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Signalization and interlocking design is one of the most crucial components that provide safe travelling and transportation on railways. In order to satisfy the requirements of CENELEC (European Committee for Electrotechnical Standardization) standards that are used for railways, there is a need of formal methods. While providing these standards, Petri Net design method also brings simplicity on programming...
Fault diagnosis and protection is the key of safe running of power net. At present, the main studies of fault diagnosis and protection of power net (FDPPN) concentrate on the establishment and simulation of idiographic model, but there is not universal model. There is distinct limit between discrete character and continuous character in FDPPN, so that the paper extended HPN model to propose Hybrid...
A cluster tool consists of several wafer processing modules and material handling robot(s). Cluster tools are being prevalently used for semiconductor manufacturing. The scheduling problem is complicated due to no intermediate buffer and diverse wafer flow patterns. We examine the scheduling problem when operations are repetitively performed in a cyclic order. We propose a way of modeling a Petri...
In this paper, we propose a simultaneous optimization method for task assignment and routing problems for multiple AGVs by decomposition of Petri Nets. In the proposed method, the Petri Net is decomposed into several subnets for task subproblems and AGV subproblems. Each subproblem is solved by Dijkstrapsilas algorithm. The solution of subproblem for each subnet is repeated until a feasible solution...
Geographic dispersion and distribution of productive activities in relatively autonomous systems are viable due to the advances in mechatronics, communication and information technologies. These productive systems are then composed of several components (sub-systems) with some degree of autonomy, and these must present a collaborative relationship to assure the overall performance of the system. Therefore,...
Fault monitoring plays an important role for safety and reliability of industrial systems. We present a novel on-line monitoring technique for automated manufacturing systems employing the first order hybrid Petri nets formalism, i.e., Petri nets making use of first order fluid approximation. The proposed fault analysis approach belongs to the class of event based methodologies, so that the state...
A method is presented for the robust control of a disassembly system that undergoes process plan variations due to heterogeneity of demands and product conditions. Two colored timed Petri net (CTPN) models is proposed and extended for the hierarchical modeling of both the system architecture and disassembly plans corresponding to the products to be processed. To address the high levels of uncertainty...
In a dual-armed cluster tool, the swap operation method that exchanges a wafer on a robot arm with another wafer at a chamber has been mostly used. It is known to minimize the tool cycle time although it restricts the robot task sequence. Recent cluster tools have new scheduling requirements such as reentrant wafer flows for atomic layer deposition processes, constraints on the wafer delay times within...
Because of residency time constraints and activity time variation of cluster tools, it is very difficult to operate them. This paper addresses their real-time control issues. A Petri net (PN) model is developed to model them. This model describes the robot activity sequence with robot waits included. Via this model, to operate a cluster tool is to determine robot wait times and a two-level operation...
In this paper we extend the Petri net based scheduling model that was previously introduced (2007). The integer programming (IP) model of the scheduling problem stated previously may yield an optimal solution that is not an implementable (feasible) schedule. In this situation other alternate optimal solutions of the IP model, if any, must be generated and checked whether they are feasible schedules...
A Petri net was used to model, analyze, and ultimately control a novel laboratory robotic system designed to automatically image protein crystallization experiments per user-specified schedules. Flexibility in system operation was necessary in order to accommodate unpredictable experimental tray entry and removal by crystallographers, as well as on-the-fly modification of imaging schedules to account...
The paper provides an overview of methods and techniques for the modelling and analysis of the dependability of complex systems, with emphasis on DES, trying to identify the new and promising research directions in the field. In particular, two lines are presented and discussed. The first line tries to trade off between modeling power and analytical tractability, by localizing and confining the stochastic...
The aim of this paper is to propose an integrated modelling environment to represent globally the networked control systems (NCS) behaviour by using the high level Petri nets (HLPN) formalism. This work considers NCS based on switched Ethernet architectures. This communication architecture is modelled with HLPN and is evaluated according to different scheduling mechanisms and traffic load. After that,...
This paper deals with hybrid observer design for state switched systems described by differential Petri nets (DPN). The structure herein proposed is composed of a discrete observer and a continuous observer that are in interaction. The discrete observer reconstructs the discrete mode, by estimating both of the discrete marking and the firing vectors. Once, the active mode is obtained, the continuous...
Process modeling and rule modeling languages are both used to document organizational policies and procedures. However, little work has been done to understand their synergies and overlap. Understanding the relationship between the two modeling types would allow organizations to maximize synergies and reduce their modeling effort. In this paper we use the well-established Bunge-Wand-Weber (BWW) representation...
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