In: Lectures on Concurrency and Petri Nets: Advances in Petri Nets, pages 585-625. Volume 3098 of Lecture Notes in Computer Science / Jörg Desel, Wolfgang Reisig, Grzegorz Rozenberg (Eds.) --- Springer-Verlag, June 2004.
Abstract: We present a modular formalism and methodology for modelling and control of discrete event systems, such as flexible manufacturing systems. The formalism is based on Petri net modules which communicate via signals. Two kinds of signals are employed, namely active signals, which force occurrence of (enabled) events (typically switches), and passive signals which enable/prohibit occurring of events (typically sensors). Modelling with such modules appears to be very natural from engineering perspective, enables hierarchical structuring, and support locality principle. Further, we discuss the role of both kinds of signals in control tasks and we focus on the control aspects in general. We present a methodology for synthesis of controlled behavior for systems modelled by modules of signal sets. Given an uncontrolled system (a plant) modelled by a module of a signal net, and a control specification given as a regular language representing the desired signal output behavior of this system, we show how to synthesize the maximal permissive and non-blocking behavior of the plant respecting the control specification. Finally, we show how to synthesize the controller (as a module of a signal net) forcing the plant to realize the controlled behavior.