Abstract
This paper describes the application methodology of SFC (Sequential Function Chart) to machines' controls in the tire industry.
With the marvelous progress of micro processing and computer technology, PCs (Programmable Controllers) have become popular and indispensable equipment for machines' sequential control in FA (Factory Automation) area. The complexity and flexibility of machine control relies advancements in PC programming technology. But most of their programs are written by old fashioned Ladder Diagram, which was originally developed as an analogy of wiring circuits. The increasing volumes of programming have revealed major inherent deficiencies in Ladder Diagram. These deficiencies are manifested in programs that are so voluminous and complex that they are practically unmanageable. To overcome these problems, the SFC has been applied as a substitute of Ladder Diagram. Originally the SFC itself has several problems in practical applications. One of the most difficulty in SFC is explanation of interlocking conditions for actuators.
In this paper, authors propose the application methodology of hybrid control by SFC and Ladder Diagram. After evaluation in more than 100 machines, and over 10 kinds of machine applications, the methodology of this hybrid control is proved to be powerful both in machine control and programming. As a result, SFC has a distinct effect on machine controllability, requires less design and maintenance manpower, reduces program and documentation size, eases checkout and start-up work, and saves training time for new personnel.
