机电一体化毕业设计PLCS可编程逻辑控制器毕业论文外文文献翻译及原文Word格式文档下载.docx

机电一体化毕业设计PLCS可编程逻辑控制器毕业论文外文文献翻译及原文Word格式文档下载.docx

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PLC

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2017.02.14

PLC

1.AboutProgrammableLogicControllers（PLCs）

PLCs（programmablelogiccontrollers）arethecontrolhubsforawidevarietyofautomatedsystemsandprocesses.Theycontainmultipleinputsandoutputsthatusetransistorsandothercircuitrytosimulateswitchesandrelaystocontrolequipment.Theyareprogrammableviasoftwareinterfacedviastandardcomputerinterfacesandproprietarylanguagesandnetworkoptions.

ProgrammablelogiccontrollersI/Ochannelspecificationsincludetotalnumberofpoints,numberofinputsandoutputs,abilitytoexpand,andmaximumnumberofchannels. 

Numberofpointsisthesumoftheinputsandtheoutputs.PLCsmaybespecifiedbyanypossiblecombinationofthesevalues. 

Expandableunitsmaybestackedorlinkedtogethertoincreasetotalcontrolcapacity. 

Maximumnumberofchannelsreferstothemaximumtotalnumberofinputandoutputchannelsinanexpandedsystem. 

PLCsystemspecificationstoconsiderincludescantime,numberofinstructions,datamemory,andprogrammemory. 

ScantimeisthetimerequiredbythePLCtocheckthestatesofitsinputsandoutputs. 

Instructionsarestandardoperations（suchasmathfunctions）availabletoPLCsoftware. 

Datamemoryisthecapacityfordatastorage. 

Programmemoryisthecapacityforcontrolsoftware.

AvailableinputsforprogrammablelogiccontrollersincludeDC,AC,analog,thermocouple,RTD,frequencyorpulse,transistor,andinterruptinputs. 

OutputsforPLCsincludeDC,AC,relay,analog,frequencyorpulse,ProgrammingoptionsforPLCsincludefrontpanel,handheld,andcomputer.

Programmablelogiccontrollersuseavarietyofsoftwareprogramminglanguagesforcontrol. 

TheseincludeIEC61131-3,sequentialfunctionchart（SFC）,functionblockdiagram（FBD）,ladderdiagram（LD）,structuredtext（ST）,instructionlist（IL）,relayladderlogic（RLL）,flowchart,C,andBasic. 

TheIEC61131-3programmingenvironmentprovidessupportforfivelanguagesspecifiedbytheglobalstandard:

SequentialFunctionChart,FunctionBlockDiagram,LadderDiagram,StructuredText,andInstructionList.Thisallowsformulti-vendorcompatibilityandmulti-languageprogramming. 

SFCisagraphicallanguagethatprovidescoordinationofprogramsequences,supportingalternativesequenceselectionsandparallelsequences. 

FBDusesabroadfunctionlibrarytobuildcomplexproceduresinagraphicalformat.Standardmathandlogicfunctionsmaybecoordinatedwithcustomizablecommunicationandinterfacefunctions. 

LDisagraphiclanguagefordiscretecontrolandinterlockinglogic.ItiscompletelycompatiblewithFBDfordiscretefunctioncontrol. 

STisatextlanguageusedforcomplexmathematicalproceduresandcalculationslesswellsuitedtographicallanguages. 

ILisalow-levellanguagesimilartoassemblycode.Itisusedinrelativelysimplelogicinstructions. 

RelayLadderLogic（RLL）,orladderdiagrams,istheprimaryprogramminglanguageforprogrammablelogiccontrollers（PLCs）.Ladderlogicprogrammingisagraphicalrepresentationoftheprogramdesignedtolooklikerelaylogic. 

FlowChartisagraphicallanguagethatdescribessequentialoperationsinacontrollersequenceorapplication.Itisusedtobuildmodular,reusablefunctionlibraries. 

Cisahighlevelprogramminglanguagesuitedtohandlethemostcomplexcomputation,sequential,anddataloggingtasks.ItistypicallydevelopedanddebuggedonaPC. 

BASICisahighlevellanguageusedtohandlemathematical,sequential,datacapturingandinterfacefunctions.

Programmablelogiccontrollerscanalsobespecifiedwithanumberofcomputerinterfaceoptions,networkspecificationsandfeatures. 

PLCpoweroptions,mountingoptionsandenvironmentaloperatingconditionsareallalsoimportanttoconsider.

2.PLChardware

PLChardwaremainlyhasthecentralprocessingunit（CPU）,memory,inputunit,outputunit,thecommunicationinterface,expansioninterfacepowercomponents.Amongthem,theCPUisthecore,inputunitofPLCwithoutputunitisconnectedsiteinput/outputdevicestotheCPU,interfacecircuitbetweenthecommunicationinterfaceusedwithprogrammer,connectingperipheralssuchasthePC.

2.1Thecentralprocessingunit（CPU）

Thesamesortofmicrocomputerissame,theCPUisthecoreofPLC.PLCdeployedbytheCPUindifferentanddifferent,withmodelsusedintothreecategories:

generalmicroprocessor（suchas8086,Z80,80286,etc.）,singlechipmicroprocessor（suchas8031,etc）andapiece8096microprocessors（suchasAMD29W,etc.）.SmallPLCisusedmostlyeightgeneralmicroprocessorandsinglechipmicroprocessor;

MediumPLCisusedmostly16generalmicroprocessoro