自动控制毕业论文中英文资料外文翻译文献.docx
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自动控制毕业论文中英文资料外文翻译文献
毕业论文外文译文
学院 自动化与电气工程学院
专 业 自动控制
Component-basedSafetyComputerofRailway SignalInterlockingSystem
1Introduction
SignalInterlockingSystemis thecriticalequipmentwhichcanguarantee trafficsafetyandenhanceoperational efficiency in railwaytransportation.Foralong time,thecorecontrolcomputer adoptsin interlockingsystemis thespecialcustomizedhigh-gradesafetycomputer,forexample,theSIMIS ofSiemens,theEI32ofNipponSignal,and soon.Along withtherapid developmentofelectronictechnology,the customizedsafetycomputeris facingseverechallenges,for instance,thehighdevelopmentcosts,poorusability,weakexpansibilityand slowtechnology update.To overcometheflaws of thehigh-grade specialcustomized computer,theU.S.DepartmentofDefensehasputforwardtheconcept:
weshouldadoptcommercial standardstoreplace militarynormsandstandards for meetingconsumers’demand[1].Inthemeantime,thereareseveralexplorationsandpracticesaboutadoptingopensystemarchitectureinavionics.TheUnited Statedand Europehavedomuchresearchaboututilizingcost-effectivefault-tolerantcomputertoreplace thededicatedcomputerin aerospaceandother safety-criticalfields.In recent years,itisgraduallybecominganewtrendthat theutilizationof standardizedcomponentsinaerospace,industry,transportation and other safety-criticalfields.
2 Railways signalinterlockingsystem
2.1 Functions ofsignalinterlocking system
The basicfunctionofsignalinterlockingsystem istoprotecttrainsafetybycontrolling signalequipments,such as switchpoints, signalsand track unitsin astation, andithandles routes viaacertain interlocking regulation.
Since thebirthoftherailway transportation,signal interlockingsystemhasgone throughmanual signal,mechanical signal,relay-basedinterlocking,and themodern computer-based InterlockingSystem.
2.2Architectureofsignalinterlockingsystem
Generally, theInterlockingSystemhas ahierarchicalstructure.Accordingto the functionofequipments, thesystemcanbedividedto thefunctionofequipments; thesystemcan bedividedintothreelayersasshown in figure1.
Figure 1ArchitectureofSignalInterlockingSystem
3Component-basedsafetycomputerdesign
3.1 Designstrategy
The design conceptof component-based safetycriticalcomputerisdifferent fromthatofspecialcustomizedcomputer. Ourdesignstrategy of SICis onabaseoffault-toleranceandsystem integration. WeseparatetheSICintothree layers,thestandardizedcomponentunitlayer,safety softwarelayerandthesystemlayer.Differentsafetyfunctionsareallocatedforeachlayer, andthefinalintegrationof thethreelayersensuresthepredefinedsafety integritylevelofthewhole SIC.The threelayerscanbedescribedasfollows:
(1) Componentunitlayer includesfour independentstandardized CPUmodules.Ahardware “SAFETY AND”logic isimplementedinthisyear.
(2) Safetysoftwarelayer mainlyutilizesfail-safestrategyandfault-tolerant management.Theinterlockingsafetycomputingofthewholesystem adoptstwooutputsfromdifferentCPU, it canmostlyensure the diversityofsoftwaretohold with designerrorsofsignalversionand removehiddenrisks.
(3) Systemlayeraimstoimprovereliability,availabilityandmaintainabilitybymeansofredundancy.
3.2Design ofhardware fault-tolerantstructure
Asshowninfigure 2, theSICof fourindependentcomponentunits(C11,C12, C21,C22).Thefault-tolerantarchitectureadopts dual2vote2(2v2×2)structure,and a kindofhigh-performancestandardizedmodulehasbeenselectedascomputingunitwhichadoptsIntelXScalekernel,533MHZ.
Theoperationof SICisbasedona dual two-layerdatabuses.Thehighbus adopts thestandard Ethernetand TCP/IPcommunication protocol,andthelowbus isControllerAreaNetwork(CAN).C11、C12andC21、C22 respectively make upoftwo safetycomputingcomponentsIC1 andIC2,whichare of2v2structure.Andeach componenthasanexternal dynamiccircuitwatchdogthatis setforcomputing supervision andswitching.
Figure 2HardwarestructureofSIC
3.3ﻩStandardizedcomponentunit
After component module is made certain,accordingto thesafety-criticalrequirementsofrailway signal interlocking system,wehavetodoa secondarydevelopmentonthemodule. Thedesignincludes powersupply, interfacesandotherembeddedcircuits.
The fault-tolerant processing,synchronized computing,andfaultdiagnosis ofSICmostly depend onthesafetysoftware.Herethesafetysoftwaredesignmethodisdifferingfromthatofthespecialcomputertoo.Fordedicated computer,thesoftwareisoftenspecially designed basedon the barehardware.As restricted bycomputingabilityandapplicationobject,a specialschedulingprogram iscommonlydesignedassafetysoftwareforthecomputer,andnota universaloperatingsystem.Thefault-tolerantprocessingand fault diagnosis ofthededicatedcomputeraretightlyhardware-coupled.However,thesafetysoftware forSICisexotericandlooselyhardware-coupled,and itisbased onastandardLinuxOS.
Thesafetysoftwareisvitalelement ofsecondarydevelopment.Itincludes LinuxOSadjustment,fail-safeprocess,fault-tolerancemanagement,andsafetyinterlocking logic.Thehierarchy relationsbetweenthem areshownin Figure4.
Figure4 Safety softwarehierarchyofSIC
3.4Fault-tolerantmodelandsafetycomputation
3.4.1Fault-tolerantmodel
The Fault-tolerantcomputationofSICisofamultilevel model:
SIC=F1002D(F2002(Sc11,Sc12),F2002(Sc21,Sc22))
Firstly,basiccomputingunit Ci1adoptsonealgorithmtocompletethe SCi1, andCi2finishestheSCi2viaadifferentalgorithm,secondly2out of2 (2oo2)safetycomputingcomponent of SIC executes2oo2calculationandgetsFSICifromthecalculation resultsofSCi1SCi2,andthirdly, accordingthestates ofwatchdog andswitchunit block,the resultofSIC isgottenviaa 1 outof2withdiagnostics(1oo2D) calculation,whichisbasedon FSIC1andFSIC2.
The flowofcalculationsisasfollows:
(1)Sci1=Fci1(Dnet1,Dnet2,Ddi,Dfss)
(2) Sci2=Fci2 (Dnet1,Dnet2,Ddi,Dfss)
(3) FSICi=F2oo2 (Sci1, Sci2),(i=1,2)
(4) SIC_OutPut=F1oo2D (FSIC1, FSIC2)
3.4.2Safety computation
Asinterlockingsystemconsistsofafixedsetoftask,the computationalmodelofSICistask-based.Ingeneral,applications mayconformtoatime-triggered,event-triggeredormixedcomputationalmodel.Herethetime-triggeredmodeisselected,tasks are executedcyclically.Theconsistency of computingstatesbetweenthetwounitsisthefoundationofSICforensuringsafetyand credibility.AsSICworksunder aloosely coupledmode,itisdifferentfromthatofdedicatedhardware-coupled computer.Soaspecializedsynchronizationalgorithmisnecessary forSIC.
SICcanbeconsideredasa multiprocessordistributedsystem, andits computationalmodelisessentially based ondatacomparingviahighbus communication.First, ananalytical approach isusedtoconfirmtheworst-caseresponse timeofeachtask.Toguaranteethe deadline oftasks that communicateacrossthenetwork,theaccesstime and delay of communication mediumissetto a fixed possiblevalue.Moreover,the computationalmodelmustmeetstherealtimerequirementsofrailwayinterlockingsystem,within thesystemcomputingcycle,weset manycheckpoints Pi(i=1,2,...n),which aresmallenough forsynchronization,andcomputationresult votingisexecutedat eachpoint.Thesafety computationflowofSICisshowninFigure 5.
Figure5 SafetycomputationalmodelofSIC
4.Hardware safetyintegritylevelevaluation
4.1 SafetyIntegrity
Asan authoritativeinternationalstandardforsafety-relatedsystem,IEC61508presentsa definition ofsafetyintegrity:
probabilityofasafety-relatedsystemsatisfactorily performingtherequiredsafetyfunctionsunder allthestatedconditionswithin astated periodoftime.In IEC61508,therearefourlevels ofsafety integrity are prescribe,SIL1~SIL4.TheSIL1is thelowest, and SIL4highest.
AccordingtoIEC 61508,the SIC belongsto safety-relatedsystemsinhighdemandorcontinuousmodeof operation.TheSILofSICcanbeevaluatedviatheprobabilityofdangerousperhour.Theprovision ofSILabout suchsysteminIEC 61508, seetable1.
Table 1-SafetyIntegritylevels:
target failuremeasures forasafetyfunctionoperatinginhighdemand orcontinuous modeof operation
Safety Integritylevel
Highdemand or continuousmodeofOperation
(Probability ofadangerous Failureperhour)
4 ≥10-9to<10-8
3 ≥10-8to<10-7
2 ≥10-7to<10-6
1 ≥10-6 to<10-5
4.2Reliability blockdiagramof SIC
Afteranalyzing thestructureandworking principleoftheSIC,wegetthebockdiagramof reliability, asfigure6.
Figure6Blockdiagramof SICreliability
5.Conclusions
In thispaper,weproposedanavailablestandardized component-basedcomputerSIC.Railwaysignalinterlockingisafail-safesystemwitha required probabilityofless than10-9safetycriticalfailures perhour.Inorder tomeetthecriticalconstraints,fault-tolerantarchitecture andsafetytactics areusedinSIC.Althoughthecomputationalmodelandimplementationtechniques arerathercomplex,the philosophy ofSICprovidesacheerfulprospecttosafetycriticalapplications, it rendersinasimpler styleofhardware,furthermore,itcanshortendevelopmentcycle and reduce cost. SIC hasbeen putinto practical application, andhighperformance ofreliabilityandsafetyhasbeen proven.
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From:
模块化安全铁路信号计算机联锁系统
1概述
信号联锁系统是保证交通安全、提高铁路运输效率的关键设备。
长期以
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