Trapezoidal Control of BLDC Motors Using Hall Effect …

1 ApplicationReportSPRABQ6 ,it is completesolutionproposalis presentedbelow:controlstructures,powerha rdwaretopology, : A theoreticalbackgroundonfieldorientedmoto rcontrolprinciple Incrementalbuildlevelsbasedonmodularsoft wareblocks (DMC)..96 TILiteratureandDigitalMotorControl(DMC) ( ).. Three-PhaseSynchronousMotorWitha a SinusoidalMotorControlledasa (SoftChopping)..87A :PWM1 (Yellow),PWM2 (Pink)andPWM5 (Green),PWM6 (Blue)..1913 Level1 , July2013 TrapezoidalControlofBLDCM otorsUsingHallEffectSensorsSubmitDocumen tationFeedbackCopyright 2013, ,HallA,B ,BemfBandBemfC(Vdcbus= 160V).

2 2216(a)mod6 Counter(b)ImpulseOutput, (a)mod6 Counter,(b)BemfA,(c)BemfBand(d)BemfC( 25andVdcbus= 160V)..2318 Level2 (a)mod6 Counter,(b)HallGpioAccepted( 25andVdcbus= 160V)..2620(a)mod6 Counter,(b)HallGpioAccepted,(c) (Vdcbus= 160V)..2621 Level3 (a)mod6 Counter,(b)HallGpioAccepted,(c)speed,( ,Vdcbus= 160V)..2923 Level4 - (a)mod6 Counter,(b)BemfA,(c)BemfB(c)BemfC( ,Vdcbus= 160V)..3125(a)mod6counter,(b)BemfA,(c)Be mfB(c)BemfC( ,Vdcbus= 160V)..3226 Level5 - ,atthesametime, ,andfora lowercostin brushlessDC( bldc ) (theACsynchronousmotors,steppermotors,sw itchedreluctancemotors,ACinductionmotors ),theBLDC motoris conventionallydefinedasa permanentmagnetsynchronousmotorwitha (120electricaldegreeswide)

3 Rectangularstatorcurrentsarewidelyusedas theyofferthefollowingadvantagesfirst,ass umingthemotorhaspuretrapezoidalbackEMFan dthatthestatorphasescommutationprocessis accurate,themechanicaltorquedevelopedbyt hemotoris ,thebrushlessDCdrivesshowa July2013 SubmitDocumentationFeedbackCopyright 2013, anACsynchronousmotorwithpermanentmagnets ontherotor(movingpart)andwindingsonthest ator(fixedpart). (equivalenttoa barmagnet)is ,a rotatingfieldonthestatoris ,chasingaftertheelectromagnetpolesonthes tator,isthefundamentalactionusedin Three-PhaseSynchronousMotorWitha OnePermanentMagnetPairPoleRotorOnthestat orside, ,a greaternumberofpolesusuallycreatea ,byaddingmoremagnets,a pointis reachedwhere,becauseofthespaceneededbetw eenmagnets, consequence,thenumberofpolesis a compromisebetweencost, manyways,buta coupleareofinterestbecausetheydependonba ck-EMFprofiles:thebrushlessdirectcurrent ( bldc )motorandthepermanentmagnetsynchron ousmotor(PMSM).

4 ,butdifferin ,it isimportanttoidentifythetypeofmotorin ordertoapplythemostappropriatetypeofcont rol,asdescribedin ContinuousstatorfluxpositionvariationOnl ytwophasesONatthesametimePossibletohavet hreephasesONatthesametimeTorquerippleatc ommutationsNotorquerippleatcommutationsL owordercurrentharmonicsin July2013 TrapezoidalControlofBLDCM otorsUsingHallEffectSensorsSubmitDocumen tationFeedbackCopyright 2013,TexasInstrumentsIncorporated1142222 dLdRNTiBBrl iddpqqp =-+ 2 ENlrBw= theshapeoftheinducedvoltage, theBLDC motorcaseandsinusoidalin thePMSM motorcase. bldc machinescouldbedrivenwithsinusoidalcurre ntsandPMSM withdirectcurrents,butforbetterperforman ce,PMSM motorsshouldbeexcitedbysinusoidalcurrent sandBLDC machinesbydirectcurrents.

5 Thecanstructure(hardwareandsoftware)ofa ,manymotors(sinusoidalliketrapezoidal)we redrivenwithdirectcurrentforcostandsimpl icityreasons(lowresolutionpositionsensor sandsinglelowcostcurrentsensor),compromi singefficiencyanddynamicbehavior. DigitaltechniquesaddressedbytheC2000 DSPcontrollermakeit possibletochoosetherightcontroltechnique foreachmotortype:processingpoweris ,oreveneliminateit, andalsocomplexalgorithmscanhelpsimplifyt hemechanicaldrivetraindesign, bldc motoris basedonrelativelysimpletorqueandbackEMFe quations, :andthetorquetermas:whereNis thenumberofwindingturnsperphase,lis thelengthoftherotor,ris theinternalradiusoftherotor,Bis therotormagnetfluxdensity,wis themotor s angularvelocity,iis thephasecurrent,Lis thephaseinductance, is therotorposition,R is ,whichis thetorqueproductionmechanismusedin ,thebackEMFis directlyproportionaltothemotorspeedandth etorqueproductionis Figure2.

6 4 TrapezoidalControlofBLDCM otorsUsingHallEffectSensorsSPRABQ6 July2013 SubmitDocumentationFeedbackCopyright 2013,TexasInstrumentsIncorporated(a)(b)( c)SpeedSpeedComputationZero CrossingDetection and DelayPhase VoltageMeasurement3 PhaseInverterSynchronization/PWM ControlPIControllerSpeedReference+ 3 PhaseBLDCM otorSpeedSpeedComputationZero CrossingDetection and DelayPhase VoltageMeasurement3 PhaseInverterSynchronization/PWM ControlPIDC optrollerPIControllerSpeedReference+ I refI phase3 PhaseBLDCM otorZero CrossingDetection and DelayPhase VoltageMeasurement3 PhaseInverterSynchronization/PWM ControlPIDC ontrollerI ref+ 3 BLDCM otorTheBLDC motoris characterizedbya.

7 Torqueproductionfollowstheprinciplethatc urrentshouldflowin onlytwoofthethreephasesata timeandthatthereshouldbenotorqueproducti onin describestheelectricalwaveformsin theBLDC motorin : Onlyonecurrentata timeneedstobecontrolled Onlyonecurrentsensoris necessary(ornoneforspeedlooponly,asdetai ledin thenextsections) Thepositioningofthecurrentsensorallowsth euseoflowcostsensorsasa shuntTheprincipleoftheBLDC motoris,atalltimes,toenergizethephasepai r, DCcurrentwithatrapezoidalbackEMFmakesit theoreticallypossibletoproducea ,thecurrentcannotbeestablishedinstantane ouslyin a motorphase;asa consequencethetorquerippleis presentateach60 July2013 TrapezoidalControlofBLDCM otorsUsingHallEffectSensorsSubmitDocumen tationFeedbackCopyright 2013,TexasInstrumentsIncorporatedM1 ADCS huntResistorFullCompareUnitCAPTorGPIOM otorM2M3M4M5M6qTorqueqqqqIcEcIEbIaEaPhas e CPhase BPhase themotorusedhasa sinusoidalbackEMFshape,thiscontrolcanbea ppliedbuttheproducedtorqueis.

8 Notconstantbutmadeupfromportionsofa duetoitsbeingthecombinationofatrapezoida lcurrentcontrolstrategyandofa mindthata sinusoidalbackEMFshapemotorcontrolledwit ha sinewavestrategy(threephaseON)producesa constanttorque. Thetorquevalueproducedis SinusoidalMotorControlledasa July2013 SubmitDocumentationFeedbackCopyright 2013, derivedfromthepositioninformationcomingf romsensors, ,thecontrollerdeterminestheappropriatepa iroftransistors(Q1toQ6) fixed60 referencecanberealizedin eitherofthetwodifferentmodes: ThePulseWidthModulation(PWM)Mode:Thesupp lyvoltageis choppedata fixedfrequencywitha , a fixedparameter.

9 Hence, , theneasiertodesignandis alsocheaperasit disadvantageofthehardchoppingoperationis thatit increasesthecurrentripplebya largefactorin controlofthecurrentandoftherateofchangeo fthecurrentbuta ,thelowsidetransistoris ,thepowerelectronicsboardhastohandlesixP WMsignals. TheHysteresisMode:Inthehysteresis-typecu rrentregulator,thepowertransistorsareswi tchedoffandonaccordingtowhetherthecurren tis greaterorlessthana fixed,theresultis ,thecurrentchoppingoperationis nota morecommonlyimplementedin driveswheremotorspeedandloaddonotvarytoo much,sothatthevariationin switchingfrequencyis , a designparameter,thismodeallowscurrentcon troltobeaspreciseasdesired, usedtogenerateprecisefiringcommandsforth epowerconverter, alsousedin ,eliminatinga :theincrementalsensors,thethreeHallEffec tsensor,andtheresolver.

10 Theincrementalsensorsuseopticallycodeddi skswitheithersingletrackorquadraturereso lutiontoproducea determinedbycountingthenumberofpulsesfro ma outputlinesandcanprovide1,2 or4 availablebycountingthenumberofpulseswith ina fixtimeperiod. ThethreeHallEffectsensorsprovidethreeove rlappingsignalsgivinga 60 ,therefore, automaticallystoredbythe280xintoa ,it isnumericallypossibletogetthepreciseposi tioninformationneededforsharpfiringcomma nds. Theresolveris madeupofthreewindings(differentfromthemo tor s windings):onelinkedtotherotorandsupplied witha backEMFis inducedbytherotatingcoilin ,it is possibletogetcos(q)andsin(q)whereq is July2013 TrapezoidalControlofBLDCM otorsUsingHallEffectSensorsSubmitDocumen tationFeedbackCopyright 2013, characteristicoftheBLDC controlis tohaveonlyonecurrentata timein themotor(twophasesON).