Temporal Analysis of Data Flow Control Systems

Due to their distributed/parallel and data-driven nature, control systems can easily be modeled according to a data flow approach. Control systems are very often real-time systems; therefore, a formalism able to capture timing is required. In this paper we introduce a data flow model that includes time and priority for specifying real-time control systems and we give its formal semantics. The control system is specified by a data flow network which, beside the controller, may include the model of the plant at some abstraction level. Time is associated to any computational activity and time accounting is made directly in the model and not as a separate issue. Priorities allow to deal with events, as alarm signals, which cannot be delayed. A general framework for the indirect evaluation of the model is introduced, and a data flow network to timed Petri net transformation is defined allowing the utilization of the automatic tools of Petri nets for analyzing the temporal properties of the data flow network. The approach is illustrated by an example in which, after the application of the transformation, selected performance measures are computed.