Generic Petri Net Model Research Articles

An effective scheduling method to single-arm cluster tools for processing multiple wafer types

<p style='text-indent:20px;'>Recently, in semiconductor manufacturing, cluster tools have to process multiple wafer types concurrently due to product customization. Different wafer types may have different processing routes, which causes deadlocks and complicates the scheduling problem of cluster tools. This work aims to develop a general method to resolve the scheduling problem of single-arm cluster tools with a general mix of wafer types. To this end, a generic Petri net model controlled by self-loops is developed to optimally avoid deadlocks. Based on the Petri net model, an earliest starting strategy is adopted to operate single-arm cluster tools once wafers enter the tools. In order to maximize the productivity, a particle swarm optimization algorithm is constructed to determine the releasing sequence of raw wafers. Numerical examples are provided to validate the effectiveness and efficiency of the proposed method.</p>

A Petri net model for the optimisation and performance evaluation of production system cum packaging

A new generic Petri net model is developed for design and performance evaluation of a production system. The model allows modelling the system configuration, determining the optimal work-in-process (WIP), lead time, throughput, and utilisation of each station. The sequencing circuit with the largest cycle time determines the bottleneck station. The throughput is bounded by the utilisation of this bottleneck station. The maximum throughput with the minimum WIP is formulated as a linear programming (LP) problem. The PN optimisation gives the minimum WIP corresponding to the maximum production rate. The proposed Petri net model can be easily extended for inclusion of kanban cards in order to incorporate a just-in-time production philosophy.

Real-Time Scheduling and Control of Cluster Tools in Semiconductor Manufacturing

Cluster tools provide a flexible, reconfigurable, and efficient environment for semiconductor manufacturing. They become difficult to operate because of residency time constraints and process time variation. This talk addresses their real-time scheduling and control issues. A generic Petri net model is developed to model them. It describes the robot activity sequence with robot waits included. Hence, to operate a cluster tool is to determine robot wait times. A two-level operational architecture is proposed and discussed. It includes an off-line periodic scheduler and real-time controller. This proposed approach allows a cluster tool to adapt to activity time variation while operate at its highest throughput at the steady-state. MengChu Zhou is a Professor of Electrical and Computer Engineering and the Director of Discrete-Event Systems Laboratory at New Jersey Institute of Technology. His research interests are in Petri nets, semiconductor manufacturing, sensor networks, system security, and life-cycle engineering product design. He has over 300 publications including 7 books, 130+ journal papers, and 17 book-chapters. He is Editor of IEEE Transactions on Automation Science and Engineering, and Managing Editor of IEEE Transactions on Systems, Man and Cybernetics: Part C, Associate Editor of IEEE Transactions on Systems, Man and Cybernetics: Part A and IEEE Transactions on Industrial Informatics, and Editor-in-Chief of International Journal of Intelligent Control and Systems. He is Fellow of IEEE.

Integration of JIT flexible manufacturing, assembly and disassembly system using Petri net approach

This paper presents a new generic Petri net (PN) model for design and performance evaluation of a flexible assembly system (FAS) and disassembly system (DAS) with dual kanban. The architectural design of the model is derived from a generic bill of materials (BOMs) in the FAS, a reverse BOM in the DAS and the process plan in the case of flexible manufacturing system (FMS). Integration of FMS, FAS and DAS by developing a new generic PN model with the pull system is introduced. Analysis and performance evaluation of the new model based on invariant analysis and linear programming are also introduced. The method will be illustrated by a small case study.

A software environment for flexible manufacturing system control software testing

The development of flexible manufacturing system (FMS) control software is a complex task in terms of both the hardware and the software. It is therefore an important task to provide testing facilities for FMS control software in the course of its development. This paper reports on the development of an FMS control software testing environment. The architecture of this testing environment is built to make the system open and intelligent. The openness is achieved to allow for the change in requirements, and the intelligence is meant to reduce manual work in software testing. A generic Petri net (GPN) model representing the behaviour of an FMS is introduced. A set of algorithms for detecting faults in the operation of an FMS control software program is proposed on the basis of the GPN model.

A generic Petri net model for flexible manufacturing systems and its use for FMS control software testing

Developing a flexible manufacturing system (FMS) controller is a complicated task both in the hardware development and software development. To test the control software prior to putting it into use is crucial for the development of a FMS controller. An intelligent testing environment for FMS controllers is under development, the aim of which is to reduce manual work in the testing. To reach this objective the automatic building of a behavioural model of the FMS is demanded. This paper proposes a generic Petri net (GPN) model and approach for the development of control software for FMSs. The principle of this approach is based on checking the control parts of FMSs with the help of temporal relationships between physical operations, and the specification of the FMS controller with GPN. The strategy of GPN modelling is then incorporated with more general problem solving strategies in artificial intelligence. A template is first defined for a GPN model, and then the model for FMS individuals is established in the form of instances of the template. The transitions of the GPN are represented with the proposed general expressions with two syntaxes, 'verb+ noun' and 'verb+ noun+ where', from which the GPN can be formulated. GPN makes it simple to express FMS controls, and procedural language can also be used for information processing. A case study for the testing of FMS controller software is provided to show effectiveness and cost saving over development with conventional methods in which only ordinary Petri net and procedural language are used.

A generic Petri net model for dynamic process planning and sequence optimization

In this paper a Petri net based approach for dynamic process planning and sequencing is presented. By following the proposed method it is possible to: (1) represent manufacturing knowledge of the type of precedence relations constraints, (2) represent dynamically the process planning procedure itself, (3) produce and simulate all possible process-planning solutions (process plans) and (4) find alternative optimized solutions by applying simple manufacturing heuristics. The proposed method is based on the construction of an original dynamic Petri net model upon which reachability analysis is performed and a reachability tree is automatically created. Depth-first search algorithms are then applied upon the reachability tree and all possible paths (process plans) can be calculated. Manufacturing heuristics may help to reduce the volume of big original reachability trees and optimum alternative solutions may be calculated by applying optimization criteria.