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1

Modelling and control of flexible manufacturing systems by means of interpreted Petri nets

Čapkovič František

Journal of Automation Mobile Robotics and Intelligent Systems

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2018

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Vol. 12, No. 4

3--10

EN

Because flexible manufacturing systems (FMS) are discrete event systems (DES), their modelling and control by means of Petri nets (PN) is widely used. While PN transitions are observable and controllable and PN places are measurable, place/transition PN (P/T PN) are suffcient for this aim. However, when some PN transitions are unobservable and/or uncontrollable and some places are non-measurable/unobservable, P/T PN are insufficient for modelling and especially for control. In such a case interpreted Petri nets (IPN) seem to be an appropriate replacement for P/T PN. In this paper a possibility of usage of IPN for FMS modelling and control is pointed out. Illustrative examples as well as the case study on a robotized assembly cell are introduced. By means of using timed PN (TPN) also the performance evaluation of the IPN model of controlled plant is accomplished whereby the simulation in Matlab.

2

Zastosowanie max-plus algebry w modelowaniu i analizie efektywności systemów produkcyjnych

Stańczyk J.

Zarządzanie Przedsiębiorstwem

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2017

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Vol. 20, nr 3

46--53

EN

In response to increased competition, manufacturing systems are becoming more complex in order to provide the flexibility and responsiveness required by the market. The increased complexity requires decision support tools that can provide insight into the effect of system changes on performance in an efficient and timely manner. This contribution discusses the usefulness of (max, +) algebra as a mathematical framework for a class of production systems. The class can be described as a dynamic and asynchronous where the state transitions are initiated by events that occur at discrete instants of time. An event corresponds to the start or the end of an activity. A common property of such examples is that the start of an activity depends on termination of several other activities. Such systems are known as discrete event systems (DES). In the paper an overview of the modeling and analysis concepts of the (max, +) algebra approach for DES is given. Also, an application examples from manufacturing systems are provided to illustrate the potential of this approach. Considered systems have been represented as (max, +) algebraic state space models. How to model different basic manufacturing systems depends on production type, like serial line, assembly line, etc. as well as impact of capacity of interoperable buffers have been presented. Based on an analytical model, effectiveness evaluation or performance indexes have been calculated for different configurations of the same production system. So, finally the best solution, for given criteria, has been obtained. All exemplary calculations have been made using the Max-Plus Algebra Toolbox for Matlab, the software package developed by author and available on his homepage.

3

Synthesis of controller for railway – level crossing devices using Petri nets and state machine

Mielnik R.

Czasopismo Techniczne. Elektrotechnika

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2016

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Y. 113, iss. 1-E

101--112

EN

The design of modern digital measurement-control systems applied in such fields as nuclear and power, chemical, air and rail transport as well as military requires a special approach to the philosophy of design, manufacture and the use of such systems. Therefore, attention should be focused on safeguarding the required level of reliability and safety of working conditions of such systems. On an example of a controller for an automatic railway crossing devices is presented synthesis of this controller. In this fact were used Petri nets – to modeling this controller and state machine – to make programming application.

PL

Projektowanie cyfrowych systemów pomiarowo-sterujących stosowanych w takich obszarach jak: energetyka jądrowa, przemysł chemiczny, transport powietrzny i kolejowy oraz zastosowania militarne wymaga specjalnego podejścia do filozofii projektowania, produkcji i eksploatacji tego typu. Systemy te wymagają zapewnienia odpowiedniego poziomu niezawodności i bezpieczeństwa. Na przykładzie sterownika samoczynnej sygnalizacji przejazdowej przedstawiono jego syntezę z wykorzystaniem sieci Petriego – do modelowania funkcji kontrolera, oraz maszyny stanów – do wykonania oprogramowania.