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Detectability of Discrete Event Systems
"... In this paper, we investigate the detectability problem in discrete event systems. We assume that we do not know initially which state the system is in. The problem is to determine the current and subsequent states of the system based on a sequence of observation. The observation includes partial ev ..."
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Cited by 566 (11 self)
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In this paper, we investigate the detectability problem in discrete event systems. We assume that we do not know initially which state the system is in. The problem is to determine the current and subsequent states of the system based on a sequence of observation. The observation includes partial event observation and/or partial state observation, which leads to four possible cases. We further define four types of detectabilities: strong detectability, (weak) detectability, strong periodic detectability, and (weak) periodic detectability. We derive necessary and sufficient conditions for these detectabilities. These conditions can be checked by constructing an observer, which models the estimation of states under different observations. The theory developed in this paper can be used in feedback control and diagnosis. If the system is detectable, then the observer can be used as a diagnoser to diagnose the failure states of the system.
Synchronization and linearity: an algebra for discrete event systems
, 2001
"... The first edition of this book was published in 1992 by Wiley (ISBN 0 471 93609 X). Since this book is now out of print, and to answer the request of several colleagues, the authors have decided to make it available freely on the Web, while retaining the copyright, for the benefit of the scientific ..."
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Cited by 248 (10 self)
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The first edition of this book was published in 1992 by Wiley (ISBN 0 471 93609 X). Since this book is now out of print, and to answer the request of several colleagues, the authors have decided to make it available freely on the Web, while retaining the copyright, for the benefit of the scientific community. Copyright Statement This electronic document is in PDF format. One needs Acrobat Reader (available freely for most platforms from the Adobe web site) to benefit from the full interactive machinery: using the package hyperref by Sebastian Rahtz, the table of contents and all LATEX crossreferences are automatically converted into clickable hyperlinks, bookmarks are generated automatically, etc.. So, do not hesitate to click on references to equation or section numbers, on items of thetableofcontents and of the index, etc.. One may freely use and print this document for one’s own purpose or even distribute it freely, but not commercially, provided it is distributed in its entirety and without modifications, including this preface and copyright statement. Any use of thecontents should be acknowledged according to the standard scientific practice. The
On the Synthesis of Discrete Controllers for Timed Systems
 in E.W. Mayr and C. Puech (Eds), Proc. STACS'95, LNCS 900
, 1995
"... Abstract. This paper presents algorithms for the automatic synthesis of realtime controllers by nding a winning strategy for certain games de ned by the timedautomata of Alur and Dill. In such games, the outcome depends on the players ' actions as well as on their timing. We believe that these res ..."
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Cited by 188 (20 self)
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Abstract. This paper presents algorithms for the automatic synthesis of realtime controllers by nding a winning strategy for certain games de ned by the timedautomata of Alur and Dill. In such games, the outcome depends on the players ' actions as well as on their timing. We believe that these results will pave theway for the application of program synthesis techniques to the construction of realtime embedded systems from their speci cations. 1
CONTROLLER SYNTHESIS FOR TIMED AUTOMATA
"... In this work we tackle the following problem: given a timed automaton, restrict its transition relation in a systematic way so that all the remaining behaviors satisfy certain properties. This is an extension of the problem of controller synthesis for discrete event dynamical systems, where in addi ..."
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Cited by 119 (14 self)
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In this work we tackle the following problem: given a timed automaton, restrict its transition relation in a systematic way so that all the remaining behaviors satisfy certain properties. This is an extension of the problem of controller synthesis for discrete event dynamical systems, where in addition to choosing among actions, the controller have the option of doing nothing and let the time pass. The problem is formulated using the notion of a realtime game, and a winning strategy is constructed as a fixedpoint of an operator on the space of states and clock configurations.
A Survey of Computational Complexity Results in Systems and Control
, 2000
"... The purpose of this paper is twofold: (a) to provide a tutorial introduction to some key concepts from the theory of computational complexity, highlighting their relevance to systems and control theory, and (b) to survey the relatively recent research activity lying at the interface between these fi ..."
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Cited by 112 (20 self)
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The purpose of this paper is twofold: (a) to provide a tutorial introduction to some key concepts from the theory of computational complexity, highlighting their relevance to systems and control theory, and (b) to survey the relatively recent research activity lying at the interface between these fields. We begin with a brief introduction to models of computation, the concepts of undecidability, polynomial time algorithms, NPcompleteness, and the implications of intractability results. We then survey a number of problems that arise in systems and control theory, some of them classical, some of them related to current research. We discuss them from the point of view of computational complexity and also point out many open problems. In particular, we consider problems related to stability or stabilizability of linear systems with parametric uncertainty, robust control, timevarying linear systems, nonlinear and hybrid systems, and stochastic optimal control.
Task Networks for Controlling Continuous Processes
 In Proceedings of the Second International Conference on AI Planning Systems
, 1994
"... This paper describes an extension to the rap system tasknet semantics and representation language to enable the effective control of continuous processes. The representation addresses the problems of synchronizing plan expansion with events in the world, coping with multiple, nondeterministi ..."
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Cited by 101 (1 self)
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This paper describes an extension to the rap system tasknet semantics and representation language to enable the effective control of continuous processes. The representation addresses the problems of synchronizing plan expansion with events in the world, coping with multiple, nondeterministic task outcomes, and the description of a simple form of cleanup task. It is also pointed out that success and failure need no special place in a task network representation. Success and failure are really messages about the execution system's knowledge and do not explicitly define that system's flow of control. To Appear in the Second International Conference on AI Planning Systems, June 1994. 1 Introduction Recently, AI researchers have proposed several different mechanisms for programming robots reactively. These include collections of behaviors [2], schemas [1], routines [9], and reflexes [15]. Many details differ between these proposals, particularly in the area of philosop...
Synchronous Observers and the Verification of Reactive Systems
 Third Int. Conf. on Algebraic Methodology and Software Technology, AMAST'93, Twente
, 1993
"... This paper is a survey of our specification and verification techniques, in a very general, language independent, framework. Section 1 introduces a simple model of synchronous input/output machines, which will be used throughout the paper. In section 2, we show how such a machine can be designed to ..."
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Cited by 101 (10 self)
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This paper is a survey of our specification and verification techniques, in a very general, language independent, framework. Section 1 introduces a simple model of synchronous input/output machines, which will be used throughout the paper. In section 2, we show how such a machine can be designed to check the satisfaction of a safety property, and we discuss the use of such an observer in program verification. In section 3, we use an observer to restrict the behavior of a machine. This is the basic way for representing assumptions about the environment. Applications to modular and inductive verification are considered. In modular verification, one has to find, by intuition, a property of a subprogram that is strong enough to allow the verification of the whole program without fully considering the subprogram. In section 4, we consider the automatic synthesis of such a property, and in section 5, we investigate the possibility of deducing the subprogram from such a synthesized specification.
Execution Monitoring of HighLevel Robot Programs.
, 1998
"... Imagine a robot that is executing a program online, and, insofar as it is reasonable to do so, it wishes to continue with this online program execution, no matter what exogenous events occur in the world. Execution monitoring is the robot's process of observing the world for discrepancies be ..."
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Cited by 83 (8 self)
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Imagine a robot that is executing a program online, and, insofar as it is reasonable to do so, it wishes to continue with this online program execution, no matter what exogenous events occur in the world. Execution monitoring is the robot's process of observing the world for discrepancies between the actual world and its internal representation of it, and recovering from such discrepancies.
Modularity for Timed and Hybrid Systems
, 1997
"... In a tracebased world, the modular specification, verification, and control of live systems require each module to be receptive; that is, each module must be able to meet its liveness assumptions no matter how the other modules behave. In a realtime world, liveness is automatically present in ..."
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Cited by 69 (19 self)
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In a tracebased world, the modular specification, verification, and control of live systems require each module to be receptive; that is, each module must be able to meet its liveness assumptions no matter how the other modules behave. In a realtime world, liveness is automatically present in the form of diverging time. The receptiveness condition, then, translates to the requirement that a module must be able to let time diverge no matter how the environment behaves. We study the receptiveness condition for realtime systems by extending the model of reactive modules to timed and hybrid modules. We define the receptiveness of such a module as the existence of a winning strategy in a game of the module against its environment. By solving the game on region graphs, we present an (optimal) Exptime algorithm for checking the receptiveness of propositional timed modules. By giving a fixpoint characterization of the game, we present a symbolic procedure for checking the re...
DiscreteTime Control for Rectangular Hybrid Automata
"... Rectangular hybrid automata model digital control programs of analog plant environments. We study rectangular hybrid automata where the plant state evolves continuously in realnumbered time, and the controller samples the plant state and changes the control state discretely, only at the integer poi ..."
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Cited by 56 (8 self)
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Rectangular hybrid automata model digital control programs of analog plant environments. We study rectangular hybrid automata where the plant state evolves continuously in realnumbered time, and the controller samples the plant state and changes the control state discretely, only at the integer points in time. We prove that rectangular hybrid automata have nite bisimilarity quotients when all control transitions happen at integer times, even if the constraints on the derivatives of the variables vary between control states. This is in contrast with the conventional model where control transitions may happen at any real time, and already the reachability problem is undecidable. Based on the nite bisimilarity quotients, we give an exponential algorithm for the symbolic samplingcontroller synthesis of rectangular automata. We show our algorithm to be optimal by proving the problem to be EXPTIMEhard. We also show that rectangular automata form a maximal class of systems for which the samplingcontroller synthesis problem can be solved algorithmically.