基于多数据融合传感器的分布式温度控制系统.docx

基于多数据融合传感器的分布式温度控制系统.docx

《基于多数据融合传感器的分布式温度控制系统.docx》由会员分享，可在线阅读，更多相关《基于多数据融合传感器的分布式温度控制系统.docx（11页珍藏版）》请在冰豆网上搜索。

基于多数据融合传感器的分布式温度控制系统

DISTRIBUTEDTEMPERATURECONTROLSYSTEM

BASEDONMULTI-SENSORDATAFUSION

CaiYan,YangHailan,HuaXuemingandWuYixiong

Abstract:

Temperaturecontrolsystemhasbeenwidelyusedoverthepastdecades.Inthispaper,ageneralarchitectureofdistributedtemperaturecontrolsystemisputforwardbasedonmulti-sensordatafusionandCANbus.Anewmethodofmulti-sensordatafusionbasedonparameterestimationisproposedforthedistributedtemperaturecontrolsystem.Themajorfeatureofthesystemisitsgenerality,whichissuitableformanyfieldsoflargescaletemperaturecontrol.Experimentshowsthatthissystempossesseshigheraccuracy,reliability,goodreal—timecharacteristicandwideapplicationprospect

Keywords:

Distributedcontrolsystem;CANbus;intelligentCANnode;multi-sensordatafusion.

1.Introduction

Distributedtemperaturecontrolsystemhasbeenwidelyusedinourdailylifeandproduction,includingintelligentbuilding,greenhouse,constanttemperatureworkshop,largeandmediumgranary,depot,andsoon[1].Thiskindofsystemshouldensurethattheenvironmenttemperaturecanbekeptbetweentwopredefinedlimits.IntheconventionaltemperaturemeasurementsystemswebuildanetworkthroughRS-485Bususingasingle-chipmeteringsystembasedontemperaturesensors.Withtheaidofthenetwork,wecancarryoutcentralizedmonitoringandcontrolling.However,whenthemonitoringareaismuchmorewidespreadandtransmissiondistancebecomesfarther,thedisadvantagesofRS-485Busbecomemoreobvious.Inthissituation,thetransmissionandresponsespeedbecomeslower,theanti-interferenceabilitybecomesworse.Therefore,weshouldseekoutanewcommunicationmethodtosolvetheproblemsproducedbyRS-485Bus.

Duringallthecommunicationmanners,theindustrialcontrol-orientedfieldbustechnologycanensurethatwecanbreakthroughthelimitationoftraditionalpointtopointcommunicationmodeandbuilduparealdistributedcontrolandcentralizedmanagementsystem.Asaserialcommunicationprotocolsupportingdistributedreal-timecontrol,CANbushasmuchmoremeritsthanRS-485Bus,suchasbettererrorcorrectionability,betterreal-timeability,lowercostandsoon.Presently,ithasbeenextensivelyusedintheimplementationofdistributedmeasurementandcontroldomains.

Withthedevelopmentofsensorytechnology,moreandmoresystemsbegintoadoptmulti-sensordatafusiontechnologytoimprovetheirperformances.Multi-sensordatafusionisakindofparadigmforintegratingthedatafrommultiplesourcestosynthesizethenewinformationsothatthewholeisgreaterthanthesumofitsparts[3][4][5].Anditisacriticaltaskbothinthecontemporaryandfuturesystemswhichhavedistributednetworksoflow-cost,resource-constrainedsensors

2.Distributedarchitectureofthetemperaturecontrolsystem

ThedistributedarchitectureofthetemperaturecontrolsystemisdepictedintheFigure1.Ascanbeseen,thesystemconsistsoftwomodules—severalintelligentCANnodesandamaincontroller.TheyareinterconnectedwitheachotherthroughCANbus.Eachmoduleperformsitspartintothedistributedarchitecture.Thefollowingisabriefdescriptionofeachmoduleinthearchitecture.

3．1maincontroller

Asthesystem’smaincontroller,thehostPCcancommunicatewiththeintelligentCANnodes.Itisdevotedtosuperviseandcontrolthewholesystem,suchassystemconfiguration,displayingrunningcondition,parameterinitializationandharmonizingtherelationshipsbetweeneachpart.What’smore,wecanprintorstorethesystem’shistorytemperaturedata,whichisveryusefulfortheanalysisofthesystemperformance

3.2.IntelligentCANnode

EachintelligentCANnodeofthetemperaturecontrolsystemincludesfiveunits:

MCU—asinglechip,A/Dconversionunit,temperaturemonitoringunit—sensorgroup,digitaldisplayunitandactuators—acoolingunitandaheatingunit.TheoperatingprincipleoftheintelligentCANnodeisdescribedasfollows.

Inthepracticalapplication,wedividetheregionofthecontrolobjectiveintomanycells,andlaytheintelligentCANnodesinsomeofthetypicalcells.Ineachnode,MCUcollectstemperaturedatafromthetemperaturemeasurementsensorgroupswiththeaidoftheA/Dconversionunit.Simultaneously,itperformsbasicdatafusionalgorithmstoobtainafusionvaluewhichismoreclosetotherealone.Andthedigitaldisplayunitdisplaysthefusingresultofthenodetimely,sowecanunderstandtheenvironmenttemperatureineverycontrolcellseparately.

Bycomparingthefusionvaluewiththesetonebythemaincontroller,theintelligentCANnodecanimplementthedegenerativefeedbackcontrolofeachcellthroughenablingthecorrespondingheatingorcoolingdevices.IfthefusionresultisbiggerthanthesetvalueinthespecialintelligentCANnode,thecoolingunitwillbegintowork.Onthecontrary,ifthefusionresultislessthanthesetvalueinthenodetheheatingunitwillbegintowork.Bythismeanswecannotonlymonitortheenvironmenttemperature,butalsocanmakethecorrespondingactuatorworksoastoregulatethetemperatureautomatically.AtthesametimeeveryCANnodeisabletosenddataframetotheCANbuswhichwillnotifythemaincontrollerthetemperaturevalueinthecellsothatcontrollercanconvenientlymakedecisionstomodifytheparameterornot.SincetheCANnodescanregulatethetemperatureofthecellwheretheyare,thetemperatureinthewholeroomwillbekepthomogeneous.What’smore,wecanalsocontroltheintelligentnodebymodifyingthetemperature’ssettingvalueonthehostPC.

Generally,theprocessorsonthespotarenotgoodatcomplexdataprocessinganddatafusing,soitbecomesverycriticalhowtochooseasuitabledatafusionalgorithmforthesystem.Intheposteriorsection,wewillintroduceadatafusionmethodwhichissuitablefortheintelligentCANnodes。

4.Multi-sensordatafusion

Theaimtousedatafusioninthedistributedtemperaturecontrolsystemistoeliminatetheuncertainty,gainamorepreciseandreliablevaluethanthearithmeticalmeanofthemeasureddatafromfinitesensors.Furthermore,whensomeofthesensorsbecomeinvalidinthetemperaturesensorgroups,theintelligentCANnodecanstillobtaintheaccuratetemperaturevaluebyfusingtheinformationfromtheothervalidsensors.

4.1.Consistencyverificationofthemeasureddata

Duringtheprocessoftemperaturemeasurementinourdesigneddistributedtemperaturecontrolsystem,measurementerrorcomesintobeinginevitablybecauseoftheinfluenceoftheparoxysmaldisturbortheequipmentfault.Soweshouldeliminatethecarelessmistakebeforedatafusion.

Wecaneliminatethemeasurementerrorsbyusingscatterdiagrammethodinthesystemequippedwithlittleamountofsensors.Parameterstorepresentthedatadistributionstructureincludemedian—TM,upperquartilenumber—Fv,lowerquartilenumber—FLandquartiledispersion—dF.

Itissupposedthateachsensorinthetemperaturecontrolsystemproceedstemperaturemeasurementindependently.Inthesystem,thereareeightsensorsineachtemperaturesensorgroupoftheintelligentCANnode.SowecanobtaineighttemperaturevaluesineachCANnodeatthesametime.Wearrangethecollectedtemperaturedatainasequencefromsmalltolarge:

T1,T2,…,T8

Inthesequence,T1isthelimitinferiorandT8isthelimitsuperior.

Wedefinethemedian—TMas:

（1）

Theupperquartile—Fvisthemedianoftheinterval[TM,T8].Thelowerquartilenumber—FListhemedianoftheinterval[T1,TM].Thedispersionofthequartileis:

（2）

WesupposethatthedataisanaberrationoneifthedistancefromthemedianisgreaterthanadF,thatis,theestimationintervalofinvaliddatais:

（3）

Intheformula,aisaconstant,whichisdependentonthesystemmeasurementerror,commonlyitsvalueistobe0.5,1.0,2.0andsoon.

Therestvaluesinthemeasurementcolumnareconsideredastobethevalidoneswithconsistency.AndtheSingle-ChipintheintelligentCANnodewillfusetheconsistentmeasurementvaluetoobtainafusionresult

5.Temperaturemeasurementdatafusionexperiment

Byapplyingthedistributedtemperaturecontrolsystemtoagreenhouse,weobtainanarrayofeighttemperaturevaluesfromeightsensorsasfollows

Themeanvalueoftheeightmeasurementtemperatureresultis

Comparingthemeanvalue（8）Twiththetruetemperaturevalueinthecellofthegreenhouse,wecanknowthatthemeasurementerroris+0.5℃.Afterweeliminatethecarelesserrorfromthefifthsensorusingthemethodintroducedbefore,wecanobtainthemeanvalueoftherestsevendata（7）T=29.6℃,themeasurementerroris-0.4℃.

ThesevenrestconsistentsensorcanbedividedintotwogroupswithsensorS1,S3,S7inthefirstgroupandsensorS2,S4,S6,S8inthesecondone.Thearithmeticalmeanofthetwogroupsofmeasureddataandthestandarddeviationareasfollowsrespectively:

Accordingtoformula（13）,wecaneducethetemperaturefusionvaluewiththesevenmeasuredtemperaturevalue.

Theerrorofthefusiontemperatureresultis-0.3℃.

Itisobviousthatthemeasurementresultfromdatafusionismoreclosetothetruevaluethanthatfromarithmeticalmean.Inthepracticalapplication,themeasuredtemperaturevaluemaybeverydispersiveasthemonitoringareabecomesbigger,datafusionwillimprovethemeasuringprecisionmuchmoreobviously.

6.Conclusions

Thedistributedtemperaturecontrolsystembasedonmulti-sensordatafusionisconstructedthroughCANbus.Ittakesfulladvantageofthecharacteristicsoffieldbuscontrolsystem---FDCS.Dataacquisition,datafu