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778
Hybrid I/O Automata
, 1996
"... Hybrid systems are systems that exhibit a combination of discrete and continuous behavior. Typical hybrid systems include computer components, which operate in discrete program steps, and realworld components, whose behavior over time intervals evolves according to physical constraints. Important e ..."
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Cited by 170 (23 self)
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Hybrid systems are systems that exhibit a combination of discrete and continuous behavior. Typical hybrid systems include computer components, which operate in discrete program steps, and realworld components, whose behavior over time intervals evolves according to physical constraints. Important examples of hybrid systems include automated transportation systems, robotics systems, process control systems, systems of embedded devices, and mobile computing systems. Such systems can be very complex, and very dicult to describe and analyze.
Hierarchical Finite State Machines with Multiple Concurrency Models
 IEEE Transactions on Computeraided Design of Integrated Circuits and Systems
, 1999
"... This paper studies the semantics of hierarchical finite state machines (FMS's) that are composed using various concurrency models, particularly dataflow, discreteevents, and synchronous/reactive modeling. It is argued that all three combinations are useful, and that the concurrency model can b ..."
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Cited by 146 (43 self)
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This paper studies the semantics of hierarchical finite state machines (FMS's) that are composed using various concurrency models, particularly dataflow, discreteevents, and synchronous/reactive modeling. It is argued that all three combinations are useful, and that the concurrency model can be selected independently of the decision to use hierarchical FSM's. In contrast, most formalisms that combine FSM's with concurrency models, such as Statecharts (and its variants) and hybrid systems, tightly integrate the FSM semantics with the concurrency semantics. An implementation that supports three combinations is described.
Model checking large software specifications
 IEEE TRANSACTIONS ON SOFTWARE ENGINEERING
, 1998
"... In this paper, we present our experiences in using symbolic model checking to analyze a specification of a software system for aircraft collision avoidance. Symbolic model checking has been highly successful when applied to hardware systems. We are interested in whether model checking can be effect ..."
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Cited by 139 (6 self)
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In this paper, we present our experiences in using symbolic model checking to analyze a specification of a software system for aircraft collision avoidance. Symbolic model checking has been highly successful when applied to hardware systems. We are interested in whether model checking can be effectively applied to large software specifications. To investigate this, we translated a portion of the statebased system requirements specification of Traffic Alert and Collision Avoidance System II (TCAS II) into input to a symbolic model checker (SMV). We successfully used the symbolic model checker to analyze a number of properties of the system. We report on our experiences, describing our approach to translating the specification to the SMV language, explaining our methods for achieving acceptable performance, and giving a summary of the properties analyzed. Based on our experiences, we discuss the possibility of using model checking to aid specification development by iteratively applying the technique early in the development cycle. We consider the paper to be a data point for optimism about the potential for more widespread application of model checking to software systems.
Algorithmic analysis of nonlinear hybrid systems
 in Proc. CAV 95: Computeraided Verification, Lecture Notes in Computer Science
, 1995
"... Abstract—Hybrid systems are digital realtime systems that are embedded in analog environments. Modelchecking tools are available for the automatic analysis of linear hybrid automata, whose environment variables are subject to piecewiseconstant polyhedral differential inclusions. In most embedded ..."
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Cited by 138 (13 self)
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Abstract—Hybrid systems are digital realtime systems that are embedded in analog environments. Modelchecking tools are available for the automatic analysis of linear hybrid automata, whose environment variables are subject to piecewiseconstant polyhedral differential inclusions. In most embedded systems, however, the environment variables have differential inclusions that vary with the values of the variables, e.g., _x = x. Such inclusions are prohibited in the linear hybrid automaton model. We present two methods for translating nonlinear hybrid systems into linear hybrid automata. Properties of the nonlinear systems can then be inferred from the automatic analysis of the translated linear hybrid automata. The first method, called clock translation, replaces constraints on nonlinear variables by constraints on clock variables. The clock translation is efficient but has limited applicability. The second method, called linear phaseportrait approximation, conservatively overapproximates the phase portrait of a hybrid automaton using piecewiseconstant polyhedral differential inclusions. Both methods are sound for safety properties; that is, if we establish a safety property of the translated linear system, we may conclude that the original nonlinear system satisfies the property. When applicable, the clock translation is also complete for safety properties; that is, the original system and the translated system satisfy the same safety properties. The phaseportrait approximation method is not complete for safety properties, but it is asymptotically complete; intuitively, for every safety property, and for every relaxed nonlinear system arbitrarily close to the original, if the relaxed system satisfies the safety property, then there is a linear phaseportrait approximation that also satisfies the property. We illustrate both methods by using HYTECH—a symbolic model checker for linear hybrid automata—to automatically check properties of a nonlinear temperature controller and of a predator–prey ecology. Index Terms — Clock translation, formal verification, hybrid systems, HYTECH, linear hybrid automata, model checking, phaseportrait approximation, predator–prey ecologies.
Robust Hybrid Control for Autonomous Vehicle Motion Planning
, 2000
"... The operation of an autonomous vehicle in an unknown, dynamic environment is a very complex problem, especially when the vehicle is required to use its full maneuvering capabilities, and to react in real time to changes in the operational environment. A possible approach to reduce the computationa ..."
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Cited by 129 (10 self)
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The operation of an autonomous vehicle in an unknown, dynamic environment is a very complex problem, especially when the vehicle is required to use its full maneuvering capabilities, and to react in real time to changes in the operational environment. A possible approach to reduce the computational complexity of the motion planning problem for a nonlinear, high dimensional system, is based on a quantization of the system dynamics, leading to a control architecture based on a hybrid automaton, the states of which represent feasible trajectory primitives for the vehicle. This paper focuses on the feasibility of this approach: the structure of a Robust Hybrid Automaton is defined and its properties are analyzed. Algorithms are presented for timeoptimal motion planning in a free workspace, and in the presence of fixed or moving obstacles. A case study involving a small autonomous helicopter is presented: a nonlinear control law for maneuver execution is provided, and a robust hyb...
HYTECH: The next generation
 In Proceedings of the 16th IEEE RealTime Systems Symposium
, 1995
"... Abstract. We describe a new implementation of HyTech 1,asymbolic model checker for hybrid systems. Given a parametric description of an embedded system as a collection of communicating automata, HyTech automatically computes the conditions on the parameters under which the system satis es its safety ..."
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Cited by 119 (9 self)
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Abstract. We describe a new implementation of HyTech 1,asymbolic model checker for hybrid systems. Given a parametric description of an embedded system as a collection of communicating automata, HyTech automatically computes the conditions on the parameters under which the system satis es its safety and timing requirements. While the original HyTech prototype was based on the symbolic algebra tool Mathematica, the new implementation is written in C ++ and builds on geometric algorithms instead of formula manipulation. The new HyTech o ers a cleaner and more expressive input language, greater portability, superior performance (typically two to three orders of magnitude), and new features such as diagnostic errortrace generation. We illustrate the e ectiveness of the new implementation by applying HyTech to the automatic parametric analysis of the generic railroad crossing benchmark problem [HJL93] and to an active structure control algorithm [ECB94]. 1
OMinimal Hybrid Systems
, 2000
"... An important approach to decidability questions for verification algorithms of hybrid systems has been the construction of a bisimulation. Bisimulations are finite state quotients whose reachability properties are equivalent to those of the original infinite state hybrid system. In this paper we ..."
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Cited by 119 (10 self)
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An important approach to decidability questions for verification algorithms of hybrid systems has been the construction of a bisimulation. Bisimulations are finite state quotients whose reachability properties are equivalent to those of the original infinite state hybrid system. In this paper we introduce the notion of ominimal hybrid systems, which are initialized hybrid systems whose relevant sets and flows are definable in an ominimal theory. We prove that ominimal hybrid systems always admit finite bisimulations. We then present specific examples of hybrid systems with complex continuous dynamics for which finite bisimulations exist.
Modeling Heterogeneous RealTime Components in BIP
 In 4 th IEEE International Conference on Software Engineering and Formal Methods (SEFM06
, 2006
"... We present a methodology for modeling heterogeneous realtime components. Components are obtained as the superposition of three layers: Behavior, specified as a set of transitions; Interactions between transitions of the behavior; Priorities, used to choose amongst possible interactions. A parameter ..."
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Cited by 111 (34 self)
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We present a methodology for modeling heterogeneous realtime components. Components are obtained as the superposition of three layers: Behavior, specified as a set of transitions; Interactions between transitions of the behavior; Priorities, used to choose amongst possible interactions. A parameterized binary composition operator is used to compose components layer by layer. We present the BIP language for the description and composition of layered components as well as associated tools for executing and analyzing components on a dedicated platform. The language provides a powerful mechanism for structuring interactions involving rendezvous and broadcast. We show that synchronous and timed systems are particular classes of components. Finally, we provide examples and compare the BIP framework to existing ones for heterogeneous componentbased modeling. 1.
A New Class of Decidable Hybrid Systems
 In Hybrid Systems : Computation and Control
, 1999
"... One of the most important analysis problems of hybrid systems is the reachability problem. State of the art computational tools perform reachability computation for timed automata, multirate automata, and rectangular automata. In this paper, we extend the decidability frontier for classes of lin ..."
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Cited by 109 (8 self)
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One of the most important analysis problems of hybrid systems is the reachability problem. State of the art computational tools perform reachability computation for timed automata, multirate automata, and rectangular automata. In this paper, we extend the decidability frontier for classes of linear hybrid systems, which are introduced as hybrid systems with linear vector fields in each discrete location. This result is achieved by showing that any such hybrid system admits a finite bisimulation, and by providing an algorithm that computes it using decision methods from mathematical logic.
Hybrid Modeling and Simulation of Biomolecular Networks
 Hybrid Systems: Computation and Control, LNCS 2034
, 2001
"... In a biological cell, cellular functions and the genetic regulatory apparatus are implemented and controlled by a network of chemical reactions in which regulatory proteins can control genes that produce other regulators, which in turn control other genes. Further, the feedback pathways appear t ..."
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Cited by 100 (7 self)
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In a biological cell, cellular functions and the genetic regulatory apparatus are implemented and controlled by a network of chemical reactions in which regulatory proteins can control genes that produce other regulators, which in turn control other genes. Further, the feedback pathways appear to incorporate switches that result in changes in the dynamic behavior of the cell. This paper describes a hybrid systems approach to modeling the intracellular network using continuous di#erential equations to model the feedback mechanisms and modeswitching to describe the changes in the underlying dynamics. We use two case studies to illustrate a modular approach to modeling such networks and describe the architectural and behavioral hierarchy in the underlying models. We describe these models using Charon [2], a language that allows formal description of hybrid systems. We provide preliminary simulation results that demonstrate how our approach can help biologists in their analysis of noisy genetic circuits. Finally we describe our agenda for future work that includes the development of models and simulation for stochastic hybrid systems.