4毕业设计论文中英文文献翻译Word格式.docx
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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.
1Introduction
Regulatoryrequirementsformosthighriskplantsandbuildingsmandatetheinstallationoffiredetectionandwarningsystemsforallsensitiveareasoftheplantorthebuilding.Mostfirecodesstatetherequirementformonitoringandcontrolspecificallyrelatedtoatypeofaplantorbuildingsuchaschemicalplants,petroleum,nuclearplants,residentialhigh-risesetc.Ageneralconclusionofthesecodescanbespecifiedasthefollowingrequirements:
(a)Thesourceofalldetectorsignalsshouldbeexactlyidentifiablebythecentralstation
(b)Anextrapathofcommunicationbetweenthecentralstationandalllocalcontrollers
(c)Directmeansofcontrolofalarmandcentralequipmentbythecentralstation
(d)Meansofcommunicationbetweenthecentralstationandthefiredepartment
(e)Availabilityofemergencypowersupply.Thecodesusuallyalsospecifythetypesandfrequencyoftestsforallequipment.
Afiredetectionandalarmsystemisacombinationofdevicesdesignedtosignalanalarmincaseofafire.Thesystemmayalsoaccomplishfancontrol,firedoorholdorrelease,elevatorrecall,emergencylightingcontrolandotheremergencyfunctions.Theseadditionalfunctionssupplementthebasicsystemwhichconsistsofdetectionandalarmdevicesandcentralcontrolunit.
Technologyhasaninfluenceonsystemarchitecture.Whentechnologychanges,thearchitecturehastoberevisedtotakeadvantageofthesechanges.Inrecentyears,VLSItechnologyhasbeenadvancingatanexponentialrate.FirstNMOSand,inthelastyearortwo,CMOSchipshavebeenproducedwiththesamepackingdensitywithmoregatesperchipyetatalowerpowerconsumptionthanNMOS.Surelythischangeintechnologymustaffectourdesignofhardwareatboththechipandthesystemlevel.Atthechiplevel,singlechipsarenowbeingproducedwhichareequivalenttoboardlevelsofonlythepreviousyearortwo.Thesechipshavemicroprocessor,memoryinRAMandROM,IOPortsbothserialandparallel,A/Dtimer,flagsandotherfunctionsonchip.Atthesystemlevel,thenewchipsmakenewarchitecturespossible.Theobjectiveofthispaperistoshowhowtechnologycaninfluencesystemarchitectureinthefieldoffirecontrol.Thenewhighdensitysinglechipmicrocontrollersareincorporatedinthedesignofalargescalesystemandyetweobtainasmallersystemwithabetterperformance.Intermsoffiredetectionandalarmmonitoring,thisisreflecteddirectlyinthelocalstationhardware,becauseoftheirremotenessandpowersupplyrequirements.AcompletelocalstationcanbedesignedaroundasingleCMOSchipwithpowerconsumptionofafewmWdependingonsystemoperation.Thisapproachreducesthecostandcomplexityofdesign,implementationandmaintenanceandprovideseasilyexpandableandportabledesign.Thisimplementationwasnotpossiblewitholdtechnology.Mostoffiredetection/monitoringsystemsavailablearetailoredtowardsaspecificapplicationandlacktheuseofrecentadvancesinCMOSVLSItechnology.Inthisstudy,wedevelopafiredetection/monitoringsystemwhichisgeneralinconcept,readilyimplementableinamultitudeofapplicationsforearlydetectionofafirebeforeitbecomescritical,forequipmentandevacuationofpersonnel.Here,weproposeacentralcontrolanddistributedcontrol/detection/monitoringwithadequatecommunication,whereuseismadeofsingle-chipmicrocontrollersinthelocalstations,thusimprovingcontrollabilityandobservabilityofthemonitoringprocess.
2Detectionandalarmdevices
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.
2.1Controlphilosophyanddivisionoflabour
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)
3Generalhardware
I:
Fig.2depictsourdesigninthesimplestofforms.Thesystemusesanopenpartylineapproachwithfourconductorcablesgoinginaloopsharedbyalltheremotedevicesandthecontrolpanel.Thisapproachissimpleinconceptandiseconomicallyfeasible.However,onemajordisadvantageisthedependencyonasinglecableforpowerandsignaling.Incaseswherereliabilityisofextremeimportance,twooreventhreecablestakingdifferent
routesthroughoutthesystemmaybeconnectedinparallel.Fig.3givesthedrivercircuitryrequiredtoderiveanexpandablebus.Thisdesigntakesadvantageofrecentadvancesinthesinglechipmicrocomputertechnologytoreducetheinterface
betweenthecentralstationandthelocalstations.
3.1Centralcontroltask
Acentralunitprovidesacentralizedpointtomonitorandcontrolthesystemactivities.Inthesystemtobedescribedthecentralcontrolunitservesafivefoldpurpose.
(i)Itreceivesinformationfromthelocalstationsandoperatesthealarmsandotheroutputdevices.
(ii)Itnotifiestheoperatorincaseofsystemmalfunction.
(iii)Itprovidesanoverallsystemcontrolmanualandautomatic.
(iu)Itprovidesasystemtestpointoflocalstationsanditself.
(u)Itprovidesacentralpointforobservation,learningandadaptation.
3.2Localstations
Thelocalstationscantakelocaldecisionsregardingrecognitionofarisksituation,andactindependentlyonlocalaffairs.Inthistechniquewedependon‘load-typecoordination’,e.g.thelowerlevelunitsrecognizetheexistenceofotherdecisionunitsonthesamelevel;
thecentralorthetoplevelprovidesthelowerunitswithamodeloftherelationshipbetweenitsactionandtheresponseofthesystem.
Itisevidentthatapowerfulmachineisrequiredatthisstageso