Institute for Systems Research
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Item A New Framework for Supervisory Control of Discrete Event Systems(1995) Shayman, M.A.; Kumar, Ratnesh; ISRWe propose a new framework for supervisory control design for discrete event systems. Some of the features of the proposed approach are: (i) By associating control and observation capabilities and limitations with the plant as well as the supervisor, it models reactive systems, and also treats plant and supervisory processes in a symmetric way. (ii) By introducing a single general interconnection operation, called masked composition, it permits open-loop as well as closed-loop control. (iii) By viewing the uncontrollability of events as corresponding to a projection-type control mask, and considering more general nonprojection-type control as well as observation masks, it treats the controllability and observability of events in a unified way. (iv) It applies to both deterministic and nondeterministic plant models and supervisory design. The sublanguages of a given language that are realizable under control are closed under union. Hence, the supremal realizable sublanguage always exists. In addition, it yields conditions under which existence of a non-deterministic supervisor implies existence of a deterministic supervisor. (v) By encapsulating control and observation masks with process logic to form process objects, and using a single type of interconnection operator to build complex process objects out of simpler component process objects, it provides a foundation for an object-oriented approach to discrete event control.Item Non-blocking Supervisory Control of Nondeterministic Systems via Prioritized, Synchronization(1993) Kumar, Ratnesh; Shayman, M.A.; ISRIn a previous paper [15], we showed that supervisory control of nondeterministic discrete event systems, in the presence of driven events, can be achieved using prioritized synchronous composition as a mechanism of control, and trajectory models as a modeling formalism. The specifications considered in [15] were given by prefix-closed languages. In this paper, we extend the theory of trajectory models and prioritized synchronous composition to include markings so that non-closed specifications and issues such as blocking can be addressed. It is shown that the usual notion of non-blocking, called language model non- blocking, is inadequate in the setting of nondeterministic systems, and a stronger notion, called trajectory model non- blocking, is introduced. Necessary and sufficient conditions for the existence of non-marking and language model non-blocking as well as trajectory model non-blocking supervisors is obtained for nondeterministic systems in the presence of driven events. We also show that our approach is also suitable for modular supervisory control.Item Supervisory Control of Nondeterministic Systems with Driven Events via Prioritized Synchronization and Trajectory Models(1992) Shayman, M.A.; Kumar, Ratnesh; ISRWe study the supervisory control of nondeterministic discrete event dynamical systems (DEDS's) with driven events in the setting of prioritized synchronization and trajectory models introduced by Heymann. Prioritized synchronization captures the notions of controllable, uncontrollable, and driven events in a natural way, and we use it for constructing supervisory controllers. The trajectory model is used for characterizing the behavior of nondeterministic DEDS's since it is a sufficiently detailed model (in contrast to the less detailed language or failures models), and serves as a language congruence with respect to the operation of prioritized synchronization. We obtain results concerning controllability and observability in this general setting.