc.inthispublicationdoesnotimply,evenintheabsenceofaspecificstatement, thatsuchnamesareexemptfromtherelevantlawsandregulationsandthereforefreeforgeneraluse. Thepublishermakesnorepresentation,expressorimplied,withregardtotheaccuracyoftheinformationcontainedinthis bookandcannotacceptanylegalresponsibilityorliabilityforanyerrorsoromissionsthatmaybemade. Typesetting:IanKingstonPublishingServices,Nottingham,UK PrintedintheUnitedStatesofAmerica 69/3830-543210 Printedonacid-freepaper SPIN10894354 For the gift ofloving parents and family and for my grandchildren,Ethan and Teigan MichaelA.Johnson To my wife,Mehri,and my sons,Arefand Ali,for their understanding and consideration;To my parents for their love over many years and to my family for their support. MohammadH.Moradi Preface Theindustrialevidenceisthatformanycontrolproblems,particularlythoseoftheprocessindustries, theProportional,IntegralandDerivative(PID)controlleristhemaincontroltoolbeingused.Forthese industrial problems,the PID control module is a building block which provides the regulation and disturbance rejection for single loop, cascade, multi-loop and multi-input multi-output control schemes. Over the decades, PID control technology has undergone many changes and today the controllermaybeastandardutilityroutinewithinthesupervisorysystemsoftware,adedicatedhard- ware process controller unit or an input–output module within a programmable electronic system whichcanbeusedforcontrolsystemconstruction. With such a well-developed industrial technology available it is not surprising that an academic colleagueonlearningthatweplannedabookonPIDcontrolexclaimed,“Surelynot!Isthereanything lefttobesaid?”.Ofcourse,theshortansweristhattechnologydoesnotstandstill:newsolutioncapabil- itiesarealwaysemergingandPIDcontrolwillevolvetoo.Indeed,theZiegler–Nicholsruleshavebeen famousforoversixtyyearsandtheÅströmandHägglundrelayexperimenthasbeenaroundfortwenty years,soitwouldbedisappointingifsomenewapproachestoPIDcontrolhadnotemergedinthemean- time.However,thatisnottoclaimthatallthemethodsdiscussedinthisbookwillreplaceexistingtech- nologies;noristhisbookadefinitivesurveyof allthathastakenplaceinthedevelopmentsof PID controlsince,say,1985.Thebookwasoriginallyconceivedasasetofchaptersaboutnewideasthatare beinginvestigatedinPIDcontrol;itmightbemoreaccuratelysubtitled“Somenewidentificationand designmethods”. Thefirstproposalsforthisbookwereconstructedusingaclassificationschemebasedontheextentto whichamethodusedamodel,thenwhattypeofmodelandthenwhetherthemethodusedoptimisation principlesornot;averyacademicapproach.Suchaschemedoeswork,but,asonereviewerremarked,it isperhapsunnecessarilyrigid.However,anotherobjectiveoftheEditorswastoincorporateintothetext asetofcontributionsfrominternationalauthors,andthisismoredifficulttoachievewithaverystrict classificationframework.Consequently,thefinishedbookhasamorerelaxedstructurebutretainsan inherentmethodologicalagenda. ThebookopenswithtwobasicchaptersaboutPIDcontrollers.Industrialtechnologyisexamined using discussions,examples and pictures in Chapter 1.Two interesting industrial product reviews significantlyaddtothevalueofthischapter.Chapter2isconstructedaroundasetofusefulconcepts whichsaymoreaboutthePIDnotationandconventionsthananythingelse.Thematerialinthesetwo openingchaptersisdescriptiveandinformative;someofitistheory,butitisselective.Itisdesignedto bepartlyarepositoryofexistingtechnologyandexpertiseandpartlyanintroductiontosomeofthe terminologyandconceptsthatwillbeusedinsubsequentchapters.Thesectionsinthesetwochapters viii Preface arewrittenwithsomerepetitionofmaterialtoenableindividualsectionstobereadinisolationwhen usingthetextinreferencemode. Thisisfollowedby11chaptersthatmakedifferentcontributionstoideasforidentificationforPID control,andtothetuningofPIDcontrollers.Almostallofthecontributionsarisefromproblemsand researchissueswhichhaveintriguedthevariousauthors,andthechaptersdescribesomeanswersto theseproblems.Thisisnotjusttheleaveningofasetofthevariousauthors’publishedpapersbutafully explainedpresentationoftheinvestigativedirectionsbeingfollowedbythecontributors.TheEditors hopethatthereaderwillfindthepresentationsquitereadableandbeabletofollowuptheresearch literaturedirectly. Theunderlyingcontinuityinthebookisthat,asthechaptersfolloweachother,thequalityofmodel informationusedbytheproblemformulationandsolutionincreases.ThisagendastartsatChapter3, wherethemethodsassumenomodelinformationatall.Thenextgroupofchapters,numbers4to7,use nonparametric models. Because the reaction curve method is historically associated with nonparametricmethods,Chapter8onextensionstothereactioncurvemethodisplacednext.Inthegap betweennonparametricandparametricmodel-basedmethods,Chapters9and10reportonthegenetic algorithmsandfuzzymodelapproachandonaso-calledsubspaceidentificationmethod,respectively. Finally,methodsbasedonparametricmodelstakethestageinthefinalthreechaptersofthebook.The lastofthesechapterslooksattheideaofpredictivePIDcontrol. The emphasis within each chapter varies depending on what is important to the method being described.Forexample,achaptermightdescribehowtoobtaintheappropriatemodelinformationfora PIDcontroldesignmethod,orhowtousetheappropriatemodelinformationinPIDcontroldesign algorithm;sometimesbothaspectsofidentificationanddesignaretreated.Atnopointcanitbeclaimed thatexistingPIDtuningmethodsaretreatedsystematically;rather,thebookhassomechaptersthat explainsomenewideas,whilstinotherchaptersexistingtechniquesaregivenandthenextended,rein- terpretedandrenovated.ThebookismostcertainlynotacookbookforPIDcontroltuningrecipes,and toreturntoourcolleague’ssurprised,“Isthereanythinglefttobesaid?”,thebooknowwrittenshows clearlythatthePIDcontrolstillhasmanyavenuestobeexplored. Thisisalsotheplacetogivethankstovariouspeoplewhohavebeensohelpfulinthecompilation, constructionandproductionofthebook.Allthecontributorsareverygratefullythankedforagreeing toparticipateandfortheirpatienceduringtheeditorialperiod.Itwasanextraordinarypleasureto meetsomeofthemattheirhomeinstitutionsinSingaporeandTaipei,Taiwan,in2000,andothersat variousrecentinternationalcontrolconferences. ProfessorM.J.GrimbleisgratefullythankedforallowingEmeritusProfessorM.A.Johnsontheuseof facilitiesattheIndustrialControlCentre,UniversityofStrathclydeinGlasgow,duringthewritingof thisbook. Finally,theEditorswouldliketothankthepublishingstaffatSpringer-VerlagLondon,OliverJackson andAnthonyDoyle,andatSpringerVerlag’sNewYorkoffices,JennyWolkowicki,fortheirkindencour- agement,andpatienceduringthegestationperiodofthebook.Alsothecopyeditorandtypesetter,Ian Kingston,isthankedforhisthoroughnesswiththemanuscriptandfortheexcellentmoderntypograph- icalinterpretationofthetext. MichaelA.JohnsonandMohammadH.Moradi December2004 How to Use This Book Inmanycasestheproductionofacontributedbookleadstoanopuswhichlookslikesetofcollected papersfromtheauthors.Inthecaseof thisbook,carehasbeentakentohavesufficientexplanation introducedsothatthebookmightalsobeusedconstructively.Withthisagenda,thetypicalstructure forachapteris: (cid:1) Learningobjectives (cid:1) Introductorymaterial (cid:1) Mainalgorithmsdescribed (cid:1) Workedexamplesandcasestudies (cid:1) Conclusionsanddiscussion (cid:1) Referencesandbibliography Thusitishopedthatthisbookcanbeusedfor: (cid:1) Supportmaterialforpossibleadvancedcoursestudy (cid:1) Selfstudybyindustrialandacademiccontrolengineers (cid:1) Asourceforfutureresearchideasandprojects (cid:1) Areferenceresourceandasourceofreferences (cid:1) ContactingresearchersworkingonparticularPIDcontroltopics Toassistthereaderinnavigatingthevariousapproachesandmethodsitisusefultohaveamapofthe book.Firstly,thedesignapproachesaregivenbroaddefinitions,andatreediagramofthebookstruc- turefollows.Thebroadclassificationschemethathasbeenusedtoorganisethisbookisbasedonthe qualityandtypeoftheprocessmodelinformationusedandthenwhetherornotoptimisationconcepts havebeenusedtogeneratethePIDcontrollertunings.Abriefdescriptionofthemaincategoriesfollows next. (cid:1) Model-freemethods:themethoddoesnotusetheexplicitidentificationofsignificantmodelpointsor aparametricmodelperse. (cid:1) Nonparametric model methods: the method uses the explicit identification of significant model pointsoranonparametricmodel,butdoesnotuseaparametricmodelperse. x HowtoUseThisBook (cid:1) Data-intensive methods: these methods are halfway between the nonparametric and parametric model-basedmethods.Theyarecharacterisedbytheuseofprocessdata,asinthesubspacemethod, orgreyknowledge,asinthecaseoffuzzy-logicmethods. (cid:1) Parametricmodelmethods:themethodstraightforwardlydependsontheuseofaparametricmodel; usuallyatransferfunctionmodel. Thesecondcategorisationdependsonwhetherthetuningmethodusesoptimisationconcepts.Asan example,manyoptimisation-basedmethodsusetheappropriateclassiclinearquadraticcostfunction overadeterministicorstochasticproblemformulation.Figure1showsthetreediagrammapof the bookchapters. PIDtuningmethods Basicmaterial:Chapters1and2 Model-free Non-parametric Data-intensive Parametric methods methods methods methods Optimal Non-optimal Non- Optimal Non- Optimal methods methods optimal methods optimal methods methods methods Chapter3 Chapters4,5,6,7 Chapter Chapters Chapter9 10 Chapters 12,13 4,8,11, Figure1 Bookchapters:treediagrammap. Contents EditorialResponsibilities · · · · · · · · · · · · · · · · · · · · · · · · · · · · · · · · · · · · · · · · · · · xix Notation · · · · · · · · · · · · · · · · · · · · · · · · · · · · · · · · · · · · · · · · · · · · · · · · · · · · · · · xxv 1 PIDControlTechnology · · · · · · · · · · · · · · · · · · · · · · · · · · · · · · · · · · · · · · · · 1 LearningObjectives . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 1 1.1 BasicIndustrialControl . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 2 1.1.1 ProcessLoopIssues–aSummaryChecklist . . . . . . . . . . . . . . . . . . . . . . . . . 6 1.2 Three-TermControl . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 7 1.2.1 ParallelPIDControllers . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 9 1.2.2 ConversiontoTimeconstantPIDForms . . . . . . . . . . . . . . . . . . . . . . . . . . . 10 1.2.3 SeriesPIDControllers . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 12 1.2.4 SimplePIDTuning . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 14 1.3 PIDControllerImplementationIssues . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 17 1.3.1 Bandwidth-LimitedDerivativeControl . . . . . . . . . . . . . . . . . . . . . . . . . . . . 18 1.3.2 ProportionalKick . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 22 1.3.3 DerivativeKick . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 24 1.3.4 IntegralAnti-WindupCircuits . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 26 1.3.5 Reverse-ActingControllers . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 29 1.4 IndustrialPIDControl . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 29 1.4.1 TraditionalIndustrialPIDTerms . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 30 1.4.2 IndustrialPIDStructuresandNomenclature . . . . . . . . . . . . . . . . . . . . . . . . . 32 1.4.3 TheProcessControllerUnit . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 33 1.4.4 SupervisoryControlandtheSCADAPIDController . . . . . . . . . . . . . . . . . . . . 35 Acknowledgements . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 46 References . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 46 2 SomePIDControlFundamentals · · · · · · · · · · · · · · · · · · · · · · · · · · · · · · · · · 47 LearningObjectives . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 47 2.1 ProcessSystemModels . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 48 2.1.1 StateSpaceModels . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 49 2.1.2 ConvolutionIntegralProcessModels . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 52 2.1.3 LaplaceTransferFunctionModels . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 53
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