Modular discrete-event systems: Modeling, control with priorities, and incremental model evolution

Modularization is a commonly-used technique for modeling and control of large-scale systems. It can reduce the complexity of controllers, enhance the flexibility in the design of system models and controllers, and facilitate the redesign of controllers when changes are required to the system models. However, the modular design of systems and controllers can also create unexpected conflicts among controllers. This work is set in the context of the theory of supervisory control of discrete event systems. The three main contributions of this thesis address modeling, control with priorities, and incremental model evolution of modular discrete event systems.; An important motivation for this thesis is the problem of feature interactions in telecommunication networks. When a new feature, such as call waiting or call forwarding, is added to the system, it may interact unexpectedly with the existing features and result in undesirable system behavior. Meanwhile, the introduction of new system components or features sometimes requires the complete redesign of the existing features.; In this thesis, we model the logical behavior of telecommunication networks as discrete event systems, where features are implemented as modular supervisors that jointly control the telecommunication system. Techniques are proposed to detect the potential interactions between these supervisors.; We then propose a new scheme for modular control of discrete event systems. This scheme provides a new approach to resolve conflicts among modular supervisors, such as blocking and loss of functionality, through the use of a priority mechanism. We develop algorithms that use this priority mechanism to synthesize nonblocking modular supervisors.; In the case of incremental system evolution, we investigate the feasibility of reusing the existing modular supervisors. We propose systematic methods for the reuse of existing supervisors based on the automatic synthesis of input and output interfaces.; Although this work was originally motivated by the problem of feature interactions, the results presented in this thesis can be readily applied to other discrete event system applications such as manufacturing systems.