The Design Of Petri Nets Controller For Discrete Event Systems

A discrete event system (DES)is a kind of dynamic system which describe the evolves of the discrete events. The events whether occurs in systems operation are unknown, and they occur also at possibly unknown irregular intervals. A Petri net is a kind of powerful tool of simulating and analyzing system, in recent years it is widely applied in the field of the discrete event systems. In this paper the control theory and method are studied based on Petri nets model of the discrete event system.The contributions of this dissertation are as follows:1. For the mix linear inequality constraint control problems which contain both places and transitions ,firstly,we consider the situation that the system doesn't contain uncontrollable transitions, and design the optimal controller. This kind of method doesn't need to consider the whole incidence matrix of the net,the only thing to consider is the partially of the net.Secondly, we design controller for the situation that the system contains uncontrollable transitions, the controller designed here is not optimal. Then , we give the concept of sub-optimal controller , because not all of the controller designed by this method is sub-optimal, we find out and proof the subclass of the net which can be sub-optimal.2. There is a condition that the system does not deadlock ,but because the insert of the controller ,the system sometimes may cause deadlock . For this condition, we design the deadlock prevention algorithm.3. Regarding the system contains uncontrollable transitions, with the control problem is linear inequality, we propose the sub-optimal logic controller . The method proposed here convert the constraints to the or-logical linear inequality constraints. Then we design the controller by the colored weighed inhibitor petri nets. The controller designed here allow the whole transitions concurrent in the system.4. Now most of articles research the forbidden states expressed by linear inequality constraints, but in many systems, very often the forbidden states can not be expressed by linear inequality constraints. We deal with finite, arbitrary forbidden state problems, especially when the forbidden states can not be expressed by linear inequality constraints using existing methods, we improve the method based on synthesis method and state feedback based synthesis method as mentioned in [41] so as to deal with the unbounded net. As mentioned above, this thesis makes some studies to the Petri net controller of the DES, the controller designed here both have structural controller and logical controller. These studies have many other problems to discuss ,and deserve the further consideration.