Table Of ContentAdvances in Industrial Control
Forfurthervolumes:
www.springer.com/series/1412
Mohieddine Jelali
Control Performance
Management
in Industrial
Automation
Assessment, Diagnosis and Improvement
of Control Loop Performance
Dr.-Ing.MohieddineJelali
FacultyofPlant,EnergyandMachine
Systems
CologneUniversityofAppliedSciences
Koeln,Germany
ISSN1430-9491 ISSN2193-1577(electronic)
AdvancesinIndustrialControl
ISBN978-1-4471-4545-5 ISBN978-1-4471-4546-2(eBook)
DOI10.1007/978-1-4471-4546-2
SpringerLondonHeidelbergNewYorkDordrecht
LibraryofCongressControlNumber:2012951835
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FürDoris,YasminundDunja
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.
ProfessorThomasJ.Harris’s1989paperonthe“AssessmentofClosed-loopPer-
formance”demonstratedhowtobenchmarktheperformanceofcommissionedcon-
trollersusingindustrialplantdatawithouttheneedforintrusivecontrolexperiments
on production plant. This paper appeared against a background of control system
auditsthatshowedalargeproportionofcontrolloopsinmanyindustriestobeper-
forming poorly and capable of much better performance. The causes of poor per-
formanceincludepoorlytunedcontrollers,controllerstiction,andotherproblems.
From 1989,and buildingon the foundation of Professor Harris’s work, many new
controllerassessmenttechniquesweredevisedandaddedtothepublishedliterature.
Otheracademicsandengineersbegantolookmorepreciselyatthecausesofpoor
controlthusbroadeningthescopeandanalysisoftheissuesthatcontrolassessment
techniquesshouldaddress.
As Editors of the Advances in Industrial Control monograph series, we were
keen to have a small corpus of influential volumes in the series on this growing
and important field in industrial control. In consequence, the series contains the
monographs:
• Performance Assessment of Control Loops by Biao Huang and Sirish L. Shah
(ISBN978-1-85233-639-4,1999).
• Process Control Performance Assessment: From Theory to Implementation by
Andrzej W. Ordys, DamienUduehiand MichaelA. Johnson (Eds.) (ISBN 978-
1-84628-623-0,2007).
vii
viii SeriesEditors’Foreword
• DiagnosisofProcessNonlinearitiesandValveStiction:Data-DrivenApproaches
byMd.AliAhammadShoukatChoudhury,SirishL.ShahandNinaF.Thornhill
(ISBN978-3-540-79223-9,2008).
• Detection and Diagnosis of Stiction in Control Loops: State of the Art and Ad-
vanced Methods by Mohieddine Jelali and Biao Huang (Eds.) (ISBN 978-1-
84882-774-5,2010).
Theseinfluentialmonographsremainveryrelevanttothefieldofcontrollerper-
formanceassessmentstudiesandarestillavailable.
Now, just over two decades on from Professor Harris’s initial impetus there is
anextensivebodyofcontrollerassessmenttheoryandmethodsinthearchivalpub-
lishedliterature.Thus,itisanappositetimetohavethisworkdocumentedandde-
scribedasafullyformedindustrialscience.Wearethereforefortunatetowelcome
intotheseries MohieddineJelali’s monograph,ControlPerformanceManagement
inIndustrialAutomation:Assessment,Diagnosis,andImprovementofControl-Loop
Performance.Itisacomprehensivevolumethatcoversthefieldinfourparts:tech-
niquesforcontrollerperformanceassessment,detection,anddiagnosisofcontroller
performance problems, techniques for controller improvement and closes with in-
dustrialapplicationsandtools.Alsousefulisthereferencesectionthatarchivesthe
detailsofover480contributionstotheextensiveliteratureofthefield.
Dr.Jelali’smonographshowsthatthescienceofcontrollerperformanceassess-
mentiswellfoundedandthriving.However,itisinterestingtoreflectwherefuture
developmentsinthefieldmightarise.Oneperenniallyvexingtopicisthatofestab-
lishingtherelationshipbetweeninvestingincontrolperformancemanagement(and
moregenerally,controlsystemsperse)andeconomicbenefittothecompanyenter-
prise. There is still a dearth of analysis and methods in this direction. In a similar
vein,asalutaryChap.15inthemonographlooksatindustrialapplicationsandthe
take-up of the ideas and methods presented. Dr. Jelali gives it as his opinion that
only three commercial software products comprehensively cover the concepts and
algorithmsofcontrolperformancemanagementfoundinthemonograph,andgoes
ontosaythatofthelistoftenorsopackagesdescribed“onlyasmallproportionof
themethodsfoundinthisbookcanbefoundinthesepackages”.Clearly,thereisa
wealthofideas,methods,andalgorithmscollatedinthismonographthatareavail-
ableforusebytheindustrialcontrolandprocessengineer;thepotentialisthere.In
thisway,Dr.Jelali’smonographmeetsoneofthekeyobjectivesoftheAdvancesin
IndustrialControlseries;thatofpromotingnewideasandtechniquesthatcanhelp
theindustrialengineerenhancetheperformanceofcontrolsystemstechnology.
IndustrialControlCentre, M.J.Grimble
Glasgow,Scotland,UK M.A.Johnson
Preface
Aimof theBook
Control loops are the most important components in automation systems. Product
quality, operation safety, material and energy consumption, and thus the financial
performance,aredirectlyorindirectlylinkedtotheperformanceofcontrolsystems.
Toachieve,restore andsustaintopperformanceof controlloopsis thus avitalin-
terest for any company. Since process control systems are very complex, usually
comprising different hierarchical levels, it is hopeless to maintain them on regular
basisbyplantpersonal.Thisisalsothemainreasonwhyalargeportionofindustrial
controlloopshassignificantperformanceproblems,asfoundoutbyauditscarried
out regularly since the 1990s. All these factors have contributed to the growth of
thecontrolperformancemonitoring(CPM)technologyandapplicationsinthelast
decade. CPM provides a framework for automatically and systematically assess-
ingtheperformanceofcontrolloops,detectinganddiagnosingroot-causesofpoor
performance, as well as suggesting measures to improve control performance or
avoidperformancedegradation.Atthispoint,itisstressedthatanyCPMtechnique
should be non-invasive to be accepted in industrial practice. That is, the analysis
shouldalways be carried outbased ononlyroutine operatingdatawith limitedor
noadditionalprocessknowledgeandwithouttheneedforanyexperimentationwith
theplant,noteveninclosedloop.
Since the key research by Harris (1989), the control community has developed
numerous methods that focus on the performance assessment of control loops. At
the centre of these approaches is the concept of minimum variance benchmark-
inganddifferentmodificationsorextensions,whichhaveattractedmuchattention.
Meanwhile, there is a large number of techniques for basic and advanced perfor-
manceassessment,detectionanddiagnosisofdifferentsourcesofpoorperformance
(badcontrollertuning,processnonlinearities,oscillations,etc.).Usually,emphasis
isplacedonsingletechniquestodetectspecialperformanceproblemsorplantfaults.
ThisisthefirstmonographthatdealswiththecompleteCPMtechnology,from
controller assessment (minimum-variance-control-based and advanced methods),
ix
x Preface
overdetectionanddiagnosisofcontrolloopproblems(processnonlinearities,oscil-
lations, actuator faults), to the improvement of control performance (maintenance,
re-designofloopcomponents,automaticcontrollerre-tuning).Itprovidesacontri-
bution towards the development and application of completely self-contained and
automaticmethodologiesinthefield.Moreover,withinthiswork,manyCPMtools
have been developed that go far beyond available CPM packages. Industrial data
fromalargenumberofcontrolloopsindifferentindustrialfields(building,chem-
icals, mining, mineral and metal processing) have been used to demonstrate the
presented strategies and methods. Systematic procedures for automatic and con-
tinuous control performance monitoring, maintenance and optimisation have been
recommended, combining different control performance metrics and assessment,
diagnosis and improvement methods. The main objective is to sustain top control
performanceduringthewholelifecycleofthecontrolsystem,despitedifferentand
changingoperationalconditions.
Contributionsof theBook
Inthelightofthecontrol-systemlife-cyclemanagementintroducedabove,thefirst
contributionofourworkistoprovidestrategiesandmethodsforestablishinganew
practiceofintegratedcontroldesignandperformancesupervisionoftechnicalpro-
cesses,asillustratedinFig.1.
The focus of this book is only on the last three stages, i.e., performance mon-
itoring, condition monitoring and diagnosis, and CPM-based controller re-tuning.
The book is however NOT on control system design or implementation, which is
the topic of many standard texts. To the knowledge of the author, all major as-
pects of CPM, from controller assessment (minimum-variance-control-based and
advancedmethods),overdetectionanddiagnosisofcontrolloopproblems(process
non-linearities, oscillations, actuator faults), to the improvement of control perfor-
mance(maintenance,re-designofloopcomponents,automaticcontrollerre-tuning)
aretreatedforthefirsttimeinthisworkfromacommonviewpoint.
Morespecifically,thecontributionsandmessagesofthepresentbookarestated
asfollows:
1. Review, Evaluation and Industrial Application of Available Methods and Sys-
tems.Acomprehensiveandcriticalreviewofthecurrentstatusinthecomplete
CPM technology, including techniques for performance assessment, diagnosis
and improvement. Standard methods and advanced new methods are presented
as well. This provides an insight into the assumptions and fundamental limita-
tionsofeachcontrolperformanceassessmentmethod,sinceeachofthevarious
techniques signifies specific information about the nature of the process. Most
CPMalgorithmspresentedinthebookhavebeenimplementedandtestedbythe
authorinMATLAB/Simulink.
An evaluation of publications during the 15 years after the key work by Har-
ris (1989) shows some trends in the application of a number of control perfor-
mance metrics and methods in different process industries. Also included is an
Preface xi
Fig.1 Flowdiagramoftheprocesscontroldesignandsupervisionprocedure
overviewofCPMpackagesthathavebeendevelopedand/orwhicharecommer-
ciallyavailable.Meritsanddrawbacksofthemethodsarealsohighlighted.Some
control benchmarking techniques are compared in terms of parameters/data re-
quirementsandperformancetodrawguidelinesforthechoiceofthemostsuit-
abletechniqueorcombinationoftechniques.
The majority of the methods presented are illustrated with real data from in-
dustrialcontrolloopsfromdifferentindustrialfields,includingchemicals,petro-
chemicals, pulp & paper plants, commercial buildings, power plants, mineral
processing,miningandmetalprocessing.Someinformationabouttheseloopsis
giveninAppendixC.
2. Improved and New Methods for Control Performance Assessment and Diagno-
sis.Itisnotsufficientandoftendangeroustorelyonasingleindex,orasingle
performance analysis method, by itself for performance monitoring and diag-
nosis,aseachcriterionhasitsmeritsandlimitations.Thebestresultsareoften
xii Preface
Fig. 2 Proposed framework for control-performance-monitoring-based optimisation of control
loops
obtainedbythecollectiveapplicationofseveralmethodsthatreflectcontrolper-
formancemeasuresfromdifferentaspects.Basedonourexperiencefromappli-
cationofdifferentassessmentmethodstocontrolsystemsinthesteelprocessing
field,systematic proceduresforautomaticand continuouscontrol performance
monitoring,maintenanceandoptimisationwillberecommended,combiningdif-
ferentcontrolperformancemetricsandassessmentmethods.Guidelinesforhow
toselectordeterminethespecificparameters,e.g.,modelordersandtimedelay,
areworkedout.ManyimprovedandnewCPMtechniquesdevelopedbytheau-
thorarepresented.Forinstance,anewframeworkandmethodfordetectionand
quantification of stiction in control valves is developed based on Hammerstein
modellingandestimationusingglobalsearchalgorithms.Moreover,themethod
isextendedforcomprehensiveoscillationdiagnosis,i.e.,discriminatingbetween
differentcausesgeneratingtheoscillation,eveninthecaseofmultiplefaults.
3. Introducing Anticipatory Control Maintenance Practices. Bridging the fields
“ConditionMonitoringandDiagnosis”,“ControlPerformanceAssessmentand
Monitoring”and“AutomaticControllerTuningandAdaptation”isacoreobjec-
tiveof this monograph;see Fig. 2. Loop conditionmonitoringand diagnosis is
neededtoinvestigatethepropertiesofcontrolloopcomponentsintermsofsignal
levels,noiselevels,nonlinearitiesandequipmentconditions.Thisparticularlyin-
cludes the detection of oscillations possibly generated by aggressive controller
tuning, the presence of nonlinearities (e.g., static friction, dead-zone, hystere-
sis), or (internal and external) disturbances. Performance assessment is used to
supervisethecontrolloopsduringoperationandensurethattheymeettheperfor-
mancespecifications.Failuretomeetthespecificationsshouldgiveanalert.Itis
