基于单片机的火灾探测和监控系统外文文献翻译xWord文档格式.docx
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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
LCVtl)
LOC
AL
CfMTRAlCOMTHOLLCA
CONTROLLER
LOC
LOCALCOHTROklCR
fig1Cetrr
衣用
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.2depictsourdesigninthesimplestoff