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1、Chapter5PIDControlSystemTheinformationofaprogramblockformovingtheaxisofamachinetoolpassessequentiallythroughtheinterpreter,theinterpolator,andtheAcc/Deccontrollerbe-forebeingfinallytransmittedtothepositioncontroller.Thepositioncontrollerhasthedisplacementateachinte
2、rpolationintervalfromtheinterpolatorasinputandperformsfeedbackcontroltominimizethepositionerror.Inthischapter,thePro-portionalIntegralDerivative(PID)controller,whichiswidelyusedinindustry,willbeintroducedandgaintuningforPIDcontrolwillbeaddressed.Inaddition,thefeed
3、forwardcontrollerforhigh-speedapplicationswillbeintroduced.5.1IntroductionIngeneral,theaxiscontrolmoduleforCNCsystemsofmachinetoolscanbeclassi-fiedintoathree-tierarchitectureasshowninFig.5.1.Thecontrolmoduleconsistsoftheadaptivecontrolmoduleandtheerrorcompensationm
4、oduleintheupperlayer,theinterpolationmoduleinthemiddlelayer,andthespindlecontrolmoduleandservocontrolmoduleinthelowerlayer.Theadaptivecontrolmoduleintheupperlayergeneratesoptimizedcuttingcon-ditionssuchasspindlespeedandfeedratebasedontheprogrammedspindlespeed,thep
5、rogrammedfeedrate,measuredactualcuttingforce,andthecuttingcapacityofmachinetools.Accordingly,theadaptivecontrolmoduleplaystheroleofincreasingMaterialRemovalRate(MRR)anddecreasingmachiningtimetoincreaseproduc-tivity.Anothermoduleintheupperlayer,theerrorcompensation
6、module,carriesoutthecompensationoferrorfactorsthatcausedeviationsfromtheprogrammedpath.Thismodulehandlesvariouskindsoferrorincludingtheheatfrommovingelements,thevolumetricerrorofmachinetools,toolwear,andtooldeflection.Theoptimizedandcompensatedfeedrateandpositionin
7、structionsfromtheupperlayeraretransmittedintotheinterpolatorinthemiddlelayer.Finally,theinterpolated1571585PIDControlSystemProgrammedRequiredProgrammedSpeed&FeedForcePositionCuttingforceAdaptiveControlErrorCompensionFeedPositionInterpolationAxialCommandServoContro
8、lSpindleControlDrivePositionDriveSpeedFeedbackFeedbackFig.5.1Three-tierCNCsystemarchitecturepositioninstructionsforeachaxisarefedtotheservocontrolmodule