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Systems, Man, and Cybernetics, Part B: Cybernetics, IEEE Transactions on

Issue 5 • Date Oct. 2000

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Displaying Results 1 - 16 of 16
  • List of reviewers

    Page(s): 642
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    Freely Available from IEEE
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  • A controlled genetic algorithm by fuzzy logic and belief functions for job-shop scheduling

    Page(s): 812 - 818
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    Most scheduling problems are highly complex combinatorial problems. However, stochastic methods such as genetic algorithm yield good solutions. In this paper, we present a controlled genetic algorithm (CGA) based on fuzzy logic and belief functions to solve job-shop scheduling problems. For better performance, we propose an efficient representational scheme, heuristic rules for creating the initial population, and a new methodology for mixing and computing genetic operator probabilities View full abstract»

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  • On the complexity of supervisory control design in the RW framework

    Page(s): 643 - 652
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    The time complexity of supervisory control design for a general class of problems is studied. It is shown to be very unlikely that a polynomial-time algorithm can be found when either (1) the plant is composed of m components running concurrently or (2) the set of legal behaviors is given by the intersection of n legal specifications. That is to say, in general, there is no way to avoid constructing a state space which has size exponential in m+n. It is suggested that, rather than discouraging future work in the field, this result should point researchers to more fruitful directions, namely, studying special cases of the problem, where certain structural properties possessed by the plant or specification lend themselves to more efficient algorithms for designing supervisory controls. As no background on the subject of computational complexity is assumed, we have tried to explain all the borrowed material in basic terms, so that this paper may serve as a tutorial for a system engineer not familiar with the subject View full abstract»

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  • Reliable decentralized supervisory control of discrete event systems

    Page(s): 661 - 667
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    We consider a discrete event system controlled by a decentralized supervisor consisting of n local supervisors, and formulate a new decentralized supervisory control problem, called a reliable decentralized supervisory control problem. A decentralized supervisor is said to be k-reliable (1⩽k⩽n) if it exactly achieves a specification language under possible failures of any ⩽n-k local supervisors. So, k denotes the minimal number of local supervisors required to achieve the specification. First, we present necessary and sufficient conditions for the existence of a k-reliable decentralized supervisor. Next, we consider the case that a k-reliable decentralized supervisor for a given specification language does not exist. We take two approaches in this case. In the first approach, we present an algorithm for computing a sublanguage of the specification that satisfies the existence conditions of a k-reliable decentralized supervisor. In the second one, we use a coordinator to synthesize a k-reliable decentralized supervisor without altering the specification View full abstract»

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  • Avoidance versus detection and recovery problem in buffer-space allocation of flexibly automated production systems

    Page(s): 799 - 811
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    Motivated by recent developments in the semiconductor manufacturing industry, this paper undertakes an analytical investigation of the problem of selecting optimally the deadlock resolution strategy for buffer space allocation in flexibly automated production systems. In the process, it extends the behavioral models for the aforementioned systems currently considered in the literature, to account for probabilistic uncontrollable effects like the requirement for extra finishing steps and/or rework, and it introduces a new deadlock resolution scheme, characterized as randomized deadlock avoidance. The combination of these two extensions brings the considered system behavior(s) to the realm of probabilistic automata, an area of increasing academic interest. For the resulting model, and under the assumption of Markovian timings, it develops an analytical methodology for selecting the optimal deadlock resolution strategy that maximizes the steady-state system throughput, and it demonstrates its effectiveness through application to a “prototype” system configuration. The obtained results provide an interesting analytical expression of the need to assess the gains obtained by the increased concurrency supported by the deadlock detection and recovery strategy versus the productivity losses experienced under this approach due to increased system blocking, and/or additional material handling overheads. It turns out that, for the considered system configuration, the optimal selection scheme switches between detection and recovery and pure deadlock avoidance, every time that the time cost of deadlock recovery, τd, crosses a threshold Θ, which is a function of the remaining system behavioral and timing parameters. Beyond its own theoretical merit, this last result raises also the question of whether the policy randomization introduced in this work will ever enhance the performance of any configuration in the considered class of Resource Allocation Systems (RAS); this issue will be investigated in a sequel paper View full abstract»

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  • Control synthesis of timed discrete event systems based on predicate invariance

    Page(s): 713 - 724
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    In this paper, arc-timed Petri nets are used to model controlled real-time discrete event systems, and the control synthesis problem that designs a controller for a system to satisfy its given closed-loop behavior specification is addressed. For the problem with the closed-loop behavior specified by a state predicate, real-time control-invariant predicates are introduced, and a fixpoint algorithm to compute the unique extremal control-invariant subpredicate of a given predicate, key to the control synthesis, is presented. For the problem with the behavior specified by a labeled arc-timed Petri net, it is shown that the control synthesis problem can be transformed into one that synthesizes a controller for an induced arc-timed Petri net with a state predicate specification. The problem can then be solved by using the fixpoint algorithm as well. The algorithm involves conjunction and disjunction operations of polyhedral sets and can be algorithmically implemented, making automatic synthesis of controllers for real-time discrete event systems possible View full abstract»

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  • Markovian timed Petri nets for performance analysis of semiconductor manufacturing systems

    Page(s): 757 - 771
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    A subclass of generalized stochastic Petri nets (GSPNs) with priorities, called Markovian timed Petri nets, are proposed to model semiconductor manufacturing systems that consider process priorities, routing priorities, resource re-entrance, and nonpreemptive operations. Uniformization technique is used to establish both lower and upper bounds of the performance of interest. These bounds are computable using linear programming. Numerical experiments have been conducted to evaluate the accuracy of the bounds using models adapted from real-world systems. The experiments show that the upper bounds are very close to the simulation results. Thus, performance measures can be accurately estimated using these bounds View full abstract»

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  • Modeling and analysis of equipment managers in manufacturing execution systems for semiconductor packaging

    Page(s): 772 - 782
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    Equipment Managers (EMs) play a major role in a Manufacturing Execution System (MES). They serve as the communication bridge between the components of an MES and the equipment. The purpose of this paper is to propose a novel methodology for developing analytical and simulation models for the EM such that the validity and performance of the EM can be evaluated. Domain knowledge and requirements are collected from a real semiconductor packaging factory. By using IDEFO and state diagrams, a static functional model and a dynamic state model of the EM are built. Next, these two models are translated into a Petri net model. This allows qualitative and quantitative analyses of the system. The EM net model is then expanded into the MES net model. Therefore, the performance of an EM in the MES environment can be evaluated. These evaluation results are good references for design and decision making View full abstract»

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  • Reachability analysis of real-time systems using time Petri nets

    Page(s): 725 - 736
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    Time Petri nets (TPNs) are a popular Petri net model for specification and verification of real-time systems. A fundamental and most widely applied method for analyzing Petri nets is reachability analysis. The existing technique for reachability analysis of TPNs, however, is not suitable for timing property verification because one cannot derive end-to-end delay in task execution, an important issue for time-critical systems, from the reachability tree constructed using the technique. In this paper, we present a new reachability based analysis technique for TPNs for timing property analysis and verification that effectively addresses the problem. Our technique is based on a concept called clock-stamped state class (CS-class). With the reachability tree generated based on CS-classes, we can directly compute the end-to-end time delay in task execution. Moreover, a CS-class can be uniquely mapped to a traditional state class based on which the conventional reachability tree is constructed. Therefore, our CS-class-based analysis technique is more general than the existing technique. We show how to apply this technique to timing property verification of the TPN model of a command and control (C2) system View full abstract»

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  • Supervisory control of multiworkcell manufacturing systems with shared resources

    Page(s): 668 - 683
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    Flexible-manufacturing systems (FMSs) may comprise a number of workcells where production resources are shared among the workcells for a variety of practical reasons. Although the utilization of independent workcells with sharing resources improves the flexibility of FMSs, avoiding deadlocks is essential for their successful implementation. This paper introduces a novel methodology for the synthesis of a set of conflict- and deadlock-free supervisors to individually control every workcell within a FMS inter-related by common (shared) resources. The proposed methodology is based on Extended Moore Automata (EMA) and Controlled-Automata theories. A new algorithmic procedure to analyze the concurrent operation of supervisors is also introduced in order to check for the existence or absence of deadlock states View full abstract»

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  • Modeling and performance analysis using extended fuzzy-timing Petri nets for networked virtual environments

    Page(s): 737 - 756
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    Despite their attractive properties, networked virtual environments (net-VEs) are notoriously difficult to design, implement, and test due to the concurrency, real-time and networking features in these systems. Net-VEs demand high quality-of-service (QoS) requirements on the network to maintain natural and real-time interactions among users. The current practice for net-VE design is basically trial and error, empirical, and totally lacks formal methods. This paper proposes to apply a Petri net formal modeling technique to a net-VE-NICE (narrative immersive constructionist/collaborative environment), predict the net-VE performance based on simulation, and improve the net-VE performance. NICE is essentially a network of collaborative virtual reality systems called the CAVE-(CAVE automatic virtual environment). First, we introduce extended fuzzy-timing Petri net (EFTN) modeling and analysis techniques. Then, we present EFTN models of the CAVE, NICE, and transport layer protocol used in NICE: transmission control protocol (TCP). We show the possibility analysis based on the EFTN model for the CAVE. Then, by using these models and design/CPN as the simulation tool, we conducted various simulations to study real-time behavior, network effects and performance (latencies and jitters) of NICE. Our simulation results are consistent with experimental data View full abstract»

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  • Comparing digraph and Petri net approaches to deadlock avoidance in FMS

    Page(s): 783 - 798
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    Flexible manufacturing systems (FMSs) are modern production facilities with easy adaptability to variable production plans and goals. These systems may exhibit deadlock situations occurring when a circular wait arises because each piece in a set requires a resource currently held by another job in the same set. Several authors have proposed different policies to control resource allocation in order to avoid deadlock problems. These approaches are mainly based on some formal models of manufacturing systems, such as Petri nets (PNs), directed graphs, etc. Since they describe various peculiarities of the FMS operation in a modular and systematic way, PNs are the most extensively used tool to model such systems. On the other hand, digraphs are more synthetic than PNs because their vertices are just the system resources. So, digraphs describe the interactions between jobs and resources only, while neglecting other details on the system operation. The aim of this paper is to show the tight connections between the two approaches to the deadlock problem, by proposing a unitary framework that links graph-theoretic and PN models and results. In this context, we establish a direct correspondence between the structural elements of the PN (empty siphons) and those of the digraphs (maximal-weight zero-outdegree strong components) characterizing a deadlock occurrence. The paper also shows that the avoidance policies derived from digraphs can be implemented by controlled PNs View full abstract»

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  • Automated synthesis and composition of taskblocks for control of manufacturing systems

    Page(s): 696 - 712
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    Automated control synthesis methods for discrete-event systems promise to reduce the time required to develop, debug, and modify control software. Such methods must be able to translate high-level control goals into detailed sequences of actuation and sensing signals. In this paper, we present such a technique. It relies on analysis of a system model, defined as a set of interacting components, each represented as a form of condition system Petri net. Control logic modules, called taskblocks, are synthesized from these individual models. These then interact hierarchically and sequentially to drive the system through specified control goals. The resulting controller is automatically converted to executable control code. The paper concludes with a discussion of a set of software tools developed to demonstrate the techniques on a small manufacturing system View full abstract»

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  • Supervisory control of Petri nets using routing functions: starvation avoidance issues

    Page(s): 684 - 695
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    In this paper, we present a new point of view on supervisory control of Petri nets by using routing functions instead of the traditional control places. We first show the relation between the two notions. In the second part of the paper, we illustrate the use of routing functions by showing how to compute a routing function in order to avoid starvation in general Petri nets. This control uses a continuous version of the net and a description of the evolution of the net under the form of linear algebraic equations. As for the computational part, we use algebraic polynomial geometry in the continuous case and Diophantine equations for the discrete version of the Petri net under study View full abstract»

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  • Decentralized control of discrete event systems with specializations to local control and concurrent systems

    Page(s): 653 - 660
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    The decentralized supervisory control problem of discrete event systems under partial observation is studied in this paper. The main result of the paper is a necessary and sufficient condition for the existence of decentralized supervisors for ensuring. That the controlled behavior of the system lies in a given range. The contribution of the paper is (1) our setting of decentralized control generalizes the prior ones; (2) we present an alternative approach for solving the decentralized control problem, which leads to computational saving for concurrent systems and certain other systems; and (3) our generalized formulation and its solution lets us extend several of the existing results reported previously. The results of our paper are illustrated by an example of a simple manufacturing system View full abstract»

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Aims & Scope

IEEE Transactions on Systems, Man, and Cybernetics, Part B: Cybernetics focuses on cybernetics, including communication and control across humans, machines and organizations at the structural or neural level

 

This Transaction ceased production in 2012. The current retitled publication is IEEE Transactions on Cybernetics.

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Meet Our Editors

Editor-in-Chief
Dr. Eugene Santos, Jr.
Thayer School of Engineering
Dartmouth College