过程控制第1章演示文稿课件.ppt

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1、ChapterOneINTRODUCTION1.1BLOCKDIAGRAMSANDTRANSFERFUNCTIONS1.2OPEN-LOOPCONTROL1.3CLOSED-LOOPCONTROL:FEEDBACK1-4BENEFITSOFAUTOMATICCONTROL1-5DAMPINGANDINSTABILITY1-6OBJECTIVESOFACONTROLSYSTEM1-7CRITERIAOFGOODCONTROLINTRODUCTIONDefinitionofaControlSystem：Acontrolsystemis

2、agroupofcomponentsthatmaintainsadesiredresultbymanipulatingthevalueofanothervariableinthesystem.给定值眼脑手测量变送器控制器执行机构气鼓手阀控制阀给水水位计蒸汽燃气Thedesiredresultisavalueofsomevariableinthesystem,forexample,thedirectionofanautomobile,thetemperatureofaroom,thelevelofliquidinatank,orth

3、epressureinapipe.Setpoint:Thecontrollersignalthatdefinesthedesiredvalueofthecontrolledvariable.Controlledvariable:Thevariablewhosevalueiscontrollediscalledthecontrolledvariable.Toachievecontrol,theremustbeanothervariableinthesystemthatcaninfluencethecontrolledvariable

4、.Thereareseveralsuchvariablesinalotsofsystems.Thecontrolsystemmaintainsthedesiredresultbymanipulatingthevalueofoneoftheseinfluentialvariables.Manipulatedvariable:Thevariablethatismanipulatediscalledthemanipulatedvariable.1.1BLOCKDIAGRAMSANDTRANSFERFUNCTIONSTheblockdia

5、gramisamethodofrepresentingacontrolsystemthatretainsonlythisimportantfeatureofeachcomponent.Signallinesindicatetheinputandoutputsignalsofthecomponent,asshowninFigure1.1.Theblockdiagram:TransferFunctions:Themostimportantcharacteristicofacomponentistherelationshipbetwee

6、ntheinputsignalandtheoutputsignal.Thisrelationshipisexpressedbythetransferfunctionofthecomponent,whichisdefinedastheratiooftheoutputsignaldividedbytheinputsignal.(Mostly,itistheLaplacetransformoftheoutputsignaldividedbytheLaplacetransformoftheinputsignal.)Thetransferf

7、unctionconsistsoftwoparts.Onepartisthesizerelationshipbetweentheinputandtheoutput.Theotherpartisthetimingbetweentheinputandoutput.1.2OPEN-LOOPCONTROLopen-loopcontrol:Anopen-loopcontrolsystemdoesnotcomparetheactualresultwiththedesiredresulttodeterminethecontrolaction.I

8、nstead,acalibratedsetting--previouslydeterminedbysomesortofcalibrationprocedureorcalculation--isusedtoobtainthedesiredresult