Modelling and compilation method for multi-PLC control program

For the large-scale multi-PLC control system, a network-oriented programming method is proposed. Regarding the control network as a large-scale virtual PLC device, the engineers can program the whole system using all of the resources in the control network directly. A modelling and compilation method for control program is also put forwarded and an event graph model for the programs is created. The serial control program can be decomposed into parallel tasks by event graph model analyse and traversal rule. According to the topology of control network, the event graphs are grouped, and the instructions can be downloaded to the corresponding PLC automatically. The variables of devices can be synchronised through network communication. The experimental result shows that this method can improve the program efficiency of the networked PLC control system, and keep the running logic according with the original program

Analysis of Parameterized-Chain Networks: The Dependency Graph and Its Full, Consistent Subgraphs

This thesis studies algorithmic aspects of deadlock analysis for parameterized networks of discrete-event systems. A parameterized network consists of a finite, but arbitrarily large, number of interacting finite-state subsystems, each within one of a fixed, finite number of isomorphism classes. While deadlock analysis of such systems is generally undecidable, decidable subproblems have recently been identified. The decision procedure rests on the construction of a finite dependency graph for the network, and the computation of its full, consistent subgraphs. We present a software tool for such computations, and apply it to a train network example that extends beyond the current theoretical framework. The results suggest ways in which the framework could usefully be extended

Weak invariant simulation and analysis of parameterized networks

Multi-process networks figure in many engineering applications such as communication networks, transportation networks, manufacturing and logistic systems, and computer hardware and software. Parameterized discrete event systems provide a convenient means of modeling such networks when the number of subprocesses is arbitrary, unknown or time-varying. Unfortunately, some key properties of these networks, such as nonblocking and deadlock-freedom, are undecidable. Moreover, mathematical tools supporting analysis of these networks are limited. This thesis introduces a novel mathematical notion, weak invariant simulation and proposes an efficient method to check whether a finite-state generator weakly invariantly simulates another finite-state generator with respect to a specific subalphabet. This new simulation relation is first used to define a tractable subclass of parameterized ring networks of isomorphic subprocesses in which deadlock-freedom is decidable. Within this framework, a procedure is given to determine the reachable deadlocked states of the network. The effectiveness of the procedure is demonstrated by the deadlock analysis of a version of the dining philosophers problem. To generalize the results on ring networks, we consider a network consisting of several linear parameterized sections but exhibiting a branching topology. To model these networks we introduce Generalized Parameterized Discrete Event Systems (GPDES). The difficulty in analysis of a GPDES is the fact that some of the subprocesses interact with several parameterized sections of the network. Hence the analysis proposed in this thesis involves careful study of interaction among different branches of the network. Here again, we use `weak invariant simulation' to limit the behavior of subprocesses of the network. Then we investigate interactions among different components of the network, using a dependency graph. The dependency graph is a directed graph developed to characterize reachable partial deadlocks caused by generalized circular waits in the proposed GPDES. Our results implicitly characterize reachable generalized circular waits as a language accepted by a finite automaton. Our framework allows for modeling and analysis of new parameterized problems. We investigated deadlock in a large-scale factory as an illustrative example