Time Predictable Programming Framework

With the rapid developIment of hardware and software techniques,embedded real-time system has been widely used in safety-critical areas like industry-automation,medical equipment and avionics.In real-time systems of these areas,time determinism of tasks is crucial.How to incorporate timing constraints during the design and assure they are met in the implementation becomes a hot research topic.Henzinger has come up with LET(Logical Execution Time)model,which introduces semantic to deal with timing in an explicit way.This model express control logic and timing constraints of tasks with coordinate control semantics,however,its functionality design is still based on process/thread model.As functionality design is based on a different abstraction from control design,and process/thread model lacks timing semantics,hardly can the control logic be translated into the runtime design in a direct way,nor can the timing properties be assured.SEFM(Servant/Exe-Flow Model)is a novel operating system model,in which a program is composed of a series of services.Services interact explicitly with each other,uncertain synchronization and competition does not exist.The running of service is of better timing determinism and controllability than the running of tasks in process/thread model.SEFM can express the control logic of-LET model in a direct way.We combine LET and SEFM,defining a novel programing model(Timed SEFM),in which control logic and functionality are developed separately in the way of LET and SEFM.Timed SEFM improves the two models,and results in a more flexible control model and time-triggered,coor-dinate functionality model,better assuring that the actual timing properites of program satisfy the control logic.Timed SEFM redefined the definition of model introduced in TDL and HTL,and introduces the notion of mode-switch period,which makes mode-switch more determinate and simplifies schedulability analysis.Timed SEFM also introduces the notion of service-combination,which means that a task consists of a set of services,making tasks more controllable.A Timed SEFM program is compiled into a set of triggers,which can fully express the control logic of the program.This saves the interpretation process of E code,making the actual Cxecution of the program more determinate,compared with Giotto,TDL and HTL.This dissertation describes Timed SEFM programming model and its runtime system in detail.As a case study,an implementation of an intelligent vehicle control system is presented to prove the feasibility of Timed SEFM programming framework(Timed SEFM model and its runtime system).