物件導向軟體之架構(Object-Oriented Software Construction)探討

A variety of important Petri net-based methods to prevent deadlocks arising in flexible manufacturing systems (FMS) are to add some control places and related arcs to strict minimal siphons (SMS) such that no siphon can be emptied. Since the number of minimal siphons grows in general exponentially with respect to a Petri net size, their disadvantages lie in that they often add too many additional places to the net, thereby making the resulting net model much more complex than the original one. This paper explores ways to minimize the new additions of places while achieving the same control purpose. It proposes for the first time the concept of elementary siphons that are a special class of siphons. The set of elementary siphons in a Petri net is generally a proper subset of the set of all SMS. Its smaller cardinality becomes evident in large Petri net models. This paper proves that by adding a control place for each elementary siphon to make sure that it is marked, deadlock can be successfully prevented. Compared with the existing methods, the new method requires a much smaller number of control places and, therefore, is suitable for large-scale Petri nets. An FMS example is used to illustrate the proposed concepts and policy, and show the significant advantage over the previous methods.

Elementary siphons of Petri nets and their application to deadlock prevention in flexible manufacturing systems

On-line and indirect tool wear monitoring in turning with artificial neural networks: a review of more than a decade of research

This paper is a survey of the presently available literature on disassembly sequencing, including the papers that are closely related to this topic. Disassembly theory is applied to complex products such as mechanical, electromechanical and electronic appliances. It is required for end-of-life processing and for maintenance and repair. Apart from these applications, disassembly is studied for supporting the analysis of assembly processes. Disassembly sequencing involves the search for all possible disassembly sequences and the selection of the optimum solution out of these. In each application, a slightly different approach can be observed, including level of detail, degrees of freedom, and the role of uncertainty. Disassembly sequencing also plays a major role in the modern design process and is an invaluable tool in concurrent engineering. Its connection with the more detailed or component level and the less detailed level or process level including logistics, is highlighted. This presentation of the state of the art is intended as a stimulus for further research in this interesting field.

Disassembly sequencing : a survey

This text sets out a series of approaches to the analysis and synthesis of the World Wide Web, and other web-like information structures. A comprehensive set of research questions is outlined, together with a sub-disciplinary breakdown, emphasising the multi-faceted nature of the Web, and the multi-disciplinary nature of its study and development. These questions and approaches together set out an agenda for Web Science, the science of decentralised information systems. Web Science is required both as a way to understand the Web, and as a way to focus its development on key communicational and representational requirements. The text surveys central engineering issues, such as the development of the Semantic Web, Web services and P2P. Analytic approaches to discover the Web's topology, or its graph-like structures, are examined. Finally, the Web as a technology is essentially socially embedded; therefore various issues and requirements for Web use and governance are also reviewed.

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A Framework for Web Science

Flexible manufacturing systems - an overview Petri nets as an integrated tool and methodology in FMS design fundamentals of Petri nets modelling FMS with Petri nets FMS performance analysis Petri net simulation and tools performance evaluation of pull and push paradigms in flexible automation augmented-timed Petri nets for modelling breakdown handling real-time Petri nets for discrete event control comparison of real-time Petri nets and ladder logic diagrams an object-oriented design methodology for development of FMS control software scheduling using Petri nets Petri nets and future research.

Modeling, Simulation, and Control of Flexible Manufacturing Systems: A Petri Net Approach

Design methods for sequence controllers play a very important role in advancing industrial automation. The increasing complexity and varying needs of modern discrete manufacturing systems have challenged the traditional design methods such as the use of ladder logic diagrams (LLDs) for programmable logic controllers. The methodologies based on research results in computer science have recently received growing attention by academic researchers and industrial engineers in order to design flexible, reusable, and maintainable control software. Particularly, Petri nets are emerging as a very important tool to provide an integrated solution for modeling, analysis, simulation, and control of industrial automated systems. This paper identifies certain criteria to compare LLDs and Petri nets in designing sequence controllers and responding to the changing control requirements. The comparison is performed through a practical system after introducing "real-time Petri nets" for discrete-event control purposes. The results reported in this paper will help: (a) further establish Petri net based techniques for discrete-event control of industrial automated systems; and (b) effectively convince industrial practitioners and researchers that it is worthy and timely to consider and promote the applications of Petri nets to their particular discrete-event control problems. >

Comparing ladder logic diagrams and Petri nets for sequence controller design through a discrete manufacturing system

An on-line scheme for tool wear monitoring using artificial neural networks (ANNs) has been proposed. Cutting velocity, feed, cutting force and machining time are given as inputs to the ANN, and the flank wear is estimated using the ANN. Different ANN structures are designed and investigated to estimate the tool wear accurately. An existing analytical model is used to obtain the data for various cutting conditions in order to eliminate the huge cost and time associated with generation of training and evaluation data. Motivated by the fact that the tool wear at a given instance of time depends on the tool wear value at a previous instance of time, memory is included in the ANN. ANNs without memory, with one-phase memory, and with two-phase memory are investigated in this study. The effect of various training parameters, such as learning coefficient, momentum, temperature, and number of hidden neurons, on these architectures is studied. The findings and experience obtained should facilitate the design and implementation of reliable and economical real-time systems for tool wear monitoring and identification in intelligent manufacturing.

Kurapati Venkatesh

Papers

Modeling, Simulation, and Control of Flexible Manufacturing Systems: A Petri Net Approach

Comparing ladder logic diagrams and Petri nets for sequence controller design through a discrete manufacturing system

Design of artificial neural networks for tool wear monitoring

Object-oriented design of FMS control software based on object modeling technique diagrams and Petri nets

Augmented timed petri nets for modeling, simulation, and analysis of robotic systems with breakdowns