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Synthesis Of Controller For Discrete Event Systems Based Reduction

Posted on:2006-05-18Degree:DoctorType:Dissertation
Country:ChinaCandidate:S G WangFull Text:PDF
GTID:1102360152490832Subject:Control theory and control engineering
Abstract/Summary:PDF Full Text Request
Due to the rapid development of computer science and its extensive application in modern society, some scholars found a new type of dynamic systems named as discrete event systems (DES), which is different from continuous variable dynamic systems. The dominating characteristic of DES is that its evolution is not driven by times but events. Essentially, DES is a manmade system. The typical DES includes the manufacturing system (especially FMS and CIMS), system scheduling, communication network, traffic control system, random service system and computer operating system and so on. The research aim of DES is two-fold: one is to provide tools for performance analysis, the other is to offer supervisory control methods for DES.First, based on a fusion technology proposed in this paper, this paper describes two methods for constructing a Petri net feedback controller enforcing a set of inequality constraints on the reachable markings of the Petri net model. One of two methods, first fuses all the constrained places into one equal place whose marking is equal to the sum of the markings of the constrained places based on the fusion technology presented in this paper, and then designs control place for the equal place based on concept of Petri net place invariants. The other method, first designs control place for each constrained place based on concept of Petri net place invariants, and then fuses these control places into one control place based on the fusion technology presented in this paper. The two methods are proved to be simpler and more efficient than the method presented by Moody, et al., using an applied instance that was also used by Moody et al. Second, starting with reducing incidence matrix of Petri net, we propose the concept of local incidence matrix that is an incidence matrix of a subnet, which is constituted by the constrained places and their input transitions and output transitions. Compared with the technique based on incidence matrix, the method based on local incidence matrix in this paper is simpler, more effective. Third, the problem of enforcing linear inequality constraints involving the marking vector and the Parikh vector on a discrete event system modeled by Petri nets is discussed in thispaper. A novel method for design of controller enforcing the constraints is presented. First the constraints involving the marking and the Parikh vector are transformed into the constraints involving Parikh vector only, and then the controller is constructed based on the viewpoint that a place can be seen as a linear inequality constraint on Parikh vector. The method is proved to be simpler and more efficient than the method presented by Iordache and Moody through an applied instance that was also cited by Moody et al., and holds remarkable advantage especially for large systems. Finally, we consider the liveness based on networking unfolding. Networking unfolding is a reduction to avoid the state explosion problem in the verification of distributed systems. We propose necessary and sufficient conditions for the original net's liveness and the existence of maximally permissive supervisory policies that enforce liveness based on the networking unfolding, and then design controller that enforces liveness for the original net.All conclusions and algorithms in this dissertation are obtained via strict theory proof. Many examples are provided throughout the text to verify and illustrate the efficiency and feasibility of the theorems and algorithms.
Keywords/Search Tags:discrete event systems, Petri nets, supervisory control, controller, inequal constraint, liveness, networking unfolding, verification
PDF Full Text Request
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