Position and Speed Control of Brushless DC Motors

Sensors2010,10,6901-6947;doi:10.3390/s100706901sensorsISSN1424-8220éCarlosGamazo-Real*,ErnestoVázquez-SánchezandJaimeGómez-GilDepartmentofSignalTheory,CommunicationsandTelematicEngineering,UniversityofValladolid(UVA),47011Valladolid,Spain;E-Mails:[e-mail](E.V.-S.);[e-mail](J.G.-G.)*Authortowhomcorrespondenceshouldbeaddressed;E-Mail:[e-mail];Tel.:[phone];Fax:[phone].Received:10June2010;inrevisedform:30June2010/Accepted:5July2010/Published:19July2010Abstract:ThispaperprovidesatechnicalreviewofpositionandspeedsensorlessmethodsforcontrollingBrushlessDirectCurrent(BLDC)motordrives,includingthebackgroundanalysisusingsensors,limitationsandadvances.TheperformanceandreliabilityofBLDCmotordrivershavebeenimprovedbecausetheconventionalcontrolandsensingtechniqueshavebeenimprovedthroughsensorlesstechnology.Then,inthispapersensorlessadvancesarereviewedandrecentdevelopmentsinthisareaareintroducedwiththeirinherentadvantagesanddrawbacks,includingtheanalysisofpracticalimplementationissuesandapplications.Thestudyincludesadeepoverviewofstate-of-the-artback-EMFsensingmethods,whichincludesTerminalVoltageSensing,ThirdHarmonicVoltageIntegration,TerminalCurrentSensing,Back-EMFIntegrationandPWMstrategies.Also,themostrelevanttechniquesbasedonestimationandmodelsarebrieflyanalysed,suchasSliding-modeObserver,ExtendedKalmanFilter,ModelReferenceAdaptiveSystem,Adaptiveobservers(Full-orderandPseudoreduced-order)andArtificialNeuralNetworks.Keywords:BLDC;back-EMF;sensorless;position;speed;estimator;Hall-effectsensors;electronicprocessorsOPENACCESSSensors2010,1069021.IntroductionForthepasttwodecadesseveralAsiancountriessuchasJapan,whichhavebeenunderpressurefromhighenergyprices,haveimplementedvariablespeedPMmotordrivesforenergysavingapplicationssuchasairconditionersandrefrigerators[1].Ontheotherhand,theU.S.A.haskeptonusingcheapinductionmotordrives,whichhavearound10%lowerefficiencythanadjustablePMmotordrivesforenergysavingapplications.Thereforerecently,theincreaseinenergypricesspurshigherdemandsofvariablespeedPMmotordrives.Also,recentrapidproliferationofmotordrivesintotheautomobileindustry,basedonhybriddrives,generatesaseriousdemandforhighefficientPMmotordrives,andthiswasthebeginningofinterestinBLDCmotors.BLDCmotors,alsocalledPermanentMagnetDCSynchronousmotors,areoneofthemotortypesthathavemorerapidlygainedpopularity,mainlybecauseoftheirbettercharacteristicsandperformance[2].Thesemotorsareusedinagreatamountofindustrialsectorsbecausetheirarchitectureissuitableforanysafetycriticalapplications.ThebrushlessDCmotorisasynchronouselectricmotorthat,fromamodellingperspective,looksexactlylikeaDCmotor,havingalinearrelationshipbetweencurrentandtorque,voltageandrpm.Itisanelectronicallycontrolledcommutationsystem,insteadofhavingamechanicalcommutation,whichistypicalofbrushedmotors.Additionally,theelectromagnetsdonotmove,thepermanentmagnetsrotateandthearmatureremainsstatic.Thisgetsaroundtheproblemofhowtotransfercurrenttoamovingarmature.Inordertodothis,thebrush-system/commutatorassemblyisreplacedbyanintelligentelectroniccontroller,whichperformsthesamepowerdistributionasabrushedDCmotor[3].BLDCmotorshavemanyadvantagesoverbrushedDCmotorsandinductionmotors,suchasabetterspeedversustorquecharacteristics,highdynamicresponse,highefficiencyandreliability,longoperatinglife(nobrusherosion),noiselessoperation,higherspeedranges,andreductionofelectromagneticinterference(EMI).Inaddition,theratioofdeliveredtorquetothesizeofthemotorishigher,makingitusefulinapplicationswherespaceandweightarecriticalfactors,especiallyinaerospaceapplications.ThecontrolofBLDCmotorscanbedoneinsensororsensorlessmode,buttoreduceoverallcostofactuatingdevices,sensorlesscontroltechniquesarenormallyused.TheadvantageofsensorlessBLDCmotorcontrolisthatthesensingpartcanbeomitted,andthusoverallcostscanbeconsiderablyreduced.Thedisadvantagesofsensorlesscontrolarehigherrequirementsforcontrolalgorithmsandmorecomplicatedelectronics[3].Alloftheelectricalmotorsthatdonotrequireanelectricalconnection(madewithbrushes)betweenstationaryandrotatingpartscanbeconsideredasbrushlesspermanentmagnet(PM)machines[4],whichcanbecategorisedbasedonthePMsmountingandtheback-EMFshape.ThePMscanbesurfacemountedontherotor(SMPM)orinstalledinsideoftherotor(IPM)[5],andtheback-EMFshapecaneitherbesinusoidalortrapezoidal.Accordingtotheback-EMFshape,PMACsynchronousmotors(PMACorPMSM)havesinusoidalback-EMFandBrushlessDCmotors(BLDCorBPM)havetrapezoidalback-EMF.APMACmotoristypicallyexcitedbyathree-phasesinusoidalcurrent,andaBLDCmotorisusuallypoweredbyasetofcurrentshavingaquasi-squarewaveform[6,7].Becauseoftheirhighpowerdensity,reliability,efficiency,maintenancefreenatureandsilentoperation,permanentmagnet(PM)motorshavebeenwidelyusedinavarietyofapplicationsinSensors2010,106903industrialautomation,computers,aerospace,military(gunturretsdrivesforcombatvehicles)[3],automotive(hybri