Ejercicio de programación con GRAFCET de un PLC

Ejercicios de la práctica 2. Programación con GRAFCET de un PLC.

Del diseño a la programación de sistemas de control para la automatización de procesos industriales basados en PLC`s

Actualmente las mayoría de sistemas de automatización industrial utilizan los Autómatas Programables (PLC - Programmable Logic Controller) como sistemas de control y el diseño de dicho sistema se realiza mediante el lenguaje de modelado Grafcet. SFCEdit es un editor de Grafcet que permite el diseño de estos sistemas de control y la exportación de los mismos en un formato XML. Resumen Por otra parte tenemos la norma IEC 61131-3 que busca estandarizar los lenguajes de programación de los PLC de esta manera no se tendría que usar un lenguaje distinto por cada fabricante, y la organización PLCOpen rigiéndose por la norma ha creado un formato XML para cada lenguaje, en los cuales se basa el traductor. Resumen Habitualmente el paso del diseño a la programación se realiza de forma manual. La automatización de este proceso es el objetivo general del proyecto realizado. En esté se ha desarrollado una herramienta que permite realizar la traducción del diseño gráfico al estándar IEC 61131-3 considerando las particularidades de algunos fabricantes de PLCs como Beckhoff (TwinCAT) y TSX Micro (PL7Pro). Además la herramienta realiza la traducción al formato XML de PLCOpen. Resumen El traductor funciona recibiendo un fichero XML (exportado de SFCEdit) procesa su información y genera los ficheros en función de la compatibilidad que el usuario seleccione.

Development of real-time process control systems using formal techniques

A major application of computers has been to control physical processes in which the computer is embedded within some large physical process and is required to control concurrent physical processes. The main difficulty with these systems is their event-driven characteristics, which complicate their modelling and analysis. Although a number of researchers in the process system community have approached the problems of modelling and analysis of such systems, there is still a lack of standardised software development formalisms for the system (controller) development, particular at early stage of the system design cycle. This research forms part of a larger research programme which is concerned with the development of real-time process-control systems in which software is used to control concurrent physical processes. The general objective of the research in this thesis is to investigate the use of formal techniques in the analysis of such systems at their early stages of development, with a particular bias towards an application to high speed machinery. Specifically, the research aims to generate a standardised software development formalism for real-time process-control systems, particularly for software controller synthesis. In this research, a graphical modelling formalism called Sequential Function Chart (SFC), a variant of Grafcet, is examined. SFC, which is defined in the international standard IEC1131 as a graphical description language, has been used widely in industry and has achieved an acceptable level of maturity and acceptance. A comparative study between SFC and Petri nets is presented in this thesis. To overcome identified inaccuracies in the SFC, a formal definition of the firing rules for SFC is given. To provide a framework in which SFC models can be analysed formally, an extended time-related Petri net model for SFC is proposed and the transformation method is defined. The SFC notation lacks a systematic way of synthesising system models from the real world systems. Thus a standardised approach to the development of real-time process control systems is required such that the system (software) functional requirements can be identified, captured, analysed. A rule-based approach and a method called system behaviour driven method (SBDM) are proposed as a development formalism for real-time process-control systems.