Design Of Petri Net Controller For Discrete Event Systems

Discrete Event System (DES) is a kind of dynamic system that driven by the outside discrete events and these events interacts by certain rules and results in status evolution. DES is essentially a kind of man-made system, for example:flexible manufacturing system, communication network system, traffic control system, computer operating system, military command system and so on.The research of DES mainly consists of system performance analysis and supervisory control theory. The main research tools of the latter are automata and Petri Nets. As Petri Nets has Powerful modeling and analysis ability, the present dissertation uses Petri Nets as tool to study the controller synthesis of DES with inequality constraint.For a system in application, specifications and targets are proposed to make sure that the system can only evolve in some admissible states instead of forbidden states, which are described by the linear vector constraints. The supervisor with only controllable and observable events in DES can be directly achieved through linear vector constraints. However, in the presence of uncontrollable or unobservable events, the specified linear vector constraint may become illegal, while will result in an illegal supervisor. In order to solve this problem, this thesis proposed a method to transform the illegal constraint into a legal one, based on which we can obtain the legal supervisor.The base of the method of synthesis Petri Nets controller for DES based on the finite capacity places is generalized inverse matrix. A new method was proposed to transform the forbidden constraint into admissible one. And then, an improved method for constructing a Petri Net feedback controller based on part design and Petri Net reduction technique. Through example, the method given here is proved to be clear in structure and concise in computation, and will greatly simplify controller synthesis when applied to constraints in complex Petri Net. All conclusions and algorithms in this thesis are obtained via strict theory proof. Many examples are provided through out the text to verify and illustrate the efficiency and feasibility of the theorems and algorithms.