Themaincontrolstrategyofthisdesignincludesthefollowingtwoaspects.

    2.1singlecircuitmotorcontrolstrategy

    SinglecircuitmotoradoptsPIDclosed-loopcontroltoadjustthespeed.Theclosed-loopperformanceofthesystemdirectlydeterminesthedynamicandstaticperformanceoftheservosystem,whichisthekeypartofthesystemcontrol.

    PIDalgorithmhasthecharacteristicsofsimplestructureandconvenientdebugging.Althoughtheamountofchangeiscertainintheregulation,butbecausethefrequencyoftheclosed-loopisveryhigh,whenthechangevariableissettoasmallamount,itcanalsomeettheperformancerequirementsofthesystem.OnthebasisofsettingKi,KPandKD,byfinetuningtheactualcircuitparameters,thesystemcanachievebetterovershootonthebasisofbasicallysatisfyingthesystemrapidity,soastoimprovethesystemstability.

    2.2controlstrategyoftwo-waymotor

    Itisthecontrolsystemblockdiagramoftheelectricwheelwithtwoindependentdrives.Sincethetwomotorsareinstalledontheshaftsofthetwodrivingwheelsrespectively,whentheinternalparametersandexternalroadconditionsofthedrivingdevicesofthetwowheelsaredifferent,eveniftheinputofthetwomotorsisthesame,thespeedofthetwodrivingwheelscannotbeguaranteedtobethesame.Here,acompensationsystemisusedtoeliminatethespeeddifferencebetweenthetwoelectricwheelsgeneratedduringtheoperationofthesystem.

    Inthelinearoperation,thespeeddifferencecoordinationsystemisusedtoadjustthespeedofthetwoelectricwheels.Setadrivingwheel,letthespeedofthedrivenwheelfollowthedrivingwheel,andmakethespeedofthetwoelectricwheelsasconsistentaspossible.Whenturning,themotorontheinnerandoutersidedeceleratesatthesametime,andthereductionoftheinnermotorismuchlargerthanthatoftheoutermotor.ThetwomotorsusetheirownreferencespeedtocarryoutindependentPIDcalculation,soastoensurethatthewheelchaircanturnwhentheroadconditionisnotverygood[2].

    3systemhardwaredesign

    Accordingtothefunctionalrequirementsoftheelectricwheelchair,thedesignismainlycomposedofaDSPandtwoBLDCMdrivingcircuits,aswellasthenecessarylevelconversioncircuit.DSPisresponsibleforthedesignandcontrolofthewholesystem.AllsignalacquisitionandprocessingarecompletedbyDSP,andPWMsignalandfaultprotectioninterruptrequestarealsogenerated.Combinedwiththeactualsituation,TMS320LF2407Aisusedasthecontrolcoreinthedesign.Itincludestwoindependenteventmanagers:eachincludestwo16BitUniversaltimers,eight16bitPWMoutputchannels,threecaptureunits,andthemainfrequencyofDSPis40MHz[3].

    ThedrivercircuitismainlydrivenbythedriverchipIR2130.Themainbodyoftheinverterconsistsofsixpowerswitchdevicestoformathree-phasefullcontrolbridgecircuit.Inordertopreventthevoltagedischargeatbothendsofthebootstrapcapacitor,thehighfrequencyrecoverydiodeher107shouldbeselected.Ontheotherhand,inordertopreventthevoltageatbothendsofthebootstrapcapacitorfrombeinglowerthanthethresholdvalueofundervoltageprotectionactionduetothedischargeofthebootstrapcapacitor,thevalueofthecapacitanceshouldbelargeenough.Inthisdesign,47Zfcapacitorisselected,withawithstandvoltageof25V[4].

    4systemsoftwaredesign

    TheflowchartofinterruptsubroutineforgeneratingPWMwaveofinverterdrivingsignal.Figure6showstheflowchartofthetwo-wayBLDCMspeedcoordinationcontrolinterruptsubroutine.T2andT4areselectedasthetimebaseofthetwoBLDCMs,soastoaccuratelycapturethetimeintervalbetweentwointerrupts.Thecontinuousincreasingcountingmodeisselectedforbothclocks.