ABSTRACT
Industrial control applications use controllers, sensors, and actuators to close control loops. Sensors andactuatorsareusuallydistributedtopologicallythroughthecontrolledplant.Asubiquitousembeddedcontrollers,sensors,andactuatorsaremoreandmorecommon,whileinexpensiveandreliable communicationsystemsarereadyforuseintheindustry,manyofthecontrolloopsareclosedusing industrialcommunicationsystems.Alargepartoftheindustrycontrolloopsarediscreteinnature, whereasequenceofdiscreteactionsaredonea¯erasequenceofsensings,e.g.,a¯eradisplacementhas beencompleted,amotorhastostop.Fromthecontrolside,adiscretesystemhasasmajorconstraint, thesystemresponsetime,orthemaximumtimethatcanbeacceptedbetweenoccurrenceofastimulus andthereactionontheplant.Previouschaptersofthebookaddresshowtheindustrialcommunication systems attain the goal of sending messages keeping this constraint.
