The supervisory control of timed discrete-event systems

The framework given by P.J. Ramadge and W.M. Wonham (SIAM J. Control Optim., Vol. 25, no.1, p.206-30, 1987) for control of discrete event systems is augmented with timing features by use of Ostroff´s semantics for timed transition models (1989, 1990). It is shown that the corresponding concept of controllability, and the existence of minimally restrictive supervisory controls can be suitably generalized. The enhanced setting admits subsystem composition, and the concept of forcible event as an event that preempts the tick of a global clock. An example of a simple manufacturing cell illustrates how the new framework can be used to solve synthesis problems which may include logic-based, temporal and quantitative optimality specifications