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1、1、PLCdesigncriteriaAsystematicapproachtodesigningPLCsoftwarecanovercomedeficienciesinthetraditionalwayofprogrammingmanufacturingcontrolsystems,andcanhavewideramificationsinseveralindustrialapplications.Automationcontrolsystemsaremodeledbyformallanguagesor,e
2、quivalently,bystatemachines.Formalrepresentationsprovideahigh-leveldescriptionofthebehaviorofthesystemtobecontrolled.Statemachinescanbeanalyticallyevaluatedastowhetherornottheymeetthedesiredgoals.Secondly,astatemachinedescriptionprovidesastructuredrepresent
3、ationtoconveythelogicalrequirementsandconstraintssuchasdetailedsafetyrules.Thirdly,well-definedcontrolsystemsdesignoutcomesareconducivetoautomaticcodegeneration-Anabilitytoproducecontrolsoftwareexecutableoncommercialdistinctlogiccontrollerscanreduceprogramm
4、inglead-timeandlaborcost.Inparticular,thethesisisrelevantwithrespecttothefollowingaspects.Inmodernmanufacturing,systemsarecharacterizedbyproductandprocessinnovation,becomecustomer-drivenandthushavetorespondquicklytochangingsystemrequirements.Amajorchallenge
5、isthereforetoprovideenablingtechnologiesthatcaneconomicallyreconfigureautomationcontrolsystemsinresponsetochangingneedsandnewopportunities.Designandoperationalknowledgecanbereusedinreal-time,therefore,givingasignificantcompetitiveedgeinindustrialpractice.St
6、udieshaveshownthatprogrammingmethodologiesinautomationsystemshavenotbeenabletomatchrapidincreaseinuseofcomputingresources.Forinstance,theprogrammingofPLCsstillreliesonaconventionalprogrammingstylewithladderlogicdiagrams.Asaresult,thedelaysandresourcesinprog
7、rammingareamajorstumblingstonefortheprogressofmanufacturingindustry.Testinganddebuggingmayconsumeover50%ofthemanpowerallocatedforthePLCprogramdesign.Standards[IEC60848,1999;13IEC-61131-3,1993;IEC61499,1998;ISO15745-1,1999]havebeenformedtofixanddisseminatest
8、ate-of-the-artdesignmethods,buttheynormallycannotparticipateinadvancingtheknowledgeofefficientprogramandsystemdesign.Asystematicapproachwillincreasethelevelofdesignautomationthroughreusingexistingsoftw
