Research Of Two Types Of DES Controller Design Based On Petri Nets

The research on discrete event systems (DES) is begun in the 1980's.With the rapid development of information techniques, computer science and robotics, lots of manmade systems have appeared in communications, manufacture, traffic and military affairs. The flexible manufacturing system (FMS), communication network, aerodrome traffic control system and military C3I system are the typical examples of manmade systems. In these manmade systems, it is not continuous variable but discrete event to impact the behavior of the system. It is the research requirement of the manmade system behavior to impulse the development of DES.The research of DES mainly consists of system performance analysis and control synthesis. The present dissertation uses Petri nets (PN) as tool to study the controller synthesis of DES. The principal research results can be outlined two aspects:Firstly, a controller synthesis method based on colored Petri nets (CPN) is proposed. It is effective to synthesis a controller to satisfy the constrains with the forms of OR-logic based on colored Petri nets. However there is usually an assumption in the reported literatures that the transitions in the net are not concurrent. In this paper, a control method for discrete event systems (DES) based on colored Petri nets is proposed. The constrains with the forms of OR-logic are enforced and all of the transitions in the net are permitted to be concurrent.Secondly, for the Petri nets controller synthesis of DES, linear integer program (LIP) is an efficient technique for the on-line computation of the control policy when the maximal uncontrollable subnet is loop-free. When the maximal uncontrollable subnet is loop-in, the problem is a nonlinear integer program (NIP), which is difficult to be solved. In this paper, for the maximal uncontrollable loop-in subnet with a special form, the maximal permissive control policy is obtained through applying the LIP to the loop-free subnet that is equivalent to the maximal uncontrollable loop-in subnet.In the end, on the basis of summarization of the major work in this dissertation, a few problems to be studied and future research trends are given.