Supervisory Control of Discrete Event Systems With Dynamic Control Specifications by Petri Nets
LI Cheng-zong, Yufeng Chen, Zhiwu Li
Abstract
Supervisory control can enforce a desired control specification for discrete event systems (DESs). If the specification of a system is changed over time, i.e., the system is subject to dynamic control specifications, control reconfiguration methods are proposed to implement the new specification. However, the existing reconfiguration methods require redesigning and adding controllers for the new specification. In this article, we propose a dynamic control policy for a Petri net model with dynamic control specifications. First, a fully functional supervisor is designed for the net model, which is dynamically optimal since it can dynamically adjust control actions for the net model and prevent all illegal markings, while all legal markings are permitted for each specification. Then, by the dynamically optimal supervisor, the dynamic control policy consists of two steps: 1) guide the system from the current illegal state to a marking that satisfies the new specification and 2) switch control actions of the supervisor. By using the proposed method, the system can satisfy the dynamically changeable specifications. Finally, some examples are used to illustrate the proposed method.