完整版毕业设计基于PLC的液位控制系统设计.docx

完整版毕业设计基于PLC的液位控制系统设计.docx

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完整版毕业设计基于PLC的液位控制系统设计

电信学院毕业设计任务书

题目基于PLC的污水池液位控制系统设计

学生姓名班级学号

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