《机械工程师手册,仪器仪表,系统,控制系统,和memch11》由会员分享，可在线阅读，更多相关《机械工程师手册,仪器仪表,系统,控制系统,和memch11（60页珍藏版）》请在金锄头文库上搜索。
1、383383CHAPTER11CHAPTER11 BASICCONTROLSYSTEMSDESIGNBASICCONTROLSYSTEMSDESIGNWilliamJ.PalmIIIWilliamJ.PalmIII DepartmentofMechanicalEngineeringDepartmentofMechanicalEngineering UniversityofRhodeIslandUniversityofRhodeIsland Kingston,RhodeIslandKingston,RhodeIsland1INTRODUCTION3831INTRODUCTION3832CONTR
2、OLSYSTEM2CONTROLSYSTEM STRUCTURE386STRUCTURE386 2.1AStandardDiagram386 2.2TransferFunctions388 2.3System-TypeNumberandErrorCoefficients3883TRANSDUCERSANDERROR3TRANSDUCERSANDERROR DETECTORS389DETECTORS389 3.1DisplacementandVelocity Transducers389 3.2TemperatureTransducers391 3.3FlowTransducers391 3.4
3、ErrorDetectors392 3.5DynamicResponseof Sensors3924ACTUATORS3924ACTUATORS392 4.1Electromechanical Actuators392 4.2HydraulicActuators394 4.3PneumaticActuators3965CONTROLLAWS3995CONTROLLAWS399 5.1ProportionalControl399 5.2IntegralControl401 5.3Proportional-plus-Integral Control403 5.4DerivativeControl4
4、04 5.5PIDControl4056CONTROLLERHARDWARE4056CONTROLLERHARDWARE405 6.1FeedbackCompensation andControllerDesign405 6.2ElectronicControllers406 6.3PneumaticControllers407 6.4HydraulicControllers4077FURTHERCRITERIAFOR7FURTHERCRITERIAFOR GAINSELECTION409GAINSELECTION409 7.1PerformanceIndices410 7.2Optimal-
5、ControlMethods4117.3TheZieglerNicholsRules412 7.4Nonlinearitiesand ControllerPerformance413 7.5ResetWindup4148COMPENSATIONAND8COMPENSATIONAND ALTERNATIVECONTROLALTERNATIVECONTROL STRUCTURES414STRUCTURES414 8.1SeriesCompensation415 8.2FeedbackCompensation andCascadeControl415 8.3FeedforwardCompensati
6、on415 8.4State-VariableFeedback417 8.5PseudoderivativeFeedback4189GRAPHICALDESIGN9GRAPHICALDESIGN METHODS418METHODS418 9.1TheNyquistStability Theorem419 9.2SystemswithDead-Time Elements420 9.3Open-LoopDesignfor PIDControl420 9.4DesignwiththeRootLocus42110PRINCIPLESOFDIGITAL10PRINCIPLESOFDIGITAL CONT
7、ROL424CONTROL424 10.1DigitalControllerStructure425 10.2DigitalFormsofPID Control42511UNIQUELYDIGITAL11UNIQUELYDIGITAL ALGORITHMS427ALGORITHMS427 11.1DigitalFeedforward Compensation427 11.2ControlDesigninthe z-Plane428 11.3DirectDesignofDigital Algorithms43212HARDWAREAND12HARDWAREAND SOFTWAREFORDIGIT
8、ALSOFTWAREFORDIGITAL CONTROL433CONTROL433RevisedfromWilliamJ.PalmIII,Modeling,AnalysisandControlofDynamicSystems,2nded.,Wiley, 2000,bypermissionofthepublisher.Mechanical Engineers Handbook: Instrumentation, Systems, Controls, and MEMS, Volume 2, Third Edition. Edited by Myer Kutz Copyright 2006 by J
9、ohn Wiley (b)blockdiagram.1Figure3Figure3Aclosed-loopsystem.ofAaslongasAremainslarge.IfR1andR2areknownaccurately,thenthesystemgainis nowreliable. Figure4showstheblockdiagramofaclosed-loopsystem,whichisasystemwith feedback.Anopen-loopsystem,suchasatimer,hasnofeedback.Figure4servesasafocus foroutlinin
10、gtheprerequisitesforthischapter.Thereadershouldbefamiliarwiththetransfer functionconceptbasedontheLaplacetransform,thepulsetransferfunctionbasedonthe z-transform,fordigitalcontrol,andthedifferentialequationmodelingtechniquesneededto obtainthem.Itisalsonecessarytounderstandblockdiagramalgebra,charact
11、eristicroots,thefinal-valuetheorem,andtheiruseinevaluatingsystemresponseforcommoninputslike thestepfunction.AlsorequiredarestabilityanalysistechniquessuchastheRouthcriterion386386BasicControlSystemsDesignFigure4Figure4Feedbackcompensationofanamplifier.Figure5Figure5Positioncontrolsystemusingadcmotor
12、.1andtransientperformancespecificationssuchasthedampingratio,naturalfrequencyn, dominanttimeconstant,maximumovershoot,settlingtime,andbandwidth.Theabove materialisreviewedinthepreviouschapter.TreatmentindepthisgiveninRefs.14.2CONTROLSYSTEMSTRUCTURE2CONTROLSYSTEMSTRUCTURETheelectromechanicalpositionc
13、ontrolsystemshowninFig.5illustratesthestructureofa typicalcontrolsystem.AloadwithaninertiaIistobepositionedatsomedesiredangler. Adcmotorisprovidedforthispurpose.Thesystemcontainsviscousdamping,andadis- turbancetorqueTdactsontheload,inadditiontothemotortorqueT.Becauseofthe disturbance,theangularposit
14、ionoftheloadwillnotnecessarilyequalthedesiredvalue r.Forthisreason,apotentiometer,orsomeothersensorsuchasanencoder,isusedto measurethedisplacement.Thepotentiometervoltagerepresentingthecontrolledposition iscomparedtothevoltagegeneratedbythecommandpotentiometer.Thisdeviceenables theoperatortodialinth
15、edesiredangler.Theamplifierseesthedifferenceebetweenthetwopotentiometervoltages.Thebasicfunctionoftheamplifieristoincreasethesmallerror voltageeuptothevoltagelevelrequiredbythemotorandtosupplyenoughcurrentrequiredbythemotortodrivetheload.Inaddition,theamplifiermayshapethevoltagesignalin certainwayst
16、oimprovetheperformanceofthesystem. Thecontrolsystemisseentoprovidetwobasicfunctions:(1)torespondtoacommandinputthatspecifiesanewdesiredvalueforthecontrolledvariableand(2)tokeepthe controlledvariablenearthedesiredvalueinspiteofdisturbances.Thepresenceofthefeed- backloopisvitaltobothfunctions.AblockdiagramofthissystemisshowninFig.6.Thepowersuppliesrequiredforthepotentiometersandtheamplifierarenotshowninblock diagramsofcontrolsystemlogicbecausetheydonotcontributetothecontrollogic.2.1A
