Sequential Function Chart Research Articles

Synchronous Approach for Computer Integrated Manufacturing Engineering

The work which is presented in this paper has been achieved as part of the YUM project (Yoghurt Under Maintenance). Our purpose is to modelize a manufacturing system dedicated to yoghurt. In this paper, we focus on the methodological approach with which we propose to modelize this hybrid system (sequential and continuous):functional description in IDEF-0.sequential components in Sequential Function Charts [IEC88] (Grafcet),continuous components in a job language specially designed for bioprocessing.All these components are automatically translated in SIGNAL which is a synchronous data flow language. We present in this paper the automatic translation that has been realized from Sequential Function Charts (Grafcet) to SIGNAL and from the job language to SIGNAL. We conclude this paper with the benefits of such a synchronous approach to implement our model of the manufacturing system: safety and determinism of all generated software and also the semantic coherence of the implemented model.

Design recovery for relay ladder logic

An algorithm for converting relay ladder logic (RLL) programs for programmable logic controllers (PLCs) into sequential function chart (SFC) programs is introduced. Since an SFC (a standardization of Grafcet) better represents the sequential flow of control logic, it is considerably easier to understand and modify SFC programs. The practical motivation for this study is to provide a tool for converting existing RLL programs into SFC programs by recovering the underlying sequential control logic. A basic design recovery algorithm is presented and applied to a simple RLL program for one stage of a batch chemical process. Several fundamental issues in discrete control logic representation and analysis are identified as fertile areas for future research. >

Sequential function charts for knowledge-based, real-time applications

A toolbox for Grafcet style sequential function charts has been implemented in G2. The toolbox supports steps, transitions, alternative paths, parallel paths, macro steps and procedures. The toolbox also contains exception transitions that can be used for exception handling. The toolbox can be used for control, monitoring, diagnosis and simulation of discrete, sequential processes and as a general tool for implementing graphical procedures or state machines. The implementation of the toolbox is described and examples are given of how it is used.

Advanced configuration tools for DCS

Various software packages have been prepared to configure application functions of new distributed process control systems (DCS). These packages, including control function configuration, CRT display definition, and report and graphics construction, run on personal computer, enabling a personal engineering environment. The configuration package for a process control station provides five languages: Ladder Diagram, DataFlow, SFC (Sequential Function Chart), LPC (Loop Function Chart), and IFC (Instrumentation Flow Chart). IFC is a high-level language used for applications that combine analog control loops, sequential controls, and logic controls. Symply drawing flow charts with descriptive conditions or comments enables creation of an object program that is self-documenting and ready to run.

A sequential function chart (SFC) language for batch control

In recent years, the applications of DCS (Distributed Control Systems) have broadened to cover not only continuous processes but also batch processes, and there are increasing demands for batch control systems which are both sophisticated and easy to use (easy to operate and easy to engineer), for multi-purpose plants. The paper describes a new sequence language which covers a wide range of process control applications. It uses SFC (Sequential Function Charts) to allow unit sequences to be executed in parallel. This sequence language is useful for batch sequences because it can communicate with feedback process control functions, and its interactive user interface makes it easy for the operator to select execution sequences or modify production quantities.

Cell controllers, map communications, and sequential function chart programming: Is this the ideal batch control system?

Many vendors now claim to have hardware and software configurations designed for batch plant environments. The traditional cotnrol system vendors are offering distributed control systems for these applications. Manufacturers that have historically been involved in discrete manufacturing are basing their systems for batch processing plants on programmable controllers. Some suppliers can merge equipment of both types in their systems. Unfortunately, this issue is far from being settled. There have been some fairly recent developments in hardware (cell controllers), communications (MAP-Manufacturing Automation Protocol), and software (sequential function chart programming) that are going to have a tremendous impact on batch control systems. This paper will discuss these developments and look at how they can solve some of the current problems that users have in implementing batch control systems.