The design of logic controllers for event-driven systems continue to rely largely on intuitive methods rather than on formal techniques. This approach results in a control code that requires extensive verification, is hard to maintain and modify, and may even fail at times. Supervisory control theory (SCT) provides a formal approach to logic control synthesis. In order to demonstrate the usefulness of the supervisory control theory in manufacturing systems, an educational test-bed that simulates an automated car assembly line has been built using LEGO/spl reg/ blocks. Finite state machines (FSMs) are used for modeling operations of the assembly line, and for the specifications that accomplish the task of successfully completing the assembly repeatedly. Using the technique of SCT, we derive a supervisor that enforces the specifications while offering the maximum flexibility of assembly. Subsequently a controller is extracted from the maximally permissive supervisor for the purpose of implementing the control by selecting, when possible, at most one controllable event from among the ones allowed by the supervisor. Testing to check the correctness of the control code is reduced, since the controller is guaranteed to enforce the specifications.

The traditional framework for discrete-event control is extended to include the case of control with active events, in which both the user and the environment have events that they can trigger. A variety of liveness and safety specifications can be considered within this extended framework. A synthesis algorithm of minimally restrictive controllers is outlined.

An optimal control theory for designing a controller, that selects unique control actions is developed for controlling discrete event systems (DESs). Prior work on supervisor synthesis problems studied the design of supervisors for satisfying qualitative specifications within the framework of the DESs. In this paper we define and investigate the synthesis of an optimal controller in the sense that, regardless the state of the plant, the worst cost of all surviving paths from that state to the set of frontier marked states is minimized. Our work differs from prior works on optimal control of DESs in that the controller selects a unique controllable event to be executed per state, rather than a set of admissible controllable events. An efficient algorithm is provided to solve this problem under complete observation.