Design Rules for Actuators in Active Mechanical Systems

216 Pages·2010·10.47 MB·English

by  Oriol Gomis-Bellmunt

Design Rules for Actuators in Active Mechanical
Systems
Oriol Gomis-Bellmunt • Lucio Flavio Campanile
Design Rules
for Actuators in Active
Mechanical Systems

123
Oriol Gomis-Bellmunt, Dr. Lucio Flavio Campanile, Dr.
CITCEA-UPC (Technical University Swiss Federal Laboratories for Materials
of Catalonia) Testing and Research (EMPA)
Avinguda Diagonal, 647 Überlandstrasse 129
08028 Barcelona 8600 Dübendorf
Spain Switzerland
[email protected] [email protected]

ISBN 978-1-84882-613-7 e-ISBN 978-1-84882-614-4
DOI 10.1007/978-1-84882-614-4
Springer London Dordrecht Heidelberg New York

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Preface
The seed of this book was set in 2003, at the Institute of Structural Mechanics of
theGermanAerospaceCenter(DLR)inBraunschweig.OrioljoinedtheInstituteas
aMarieCurieFellowandFlavio,asamemberoftheCenterofExcellence“Adap-
tronics”atDLR,wasinchargeofcoordinatingtheMarieCurieTrainingSite“Smart
lightweightstructuresandtransportationapplication”.The“dailybread”oftheCen-
terofExcellenceand,asaconsequence,thefocusoftheMarieCurieTrainingSite,
wassolid-stateactuation,inparticularpiezoceramicactuation.
Whileworkingwithsolid-stateactuation,scientistsalwaysencounter(sooneror
later) fancy histograms or tables showing the comparison between different actu-
ator principles on a quantitative and seemingly objective basis. After having seen
suchcomparisonsacoupleoftimes,(andatlatestafteracoupleoflecturesorcon-
ference talks in which he shows such a histograms or table himself) the scientist
beginstowonderwhatisbehindthosenumbers,whichclaim,forinstance,thatthe
performanceofShape-Memory-Alloyactuatorsis,say,twiceaslargeastheoneof
hydrauliccylinders.
Andsincewecouldnotfindanexhaustiveanswerinpublishedliterature,wetried
tocomputeperformancequantitiesforconventionalactuatorsonamodelbasis,in
thewayweknewfromsolid-stateactuators.Werealizedsoonthatthedesignerof
solid-stateactuatorslivesinaquiteidealandcomfortableuniverse,inwhichpower-
fuldesignrulesandmeaningfulperformancequantitiescanbeobtained,onthebasis
ofsimpleassumptions,inastraightforwardway.Forconventionalactuationthings
revealeddefinitelymorecomplicated,andintriguingenoughtobeworthstartinga
researchproject.ThisprojecteventuallybecamepartofOriol’sdoctoralthesis,and
we kept working on this topic after he went back to Catalonia to get involved in
CITCEA-UPCandFlaviotookanewprofessionalchallengeatEmpainDu¨bendorf,
Switzerland.
The model-based definition of performance quantities implies dealing with the
wholedesignandoptimizationprocessofactuatorsinasystematicway,whichgave
addedvaluetothisworkandtaughtusalotofnewthingsonsolid-stateactuation
aswell.Lastyear,wefinallydecidedthatthetopicofmodel-baseddesignrulesfor
vii
viii Preface
actuators(conventionalaswellassolid-stateones)couldbeaninterestingtopicfor
abook.
Besidestheoriginalissue,i.e.onwhichobjectiveandquantitativebasisdifferent
actuatorprinciplescanbecomparedtoeachother,thecontentsofthisbooktriesto
givean answertothe followingquestions, whicharestrongly relatedtothe above
mentionedone:
• which is the dependance of the actuator’s primary output quantities force and
strokefromthemechanicalloadappliedtotheactuator?
• foragivenactuatorkind(i.e.actuatorsbasedonthesameprinciple),whichisthe
relationshipbetweenactuatorgeometryandprimaryoutputquantities?
• howscalableareactuatorsofagivenkind?
• howareenergeticoutputquantities(workandpower)relatedtomechanicalload
andgeometry?
• how should actuators be designed and sized to obtain the best performance for
thechosenactuatorkindandforagivenapplication?
Of course it was not possible to answer the above mentioned questions in an
exhaustivewayandforallexistingactuatorclassesinthetimeandspaceframework
whichwasavailableforthisbook.Sowehadtolimittherangeofourtreatmentin
atwofoldsense:
• we reduced the number of dimensions of the design space by successive opti-
mization:afterhavingidentifiedproperspecificquantities,welookforthebest
combinationbetweenactuatorandload,thenweanalyzetheoptimalvalueofthe
specificquantitieswithrespecttotheactuatordesignvariables;
• werestrictedourfocustofouractuatorprinciples:solenoidactuators,voice-coil
actuators,hydraulicactuatorsandsolid-state,strain-inductionbasedactuators.
Thereaderwhowillmakeittotheendofthisbookwilldiscoverthreedistinct
parts:
Inthefirstone,themostcommonactuatorprinciplesareintroduced,andthephi-
losophybehindtheabovesketchedactuatoranalysisisdescribedindetail.Thesec-
ondoneisdedicatedtotheapplicationofthedescribedanalysisproceduretothree
classesofconventionalactuators:solenoid,voice-coilandhydraulicactuators.The
third part, dedicated to solid state actuation, is – paradoxically – of more conven-
tionalnatureinthecontextofthisbook.Asmentionedabove,model-basedanalysis
ofsolid-stateactuatorisacommontoolandseveralpapersorbookchapterscanbe
foundinliteraturewhichdealwiththebasicconcepttreatedinpartthree,likeblock-
ingforce,freestroke,energydensityordesignofapre-stressedsolid-stateactuator.
Additionally, due to the exact mechanical scalability of solid-state actuators (un-
dertheassumptionsoftheprescribed-straintheory)thedesignanalysisintroduced
in Chapter 2 and applied to conventional actuators in Chapters 3 to 5 reduces to a
few quite simple concepts when applied to solid-state actuators. In order to make
things more interesting, we put this material in an unusual form by introducing a
new kind of graphic representation and by complementing the classic issues with
Preface ix
someremarksonhybridactuatorsrelyingonacompliantpassiveelementaswellas
ondesignanalysisforsolid-stateactuatorsfordynamicapplications.
We believe that this book can be of interest for anyone dealing with actuator
design,andinparticular:
• as a textbook for undergraduate and graduate students of mechanical engineer-
ing,aerospaceengineering,mechatronicscontrolandvirtuallyallotherspecial-
izations dealing with actuators and active materials; in particular, the graphic
representation introduced in Chapter 6 can be an useful didactic tool to learn –
bysolvingexercises–howtoanalyzesolid-stateactuatorscoupledwithpassive
structuralelements;
• as a reference for engineers dealing with the design of conventional as well as
solid-stateactuators;
• asabasisforresearchersoperatinginthefascinatingareasofsmartmechanical
systemsaswellascoupledmechanicaldesignandoptimization,whocanprofit
fromsomecriteriaandgeneralconceptsexposedinthisbook,inparticularwhile
approaching–inasimultaneousway–thedesignofpassiveandactivecompo-
nentsofmechatronicandadaptivestructuralsystems.
We are aware of the fact that if no book at all is perfect, a book which was
compiled in one – even if intensive – year is quite far from being perfect. We are
therefore thankful for any suggestion and comment which can help us to improve
andenrichpossibleneweditionsofthiswork.
Du¨bendorf,Switzerland LucioFlavioCampanile
Barcelona,Spain OriolGomis-Bellmunt
November2008
Acknowledgements
Partofthisbookisaresultofaresearchtrainingprojectwhichhasbeendevelopedin
theDLR(GermanAerospaceCenter)inBraunschweig(Germany)andsupportedby
aMarieCurieFellowshipoftheEuropeanCommunityprogramSmartLightweight
Structures And Transportation Application under the contract number HPMT-CT-
2001-00298.
xi
Contents
PartI IntroductoryRemarks
1 ActuatorPrinciplesandClassification ............................ 3
1.1 ActuatorPrinciples ......................................... 5
1.1.1 ElectromagneticActuators ............................ 5
1.1.2 FluidPowerActuators ................................ 11
1.1.3 PiezoelectricActuators ............................... 13
1.1.4 ThermalShapeMemoryAlloyActuators ................ 20
1.1.5 OtherActuators ..................................... 22
1.2 Solid-StateversusConventionalActuation ..................... 25
References..................................................... 27
2 ActuatorDesignAnalysis ....................................... 29
2.1 NatureandObjectivesofActuatorDesignAnalysis .............. 29
2.2 PerformanceIndexes........................................ 33
2.3 DesignParameters.......................................... 36
2.3.1 GeometricalFactors.................................. 37
2.3.2 AspectRatios ....................................... 40
2.3.3 FillingFactors....................................... 41
2.4 OutputQuantities .......................................... 43
2.4.1 OutputQuantitiesExpression .......................... 43
2.4.2 Steady-StateAnalysis ................................ 45
2.5 Thresholds ................................................ 48
2.6 MaximumTargetQuantityforaGivenSize..................... 50
2.6.1 OutputMechanicalQuantitiesMaximization ............. 51
2.6.2 OtherQuantities ..................................... 53
2.7 Scalability ................................................ 54
2.8 DimensionalAnalysis....................................... 55
2.8.1 TheBuckinghamPiTheorem .......................... 55
2.8.2 Non-DimensionalNumbers............................ 59
2.9 Validation................................................. 61
xiii
xiv Contents
2.9.1 PrototypeConstruction ............................... 61
2.9.2 IndustrialActuators .................................. 61
2.9.3 Simulation.......................................... 62
2.10 ConsiderationsonActuatorsDynamics ........................ 71
2.10.1 DynamicalAnalysis.................................. 71
2.10.2 ControlSystem...................................... 73
References..................................................... 78
PartII ConventionalActuators
3 DesignAnalysisofSolenoidActuators ............................ 81
3.1 DesignParameters.......................................... 81
3.2 OutputQuantities .......................................... 82
3.3 Thresholds ................................................ 84
3.4 MaximumOutputQuantities ................................. 86
3.5 Scalability ................................................ 90
3.6 DimensionalAnalysis....................................... 92
3.7 FiniteElementAnalysis ..................................... 94
3.8 ComparisonwithIndustrialActuators ......................... 96
3.9 Dynamics .................................................102
3.9.1 SystemModeling ....................................102
3.9.2 OpenLoopSimulation................................103
3.9.3 ControlDesign ......................................103
3.9.4 ClosedLoopSimulation ..............................105
References.....................................................109
4 DesignAnalysisofMovingCoilActuators ........................111
4.1 DesignParameters..........................................111
4.2 OutputQuantities ..........................................111
4.3 Thresholds ................................................114
4.4 MaximumOutputQuantities .................................114
4.5 Scalability ................................................116
4.6 DimensionalAnalysis.......................................116
4.7 FiniteElementAnalysis .....................................118
4.8 ComparisonwithIndustrialActuators .........................120
4.9 Dynamics .................................................120
4.9.1 SystemModeling ....................................120
4.9.2 ControlDesign ......................................126
4.9.3 ClosedLoopSimulation ..............................127
References.....................................................131
5 DesignAnalysisofHydraulicActuators ..........................133
5.1 DesignParameters..........................................133
5.2 Force-StrokeandWork-StrokeCharacteristic ...................133
5.3 Thresholds ................................................135
5.4 MaximumForce,StrokeandWork ............................136