完整版毕业设计基于PLC的液位控制系统设计Word格式文档下载.docx
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题目类型工程设计指导教师魏祥林系主任
一、毕业设计(论文)的技术背景和设计依据:
与传统的人工调节液位控制系统相比,变频液位自动控制系统具有节能效果显著、人工劳动强度低,系统工作可靠、自动化程度高等优点。
为了实现污水池液位的恒定控制,本设计要求S7-200PLC作为控制器,完成对现场数据的采集、变频器的控制、PID控制算法的实现。
二、毕业设计(论文)的任务
1、熟悉题目要求,查阅相关科技文献,写出开题报告;
2、方案设计(包括方案论证与确定、技术经济分析等内容);
3、硬件系统设计;
4、软件系统设计;
6、撰写设计说明书,绘制图纸;
6、翻译一篇与自己所学专业或设计有关的英文资料;
三、毕业设计(论文)的主要内容、功能及技术指标:
1、系统要求用户能够直观地了解现场设备地工作状况及水位的变化;
2、要求用户能够远程控制变频器的启动和停止;
3、用户可以自行设置水位的高、低,以及控制变频器的启、停;
4、变频器及其他设备的故障信息能够及时反映在远程单片机上;
5、具有水位过高、过低报警和提示用户功能。
6、专业英文文献翻译;
PLCs--Past,PresentandFuture
Everyoneknowsthere'
sonlyoneconstantinthetechnologyworld,andthat'
schange.ThisisespeciallyevidentintheevolutionofProgrammableLogicControllers(PLC)andtheirvariedapplications.Fromtheirintroductionmorethan30yearsago,PLCshavebecomethecornerstoneofhundredsofthousandsofcontrolsystemsinawiderangeofindustries.
Atheart,thePLCisanindustrializedcomputerprogrammedwithhighlyspecializedlanguages,anditcontinuestobenefitfromtechnologicaladvancesinthecomputerandinformationtechnologyworlds.Themostprominentofwhichisminiaturizationandcommunications.
TheShrinkingPLC
WhenthePLCwasfirstintroduced,itssizewasamajorimprovement-relativetothehundredsofhard-wiredrelaysandtimersitreplaced.AtypicalunithousingaCPUandI/Owasroughlythesizeofa19televisionset.Throughthe1980sandearly1990s,modularPLCscontinuedtoshrinkinfootprintwhileincreasingincapabilitiesandperformance(seeDiagram1fortypicalmodularPLCconfiguration).
Inrecentyears,smallerPLCshavebeenintroducedinthenanoandmicroclassesthatofferfeaturespreviouslyfoundonlyinlargerPLCs.ThishasmadespecifyingalargerPLCjustforadditionalfeaturesorperformance,andnotincreasedI/Ocount,unnecessary,aseventhoseinthenanoclassarecapableofEthernetcommunication,motioncontrol,on-boardPIDwithautotune,remoteconnectivityandmore.
PLCsarealsonowwell-equippedtoreplacestand-aloneprocesscontrollersinmanyapplications,duetotheirabilitytoperformfunctionsofmotioncontrol,dataacquisition,RTU(remotetelemetryunit)andevensomeintegratedHMI(humanmachineinterface)functions.Previously,thesefunctionsoftenrequiredtheirownpurpose-builtcontrollersandsoftware,plusaseparatePLCforthediscretecontrolandinterlocking.
TheGreatCommunicator
Possiblythemostsignificantchangeinrecentyearsliesinthecommunicationsarena.Inthe1970sModiconintroductionofModbuscommunicationsprotocolallowedPLCstocommunicateoverstandardcabling.ThistranslatestoanabilitytoplacePLCsincloserproximitytorealworlddevicesandcommunicatebacktoothersystemcontrolsinamainpanel.
Inthepast30yearswehaveseenliterallyhundredsofproprietaryandstandardprotocolsdeveloped,eachwiththeirownuniqueadvantages.Today'
sPLCshavetobedatacompilersandinformationgateways.Theyhavetointerfacewithbarcodescannersandprinters,aswellastemperatureandanalogsensors.Theyneedmultipleprotocolsupporttobeabletoconnectwithotherdevicesintheprocess.Andfurthermore,theyneedallthesecapabilitieswhileremainingcost-effectiveandsimpletoprogram.
AnotherprimarydevelopmentthathasliterallyrevolutionizedthewayPLCsareprogrammed,communicatewitheachotherandinterfacewithPCsforHMI,SCADAorDCSapplications,camefromthecomputingworld.
UseofEthernetcommunicationsontheplantfloorhasdoubledinthepastfiveyears.Whileserialcommunicationsremainpopularandreliable,Ethernetisfastbecomingthecommunicationsmediaofchoicewithadvantagesthatsimplycan'
tbeignored,suchas:
*Networkspeed.*Easeofusewhenitcomestothesetupandwiring.*Availabilityofoff-the-shelfnetworkingcomponents.*Built-incommunicationssetups.
IntegratedMotionControl
AnotherresponsibilitythePLChasbeentaskedwithismotioncontrol.Fromsimpleopen-looptomulti-axisapplications,thetrendhasbeentointegratethisfeatureintoPLChardwareandsoftware.
Therearemanyapplicationsthatrequireaccuratecontrolatafastpace,butnotexactprecisionatblazingspeeds.Theseareapplicationswherethestand-alonePLCworkswell.ManynanoandmicroPLCsareavailablewithhigh-speedcountingcapabilitiesandhigh-frequencypulseoutputsbuiltintothecontroller,makingthemaviablesolutionforopen-loopcontrol.
Theonecaveatisthatthecontrollerdoesnotknowthepositionoftheoutputdeviceduringthecontrolsequence.Ontheotherhand,itsmainadvantageiscost.Evensimplemotioncontrolhadpreviouslyrequiredanexpensiveoptionmodule,andattimeswasrestrictedtomoresophisticatedcontrolplatformsinordertomeetsystemrequirements.
Moresophisticatedmotionapplication