Authors: Leduc, Ryan; Malik, Robi

Abstract: Hierarchical Interface-based Supervisory Control (HISC) decomposes a discrete-event system into a high-level subsystem which communicates through interfaces with several low-level subsystems. The framework provides a set of local conditions that can be checked for each subsystem individually to conclude global conditions such as nonblocking and controllability. The size of HISC systems that can be verified automatically is primarily limited by the size of the largest subsystem. To overcome this limitation, this paper proposes the use of compositional verification. Most of the HISC conditions can be verified efficiently using existing methods for compositional verification, but a few are more challenging. This paper shows how these more challenging conditions can be expressed equivalently as generalized nonblocking problems, so the compositional approach for generalized nonblocking developed by the authors in (Malik and Leduc, 2009) is applicable. This makes all the HISC conditions amenable for compositional verification, considerably increasing the size of systems that can be handled using the framework.

Keywords: discrete event systems,large-scale systems,hierarchical control,finite state machines,verification

Identifier: 10.3182/20100830-3-DE-4013.00019

Conference: 10th International Workshop on Discrete Event Systems (2010)

Location: Technische Universität Berlin, Germany

Start Date: Mon Aug 30 2010 - End Date: Wed Sep 01 2010

Authors: Shang, Ying

Abstract: This paper surveys recent investigations on a frequency-domain approach to study max-plus linear systems, which can be used to model queueing systems, communication networks, and manufacturing systems. The challenging problem for a well-developed frequency-domain theory of such systems is the lack of inverse operations. This paper proposes a frequency-domain approach by revisiting Kalman's original realization theory for max-plus linear systems. The main advantage of Kalman's theory is that the frequency-domain method and the state-variable method merge into a single framework. Moreover, it introduces the concepts of poles and zeros as semimodules instead of point poles and zeros, which cannot be traditionally defined without inverse operations. Moreover, the pole and zero semimodules can characterize the common Petri net components in the solutions to the model matching problem.

Keywords: frequency domains,state-space realization,discrete-event systems,and model matching problem

Identifier: 10.3182/20100830-3-DE-4013.00065

Conference: 10th International Workshop on Discrete Event Systems (2010)

Location: Technische Universität Berlin, Germany

Start Date: Mon Aug 30 2010 - End Date: Wed Sep 01 2010

Authors: Lefebvre, D.; Leclercq, E.; El Akchioui, N.; De Cursis, E. Souza; Khalij, L.

Abstract: Reliability analysis is often based on stochastic discrete event models like stochastic Petri Nets. For complex dynamical systems with numerous components, analytical expressions of the steady state are tedious to work out because of the combinatory explosion with discrete models. For this reason, fluidification is an interesting alternative to estimate the asymptotic behaviour of stochastic processes with continuous Petri nets. Unfortunately, the asymptotic mean marking of stochastic and continuous Petri nets with same structure and same initial marking are mainly often different. This paper shows that this difficulty is related to the partition in regions of the reachability state space. A geometric approach is developed to characterize the regions and to get a partial homothetic approximation of the stochastic steady state.

Keywords: stochastic Petri nets,continuous Petri nets,fluidification,steady state,reliability analysis

Identifier: 10.3182/20100830-3-DE-4013.00040

Conference: 10th International Workshop on Discrete Event Systems (2010)

Location: Technische Universität Berlin, Germany

Start Date: Mon Aug 30 2010 - End Date: Wed Sep 01 2010

Authors: Cabasino, Maria Paola; Giua, Alessandro; Paoli, Andrea; Seatzu, Carla

Abstract: In this paper we deal with the problem of failure diagnosis of discrete event systems with decentralized information. The decentralized architecture that we use is composed by a set of sites communicating their diagnosis information with a coordinator that is responsible of detecting the occurrence of failures in the system. In particular, first we present a protocol that defines the communication rules between the sites and the coordinator. Secondly, we prove that this protocol does not produce false alarms. Moreover, we give sufficient conditions for diagnosability based on the notion of failure ambiguous strings. Finally, we compare the protocol here presented with two other protocols that we presented in a previous work.

Keywords: decentralized fault diagnosis,discrete event systems,Petri nets

Identifier: 10.3182/20100830-3-DE-4013.00022

Conference: 10th International Workshop on Discrete Event Systems (2010)

Location: Technische Universität Berlin, Germany

Start Date: Mon Aug 30 2010 - End Date: Wed Sep 01 2010

Authors: Jia, Qing-Shan

Abstract: Event-based decision process (EDP) has provided a general framework for many event-based control, decision making, and optimization problems. Since the number of events could increase only linearly w.r.t. the system scale, EDP provides a computationally feasible way for many problems, which are time-consuming to solve in the Markov decision process (MDP) framework. Because the event sequence usually is not Markovian, policies that only depend on the current observable event usually are not optimal. In this paper, we develop a rollout method for finite-stage EDP, which uses simulation under a base policy to estimate the performances of action candidates. We show that this leads to a policy better than the base policy. This rollout method is easy to implement. The advantage is also demonstrated through a node activation policy optimization problem in wireless sensor network.

Keywords: discrete event dynamic systems,event-based decision process,rollout

Identifier: 10.3182/20100830-3-DE-4013.00042

Conference: 10th International Workshop on Discrete Event Systems (2010)

Location: Technische Universität Berlin, Germany

Start Date: Mon Aug 30 2010 - End Date: Wed Sep 01 2010

Authors: Cano, Elia E.; Rovetto, Carlos A.; Colom, José-Manuel

Abstract: Minimal siphons in the class of S4PR nets have become a conceptual and practical central tool. Therefore the availability of efficient algorithms to compute the minimal siphons is very important. In this paper we try to take advantage from the particular properties of the siphons in S4PR to obtain an efficient algorithm. These properties allow to express minimal siphons as the union of pruned minimal siphons containing only one resource. The pruning operation is defined as a relation and represented in a graph. The computation of the minimal siphons is based in the maximal strongly connected components of this graph. The algorithm is very economic in memory in all intermediate steps with respect to the classical algorithms.

Keywords: Petri-nets,structural analysis,siphons,graph theory,strongly connected component

Identifier: 10.3182/20100830-3-DE-4013.00005

Conference: 10th International Workshop on Discrete Event Systems (2010)

Location: Technische Universität Berlin, Germany

Start Date: Mon Aug 30 2010 - End Date: Wed Sep 01 2010

Authors: Farahani, Samira S.; Van Den Boom, Ton; Van Der Weide, Hans; De Schutter, Bart

Abstract: Model Predictive Control (MPC) is a model-based control method based on a receding horizon approach and online optimization. In previous work we have extended MPC to a class of discrete-event systems, namely the max-plus linear systems, i.e., models that are "linear" in the max-plus algebra. Lately, the application of MPC for stochastic max-plus-linear systems has attracted a lot of attention. At each event step, an optimization problem then has to be solved that is, in general, a highly complex and computationally hard problem. Therefore, the focus of this paper is on decreasing the computational complexity of the optimization problem. To this end, we use an approximation approach that is based on the p-th raw moments of a random variable. This method results in a much lower computational complexity and computation time while still guaranteeing a good performance.

Keywords: stochastic discrete event systems,stochastic max-plus linear systems,model predictive control,approximation,raw moments

Identifier: 10.3182/20100830-3-DE-4013.00062

Conference: 10th International Workshop on Discrete Event Systems (2010)

Location: Technische Universität Berlin, Germany

Start Date: Mon Aug 30 2010 - End Date: Wed Sep 01 2010

Authors: Jarvis, Donald E.

Abstract: Compared to time-driven systems, few tools are available for identification of timed event-driven systems. Here we address the identification problem for those systems that require not only proper ordering, but also correct timing, of input and output events for their complete description. First we review well-known results from computational learning theory, noting their roots in classical systems theory and interpreting their relevance to the identification problem. Next, as a prerequisite to identification, we introduce a simple formalism for timed deterministic event-based system behavior that is also well-adapted to identification. Then we present the main result of the paper, an algorithm that under appropriate conditions computes an automaton whose behavior reliably imitates a given timed event system. Simulation results illustrate best-case and worst-case identification conditions.

Keywords: identification,discrete-event systems,simulation,automata,realisation theory

Identifier: 10.3182/20100830-3-DE-4013.00031

Conference: 10th International Workshop on Discrete Event Systems (2010)

Location: Technische Universität Berlin, Germany

Start Date: Mon Aug 30 2010 - End Date: Wed Sep 01 2010

Authors: Ye, Lina; Dague, Philippe

Abstract: Diagnosability is a crucial system property that determines at design stage how accurate any diagnosis algorithm can be on a partially observable system. The existence of two indistinguishable behaviors, i.e. holding the same observations, with exactly one of them containing the fault violates the diagnosability property. A classical approach for diagnosability verification consists in constructing a finite state machine called twin plant to search for a path representing such indistinguishable behaviors, called a critical path. To avoid the unrealistic hypothesis about the monolithic model of a complex system, recent work constructs local twin plants and then incrementally synchronizes some of them until diagnosability is decided without computing the impractical global twin plant. In this paper, we optimize the distributed approach by abstracting necessary and sufficient diagnosability information from local twin plants to check the existence of critical paths. Thus diagnosability can be analyzed with as small search space as possible. Furthermore, our approach describes how to improve the diagnosis algorithm by using our diagnosability results in a formal way when the system is verified to be diagnosable. Finally, when the system is not diagnosable, the algorithm returns some useful information about its indistinguishable behaviors, which can help in upgrading system diagnosable level.

Keywords: discrete event systems,fault diagnosis,models,algorithms,distributed systems

Identifier: 10.3182/20100830-3-DE-4013.00025

Conference: 10th International Workshop on Discrete Event Systems (2010)

Location: Technische Universität Berlin, Germany

Start Date: Mon Aug 30 2010 - End Date: Wed Sep 01 2010

Authors: Khoumsi, Ahmed

Abstract: We develop a decision-making framework for DES, which is unifying in two ways. Firstly, it unifies the architectures: we develop a decision-making system for a generic well-formed architecture; and then, we specialize the framework for centralized and decentralized architectures. Secondly, it unifies supervisory control, diagnosis and prognosis: we develop a framework for a generic well-formed decision-maker; and then, we apply the framework to the three subjects. We hope that this unifying framework will contribute to a better understanding of the decision-making mechanism, and will promote its development.

Keywords: discrete event systems,unifying decision-making,well-formed architecture,decidability,centralized architecture,decentralized inference architecture,supervisory control,diagnosis,prognosis

Identifier: 10.3182/20100830-3-DE-4013.00024

Conference: 10th International Workshop on Discrete Event Systems (2010)

Location: Technische Universität Berlin, Germany

Start Date: Mon Aug 30 2010 - End Date: Wed Sep 01 2010

Authors: Forschelen, S. T. J.; Van De Mortel-Fronczak, J. M.; Su, R.; Rooda, J. E.

Abstract: Due to increasing system complexity, time-to-market and development costs reduction, new engineering processes are required. Model-based engineering processes are suitable candidates because they support system development by enabling the use of various model-based analysis techniques and tools. As a result, they are able to cope with complexity and have the potential to reduce time-to-market and development costs. Moreover, supervisory control synthesis can be integrated in this setting, which can further contribute to the development of control systems. To evaluate the applicability of recently developed supervisor synthesis techniques and to show how they can be integrated in an engineering process, a theme park vehicle is chosen as a case study. The supervisor synthesized for the theme park vehicle has successfully been implemented and integrated in the existing resource-control platform.

Keywords: supervisory control,distributed control,control engineering,control applications,implementation

Identifier: 10.3182/20100830-3-DE-4013.00049

Conference: 10th International Workshop on Discrete Event Systems (2010)

Location: Technische Universität Berlin, Germany

Start Date: Mon Aug 30 2010 - End Date: Wed Sep 01 2010

Authors: Moor, Thomas; Schmidt, Klaus; Perk, Sebastian

Abstract: This paper presents a case study in the design and implementation of a discrete event system (DES) of real-world complexity. Our DES plant is a flexible manufacturing system (FMS) laboratory model that consists of 29 interacting components and is controlled via 107 digital signals. Regarding controller design, we apply a hierarchical and decentralised synthesis method from earlier work in order to achieve nonblocking and safe closed-loop behaviour. Regarding implementation, we discuss how digital signals translate to discrete events from a practical point of view, including timing issues. The paper demonstrates how both, design and implementation, are supported by the open-source software tool libFAUDES.

Keywords: discrete event systems,supervisory control,manufacturing system,implementation

Identifier: 10.3182/20100830-3-DE-4013.00043

Conference: 10th International Workshop on Discrete Event Systems (2010)

Location: Technische Universität Berlin, Germany

Start Date: Mon Aug 30 2010 - End Date: Wed Sep 01 2010

Authors: Merlet, G.

Abstract: In a Max-plus linear system every coordinate is known to have an asymptotic cycle time. For their stochastic counterpart, this is only true for the backward systems. We investigate the conditions under which this fact implies the existence of asymptotic cycle time for the original system and show that there are two types of obstructions. This gives a necessary and sufficient condition for i.i.d. systems and a bunch of sufficient conditions under weaker assumptions.

Keywords: max-plus,stochastic linear systems,asymptotic throughput,networks,matrices

Identifier: 10.3182/20100830-3-DE-4013.00064

Conference: 10th International Workshop on Discrete Event Systems (2010)

Location: Technische Universität Berlin, Germany

Start Date: Mon Aug 30 2010 - End Date: Wed Sep 01 2010

Authors: Whittaker, Sarah-Jane; Rudie, Karen; McLellan, James; Haar, Stefan

Abstract: An outbreak of an infectious illness can be devastating for a population. Once confirmed, local health-care organizations will attempt to reduce the spread of the disease by adopting a protocol in response. Modelling health-care protocols requires the inclusion of both timing and probability constraints. Choice-point nets, a form of augmented Petri nets, are ideal for the task. In this data structure, time is associated with event-based transitions that may result in several possible outcomes, each of which is given a probability of occurrence. These nets may be analyzed by unravelling them into finite-state automata. By translating questions about the protocol into the mathematical language of the net, recursive algorithms may then be employed to provide health-care professionals with answers.

Keywords: Petri-nets,events,system analysis

Identifier: 10.3182/20100830-3-DE-4013.00055

Conference: 10th International Workshop on Discrete Event Systems (2010)

Location: Technische Universität Berlin, Germany

Start Date: Mon Aug 30 2010 - End Date: Wed Sep 01 2010

Authors: Zhang, Y.; Bérard, B.; Kordon, F.; Thierry-Mieg, Y.

Abstract: Computation of a maximally permissive controller in the Ramadge-Wonham framework promises a general solution to automatically design a controller for a discrete event system, when it exists. However, like for all similar model-checking approaches, the combinatorial explosion of the state space remains a practical issue. The work presented here investigates how to exploit both hierarchical modeling and a symbolic model-checking engine to tackle this problem. This engine is based on a powerful class of Decision Diagrams called Hierarchical Set Decision Diagrams combined with a framework called Instantiable Transition Systems, in order to describe hierarchical models. To implement the controller activity, we propose to store the set of safe states, computed offline, as a decision diagram in the controller software, allowing to take decisions on-line. We run a prototype tool on several benchmark examples, including a problem of automated guided vehicles and a train crossing version with explicit discrete time. Results suggest good scalability, although the procedure is computationally intensive.

Keywords: controller synthesis,discrete event system,hierarchical set decision diagrams

Identifier: 10.3182/20100830-3-DE-4013.00047

Conference: 10th International Workshop on Discrete Event Systems (2010)

Location: Technische Universität Berlin, Germany

Start Date: Mon Aug 30 2010 - End Date: Wed Sep 01 2010

Authors: Bouillard, Anne; Jouhet, Laurent; Thierry, Éric

Abstract: In envelope-based models for worst-case performance evaluation like Network Calculus or Real-Time Calculus, several types of service curves have been introduced to quantify some deterministic service guarantees. This paper studies the expressiveness of those different definitions of service curves. We revisit the hierarchy ranging from the most restrictive definition linked to variable capacity nodes to the most general definition of simple service curves. We state the conditions when the different definitions overlap and discuss the existence of canonical descriptions for systems specified through those definitions.

Keywords: network calculus,(min,+)-algebra,service curves

Identifier: 10.3182/20100830-3-DE-4013.00051

Conference: 10th International Workshop on Discrete Event Systems (2010)

Location: Technische Universität Berlin, Germany

Start Date: Mon Aug 30 2010 - End Date: Wed Sep 01 2010

Authors: Ware, Simon; Malik, Robi

Abstract: This paper proposes to enhance compositional verification of the nonblocking property of discrete event systems by introducing annotated automata. Annotations store nondeterministic branching information, which would otherwise be stored in extra states and transitions. This more succinct representation makes it easier to simplify automata and enables new efficient means of abstraction, further reducing the size of automata to be composed and thus the size of the synchronous product state space encountered in verification. The abstractions proposed are of polynomial complexity, and they have been successfully applied for nonblocking verification of the same set of large-scale industrial examples as used in related work.

Keywords: discrete event systems,finite state machines,verification,deadlock

Identifier: 10.3182/20100830-3-DE-4013.00060

Conference: 10th International Workshop on Discrete Event Systems (2010)

Location: Technische Universität Berlin, Germany

Start Date: Mon Aug 30 2010 - End Date: Wed Sep 01 2010

Authors: Schmidt, Klaus

Abstract: The verification of language-diagnosability (LD) for discrete event systems (DES) generally requires the explicit evaluation of the overall system model which is infeasible for practical systems. In order to circumvent this problem, our previous work proposes the abstraction-based LD verification using natural projections that fulfill the loop-preserving observer (LPO) property. In this paper, we develop algorithms for the verification and computation of such natural projections. We first present a polynomial-time algorithm that allows to test if a given natural projection is a loop-preserving observer. Then, we show that, in case the LPO property is violated, finding a minimal extension of the projection alphabet such that the LPO condition holds is NP-hard. Finally, we adapt a polynomial-time heuristic algorithm by Feng and Wonham for the efficient computation of loop-preserving observers.

Keywords: discrete event systems,failure diagnosis,language-diagnosability,abstraction

Identifier: 10.3182/20100830-3-DE-4013.00034

Conference: 10th International Workshop on Discrete Event Systems (2010)

Location: Technische Universität Berlin, Germany

Start Date: Mon Aug 30 2010 - End Date: Wed Sep 01 2010

Authors: Brunsch, T.; Hardouin, L.; Raisch, J.

Abstract: In previous work we have shown how (max; +)-algebra can be used to model cyclically operated high-throughput screening systems. In this paper the system is modeled in a two-dimensional dioid Minax [γ δ]. A controller is determined using residuation theory. The resulting control guarantees just-in-time operation of the plant. A small example is used to demonstrate the approach to model and control HTS systems. To apply the determined controller, it is rewritten in terms of counter-functions. A simulation of the system with and without controller is given and results are discussed.

Keywords: cyclic discrete-event systems,dioid algebra,residuation theory,high-throughput screening,scheduling

Identifier: 10.3182/20100830-3-DE-4013.00029

Conference: 10th International Workshop on Discrete Event Systems (2010)

Location: Technische Universität Berlin, Germany

Start Date: Mon Aug 30 2010 - End Date: Wed Sep 01 2010

Authors: Le Corronc, Euriell; Cottenceau, Bertrand; Hardouin, Laurent

Abstract: This paper deals with the control of uncertain (max,+)-linear systems, more precisely those of which parameters are not exactly known but assumed to belong to an interval. In this context, we aim at synthesizing a controller in order to reduce the uncertainty at the output of the controlled system. This study is possible thanks to the residuation theory and relies on solutions of fixed-point equations.

Keywords: discrete event dynamic systems,(max,+)-algebra,interval of systems,residuation theory,fixed-point equation theory,optimal control

Identifier: 10.3182/20100830-3-DE-4013.00066

Conference: 10th International Workshop on Discrete Event Systems (2010)

Location: Technische Universität Berlin, Germany

Start Date: Mon Aug 30 2010 - End Date: Wed Sep 01 2010

Authors: Markovski, J.; Jacobs, K. G. M.; Van Beek, D. A.; Somers, L. J. A. M.; Rooda, J. E.

Abstract: Control and coordination is an important aspect of the development of complex machines due to an ever increasing demand for better functionality, quality, and performance. We develop a coordinator for maintenance procedures for a high-tech Océ printer that eliminates undesired behavior which stems from unrestricted interaction of its distributed components. To this end, we extend and employ a model-based engineering framework for supervisory controller synthesis. We generalize standard state-based control requirements to increase modeling convenience. We model the use case with 23 generalized state-based requirements, which translate to 500+ requirements in the original form.

Keywords: supervisory control,model-based engineering,coordination,printers

Identifier: 10.3182/20100830-3-DE-4013.00048

Conference: 10th International Workshop on Discrete Event Systems (2010)

Location: Technische Universität Berlin, Germany

Start Date: Mon Aug 30 2010 - End Date: Wed Sep 01 2010

Authors: Basile, F.; Chiacchio, P.; De Tommasi, G.

Abstract: The problem of diagnosability of a fault after the firing of a finite number of observable events (i.e., K-diagnosability) is tackled in this paper. This problem corresponds to diagnosability of a fault within a finite delay in the context of discrete event systems (DESs). Two results for DESs modeled as labeled Petri nets are given: the first is a sufficient condition for K - undiagnosability of fault, while the second is a necessary and sufficient condition for K-diagnosability. The proposed results exploit the mathematical representation of Petri nets and the Integer Linear Programming standard optimization tool.

Keywords: diagnosability,Petri nets,integer linear programming

Identifier: 10.3182/20100830-3-DE-4013.00014

Conference: 10th International Workshop on Discrete Event Systems (2010)

Location: Technische Universität Berlin, Germany

Start Date: Mon Aug 30 2010 - End Date: Wed Sep 01 2010

Authors: Raisch, Jorg; Moor, Thomas; Bajcinca, Naim; Geist, Stephanie; Nenchev, Vladislav

Abstract: The topic of this paper is distributed state estimation for time-invariant systems with finite input and output spaces. We assume that the system under investigation can be realised by a hybrid I/S/O-machine, where some of the discrete states may also represent failure modes. Our approach is based on previous work, e.g., Moor and Raisch (1999); Moor et al. (2002), where l-complete approximations were proposed as discrete event abstractions for hybrid dynamical systems. In particular, it has been shown that l-complete approximations can be used to provide set-valued estimates for the unknown system state. Estimates are conservative in the sense that the true state can be guaranteed to be contained in the set-valued estimate. In this contribution, we show that for a class of hybrid systems the same estimate can be obtained via a distributed, or decentralised, approach involving several less complex approximations, which are run in parallel. For a larger class of systems, it can be shown that this approach provides an outer approximation of the estimate provided by a monolithic l-complete estimator. The proposed procedure implies significant computational savings during estimator synthesis, with an only modest increase in on-line effort. The latter is a result of "assembling" the global estimate from the available local estimates. The resulting computational trade-off is explicitly discussed.

Keywords: hybrid systems,discrete event systems,approximations,abstractions,behaviours,state estimation

Identifier: 10.3182/20100830-3-DE-4013.00023

Conference: 10th International Workshop on Discrete Event Systems (2010)

Location: Technische Universität Berlin, Germany

Start Date: Mon Aug 30 2010 - End Date: Wed Sep 01 2010

Authors: Pena, P. N.; Cury, J. E. R.; Malik, R.; Lafortune, S.

Abstract: This paper proposes a procedure to compute abstractions of Discrete Event System (DES) models with the observer property (OP). The procedure, named OP-Search, is based on the OP-Verifier algorithm which verifies if a given natural projection has the observer property. In case OP fails for a projection in Σr of an automaton M, OP-Search modifies M by relabelling transitions and incorporating the new events in Σr, in a way that the modified natural projection generates OP-abstractions. Although OP-Search does not guarantee minimal abstracted models, it leads in general to very reasonable solutions and is shown to be of lower time complexity compared to previous work in the literature.

Keywords: finite state machines,discrete event systems,supervisory control,abstraction,model reduction,observers,nonblocking

Identifier: 10.3182/20100830-3-DE-4013.00067

Conference: 10th International Workshop on Discrete Event Systems (2010)

Location: Technische Universität Berlin, Germany

Start Date: Mon Aug 30 2010 - End Date: Wed Sep 01 2010

Authors: Durmus, M. S.; Yíldírím, U.; Kursun, A.; Söylemez, M. T.

Abstract: Level crossings (grade crossings or railroad crossings) are one of the most crucial parts of the railway lines as two different types of transportation intersect at these points. Human failures including ignorance of warning signs, device troubles or carelessness can easily result in accidents especially at such cross-sections. In order to decrease the possibility of accidents on level crossings, several standards have been developed. In accordance with these standards, formal methods are required to be used specially in the development of interlocking systems that control safe operation of such crossings. In this study, a railway yard with a level crossing is modeled by Automation Petri Nets in order to design a fail-safe signalization system. A SCADA testbed is also developed to test several possible failure situations. The methods proposed in the design are expected to be used as part of an interlocking system in a railway station in Turkey.

Keywords: level crossing,automation Petri nets,signalization

Identifier: 10.3182/20100830-3-DE-4013.00056

Conference: 10th International Workshop on Discrete Event Systems (2010)

Location: Technische Universität Berlin, Germany

Start Date: Mon Aug 30 2010 - End Date: Wed Sep 01 2010