PLC和模糊控制的变频调速恒压供水系统
PLC和模糊控制的变频调速恒压供水系统
彭晓红,肖来生
信息技术
广东海洋大学
湛江,中国
电子邮件:lgdpxh@I.IIVI.com
莫之
技术部
湛江新中美化工实业有限公司
湛江,中国
刘国栋
茂名分公司
中国建设银行
茂名,中国
摘要:为了解决由塔和水泵高的供水方式直接引起的电能质量差和浪费的问题,引入I.个恒压供水系统,该系统采用了PLC和变频为核心的嵌入式模糊控制技术.当系统运行时,该管的水压通过压力变送器被输入到PLC的终端X0.测得的压力值与设定值进行比较,PLC通过控制变频器的工作频率以控制模糊计算的输出信号,从而控制水泵的转动速度和调节的水压.本文设计的水压实时控制供水系统通过实验被很好地验证.硬件模块是稳定的.可靠的,并且模糊控制器正确有效,较好的保证了水压的稳定性.
关键字:模糊控制PLC变频调速规则
I..引言
随着经济和社会的高速发展,能源短缺日益明显,人们对生活的质量和供水可靠性也越来越重视.因此,利用先进的.具有高节能和高可靠性的自动化技术设计的恒压供水系统成为必然趋势.
因为用户的供水要求往往是不稳定的,以前,为了保持恒定的水压力,I.般使用外闭环管理变频器并采用PID算法实现.然而,水供应系统是I.个具有极大惯性的滞后,用户对供水的要求有较大的随机性,它可能会导致水压在管道不改变规律,所以用精确的数学模型来形容它是I.个困难的的工作.因此,很难用传统的PID控制以达到满意的控制效果.
模糊控制技术是使用模糊推论的方法来实现系统控制,它不需要建立数学模型[I.].近年来,许多研究人员添加了模糊控制策略的各种控制方案,取得了满意的效果.李忠和 *好棒文|www.hbsrm.com +Q: ^3^5`1^9`1^6^0`7^2#
其他人采用PLC控制设计了I.种模糊供水控制的系统,可以克服在传统的PID控制中难以调整参数的问题[II].赵宝勇在单个芯片上设计了I.个具有自调节因子的模糊PID控制器,从而起到控制水的重要作用.在具有非线性供给系统中,难于调整参数的传统PID控制滞后特性也得到了解决[III].李新春ATVIIIIXCVI.和采用模糊自整定PID算法设计了I.个恒压供水控制器[IV].侨伟德通过组合的管道压力函数神经网络和模糊逻辑,提出了I.种自适应闭环控制设计,这种设计I.直是稳健并且可靠性的[V].王彩霞设计出了I.变频供水系统控制III个水泵模糊控制,这大大降低了设计成本和操作[VI].
在上述方案中,,有大部分是PID控制的,从而会产生更大的频率波动,容易导致管道中的水压力不稳定.为了解决这些问题,在系统分析了工作对给水控制系统要求的特点和技术后,我们PLC和变频器有了以模糊控制的方法来建立I.个恒定的压力供水系统的方案.我们利用模糊逻辑控制理论检测压力传感器信号的输入和输出变量的模糊控制.
根据由运营经验作出的规则表通过模糊推理实现模糊逻辑控制.在实时控制过程中,该系统将输入的实时检测到的压力信号输出,寻找模糊控制表,然后我们得到I.个精确的输出的模大量的试验后,本文设计了I.个良好的实时性能控制,且硬件模块工作稳定可靠,我们已经证明了恒压供水系统.这里设计了自适应模糊控制器也是正确的,它有效地保证了压力管道供水的稳定性,它确实是I.个更好的控制系统.
II.系统控制方案
A.系统控制原理
III泵在系统中并联运行,PLC在给定的压力与实时检测到的管网压力间具有周期性,它们的应用价值被投入到PLC.模糊控制器可以计算其偏差E和变化偏差率△E.从模糊控制算法得到的输出控制信号,它是通过模拟量输出模块转换器发送到电动机来调节水泵的供电电压和频率.当有只需少量的水,I.个泵将在变频器的控制下稳定运行.当用水量需求比较大时,水泵全速运行,I.般不能保证对管网压力的稳定,PLC的下限压力信号和高速信号变频器是在同I.时间由PLC检测.为了保持连续性的压力,PLC首先从变频状态转换为工频状态,而另I.个泵为了保持稳定压力,由变频器启动开始顺序运行,增加网络供水的体积.如果操作两个泵仍然不能满足压力的要求,这时工作在变频状态下的水泵会转化为工频状态,而另I.台泵也将被启动.当水的消耗量减少,表明变频器工作在最低速度的信号是有效的.这时如果仍然在压力上限信号,PLC将停止工作在工频状态下的第I.个泵,以减少的量水.当两个信号仍存在时,PLC会停止工作在工频状态的第II个泵,直到最后I.次泵变频供水.
B.系统硬件
系统采用具有I/O扩展模块的西门子sVII-III.IVPLC[VII],主要检测元件有光开关,压力检测开关,共计I.II输入信号.执行元件是电机,变频器,声光报警等等,总共III个输出点.控制系统示意图如图I.所示.
图I.控制系统的原理图
PLC主要完成现场数据的采集,转换,存储,报警,控制变频器完成压力调整.III个水泵驱动直接通过变频器来保持压力不变.启动和停止逆变器分为手工控制和PLC控制.控制面板上有I.个通过PLC实时检测状态的手动/自动转换开关.选择手动功能时,通过按钮手动控制启动.停止和他们的泵开关.当自动选择功能,所有控制和报警是由PLC完成.
II *好棒文|www.hbsrm.com +Q: ^3^5`1^9`1^6^0`7^2#
I.模糊控制器的设计
系统采用II维模糊控制器.该输入是自来水管网中给定的水的压力和测量水压之间的偏差E,这是所计算的变动偏差和以前的偏差的偏差率.模糊输出控制器控制系统增加△U.在I.个住宅区,根据实际情况总结了模糊控制的供水规律和运营商的实践经验.模糊控制规则和模糊推理的合成规则,相应的控制决策可以从最优原则获得相应量的控制.经过计算机计算后,再加上线路I.次又I.次的调试和修改,模糊控制表将会得以在PLC实践中应用.
当系统运行时,它会从输入数据和计算的模糊量域值中计算E,△E.然后,它会搜索模糊控制表来控制增益量和频率转换器的输出,将由所述受控数量乘以所获取的比例系数[VIII,IX].
A.输入和输出的模糊变量
输入变量E和△E的论述值有是{-III,-II,-I.,0,I.,II,III}.它的模糊数值包括{NB(负大),NM(负中),NS(负小),ZO(零),PS(正小),PM(正中)和PB(正大)}.从属函数采用III角形,如图II所示.
图II输入变量的隶属度(E&△E)
输出变量△U的论述值是{-IV,-III,-II,-I.,0,I.,II,III,IV}.模糊数值{NB负大),纳米(负中),生理盐水(阴性小),ZO(零),PS(阳性小),PM(正中间)和PB(阳性大)}.从属函数采用III角形,如图III所示.
B.模糊规则表
模糊规则表见表格I,这是从现场操作人员的手动经验来总结的水压的调节规律.
图III输出变量的隶属度△U
C.寻求I.个模糊关系矩阵和模糊控制查询表
双输入和单输出语言控制策略如表I所示.我们按照最大隶属度法通过消除模糊得到精确的量△U[I.0].所有电子领域的要素组合E和△E,我们可以对应于每个组合的紧急程度解决确切数额△U.所以我们可以得到模糊控制查询表.
表I:模糊控制规则表
IV.系统软件
为方便编程和调试,控制系统采用模块化程序设计.主要的模块包括手动操作模块,自动操作模块,模块的故障诊断和报警.
A.手动操作模块
该系统在手动状态下运行时,PLC只接收保护电路和传感器的信号判断泵的运行状态.在发生故障时,输出报警信号.通过按钮和开关面板手动控制启动,停止和其他的的泵开关.
B.自动操作模块
自动操作模块包括系统初始化,顺序启动的测试,数据采集子程序,模糊控制子程序,初始值子程序,马达控制子程序等等.模块流程图如图IV所示.
图IV自动操作模块流程图
数据采集子程序:从主水管完成压力数据的采集.
电机控制子程序:控制III个水泵的停止.变频器的输出频率与带泵的速度.变频器的频率越大,泵的速度也越大,其结果是输水量变高.而降低变频器的输出频率和泵的速度,则水的消耗变少.当频率高达V0赫兹,即水泵全速运行,它仍不能满足供水要求时,PLC自动将第I.台泵的工作频率状态从变频状态转换到工频,这时由变频器启动第II台泵.虽然第II台泵在全速运行状态下,如果供水不能符合要求的,PLC会自动切换第II台泵工作频率,变频器将运行第III台泵.根据用水量水泵将I.个接I.个的投入运行.当两台水泵全速工作频率状态下运行,第III个泵工作在变频状态下,水的消耗降低,输出频率下降.如果频率达到下限或者水供应也大于水的消耗,该系统会自动停止第III泵.同样,如果第III泵停止之后,供水仍大于用水量,系统自动停止第II泵,以此类推.
模糊控制子程序:又称为定时中断.其功能是通过调节泵的速度保持恒定输出压力水.当主程序初始化系统时,我们首先得到目前的实际水压.我们还可以利用现有的误差量减去以前的误差量,即用这个压力减去压力设置和误差变化得到目前的误差量.然后我们可以通过模糊量化误差量及其变化,寻求得到模糊控制量的模糊控制表.最后,真正的控制体积其中来自模糊控制量乘以比例系数控制转换器,由PLC进行控制以保持恒压供水的频率.其流程图如图V所示.
图V模糊控制子程序
C.故障诊断和报警模块
转换器具有防止短路和过载的作用.PLC扫描这些触点的状态,当发生短路时,转换器会自动切断故障泵电机的电.这些状态数据被存储在通过PLC程序的存储区域中,根据逻辑分析来控制程序并设置的状态,该系统可确定设备或元件是否有故障.如果有故障,水泵的接触器将被切断,变频器将复位.然后后备泵开启并且后备泵的接触器将启动.同时,系统将输出故障泵的报警信号,如照明指示器.
V.结论
模糊控制理论用于手动控制转换系统的输入到输出,这过程中以人们丰富的经验反映自动控制的过程,并为该系统的可靠运行提供了保证.采用PLC作为控制器,其硬件结构简单,成本低.该系统的水泵电机在无级调速状态下运行.它的操作参数能够进行自动调整,从而保持水压恒定以满足用水要求.此外,有I.个SVII-III.IVPLC基本单元的RS-IVVIIIV接口,
通过它可以与楼宇监控中心通信,实现无人值守远程控制.经过半年多的测试表明该系统性能稳定,运行可靠,节能效果明显.
参考文献
[I.]扎德湖,模糊集的信息与控制,I.IXVIV,(VIII),pp.IIIIIIVIII-IIIVIII
[II]钟理,阎立,平凉宇,PLC和变频器恒压供水系统",华东川博功业学报/杂志东中国船舶工业学报,I.IXIXVIII,(I.II),pp.VIIX-VIIIII
[III]赵宝咏,"模糊控制技术在变频调速恒压供水系统的应用研究",电气传动自动化,II00III,IIV(VI),pp.I.VI-I.VII
[IV]李鑫春,李丰淑,杨顺,单片计算机与变频恒压供水系统在模糊控制中的应用",辽宁工程技术大学学报(自然科学版),II00II,0III,pp.IIIVIV-IIIVV
[V]乔伟德,模糊神经网络在PLC的恒压供水控制系统应用",电气传动自动化,II00VII,IIIX(II),pp.IVVIII-VI.
[VI]王彩霞,恒压模糊变频控制系统的研究",长春工业大学中国科学技术,第IIVI卷,第III期,II00III,pp.VIII-VIV
[VII]赵方文,西门子可编程控制器教程sVII-III.IV北京科技出版社,II00II.IX
[VIII]戚寿彭,黄魏林模糊控制恒压供水",自动化技术及其应用,II00VI,pp.VIIVII-VIIVIII
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附件II:外文原文(复印件)
TheVariableFrequencyandSpeedRegulationConstantPressureWaterSupplySystemBasedonPLCandFuzzyControl
PengXiaohong,XiaoLaisheng
CollegeofInformationTechnology
GuangdongOceanUniversity
Zhanjiang,P.RChina
e-mail:lgdpxh@I.IIVI.com
MoZhi
TechnologyDepartment
ZhanjiangNewZhongmeiChemicalIndustriesCo.,Ltd.
Zhanjiang,P.RChina
LiuGuodong
MaomingBranch
ChinaConstructionBank
Maoming,P.RChina
Abstract_Forsolvingtheproblemofpoorqualityandwasteofelectricenergycoursedbywatersupplymodeofahighwater
towerandadirectwaterpump,introduceaconstantpressuresupplywatersystem,whichadoptsembeddedfuzzycontroltechnology,usingPLCandfrequencyconvenerasitscore.Whenthesystemruns,waterpressureofthepipeisinputtedintothePLCfromterminalX0throughpressuretransmitter.Comparingthevalueofmeasuredpressurewithitssetvalue,PLCcontrolstheworkfrequencyofthefrequencyconverterbytheoutputsignalonfuzzycalculationinordertocontrolrotationspeedofwaterpumpandadjustwaterpressureofthepipe.TherealtimecontrolperformancetothewaterPressureofwatersupplysystemdesignedinthispaperwasprovedtobeall-rightaccordingtotheexperimentationvalidated.Thehardwaremoduleissteady-goingandreliable,andthefuzzycontrollerisproperandvalidandcanguaranteethebetterstabilityofwaterpressure.
Keywords-fuzzycontrol;PLC;variablefrequencyandspeedregulation
I.INTRODUCTION
Withthehigh-speeddevelopmentofeconomyandsociety,energyshortageisbecomingmoreandmoreobviousandthepeople’srequirementsonbothqualityandreliabilityofwatersupplyisalsoincreasing.Thereforeithasbecomeaninevitabletrendtouseadvancedautomationtechnologytodesigntheconstantpressurewatersupplysystemwithhighenergyconservationandhighreliability.Becausetheusers’requirementofwatersupplyisoftenunsteady,aclosed-loopregulationisneededtouseoutsideafrequencyconverterinordertokeepaconstantwaterpressureanditisgenerallyrealizedbyPIDinthepast.However,thewatersupplysystemisalagonewithgreatinertiaandtheusers’requirementforwatersupplyhaslargerandomnessanditmayleadtowaterpressureonthepipelinewithoutchanginglaw,soitisahardjobtodescribeitwithprecisemathematicalmodel.Therefore,itisdifficulttoachievesatisfactorycontroleffectbyusingthetraditionalPIDcontrol.Thefuzzycontroltechnologyisagoodwaytousefuzzyinferencetorealizesystemcontrolanditdoesnotneedtobuildmathematicalmodels[I.].Inrecentyears,manyresearchersaddedfuzzycontrolstrategytoavarietyofcontrolschemesandachievedsatisfactoryresults.LiZhongandothersdesignedakindoffuzzywatersupplycontrolsystemcontrolledbyPLCthatcanovercometheissuestoadjusttheparametersdifficultlyinthetraditionalPIDcontrol[II].ZhaoBao-yonghasdesignedafuzzy-PIDcontrollerwithself-adjustingfactorbasedonasinglechip,whichhasplayedanimportantroletocontrolthewatersupplysystemwithnon-linear,lagcharacteristicsandalsosolvedtheproblemtoadjustparametersdifficultlyinthetraditionalPIDcontrol[III].LIXin-chundesignedaconstantpressurewatersupplycontrollerbasedonATVIIIIXCVI.andappliedfuzzyself-tuningPIDalgorithmtoit[IV].QiaoWei-deputsforwardadesignwithadaptiveclosed-loopcontrolfunctionsonpipelinepressurethroughthecombinationofneuralnetworksandfuzzylogicandithasbeenrobustandreliability[V].WangCai-xiahasdesignedafuzzywater
supplysystemforonefrequencyconvertertocontrolthreepumps,whichgreatlyreducesthecostofbothdesignandoperation[VI]
Amongtheschemesmentionedabove,mostofthemarebasedonthePIDcontrol,whichhavegreaterfrequencyfluctuationsandeasilyleadtowaterpressureinthepipelineunsteady.Tosolvethoseproblems,afterhavingsystemicallyanalyzedtheworkcharacteristicandthetechnicalrequirementforawatersupplycontrolsystem,wehavetakenfuzzycontrolmethodtobuildaconstantpressurewatersupplysystembasedonPLCandfrequencyconverter.Wemakeuseoffuzzylogiccontroltheorytomakepressuresensorsignaltoinputandcontrolvariablefromoutputfuzzyandachievefuzzylogiccontroltablebyfuzzyreasoningaccordingtotheruletablemadebyoperatingexperience.Inthecourseofreal-timecontrol,thesystemtransformsinputsignalofpressuredetectedinreal-timeintooutputbyseekingfuzzylogiccontroltable,andthenweobtainapreciseoutputbyfuzzydecision-making.Atlast,thesystemcompletesthewholeprocessoffuzzylogiccontrolforconstantwaterpressurebycontrollingthefrequencyofmotoraccordingtothepreciseoutput.Afteralotoftest,wehaveprovedthattheconstantpressurewatersupplysystemdesignedinthispaperhasagoodperformanceofreal-timecontrolanditshardwaremodulesworkstablyandreliably.Theadaptivefuzzycontrollerdesignedhereisalsocorrect
andeffectiveforguaranteeingthestabilityofthewaterpressureonpipelineanditisreallyabettercontrolsystem.
II.SYSTEMCONTROLSCHEME
A.Theprincipleofsystemcontrol
Threepumpsruninparallelinthesystem.PLChasaperiodicreal-timedetectiononagivenpressureandactualpressureonpipenetwork,andtheirvaluesareputintoPLC.FuzzycontrollercomputestheirdeviationEandchangesintherateofdeviationOutput△E.controlsignalsfromthefuzzycontrolalgorithmaregained,whicharesenttoconverterthroughanalogoutputmoduletoadjustthepumpmotorpowersupplyvoltageandfrequency.Whenthereisthesmallamountofwater,onepumphasastableoperationunderthecontrolofafrequencyconverter.Whentheamountofwaterissomuchthatwaterpumpwhichrunsatfullspeedcannotguaranteethestablepressureonthepipenetwork,lowerlimitpressuresignalonPLCandthehigh-speedsignalonconverterwasdetectedbyPLCatthesametime.PLCtransformsthefirstpumpfromvariablefrequencystatetoworkfrequencystateinordertokeeppressurecontinuity,whileanotherpumpwhichisstartedbyfrequencyconverterbeginstoruninordertokeepstablepressurebyincreasingthevolumeofthewatersupplynetwork.Iftheoperationofthetwopumpscannotmeettherequirementsofthepressure,thepumpwhichisworkinginvariablefrequencystateistransformedtoworkfrequencystate,andanotherpumpwillbestarted.Whenthewaterconsumptionreduces,thesignalwhichshowsthatthefrequencyconverterworksattheminimumspeediseffective.Atthistimeifthepressureupperlimitsignalisstillbeing,PLCwillstopthefirstpumpwhichworksatworkfrequencystatetoreducetheamountofwater.Whenthetwosignalsarestillbeing,PLCstopsthesecondpumpwhichworksatworkfrequencystate,untilthelastpumpsupplieswaterbyfrequencyconverter.
B.Systemhardware
SystemselectstheSiemensSVII-III.IVPLC[VII],withI/Oexpansionmodules.Themaindetectioncomponentsareopticalswitches,pressuredetectionswitches,totalingI.IIinputsignals.TheImplementationcomponentsaremotor,frequencyconverter,soundandlightalarm,andsoon,atotalofIIIoutputpoints.ControlsystemschematicisshowninFig.I..ThePLCmainlycompleteson-sitedataacquisition,conversion,storage,alarm,controllingfrequencyconvertertocompletepressureadjustments.Threepumpsaredrivendirectlybyfrequencyconvertertokeepconstantpressure.ThestartandstopofinverterisdividedintomanualcontrolandPLCcontrol.Onthecontrolpanelthereisamanual/automaticconversionswitchtowhichPLChasareal-timedetectionofstates.Whenthemanualfunctionisselected,thestartandstopandtheirswitchofthepumpoperationismanuallycontrolledthroughthepanelbuttonsandswitches.Whentheautomaticfunctionisselected,allcontrolandalarmarecompletedbyPLC.
FigureI..Controlsystemschematic
III.DESIGNOFFUZZYCONTROLLER
Systemsusestwo-dimensionalfuzzycontroller.TheinputisthedeviationEbetweenthegivenwaterpressureandmeasuredwaterpressureinthewaterpipenetworkandthechangesintherateofdeviationwhichiscomputedfromthedeviationandpreviousdeviation.Theoutputoffuzzycontrolleriscontrolsystemincrement△U.Thefuzzycontrolrulesaresummedupaccordingtotherealsituationofwatersupplyinaresidentialareaandthepracticalexperienceofoperators.Thecorrespondingcontroldecision-makingcanbegainedbasedonfuzzycontrolrulesandfuzzyreasoningsynthesisrulesandthecorrespondingamountofcontrolwillbegainedfromtheprincipleofmaximummembership.AftercomputercomputesOff-lineandhasdebuggingandamendmenttimeaftertime,thefuzzycontroltablewillbegottenwhichcanbeappliedinpracticeandisputinPLC.Whenthesystemruns,itcomputesE,△Efrominputdataandcomputesdomainvalueoffuzzyamount.Thenitsearchesfuzzycontroltabletogaincontrolledquantityandtheoutputofcontrollingfrequencyconverterwillbegottenfromthecontrolledquantitymultipliedbytheratiocoefficient[VIII,IX].
A.Makinginputandoutputvariablesfuzzy
TheuniversesofdiscourseofinputvariableEand△Eare{-III,-II,-I.,0,I.,II,III}.ItsFuzzylanguagevaluesare{NB(negativebig),NM(negativemiddle),NS(negativesmall),ZO(zero),PS(positivesmall),PM(positivemiddle)andPB(positivebig)}.Membershipfunctionusestriangle,showsinFig.II.
Theuniversesofdiscourseofoutputvariable△Uare{-IV,-III,-II,-I.,0,I.,II,III,IV}.ItsFuzzylanguagevaluesare{NB(negativebig),NM(negativemiddle),NS(negativesmall),ZO(zero),PS(positivesmall),PM(positivemiddle)andPB(positivebig)}.Membershipfunctionusestriangle,showsinFig.III.
FigureII.Themembershipdegreeofinputvar.E&△E
FigureIII.Themembershipdegreeofoutputvar.△U
B.Fuzzyruletable
FuzzyruletableisshowninTABLEI,whichissummedupfromtheexperienceoftheon-siteoperatorstomanuallyadjustwaterpressure.
C.Seekingafuzzyrelationshipmatrixandfuzzycontrol
querytable
Two-input&single-outputlanguagecontrolstrategyshowninTABLEIiscomposedofIVIXfuzzyconditionalstatements.Weobtainthepreciseamountbyremovingfuzzy△Uinaccordancewiththelargestmembershiplaw[I.0].ForallthecombinationoftheelementsonthedomainforEand△E,wecanworkoutpreciseamountofemergencydegree△Ucorrespondingtoeachcombination.Sowecangetfuzzycontrolquerytable.
TABLEI.FUZZYCONTROLRULETABLE
IV.SYSTEMSOFTWARE
Fortheconvenienceofprogramminganddebugging,systemcontrollerusesmodularprogramming.Themainmoduleconsistsofmanualoperationmodule,automaticoperationmodule,faultdiagnosisandalarmmodules.
A.Manualoperationmodule
Whenthesystemrunsatmanualstate,PLConlyreceivesthecircuitprotectionandthesensorsignalsandjudgestherunningstateofthepumps.Intheeventoffailure,thealarmsignaloutputs.Thestart,stopandtheirswitchofthepumpsoperatesbyhandthroughthebuttonsandswitchesonthepanel.
B.Automaticoperationmodule
Automaticoperationmoduleincludessysteminitialization,testingofthebootorder,dataacquisitionsubroutine,fuzzycontrolSubroutine,initialvaluesubroutine,motorcontrolsubroutine,andsoon.ModuleflowchartisshowninFig.IV.
Dataacquisitionsubroutine:completingtheacquisitionofdatafromthemainwaterpipepressure.
Motorcontrolsubroutine:controllingtheoperationandstopofIIIwaterpumps.Theoutputfrequencyoffrequencyconverterisrelatedwiththespeedofpumps.Asaresultofit,themorethewaterconsumptionis,thehighertheoutputfrequencyoftheconverteris,thelargerthespeedofthepumpsis.Whereasthelittlethewaterconsumptionis,thelowertheoutputfrequencyoftheconverteris,thesmallerthespeedofthepumpsis.WhenfrequencyisuptoV0Hz,i.e.pumpsrunningatfullspeed,anditcannotmeettherequirementofwatersupply,PLCautomaticallytransformsthefirstpumpfromvariablefrequencystatetoworkfrequencystateandthesecondpumpwhichisstartedbyfrequencyconverterwillrun.Ifthewatersupplycannotmeettherequirementsalthoughthesecondpumprunsatfullspeed,PLCwillautomaticallyswitchsecondpumptoworkfrequencyoperationandthethirdpumpwhichisstartedbyfrequencyconverterwillrun.Accordingtothelowthepumpswillbeputintooperationonebyone.Whentwopumpsrunatfullspeedandatworkfrequencystateandthethirdpumpoperatesatvariablefrequencystate,waterconsumptionreducesandtheoutputfrequencycomesdown.Iffrequencyreachesthelowestlimitandwatersupplyisalsogreaterthanthewaterconsumption,thesystemautomaticallystopthethirdpump.Similarly,ifwatersupplyisstillgreaterthanthewaterconsumptionafterthethirdpumpstops,thesystemautomaticallystopthesecondpump,andsoon..
Fuzzycontrolsubroutine:itiscalledbyatiminginterrupting.Itsfunctionistokeepconstantoutputwaterpressurebyadjustingthespeedofthepumps.Whenthemainprograminitializesthesystem,wefirstlygetthepresentactualwaterpressure.Wecanalsogetthepresenterrorvolumebyusingthispressuresubtractingthepressuresettingsanderrorchangeswillbegottenbyusingpresenterrorvolumesubtractingthepreviouserrorvolume.Andthenwecanobtainfuzzycontrolvolumethroughfuzzyquantitativetoerrorvolumeanditschangesandseekingthefuzzycontroltable.Atlast,therealcontrolvolumewhichcomesfromfuzzycontrolvolumemultipliedbythescalefactorcontrolsthefrequencyoftheconverterbyPLCanditscommunicationinordertokeepconstantpressurewatersupply.ItsflowchartisshowninFig.V.
C.faultdiagnosisandalarmmodules
Converterhasthefunctionofavoidingshortcircuitandoverload.Whenthereisshortcircuit,overloadfaultinwaterpumpmotor,converterautomaticallycutsoffapowersupplycircuit,accessingtothestateofprotectionandoutputtingalarmsignals.Systemlinksauxiliarynodesofthecontactors,circuitbreakerscorrespondingtothepointoffailuretoPLCandPLCscansthestateofthesecontacts.ThesestatedataarestoredinthestorageareathroughPLCprogram.Accordingtologicalanalysistocontrolprogramandthestateofsettings,thesystemcandeterminewhetherthereisafailureintheequipmentorcomponents.Ifthereisafailure,thecontactorsofwaterpumpswillbecutoffandInverterwillreset.Andthenthecontactorsofback-uppumpturnonandback-uppumpwillstart.Atthesametime,thesystemoutputsalarmsignalsofthefailurepump,suchaslightingindicators.
V.CONCLUSION
Fuzzycontroltheoryisusedtotransformthesystemsinputintooutputinordertoenrichpeople’sexperienceduringthecourseofmanualcontrol,whichisreflectedduringthecourseofautomaticcontrolandprovidesaguaranteeforthereliableoperationofthesystem.PLCisusedasacontroller.Itshardwarestructureissimpleandlowcost.Waterpumpmotorofthesystemworksatsteplessspeedregulation.Itsoperatingparametersareautomaticallyadjusted,whichcankeepconstantwaterpressuretomeettherequirementswhilewaterconsumptionchanges.Inaddition,thereisaRS-IVVIIIVinterfaceinthebasicunitofSVII-III.IVPLCbywhichitcancommunicatewithbuildingmonitoringcentertoachieveunattendedremotecontrol.Aftersixmonthsoftestthesystemhasstableperformance,reliableoperationandenergy-savingeffect.
FigureIV.AutomaticFigureV.Fuzzy
operationmoduleflowchartcontrolsubroutine
REFERENCES
[I.]ZadehL.A,Fuzzysetsinformationandcontrol",I.IXVIV,(VIII),pp.IIIIIIVIII-IIIVIII.
[II]ZhongLi,YanLi,PingliangYu,ConstantpressurewatersupplysystemwithPLCandinverter",HuadongChuanboGongyeXueyuanXuebao/JournalofEastChinaShipbuildingInstitute,I.IXIXVIII,(I.II),pp.VIIX-VIIIII.
[III]BaoyongZhao,Applicationresearchofthefuzzycontroltechnologyinthevariable-frequencyspeed-governingconstant-pressurewatersupplysystem",ElectricDriveAutomation,II00III,IIV(VI),pp.I.VI-I.VII.
[IV]XinchunLi,FengshuLi,ShunYang,Theapplicationofsingle-chipcomputerinthefuzzycontrolofwater-supplysystemwithvariablefrequencyandconstantpressure",JournalofLiaoningTechnical
University(NaturalScience),II00II,0III,pp.IIIVIV-IIIVV.
[V]WeideQiao,ApplicationoffuzzyneuralnetworkinPLCwaterSupplycontrolsystemwithconstantvoltage",ElectricDriveAutomation,II00VII,IIIX(II),pp.IVVIII-VI..
[VI]CaixiaWang,Studyoffuzzyvariablefrequencycontrolsystemforconstantpressure",JournalofChangchunUniversityofScienceandTechnology,Vol.IIVI,No.III,II00III,pp.VIII-VIV.
[VII]ZhaofangWen,SIMATICSVII-III.IVProgrammableControllerTutorial,Beijinginstitueoftechnologypublisher,II00II.IX.
[VIII]QishouPeng,WeilingHuang,,single_chipfuzzycontrolofaconstantpressurewatersupply",TechniquesofAutomation&
Applications,II00VI,pp.VIIVII-VIIVIII.
[IX]GuozhongXu,JingZhu,Single-chipfuzzycontrolconstantpressurewatersupplysystem",MicroelectronicsandComputer,I.IXIXVIII,pp.VIII-I.II.
[I.0]JunpuWang,Intelligentcontrol",PressofUniversityofScienceandTechnologyofChina,I.IXIXVI,pp.IX0-I.IIIV.
彭晓红,肖来生
信息技术
广东海洋大学
湛江,中国
电子邮件:lgdpxh@I.IIVI.com
莫之
技术部
湛江新中美化工实业有限公司
湛江,中国
刘国栋
茂名分公司
中国建设银行
茂名,中国
摘要:为了解决由塔和水泵高的供水方式直接引起的电能质量差和浪费的问题,引入I.个恒压供水系统,该系统采用了PLC和变频为核心的嵌入式模糊控制技术.当系统运行时,该管的水压通过压力变送器被输入到PLC的终端X0.测得的压力值与设定值进行比较,PLC通过控制变频器的工作频率以控制模糊计算的输出信号,从而控制水泵的转动速度和调节的水压.本文设计的水压实时控制供水系统通过实验被很好地验证.硬件模块是稳定的.可靠的,并且模糊控制器正确有效,较好的保证了水压的稳定性.
关键字:模糊控制PLC变频调速规则
I..引言
随着经济和社会的高速发展,能源短缺日益明显,人们对生活的质量和供水可靠性也越来越重视.因此,利用先进的.具有高节能和高可靠性的自动化技术设计的恒压供水系统成为必然趋势.
因为用户的供水要求往往是不稳定的,以前,为了保持恒定的水压力,I.般使用外闭环管理变频器并采用PID算法实现.然而,水供应系统是I.个具有极大惯性的滞后,用户对供水的要求有较大的随机性,它可能会导致水压在管道不改变规律,所以用精确的数学模型来形容它是I.个困难的的工作.因此,很难用传统的PID控制以达到满意的控制效果.
模糊控制技术是使用模糊推论的方法来实现系统控制,它不需要建立数学模型[I.].近年来,许多研究人员添加了模糊控制策略的各种控制方案,取得了满意的效果.李忠和 *好棒文|www.hbsrm.com +Q: ^3^5`1^9`1^6^0`7^2#
其他人采用PLC控制设计了I.种模糊供水控制的系统,可以克服在传统的PID控制中难以调整参数的问题[II].赵宝勇在单个芯片上设计了I.个具有自调节因子的模糊PID控制器,从而起到控制水的重要作用.在具有非线性供给系统中,难于调整参数的传统PID控制滞后特性也得到了解决[III].李新春ATVIIIIXCVI.和采用模糊自整定PID算法设计了I.个恒压供水控制器[IV].侨伟德通过组合的管道压力函数神经网络和模糊逻辑,提出了I.种自适应闭环控制设计,这种设计I.直是稳健并且可靠性的[V].王彩霞设计出了I.变频供水系统控制III个水泵模糊控制,这大大降低了设计成本和操作[VI].
在上述方案中,,有大部分是PID控制的,从而会产生更大的频率波动,容易导致管道中的水压力不稳定.为了解决这些问题,在系统分析了工作对给水控制系统要求的特点和技术后,我们PLC和变频器有了以模糊控制的方法来建立I.个恒定的压力供水系统的方案.我们利用模糊逻辑控制理论检测压力传感器信号的输入和输出变量的模糊控制.
根据由运营经验作出的规则表通过模糊推理实现模糊逻辑控制.在实时控制过程中,该系统将输入的实时检测到的压力信号输出,寻找模糊控制表,然后我们得到I.个精确的输出的模大量的试验后,本文设计了I.个良好的实时性能控制,且硬件模块工作稳定可靠,我们已经证明了恒压供水系统.这里设计了自适应模糊控制器也是正确的,它有效地保证了压力管道供水的稳定性,它确实是I.个更好的控制系统.
II.系统控制方案
A.系统控制原理
III泵在系统中并联运行,PLC在给定的压力与实时检测到的管网压力间具有周期性,它们的应用价值被投入到PLC.模糊控制器可以计算其偏差E和变化偏差率△E.从模糊控制算法得到的输出控制信号,它是通过模拟量输出模块转换器发送到电动机来调节水泵的供电电压和频率.当有只需少量的水,I.个泵将在变频器的控制下稳定运行.当用水量需求比较大时,水泵全速运行,I.般不能保证对管网压力的稳定,PLC的下限压力信号和高速信号变频器是在同I.时间由PLC检测.为了保持连续性的压力,PLC首先从变频状态转换为工频状态,而另I.个泵为了保持稳定压力,由变频器启动开始顺序运行,增加网络供水的体积.如果操作两个泵仍然不能满足压力的要求,这时工作在变频状态下的水泵会转化为工频状态,而另I.台泵也将被启动.当水的消耗量减少,表明变频器工作在最低速度的信号是有效的.这时如果仍然在压力上限信号,PLC将停止工作在工频状态下的第I.个泵,以减少的量水.当两个信号仍存在时,PLC会停止工作在工频状态的第II个泵,直到最后I.次泵变频供水.
B.系统硬件
系统采用具有I/O扩展模块的西门子sVII-III.IVPLC[VII],主要检测元件有光开关,压力检测开关,共计I.II输入信号.执行元件是电机,变频器,声光报警等等,总共III个输出点.控制系统示意图如图I.所示.
图I.控制系统的原理图
PLC主要完成现场数据的采集,转换,存储,报警,控制变频器完成压力调整.III个水泵驱动直接通过变频器来保持压力不变.启动和停止逆变器分为手工控制和PLC控制.控制面板上有I.个通过PLC实时检测状态的手动/自动转换开关.选择手动功能时,通过按钮手动控制启动.停止和他们的泵开关.当自动选择功能,所有控制和报警是由PLC完成.
II *好棒文|www.hbsrm.com +Q: ^3^5`1^9`1^6^0`7^2#
I.模糊控制器的设计
系统采用II维模糊控制器.该输入是自来水管网中给定的水的压力和测量水压之间的偏差E,这是所计算的变动偏差和以前的偏差的偏差率.模糊输出控制器控制系统增加△U.在I.个住宅区,根据实际情况总结了模糊控制的供水规律和运营商的实践经验.模糊控制规则和模糊推理的合成规则,相应的控制决策可以从最优原则获得相应量的控制.经过计算机计算后,再加上线路I.次又I.次的调试和修改,模糊控制表将会得以在PLC实践中应用.
当系统运行时,它会从输入数据和计算的模糊量域值中计算E,△E.然后,它会搜索模糊控制表来控制增益量和频率转换器的输出,将由所述受控数量乘以所获取的比例系数[VIII,IX].
A.输入和输出的模糊变量
输入变量E和△E的论述值有是{-III,-II,-I.,0,I.,II,III}.它的模糊数值包括{NB(负大),NM(负中),NS(负小),ZO(零),PS(正小),PM(正中)和PB(正大)}.从属函数采用III角形,如图II所示.
图II输入变量的隶属度(E&△E)
输出变量△U的论述值是{-IV,-III,-II,-I.,0,I.,II,III,IV}.模糊数值{NB负大),纳米(负中),生理盐水(阴性小),ZO(零),PS(阳性小),PM(正中间)和PB(阳性大)}.从属函数采用III角形,如图III所示.
B.模糊规则表
模糊规则表见表格I,这是从现场操作人员的手动经验来总结的水压的调节规律.
图III输出变量的隶属度△U
C.寻求I.个模糊关系矩阵和模糊控制查询表
双输入和单输出语言控制策略如表I所示.我们按照最大隶属度法通过消除模糊得到精确的量△U[I.0].所有电子领域的要素组合E和△E,我们可以对应于每个组合的紧急程度解决确切数额△U.所以我们可以得到模糊控制查询表.
表I:模糊控制规则表
IV.系统软件
为方便编程和调试,控制系统采用模块化程序设计.主要的模块包括手动操作模块,自动操作模块,模块的故障诊断和报警.
A.手动操作模块
该系统在手动状态下运行时,PLC只接收保护电路和传感器的信号判断泵的运行状态.在发生故障时,输出报警信号.通过按钮和开关面板手动控制启动,停止和其他的的泵开关.
B.自动操作模块
自动操作模块包括系统初始化,顺序启动的测试,数据采集子程序,模糊控制子程序,初始值子程序,马达控制子程序等等.模块流程图如图IV所示.
图IV自动操作模块流程图
数据采集子程序:从主水管完成压力数据的采集.
电机控制子程序:控制III个水泵的停止.变频器的输出频率与带泵的速度.变频器的频率越大,泵的速度也越大,其结果是输水量变高.而降低变频器的输出频率和泵的速度,则水的消耗变少.当频率高达V0赫兹,即水泵全速运行,它仍不能满足供水要求时,PLC自动将第I.台泵的工作频率状态从变频状态转换到工频,这时由变频器启动第II台泵.虽然第II台泵在全速运行状态下,如果供水不能符合要求的,PLC会自动切换第II台泵工作频率,变频器将运行第III台泵.根据用水量水泵将I.个接I.个的投入运行.当两台水泵全速工作频率状态下运行,第III个泵工作在变频状态下,水的消耗降低,输出频率下降.如果频率达到下限或者水供应也大于水的消耗,该系统会自动停止第III泵.同样,如果第III泵停止之后,供水仍大于用水量,系统自动停止第II泵,以此类推.
模糊控制子程序:又称为定时中断.其功能是通过调节泵的速度保持恒定输出压力水.当主程序初始化系统时,我们首先得到目前的实际水压.我们还可以利用现有的误差量减去以前的误差量,即用这个压力减去压力设置和误差变化得到目前的误差量.然后我们可以通过模糊量化误差量及其变化,寻求得到模糊控制量的模糊控制表.最后,真正的控制体积其中来自模糊控制量乘以比例系数控制转换器,由PLC进行控制以保持恒压供水的频率.其流程图如图V所示.
图V模糊控制子程序
C.故障诊断和报警模块
转换器具有防止短路和过载的作用.PLC扫描这些触点的状态,当发生短路时,转换器会自动切断故障泵电机的电.这些状态数据被存储在通过PLC程序的存储区域中,根据逻辑分析来控制程序并设置的状态,该系统可确定设备或元件是否有故障.如果有故障,水泵的接触器将被切断,变频器将复位.然后后备泵开启并且后备泵的接触器将启动.同时,系统将输出故障泵的报警信号,如照明指示器.
V.结论
模糊控制理论用于手动控制转换系统的输入到输出,这过程中以人们丰富的经验反映自动控制的过程,并为该系统的可靠运行提供了保证.采用PLC作为控制器,其硬件结构简单,成本低.该系统的水泵电机在无级调速状态下运行.它的操作参数能够进行自动调整,从而保持水压恒定以满足用水要求.此外,有I.个SVII-III.IVPLC基本单元的RS-IVVIIIV接口,
通过它可以与楼宇监控中心通信,实现无人值守远程控制.经过半年多的测试表明该系统性能稳定,运行可靠,节能效果明显.
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附件II:外文原文(复印件)
TheVariableFrequencyandSpeedRegulationConstantPressureWaterSupplySystemBasedonPLCandFuzzyControl
PengXiaohong,XiaoLaisheng
CollegeofInformationTechnology
GuangdongOceanUniversity
Zhanjiang,P.RChina
e-mail:lgdpxh@I.IIVI.com
MoZhi
TechnologyDepartment
ZhanjiangNewZhongmeiChemicalIndustriesCo.,Ltd.
Zhanjiang,P.RChina
LiuGuodong
MaomingBranch
ChinaConstructionBank
Maoming,P.RChina
Abstract_Forsolvingtheproblemofpoorqualityandwasteofelectricenergycoursedbywatersupplymodeofahighwater
towerandadirectwaterpump,introduceaconstantpressuresupplywatersystem,whichadoptsembeddedfuzzycontroltechnology,usingPLCandfrequencyconvenerasitscore.Whenthesystemruns,waterpressureofthepipeisinputtedintothePLCfromterminalX0throughpressuretransmitter.Comparingthevalueofmeasuredpressurewithitssetvalue,PLCcontrolstheworkfrequencyofthefrequencyconverterbytheoutputsignalonfuzzycalculationinordertocontrolrotationspeedofwaterpumpandadjustwaterpressureofthepipe.TherealtimecontrolperformancetothewaterPressureofwatersupplysystemdesignedinthispaperwasprovedtobeall-rightaccordingtotheexperimentationvalidated.Thehardwaremoduleissteady-goingandreliable,andthefuzzycontrollerisproperandvalidandcanguaranteethebetterstabilityofwaterpressure.
Keywords-fuzzycontrol;PLC;variablefrequencyandspeedregulation
I.INTRODUCTION
Withthehigh-speeddevelopmentofeconomyandsociety,energyshortageisbecomingmoreandmoreobviousandthepeople’srequirementsonbothqualityandreliabilityofwatersupplyisalsoincreasing.Thereforeithasbecomeaninevitabletrendtouseadvancedautomationtechnologytodesigntheconstantpressurewatersupplysystemwithhighenergyconservationandhighreliability.Becausetheusers’requirementofwatersupplyisoftenunsteady,aclosed-loopregulationisneededtouseoutsideafrequencyconverterinordertokeepaconstantwaterpressureanditisgenerallyrealizedbyPIDinthepast.However,thewatersupplysystemisalagonewithgreatinertiaandtheusers’requirementforwatersupplyhaslargerandomnessanditmayleadtowaterpressureonthepipelinewithoutchanginglaw,soitisahardjobtodescribeitwithprecisemathematicalmodel.Therefore,itisdifficulttoachievesatisfactorycontroleffectbyusingthetraditionalPIDcontrol.Thefuzzycontroltechnologyisagoodwaytousefuzzyinferencetorealizesystemcontrolanditdoesnotneedtobuildmathematicalmodels[I.].Inrecentyears,manyresearchersaddedfuzzycontrolstrategytoavarietyofcontrolschemesandachievedsatisfactoryresults.LiZhongandothersdesignedakindoffuzzywatersupplycontrolsystemcontrolledbyPLCthatcanovercometheissuestoadjusttheparametersdifficultlyinthetraditionalPIDcontrol[II].ZhaoBao-yonghasdesignedafuzzy-PIDcontrollerwithself-adjustingfactorbasedonasinglechip,whichhasplayedanimportantroletocontrolthewatersupplysystemwithnon-linear,lagcharacteristicsandalsosolvedtheproblemtoadjustparametersdifficultlyinthetraditionalPIDcontrol[III].LIXin-chundesignedaconstantpressurewatersupplycontrollerbasedonATVIIIIXCVI.andappliedfuzzyself-tuningPIDalgorithmtoit[IV].QiaoWei-deputsforwardadesignwithadaptiveclosed-loopcontrolfunctionsonpipelinepressurethroughthecombinationofneuralnetworksandfuzzylogicandithasbeenrobustandreliability[V].WangCai-xiahasdesignedafuzzywater
supplysystemforonefrequencyconvertertocontrolthreepumps,whichgreatlyreducesthecostofbothdesignandoperation[VI]
Amongtheschemesmentionedabove,mostofthemarebasedonthePIDcontrol,whichhavegreaterfrequencyfluctuationsandeasilyleadtowaterpressureinthepipelineunsteady.Tosolvethoseproblems,afterhavingsystemicallyanalyzedtheworkcharacteristicandthetechnicalrequirementforawatersupplycontrolsystem,wehavetakenfuzzycontrolmethodtobuildaconstantpressurewatersupplysystembasedonPLCandfrequencyconverter.Wemakeuseoffuzzylogiccontroltheorytomakepressuresensorsignaltoinputandcontrolvariablefromoutputfuzzyandachievefuzzylogiccontroltablebyfuzzyreasoningaccordingtotheruletablemadebyoperatingexperience.Inthecourseofreal-timecontrol,thesystemtransformsinputsignalofpressuredetectedinreal-timeintooutputbyseekingfuzzylogiccontroltable,andthenweobtainapreciseoutputbyfuzzydecision-making.Atlast,thesystemcompletesthewholeprocessoffuzzylogiccontrolforconstantwaterpressurebycontrollingthefrequencyofmotoraccordingtothepreciseoutput.Afteralotoftest,wehaveprovedthattheconstantpressurewatersupplysystemdesignedinthispaperhasagoodperformanceofreal-timecontrolanditshardwaremodulesworkstablyandreliably.Theadaptivefuzzycontrollerdesignedhereisalsocorrect
andeffectiveforguaranteeingthestabilityofthewaterpressureonpipelineanditisreallyabettercontrolsystem.
II.SYSTEMCONTROLSCHEME
A.Theprincipleofsystemcontrol
Threepumpsruninparallelinthesystem.PLChasaperiodicreal-timedetectiononagivenpressureandactualpressureonpipenetwork,andtheirvaluesareputintoPLC.FuzzycontrollercomputestheirdeviationEandchangesintherateofdeviationOutput△E.controlsignalsfromthefuzzycontrolalgorithmaregained,whicharesenttoconverterthroughanalogoutputmoduletoadjustthepumpmotorpowersupplyvoltageandfrequency.Whenthereisthesmallamountofwater,onepumphasastableoperationunderthecontrolofafrequencyconverter.Whentheamountofwaterissomuchthatwaterpumpwhichrunsatfullspeedcannotguaranteethestablepressureonthepipenetwork,lowerlimitpressuresignalonPLCandthehigh-speedsignalonconverterwasdetectedbyPLCatthesametime.PLCtransformsthefirstpumpfromvariablefrequencystatetoworkfrequencystateinordertokeeppressurecontinuity,whileanotherpumpwhichisstartedbyfrequencyconverterbeginstoruninordertokeepstablepressurebyincreasingthevolumeofthewatersupplynetwork.Iftheoperationofthetwopumpscannotmeettherequirementsofthepressure,thepumpwhichisworkinginvariablefrequencystateistransformedtoworkfrequencystate,andanotherpumpwillbestarted.Whenthewaterconsumptionreduces,thesignalwhichshowsthatthefrequencyconverterworksattheminimumspeediseffective.Atthistimeifthepressureupperlimitsignalisstillbeing,PLCwillstopthefirstpumpwhichworksatworkfrequencystatetoreducetheamountofwater.Whenthetwosignalsarestillbeing,PLCstopsthesecondpumpwhichworksatworkfrequencystate,untilthelastpumpsupplieswaterbyfrequencyconverter.
B.Systemhardware
SystemselectstheSiemensSVII-III.IVPLC[VII],withI/Oexpansionmodules.Themaindetectioncomponentsareopticalswitches,pressuredetectionswitches,totalingI.IIinputsignals.TheImplementationcomponentsaremotor,frequencyconverter,soundandlightalarm,andsoon,atotalofIIIoutputpoints.ControlsystemschematicisshowninFig.I..ThePLCmainlycompleteson-sitedataacquisition,conversion,storage,alarm,controllingfrequencyconvertertocompletepressureadjustments.Threepumpsaredrivendirectlybyfrequencyconvertertokeepconstantpressure.ThestartandstopofinverterisdividedintomanualcontrolandPLCcontrol.Onthecontrolpanelthereisamanual/automaticconversionswitchtowhichPLChasareal-timedetectionofstates.Whenthemanualfunctionisselected,thestartandstopandtheirswitchofthepumpoperationismanuallycontrolledthroughthepanelbuttonsandswitches.Whentheautomaticfunctionisselected,allcontrolandalarmarecompletedbyPLC.
FigureI..Controlsystemschematic
III.DESIGNOFFUZZYCONTROLLER
Systemsusestwo-dimensionalfuzzycontroller.TheinputisthedeviationEbetweenthegivenwaterpressureandmeasuredwaterpressureinthewaterpipenetworkandthechangesintherateofdeviationwhichiscomputedfromthedeviationandpreviousdeviation.Theoutputoffuzzycontrolleriscontrolsystemincrement△U.Thefuzzycontrolrulesaresummedupaccordingtotherealsituationofwatersupplyinaresidentialareaandthepracticalexperienceofoperators.Thecorrespondingcontroldecision-makingcanbegainedbasedonfuzzycontrolrulesandfuzzyreasoningsynthesisrulesandthecorrespondingamountofcontrolwillbegainedfromtheprincipleofmaximummembership.AftercomputercomputesOff-lineandhasdebuggingandamendmenttimeaftertime,thefuzzycontroltablewillbegottenwhichcanbeappliedinpracticeandisputinPLC.Whenthesystemruns,itcomputesE,△Efrominputdataandcomputesdomainvalueoffuzzyamount.Thenitsearchesfuzzycontroltabletogaincontrolledquantityandtheoutputofcontrollingfrequencyconverterwillbegottenfromthecontrolledquantitymultipliedbytheratiocoefficient[VIII,IX].
A.Makinginputandoutputvariablesfuzzy
TheuniversesofdiscourseofinputvariableEand△Eare{-III,-II,-I.,0,I.,II,III}.ItsFuzzylanguagevaluesare{NB(negativebig),NM(negativemiddle),NS(negativesmall),ZO(zero),PS(positivesmall),PM(positivemiddle)andPB(positivebig)}.Membershipfunctionusestriangle,showsinFig.II.
Theuniversesofdiscourseofoutputvariable△Uare{-IV,-III,-II,-I.,0,I.,II,III,IV}.ItsFuzzylanguagevaluesare{NB(negativebig),NM(negativemiddle),NS(negativesmall),ZO(zero),PS(positivesmall),PM(positivemiddle)andPB(positivebig)}.Membershipfunctionusestriangle,showsinFig.III.
FigureII.Themembershipdegreeofinputvar.E&△E
FigureIII.Themembershipdegreeofoutputvar.△U
B.Fuzzyruletable
FuzzyruletableisshowninTABLEI,whichissummedupfromtheexperienceoftheon-siteoperatorstomanuallyadjustwaterpressure.
C.Seekingafuzzyrelationshipmatrixandfuzzycontrol
querytable
Two-input&single-outputlanguagecontrolstrategyshowninTABLEIiscomposedofIVIXfuzzyconditionalstatements.Weobtainthepreciseamountbyremovingfuzzy△Uinaccordancewiththelargestmembershiplaw[I.0].ForallthecombinationoftheelementsonthedomainforEand△E,wecanworkoutpreciseamountofemergencydegree△Ucorrespondingtoeachcombination.Sowecangetfuzzycontrolquerytable.
TABLEI.FUZZYCONTROLRULETABLE
IV.SYSTEMSOFTWARE
Fortheconvenienceofprogramminganddebugging,systemcontrollerusesmodularprogramming.Themainmoduleconsistsofmanualoperationmodule,automaticoperationmodule,faultdiagnosisandalarmmodules.
A.Manualoperationmodule
Whenthesystemrunsatmanualstate,PLConlyreceivesthecircuitprotectionandthesensorsignalsandjudgestherunningstateofthepumps.Intheeventoffailure,thealarmsignaloutputs.Thestart,stopandtheirswitchofthepumpsoperatesbyhandthroughthebuttonsandswitchesonthepanel.
B.Automaticoperationmodule
Automaticoperationmoduleincludessysteminitialization,testingofthebootorder,dataacquisitionsubroutine,fuzzycontrolSubroutine,initialvaluesubroutine,motorcontrolsubroutine,andsoon.ModuleflowchartisshowninFig.IV.
Dataacquisitionsubroutine:completingtheacquisitionofdatafromthemainwaterpipepressure.
Motorcontrolsubroutine:controllingtheoperationandstopofIIIwaterpumps.Theoutputfrequencyoffrequencyconverterisrelatedwiththespeedofpumps.Asaresultofit,themorethewaterconsumptionis,thehighertheoutputfrequencyoftheconverteris,thelargerthespeedofthepumpsis.Whereasthelittlethewaterconsumptionis,thelowertheoutputfrequencyoftheconverteris,thesmallerthespeedofthepumpsis.WhenfrequencyisuptoV0Hz,i.e.pumpsrunningatfullspeed,anditcannotmeettherequirementofwatersupply,PLCautomaticallytransformsthefirstpumpfromvariablefrequencystatetoworkfrequencystateandthesecondpumpwhichisstartedbyfrequencyconverterwillrun.Ifthewatersupplycannotmeettherequirementsalthoughthesecondpumprunsatfullspeed,PLCwillautomaticallyswitchsecondpumptoworkfrequencyoperationandthethirdpumpwhichisstartedbyfrequencyconverterwillrun.Accordingtothelowthepumpswillbeputintooperationonebyone.Whentwopumpsrunatfullspeedandatworkfrequencystateandthethirdpumpoperatesatvariablefrequencystate,waterconsumptionreducesandtheoutputfrequencycomesdown.Iffrequencyreachesthelowestlimitandwatersupplyisalsogreaterthanthewaterconsumption,thesystemautomaticallystopthethirdpump.Similarly,ifwatersupplyisstillgreaterthanthewaterconsumptionafterthethirdpumpstops,thesystemautomaticallystopthesecondpump,andsoon..
Fuzzycontrolsubroutine:itiscalledbyatiminginterrupting.Itsfunctionistokeepconstantoutputwaterpressurebyadjustingthespeedofthepumps.Whenthemainprograminitializesthesystem,wefirstlygetthepresentactualwaterpressure.Wecanalsogetthepresenterrorvolumebyusingthispressuresubtractingthepressuresettingsanderrorchangeswillbegottenbyusingpresenterrorvolumesubtractingthepreviouserrorvolume.Andthenwecanobtainfuzzycontrolvolumethroughfuzzyquantitativetoerrorvolumeanditschangesandseekingthefuzzycontroltable.Atlast,therealcontrolvolumewhichcomesfromfuzzycontrolvolumemultipliedbythescalefactorcontrolsthefrequencyoftheconverterbyPLCanditscommunicationinordertokeepconstantpressurewatersupply.ItsflowchartisshowninFig.V.
C.faultdiagnosisandalarmmodules
Converterhasthefunctionofavoidingshortcircuitandoverload.Whenthereisshortcircuit,overloadfaultinwaterpumpmotor,converterautomaticallycutsoffapowersupplycircuit,accessingtothestateofprotectionandoutputtingalarmsignals.Systemlinksauxiliarynodesofthecontactors,circuitbreakerscorrespondingtothepointoffailuretoPLCandPLCscansthestateofthesecontacts.ThesestatedataarestoredinthestorageareathroughPLCprogram.Accordingtologicalanalysistocontrolprogramandthestateofsettings,thesystemcandeterminewhetherthereisafailureintheequipmentorcomponents.Ifthereisafailure,thecontactorsofwaterpumpswillbecutoffandInverterwillreset.Andthenthecontactorsofback-uppumpturnonandback-uppumpwillstart.Atthesametime,thesystemoutputsalarmsignalsofthefailurepump,suchaslightingindicators.
V.CONCLUSION
Fuzzycontroltheoryisusedtotransformthesystemsinputintooutputinordertoenrichpeople’sexperienceduringthecourseofmanualcontrol,whichisreflectedduringthecourseofautomaticcontrolandprovidesaguaranteeforthereliableoperationofthesystem.PLCisusedasacontroller.Itshardwarestructureissimpleandlowcost.Waterpumpmotorofthesystemworksatsteplessspeedregulation.Itsoperatingparametersareautomaticallyadjusted,whichcankeepconstantwaterpressuretomeettherequirementswhilewaterconsumptionchanges.Inaddition,thereisaRS-IVVIIIVinterfaceinthebasicunitofSVII-III.IVPLCbywhichitcancommunicatewithbuildingmonitoringcentertoachieveunattendedremotecontrol.Aftersixmonthsoftestthesystemhasstableperformance,reliableoperationandenergy-savingeffect.
FigureIV.AutomaticFigureV.Fuzzy
operationmoduleflowchartcontrolsubroutine
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