基于单片机的火灾探测和监控系统外文文献翻译.docx

基于单片机的火灾探测和监控系统外文文献翻译.docx

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基于单片机的火灾探测和监控系统外文文献翻译

外文文献原稿和译文

原　　稿

Multiplesingle-chipmicrocomputerapproachto

firedetectionandmonitoringsystem

A.J.AI-Khalili,MSc,PhD

D.AI-Khalili,MSc,PhD

M.S.Khassem,MSc

Indexingterm:

Hazards,Design,Plantconditionmonitoring

Abstract:

Acompletesystemforfiredetectionandalarmmonitoringhasbeenproposedforcomplexplants.Thesystemusesmultiplesinglechiparchitectureattachedtoapartyline.Thecontrolalgorithmisbasedonatwo-levelhierarchyofdecisionmaking,thusthecomplexityisdistributed.Acompletecircuitdiagramisgivenforthelocalandthecentralstationwithrequirementsforthesoftwarestructure.Thedesigniskeptingeneralformsuchthatitcanbeadaptedtoamultitudeofplantconfigurations.Itisparticularlyshownhownewdevelopmentsintechnology,especiallyCMOSsinglechipdevices,areincorporatedinthesystemdesigntoreducethecomplexityoftheoverallhardware,e.g.bydecomposingthesystemsuchthatlowerlevelsofhierarchyareabletohavesomeautonomyindecisionmaking,andthusamorecomplexdecisionissolvedinasimpledistributedmethod.

1Detectionandalarmdevices

Abasicfiredetectionsystemconsistsoftwoparts,detectionandannunciation.Anautomaticdetectiondevice,suchasaheat,smokeorflamedetector,ultravioletorinfrareddetectorsorflameflicker,isbasedondetecting

thebyproductofacombustion.Smokedetectors,ofbothionizationandopticaltypes,arethemostcommonlyused

detectordevices.Whenatypicaldetectorofthistypeentersthealarmstateitscurrentconsumptionincreases

fromthepAtothemArange（say,fromamere15pAinthedormantmodeto60mA）intheactivemode.Inmanydetectorsthedetectoroutputvoltageiswelldefinedundervariousoperatingconditions,suchasthose

giveninTable1.Themoresensitivethedetector,the

moresusceptibleitistofalsealarms.Inordertocontrolthedetectorprecisely,eitherofthefollowingmethodsisused:

acoincidencetechniquecanbebuiltintothedetector,orafilteringtechniquesuchthatalogiccircuitbecomesactiveonlyifxalarmsaredetectedwithinatimeperiodT.Thedetectiontechniquedependsgreatlyonthelocationandplantbeingprotected;smokedetectorsareusedforsleepingareas,infraredorultravioletradiationareusedwhenflammableliquidsarebeinghandled,heatdetectorsareusedforfiresuppressionorextinguishingsystems.Ingeneral,lifeandpropertyprotectionhavedifferentapproaches.

Alarmdevices,apartfromtheusualaudibleorvisiblealarms,mayincorporatesolidstatesoundreproductionandemergencyvoicecommunicationorprintersthatrecordtime,date,locationandotherinformationrequiredbythestandardcodeofpracticeforfireprotectionforcomplexplants.Heaviside[4]hasanexcellent

reviewofalltypesofdetectorsandextinguishersystems.

1.1Controlphilosophyanddivisionoflabour

Ourcontrolphilosophyisimplementedhierarchically.Threelevelsofsystemhierarchyareimplemented,withtwolevelsofdecisionmaking.Thereisnocommunicationbetweenequipmentonthesamelevel.Interactionbetweenlevelsoccursbyupwardstransferofinformationregardingthestatusofthesubsystemsanddownwardstransferofcommands.ThisisshowninFig.1whereatlevel1isthecentralstationmicrocomputerandistheultimatedecisionmaker（whennotinmanualmode）.Atlevel2arethelocalcontrollers,whichresideinthelocalstations.Atlevel3aretheactualdetectorsandactuators.Amanualmodeofoperationisprovidedatalllevels.

Informationregardingthestatusofalldetectorsistransmittedonaperareabasistothelocalcontrollers.Theirinformationiscondensedandtransmittedupwardtothecentralmicrocomputer.Transferofstatusisalwaysunidirectionalandupwards.Transferofcommandsisalwaysunidirectionalanddownwards,withexpansionatthelocalcontrollevel.Thisapproachpreservesthestrictrulesofthehierarchyforexactmonitoringdetectionandalarmsystemsassociatedwithhighriskplants.

Theclassificationofthetwolayersofcontrolsisbaseduponlayersofdecisionmaking,withrespecttothefactsthat

（a）Whenthedecisiontimecomes,themakingandimplementationofadecisioncannotbepostponed

（b）Thedecisionshaveuncertainty

（c）Itwillisolatelocaldecisions（e.g.locallywemighthaveanalarmalthoughtheremaybeafaultwiththesystem）

2Generalhardware

I:

Fig.2depictsourdesigninthesimplestofforms.Thesystemusesanopenpartylineapproachwithfourconductorcablesgoinginaloopsharedbyalltheremotedevicesandthecontrolpanel.Thisapproachissimpleinconceptandiseconomicallyfeasible.However,onemajordisadvantageisthedependencyonasinglecableforpowerandsignaling.Incaseswherereliabilityisofextremeimportance,twooreventhreecablestakingdifferent

routesthroughoutthesystemmaybeconnectedinparallel.Fig.3givesthedrivercircuitryrequiredtoderiveanexpandablebus.Thisdesigntakesadvantageofrecentadvancesinthesinglechipmicrocomputertechnologytoreducetheinterface

betweenthecentralstationandthelocalstations.

2.1Centralcontroltask

Acentralunitprovidesacentralizedpointtomonitorandcontrolthesystemactivities.Inthesystemtobedescribedthecentralcontrolunitservesafivefoldpurpose.

（i）Itreceivesinformationfromthelocalstationsandoperatesthealarmsandotheroutputdevices.

（ii）Itnotifiestheoperatorincaseofsystemmalfunction.

（iii）Itprovidesanoverallsystemcontrolmanualandautomatic.

（iu）Itprovidesasystemtestpointoflocalstationsanditself.

（u）Itprovidesacentralpointforobservation,learningandadaptation.

2.2Localstations

Thelocalstationscantakelocaldecisionsregardingrecognitionofarisksituation,andactindependentlyonlocalaffairs.Inthistechniquewedependon‘load-typecoordination’,e.g.thelowerlevelunitsrecognizetheexistenceofotherdecisionunitsonthesamelevel;thecentralorthetoplevelprovidesthelowerunitswithamodeloftherelationshipbetweenitsactionandtheresponseofthesystem.

Itisevidentthatapowerfulmachineisrequiredatthisstagesothatalltherequiredfunctionscanbeimplemented.Theavailabilityofthenewgenerationofmicrochipsmakesthisarchitectureafeasiblesolution.

Asinglechipmicrocomputerwaschosenoverdiscretedigitalandanaloguedevicestointerfacetothefielddevicesandtothecentralmicrocomputer.Thisisthemainreasonthatpreviouslythisapproachwasnotfeasible.

Inselectingthemicrocomputerforthelocalstations,thecriterionwastherequirementforachipwhichcontainsthemostintegrationoftheanalogueanddigitalportsrequiredfortheinterfaceandtheutilizationofCMOStechnologyowingtoremotenessofthelocalstations.ThechoicewastheMotorola68HC11A4,forthefollowingreasons:

（a）ItisCMOStechnology;thisreducespowerconsumption.

（b）IthasaUARTonboard;thisfacilitatesserialcommunication.

（e）Ithasana/dconverteronboard;thiseliminatesanexternalA/D.

（d）Ithas4KofROM,256bytesofRAM,512bytesofEERROMwith401/0linesanda16bittimer;thissatisfiedallourmemoryand1/0requirementsatthelocalstationside.

3Systemimplementation

Thelocalstation:

Fig.3istheblockdiagramofthecircuitusedtoutilizetheMC68HCllA4asaremotefiredetectingcircuitwhileFig.4illustratesthesamecircuitinanexpandedform.Itcanbeseenthatthesinglemicrocontrollercanbeusedtomonitormorethanonedetector,thusreducingsystemcost.

Thelooppowersupply,whichisusuallybetween28and26V,isfurtherregulatedbya5V100mAmonolithiclowpowervoltageregulatortosupplypowertothemicrocontroller.Theonboardoscillator,coupledwithanexternalcrystalof2.4576MHz,suppliesthemicrocontrollerwithitstimingsignalwhichisdividedinternallybyfourtoyieldaprocessorfrequencyof614.4kHz,whichisanevenmultipleoftheRS232[7]baudrategenerator.InthisSectiontheterm‘supervisedinputoroutput’willbeusedtomeanthatthefunctioninquestionismonitoredforopen-andshort-circuitconditionsinadditiontoitsothernormalfunctions.MoreinformationcanbefoundinReference9.

4Mainloop

5Conclusion

Thispaperdescribesthedevelopmentofalargescalefiredetectionandalarmsystemusingmulti-singlechipmicrocomputers.Thearchitectureusedisatwo-levelhierarchyofdecisionmaking.ThisarchitectureismadepossiblebythenewCMOSmicrocontrollerswhichrepresentahighpackingdensityatalowpowerconsumptionyetarepowerfulindataprocessingandthusindecisionmaking.Eachlocalstationcouldmakeanautonomousdecisionifthehigherlevelofhierarchyallowsittodoso.Ithasbeentriedtokeepthesystemdesigningeneralformatsoitcanbeadaptedtovaryingsituations.Aprototypeofthedescribedsystemhasbeenbuiltandtested[10].ThecontrolpartofthecentralstationisimplementedwithadevelopmentcardbasedonMC68000microprocessor（MEX68KECB,byMotorola）,whichhasabuilt-inmonitorcalledTutor.Theapplicationprogramsweredevelopedusingthefeaturesprovidedbythismonitor.Thelocalstations’controllersweredesignedusingtheMC68705R3,single-chipmicrocontroller.

7References

1‘Fireprotectionguidelinesfornuclearpowerplants’,USNRCRegulatoryGuide1.120

2BAGCHI,C.N.:

‘Amulti-leveldistributedmicroprocessorsystemforanuclearpowerplantfireprotectionsystemcontrols,monitoring,andcommunication’,IEEETrans.,1982

3PUCILL,P.M.:

‘Firehazardprotection,detectionandmonitoringsystems’,Sea.Con,2,ProceedingsofSymposiumonADVinoffs