基于单片机的火灾探测和监控系统外文文献翻译x.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x.docx
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外文文献原稿和译文
Multiplesingle-chipmicrocomputerapproachtofiredetectionandmonitoringsystem
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,ultravioletor
infrareddetectorsorflameflicker,isbasedondetecting
thebyproductofacombustion.Smokedetectors,ofbothionizationandopticaltypes,arethemostcommonlyused
detectordevices.Whenatypicaldetectorofthistypeentersthealarmstateitscurrentconsumptionincreases
undervariousoperatingconditions,suchasthose
Tat>l«1:
Typicaldetectorvoltageoutputlevels
Detectorcondition
22V Detect«inop«neveuitcondition13V22V“txtortsnormal
1V-13Vdetector«malarmMate
1V detectortsmshortcircurtcondition
detectoroutputvoltageiswelldefined
fromthepAtothemArange(say,fromamere15pAinthedonnantmodeto60mA)intheactivemode.Inmanydetectorsthe
given in Table l. The more sensitive theisused:
acoincidencetechnique
detector,themoresusceptibleitistofalsealarms.Inordertocontrolthe
detectorprecisely,eitherofthefollowingmethodscanbebuiltintothedetector,orafilteringtechniquesuchthatalogiccircuitbecomesactiveonlyifxalarmsaredetectedwithinatimeperiodT.Thedetectiontechniquedependsgreatlyonthelocationandplantbeingprotected;smokedetectorsareusedforsleepingareas,infraredorultravioletradiationareusedwhenflammableliquidsarebeinghandled,heatdetectorsareusedforfiresuppressionorextinguishingsystems.Ingeneral,lifeandpropertyprotectionhavedifferentapproaches.
Alarmdevices,apartfromtheusualaudibleorvisiblealarms,mayincorporatesolidstatesoundreproductionandemergencyvoicecommunicationorprintersthatrecordtime,date,locationandotherinformationrequiredbythestandardcodeofpracticeforfireprotectionforcomplexplants.Heaviside[4]hasanexcellent
reviewofalltypesofdetectorsandextinguishersystems.
LIControlphilosophyanddivisionoflabour
Ourcontrolphilosophyisimplementedhierarchically.Threelevelsofsystemhierarchyareimplemented,withtwolevelsofdecisionmaking.Thereisnocommunicationbetweenequipmentonthesamelevel.Interactionbetweenlevelsoccursbyupwardstransferofinformationregardingthestatusofthesubsystemsanddownwardstransferofcommands.ThisisshowninFig.1whereatlevel1isthe
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centralstationmicrocomputerandistheultimatedecisionmaker(whennotinmanualmode).Atlevel2arethelocalcontrollers,whichresideinthelocalstations.Atlevel3aretheactualdetectorsandactuators.Amanualmodeofoperationisprovidedatalllevels.
Informationregardingthestatusofalldetectorsistransmittedonaperareabasistothelocalcontrollers.Theirinformationiscondensedandtransmittedupwardtothecentralmicrocomputer.Transferofstatusisalwaysunidirectionalandupwards-Transferofcommandsisalwaysunidirectionalanddownwards,withexpansionatthelocalcontrollevel.Thisapproachpreservesthestrictrulesofthehierarchyforexactmonitoringdetectionandalarmsystemsassociatedwithhighriskplants.
Theclassificationofthetwolayersofcontrolsisbaseduponlayersofdecisionmaking,withrespecttothefactsthat
(a)Whenthedecisiontimecomes,themakingandimplementationofadecisioncannotbepostponed
(b)Thedecisionshaveuncertainty
(c)Itwillisolatelocaldecisions(e.g.locallywemighthaveanalarmalthough
theremaybeafaultwiththesystem)
2Generalhardware
I:
Fig.2depictsourdesigninthesimplestofforms.Thesystemusesanopenpartylineapproachwithfourconductorcablesgoinginaloopsharedbyalltheremotedevicesandthecontrolpanel.Thisapproachissimpleinconceptandiseconomicallyfeasible.However,onemajordisadvantageisthedependencyonasinglecableforpowerandsignaling.Incaseswherereliabilityisofextremeimportance,twooreventhreecablestaking different
routesthroughoutthesystemmaybeconnectedinparallel.Fig.3givesthedrivercircuitryrequiredtoderiveanexpandablebus.Thisdesigntakesadvantageofrecentadvancesinthesinglechipmicrocomputertechnologytoreducetheinterfacebetween
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thecentralstationandthelocalstations.
2.1Centralcontroltask
Acentralunitprovidesacentralizedpointtomonitorandcontrolthesystem
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activities.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.3istheblockdiagramofthecircuitusedtoutilizethe
MC68HC11A4asaremotefiredetectingcircuitwhileFig.4illustratesthesame
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TRANSMISSION Fig.5Closrrfloo.coMtctums
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circuitinanexpandedform.Itcanbeseenthatthesinglemicrocontrollercanbeusedtomonitormorethanonedetector,thusreducingsystemcost.
Thelooppowersupply,whichisusuallybetween28and26V,isfurtherregulatedbya5V100mAmonolithiclowpowervoltageregulatortosupplypowertothemicrocontroller.Theonboardoscillator,coupledwithanexternalcrystalof2.4576MHz,suppliesthemicrocontrollerwithitstimingsignalwhichisdividedinternallybyfourtoyieldaprocessorfrequencyof614.4kHz,whichisanevenmultipleoftheRS232[7]baudrategenerator.InthisSectiontheterm'supervisedinputoroutput9willbeusedtomeanthatthefunctioninquestionismonitoredforopen-andshort-circuitconditionsinadditiontoitsothernormalfunctions.MoreinformationcanbefoundinReference9.
4Mainloop
Fig.7Mainloopflowchart
5Conclusion
Thispaperdescribesthedevelopmentofalargescalefiredetectionandalarmsystemusingmulti-singlechipmicrocomputers.Thearchitectureusedisatwo-levelhierarchyofdecisionmaki
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