PID Control in the Third Millennium: Lessons Learned and New Approaches

599 Pages·2012·10.69 MB·English

by  Aidan O’Dwyer (auth.)

Advances in Industrial Control
Forfurthervolumes:
www.springer.com/series/1412
Ramon Vilanova (cid:2) Antonio Visioli
Editors
PID Control in the
Third Millennium
Lessons Learned and New Approaches
Editors
RamonVilanova AntonioVisioli
DeptofTelecommunic.&SystemsEngin. FacoltàdiIngegneria,Dipto.Elettronicaper
SchoolofEngineering l’Automazione
UniversitatAutònomadeBarcelona UniversitàBrescia
Barcelona Brescia
Spain Italy
ISSN1430-9491 e-ISSN2193-1577
AdvancesinIndustrialControl
ISBN978-1-4471-2424-5 e-ISBN978-1-4471-2425-2
DOI10.1007/978-1-4471-2425-2
SpringerLondonDordrechtHeidelbergNewYork
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Series Editors’ Foreword
The series Advances in Industrial Control aims to report and encourage technol-
ogy transfer in control engineering. The rapid development of control technology
has an impact on all areas of the control discipline. New theory, new controllers,
actuators, sensors, new industrial processes, computer methods, new applications,
new philosophies..., new challenges. Much of this development work resides in
industrialreports,feasibilitystudypapersandthereportsofadvancedcollaborative
projects.Theseriesoffersanopportunityforresearcherstopresentanextendedex-
position of such new work in all aspects of industrial control for wider and rapid
dissemination.
TheEditorsoftheAdvancesinIndustrialControlserieshavelonghadapolicyof
supportingthepublicationofmonographsaboutthedifferentaspectsofPIDcontrol
and its implementation. This recognises the incontrovertible fact that PID control
is the ubiquitous controller applied in industry. At the turn of the century and the
beginningofthenewmillennium,theEditor-in-ChiefoftheInstrumentSocietyof
AmericaTransactionsconductedaninformalsurveyofaround100industrialcon-
trol experts and academics to determine “The Century’s Greatest Contributions to
ControlPractice”[1].Theresultsmakeinterestingreading,forinCategory3:Con-
trols,decisionandcommunicationsinstrumentation,thePIDcontrollertooksecond
place,beatenonlybythemicroprocessor.Nevertheless,boostedbyindustrialvotes,
theZeigler–NicholstuningmethodcametopofCategory2:Techniques.Theseare
some indicators of just how important the PID control field is to some industrial
sectors,especiallytheprocessindustries.
The Advances in Industrial Control Series Editors’ interest in supporting pub-
lications on PID control theory, implementation, and applications has produced a
goodlibraryofPID-focussedmonographsfortheseriesovertheyears:
1999 C.C.Yu:AutotuningofPIDControllers.ISBN978-3-540-76250-8;
1999 A. Datta, M.T. Ho and S.P. Bhattacharyya: Structure and Synthesis of PID
Controllers.ISBN978-1-85233-614-1;
1999 K.K.Tan,Q.-G.WangandC.C.HangwithT.J.Hagglund:AdvancesinPID
Control.ISBN978-1-85233-138-2;
2006 A.Visioli:PracticalPIDControl.ISBN978-1-84628-585-1;
v
vi SeriesEditors’Foreword
2007 A.W. Ordys,D.Uduehi,M.A. Johnson (eds.): Process ControlPerformance
Assessment.ISBN978-1-84628-623-0;
2010 A. Visioli and Q.-C. Zhong: Control of Integral Processes with Dead Time.
ISBN978-0-85729-069-4;and
2011 T.LiuandF.Gao:IndustrialProcessIdentificationandControlDesign.ISBN
978-0-85729-976-5.
In making the above list, Advances in Industrial Control series volumes of re-
lated interest, for example, on controller performance assessment, windup in con-
trol,fragilityofdigitalcontrollersandmanyindustrialapplications,havenotbeen
listed.So,justwhenitmightbethoughtthatthereislittlemoretobewrittenonPID
controller design, implementation and applications, PID Control in the Third Mil-
lenniumcollatedbyEditors,RamonVilanovaandAntonioVisioliprovidesatimely
reminderthatthisresearchfieldisstillvibrantlyactive.
Ateighteenchapters,thebookshowshowthemorerecentdevelopmentsincon-
trolsystemstheoryhavehadanimpactonPIDcontroldesignandhighlightsareas
where theory and technology have the potential to force changes on the software
and hardware of the PID control device. The book’s editors have managed to col-
lect,collateandevencontributetosomefascinatingchapters,andeachreaderwill
find aspects from the different contributions that illuminate or provide insight for
theirownparticularinterestsinthisveryextensivecontrolfield.
HistoricalBackground
AidanO’Dwyeriswellknownforhisencyclopaedicvolume[2],andhecontributes
anopeningchapterthatveryusefully updatesthereader onrecenttrends foundin
publicationsinthisstillgrowingfield.Inthischapter,thereaderwillalsofindsome
nicelybalancedremarksabouttheindustrialuptakeofpublicationsofthisresearch.
Principlesand Taxonomy
Having attempted to create a classification framework for PID control methods in
thepast[3],itwasinterestingtoseestructuralprinciplesconvergingtoatwo-branch
treethatwasfoundatvariouspointsinthevolume.However,authorsappliedvarious
names to the two branches, “model-based versus model-free”, “parametric versus
non-parametric”,andborrowingterminologyfromadaptivecontrol,“indirectversus
directmethods”.Thesetermsreflectedtheimportanceofwhetherornotanexplicit
model identification step was involved or whether the PID controller parameters
weregoingtobecomputeddirectlyfromtheprocessdata/knowledgebut,whichever
routewasselected,theessentialpracticaloutcomewasacarefulprescriptionforthe
wayprocessdatawascollected(detailsoftheexperimentalframeworktobeused)
andprocessed.
SeriesEditors’Foreword vii
Fig.1 AspectsofPIDcontrollerdesign
DesignforPIDControl
Theinfluenceofmethodsfromthemainstreamofnewcontroldesigntechniquesis
wellcapturedacrosstheeighteenchaptercontributions.Asummaryofmostofthe
designdirectionsisbestcapturedbytheschematicinFig.1.
Readingthechapters,oneinterestingobservationisjusthowthoroughlyrobust-
nessissueshavepermeatedthePIDcontroldesignmethod.Evenso,asFig.1shows,
thereareothernewdesignavenuesopeningup:PIDcontrollerfragility,fractional-
orderPIDcontrollers,anddata-drivenPIDmethods,tonamejustthree.
Technology,PIDImplementation, andApplications
A recent article in the IEEE Control Systems Magazine [4], noted that “PID hard-
wareisnowdominatedbyfivemajorvendors—ABB,Emerson,Foxboro(Invensys),
HoneywellandYokogawa”,andthismayaffecttherapidtakeupofnewPIDcon-
troldesignideasandconceptsinPIDhardwaremodules.However,thesamearticle
shows an extensive set of PID software modules and packages (over 25 products
were listed), and this market is probably far more flexible. This is certainly one
avenue for showcasing many of the new and fertile ideas discussed in this book.
One particularly intriguing research direction is the potential of wireless technol-
ogy to change the way PID controllers operate (Chap. 14 by G.K. McMillan). In
averycloselyrelatedchapter,event-basedPIDcontroldesignisinvestigatedusing
aninstructivetutorial-stylepresentation(Chap.16byJ.Sánchez,A.Visioli,andS.
Dormido)thatshouldinterestmanyreaders.
Inarecentconversationwithaformergraduatestudent,nowaprofessionalcon-
trolengineerinalargepetroleumindustrymajor,myenquiriesaboutPIDcontroller
tuning elucidated the response that at his level PID controller tuning was a “rare
bird” and that technicians used simple routines and looked after all the PID con-
trollertuninginthecompany.Thisobservationreturnsustotheissuethatinitiated
viii SeriesEditors’Foreword
thesearchfortheidealpush-buttonPIDtuningmodule;asearchthatwasrevitalised
inthe1980sandsawtheemergenceofÅström’srelaytuningconceptandotherde-
vicesbasedonthesimpleexpertsystemsoftheera.Withallmannerofnewideas
posited in this volume, it will be interesting to see what impact they have on PID
controltechnologyintheyearstocome.
The editors, Ramon Vilanova and Antonio Visioli are to be congratulated on
bringing together this invaluable collection of chapter-length contributions to pro-
videatimelyupdateofprogressinthemanyaspectsofPIDcontrolresearch,devel-
opment,andindustrialapplications.Weshouldalsonotethattheeditorshavedevel-
opedthisbookconceptfromapositionofstrength,fortheyarebothchapterauthors
inthisvolumeandregularcontributorstothisresearchfield.Itisalsoencouraging
to see that a new generation of PID control researchers is now contributing to the
field.
References
1. Rhinehart,R.R.:TheCentury’sgreatestcontributionstocontrolpractice.ISATrans.39,3–13
(2000)
2. O’Dwyer, A.: Handbook of PI and PID Controller Tuning Rules, 3rd edn. Imperial College
Press,London(2009).ISBN:978-1-84816-242-6
3. Johnson, M.A., Moradi, M.H. (eds.): PID Control: New Identification and Design Methods
(2005).ISBN:978-1-85233-7092-5
4. Li,Y.Ang,K.H.,Chong,G.C.Y.:Patents,softwareandhardwareforPIDcontrol:Anoverview
andanalysisofthecurrentart.IEEEControlSyst.26(1),42–54(2006)
IndustrialControlCentre M.A.Johnson
Glasgow,Scotland,UK
Preface
Proportional-Integral-Derivative(PID)controllersarebyfarthemostadoptedcon-
trollers in industry owing to the advantageous cost/benefit ratio that they are able
toprovide.Inthelastcentury,alargenumberofresearchershaveconsideredthem,
andindustrialproductshaveimprovedtheirfunctionalitysignificantly.
ProposalsforthedesignandtuningofPIDbasedcontrolsystemshavegenerated
a really vast literature during the last decades. This sparked the special attention
oftheIFACWorkshopPID’00PresentandFutureofPIDcontrolheldinTerrassa,
Spain,inApril2000.Thiseventprovidedastate-of-the-artonmanyaspectsofPID
control,rangingfromspecializedtheoreticalresearchtopicsandtuningmethodsto
interestingreviewsoftechnologicalproducts,patentsandsoftware,confirmingthat
thePIDcontrollercontinuestogeneratedeepinterestandisagoodauguryforfuture
researchinthefieldofPIDcontrollers.
Starting from this special event, in the last ten years there has been a renewed
interestintheresearchonPIDcontrollers,aswitnessedbyalargenumberofpapers
published on this subject. This book gives an overview of the advances made for
PIDcontrollersduringthislastdecade.
The book is divided into four parts in which well-known experts and special-
ists address different topics (one for each chapter) in the following fields: (i) new
approachesfortuningPIDcontrollers;(ii)controlstructuresandconfigurationsfor
PIDcontrol;(iii)issuesinPIDcontrol;(iv)non-standardapproachestoPIDcontrol.
The first part concentrates on tuning methods. It starts with a review provided
by A. O’Dwyer of the extensive literature of proposals for PI and PID controller
tuningrulesbasedonFirst-orderplusDead-timemodels.Thenextchaptersfollow
byconcentratingonspecifictopicsrelatedtoPIDtuning.A.LevaandM.Maggio
discusstheavailabilityofaprocessmodelanditsuseforassessingthebehaviorand
characteristics of the control loop with respect to its robustness and performance,
thereforeaddressingtheproblemofdeterminingwhichtuningmethodisbestsuited
to the particular problem at hand. An exposition of tuning rules for integral and
unstable systems follows. In this chapter, A.S. Rao and M. Chidambaram intro-
duce different design methods for PI/PID controllers for these systems. Different
approachesareconsidered.Inparticular,analytical,IMC,poleplacementandopti-
mizationmethods.Theadvantageofusingatwodegree-of-freedomcontrollerwill
ix
x Preface
alsobeaddressedaswellastherobustnessofthecontrollers.Robustnessisspecif-
ically addressed in Chap. 4 by R. Vilanova, V. Alfaro and O. Arrieta by revisiting
thenewtrendsinrobustPI/PIDtuning.Thischapterreviewsthemainconceptsand
measuresforrobustnessinfeedbacksystemsandreviewstheclassicalandmodern
approachesto robust PID design.The chapteralso presents aseries of newtuning
rules that appeared in the literature during recent years that are based on the use
of the maximum of the sensitivity transfer function as a robustness measure. The
attainmentofsuchrobustnessspecificationturnsouttobeachallengethatsuggests
alternative frameworks for robust PID controller tuning. As a matter of fact, one
of the interests that has appeared in recent years is that of formulating tuning ap-
proaches in the form of simple tuning rules. In that respect, S. Skogestad and C.
Grimholt present the Simple Internal Model Control approach by addressing the
choiceofthetuningparametersforfastandsmoothcontrol.Inaddition,theirnovel
set-point overshootmethodwill be presented as an alternativeapproach. This first
partofthebookconcludeswithachapterdevotedtothecontrolofMIMOsystems.
Q.G. Wang and Z.Y. Nie discuss the specific problems that appear when a MIMO
systemistobecontrolledbyusingPIDcontrollers.Withaspecialemphasisonro-
bustness,PIDcontrollerdesignforMIMOprocessestoachievethedesiredgainand
phasemarginsarepresented.TuningofdecentralizedMIMOPIDcontrollersbased
on such margins is presented. In this way, the robust stability of the multivariable
systemcanbereadilyachievedandguaranteed.
In the second part of the book, attention is turned to special control structures
frequentlyusedinconjunctionwithPIDcontrollersfortheachievementofspecific
purposes.Threechaptersaredevotedtosuchapproaches.Inthefirstchapterofthis
section, J.L. Guzmán, T. Hagglund and A. Visioli expose the use of feedforward
compensationinconjunctionwithafeedbackPIDcontroller.Bothset-pointfollow-
ingandloaddisturbancerejectiontasksareconsidered.Whilefortheset-pointfol-
lowingthegenerationofcausalandnon-causalfeedforwardactionsareconsidered,
fortheloaddisturbanceitisshownthatbothcontrollers(feedbackandfeedforward
should cooperate). The use of alternativefeedbackcompensationschemes such as
the cascade control system for improving disturbance rejection is well known. In
Chap. 8, S. Majhi presents different approaches for such series-feedback compen-
sation schemes as well as dead-time compensation systems for use when there is
a large time delay in the system. This part ends by a chapter that presents consid-
erations for multi-input multi-output processes by addressing the control problem
as a multivariable control problem per se. In this respect, R. Katebi presents and
compares existing multi-loop tuning methods for their stability and performance
robustness and formulates new design guidelines to improve their closed-loop ro-
bustness.
Thethirdpartofthebookpresentsarangeofissuesrelatedtotheapplicationof
aPIDcontroller.Inthisrespect,thispartstartswiththecontributionofK.Tsakalis
andS.Dashthataddressesissuesarisinginsystemidentification-basedplantmodel-
ingforthepurposeoftuningPIDcontrollers.Minimalandmaximalprocessmodel
information methods are considered. Especially attractive are recent methods that
provideseveralnominalmodelsaswellasadescriptionoftheuncertainty,andaim
Preface xi
foratuningthatcombineshighperformance,adequaterobustness,andhighreliabil-
ity.Besidesfindingofagoodmodel,thenominalstabilityofthefeedbackcontrol
system is always the central and first aspect to be considered. When dealing with
a restricted structure controller such as a PI/PID, the problem becomes more dif-
ficult. In Chap. 11, L.H. Keel and S.P. Bhattacharyya provide a design approach
basedonthedeterminationoftheentiresetofPIDcontrollersthatstabilizesagiven
plant.Inaddition,itisshownthattheentiresetofstabilizingPIDcontrollersfora
givenplantcanbefoundwithoutananalyticalmodelbeingavailable.Thischapter
also shows that the complete set of stabilizing PID controllers for a finite dimen-
sional LTI plant, possibly cascaded with a delay, can be calculated directly from
thefrequencyresponse(Nyquist/Bode)data.Oncethecontrollerisobtained,there
are two different aspects that come into the scenario: those of the fragility of the
resultingtuningandperformanceassessment.Thennexttwochaptersdeal,respec-
tively, with these aspects. In Chap. 12, V.M. Alfaro and R. Vilanova provide an
introductiontofragilitymeasuresforPIDcontrollers.Subsequently,thefragilityof
PID controllers tuned with several of the available performance optimized and/or
robust tuning rules will be evaluated using the delta 20 fragility index. The intro-
duction of the fragility as part of the development process of a robust tuning rule
for PID controllers is also considered. Considerations on performance assessment
follow in Chap. 13, authored by A.W. Ordys and M.J. Grimble. Since many PID
controllers are set up using intuition or very approximate tuning rules, it is even
more important that PID designs can be benchmarked and the quality of control
assessed.Furthermore,benchmarkingmethodscanprovideguidanceforcontroller
tuning.Oneoftheadvancesmadeinthelastdecadehasbeenthedevelopmentofthe
so-calledrestrictedstructurebenchmarkingwhichprovidesafigureofmeritwhich
ismuchmorerepresentativeofwhatmightbeachievableifthecontrolleristuned
optimally. The use of these methods for controller tuning is also discussed. This
third part ends with G.K. McMillan’s contribution that introduces industrial con-
siderations for PID based control loops. Different process control applications are
addressedinthischapter,anditisshownhowtodealwiththemwhenusingaPID
controller.Inparticular,challengingapplications(namely,withthepresenceofhigh
valvestiction,largewirelessrefreshtimes,highprocessnonlinearityanddead-time,
multiple process constraints, abnormal operations and communication failures, to
name a few) are discussed. Then, process control operations such as bioreaction,
chemicalreaction,crystallization,distillation,evaporation,neutralizationandcom-
pressionareconsidered.
The last part of the book comprises four chapters devoted to non-standard ap-
proachestoPIDcontrol.TheyconstitutenovelapproachesofPIDcontrolthathave
recentlyappearedinthePIDfield.A(now)verypopularthemeisthatoffractional-
order PID control. B.M. Vinagre and C.A. Monje present the main characteristics
ofFractional-orderControl(FOC),anapproachthathasattractedagrowinginter-
est in the last decade. The application of the fractional order operators to the PID
algorithm, thus giving the fractional-order PID (FOPID) controller, is first intro-
duced. Then, the FOPID controller is studied in both the frequency and the time
domains,andthestructures,thetuningrules,andthewaysfortheirimplementation