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CAN总线中改进的EDF调度算法可调度性分析.docx

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CAN总线中改进的EDF调度算法可调度性分析 Introduction ControllerAreaNetwork(CAN)isacommunicationprotocolusedintheautomotiveindustryforvariousapplications,suchasenginemanagement,brakecontrol,andmanymore.Itisarobustandreliableprotocolthatsupportsbidirectionalcommunicationbetweenvariouselectroniccontrolunits(ECUs)inavehicle.However,asthecomplexityofautomotivesystemsincreases,itbecomeschallengingtoscheduleCANmessagesefficiently.Hence,schedulingtechniquesarerequiredtoensurethatthemessagesaretransmittedtimelyandcorrectly. Inthispaper,wewilldiscusstheimprovedEarliestDeadlineFirst(EDF)schedulingalgorithmforCANnetworksandanalyzeitsschedulability. Background CANimplementsatime-triggeredcommunicationschemewhereamessageissentatfixedintervals.ThetimeintervalisspecifiedbythesendingECUandisknownasthemessage’stransmissionperiod.ThemaximumtimerequiredforaCANframetotraversetheentirenetworkisknownastheworst-casepropagationdelay(WCPD).Theschedulingofmessagesissignificantfortworeasons:toensurethatthenetworkresourcesareutilizedefficientlyandtoguaranteetimelydeliveryofmessages. SchedulingofmessagesinCANisacomplextask,primarilyduetothevariousconstraintsandlimitationsthatneedtobeconsidered.OneofthemostcommonlyusedschedulingalgorithmsinCANistheEDFalgorithm.TheEDFalgorithmassignsaprioritybasedonthedeadlineofamessage,withtheearliestdeadlinehavingthehighestpriority.Itisadynamicpriorityalgorithmthatensuresthathigherprioritymessagesareservicedbeforelowerprioritymessages. However,thestandardEDFalgorithmhasseverallimitationsthatmakeitunsuitableforschedulingmessagesinCANnetworks.Oneofthemostsignificantlimitationsisthatitassumesthatallmessageshavethesametransmissionperiodandpriority.ThisassumptionisnotvalidinCANnetworks,wheremessageshavedifferenttransmissionperiodsandpriorities. ImprovedEDFSchedulingAlgorithm ToaddressthelimitationsofthestandardEDFalgorithm,animprovedEDFschedulingalgorithmwasproposed.TheimprovedEDFalgorithmdynamicallyadjuststhepriorityofmessagesbasedontheirtransmissionperiodsanddeadlines.Thealgorithme