A Representation of Sequential Control Systems by T-SFC

Material Handing System (MHS) is regarded as important as a mother machine in Factory Automation (FA) or Computer Integrated Manufacturing (CIM). Accurate description of specifications and control actions is one of basic techniques to construct a MHS. Sequential Function Chart (SFC) is such a kind of graphic representation included in IEC standard for sequential control systems. SFC surpasses Ladder Diagram which has been widely used until now,because of its simplicity of graphic representations and the clarity of relations of sequences.However,it is hard to represent extraordinary or emergency processes, and interlocks, which frequently occur in MHS. In this paper, we propose a new method called Total-SFC (T-SFC) which consists of three parts, i.e., SFC describing sequential processes, Random Function Chart(RFC)describing extraordinary or emergency processing,and Interlock Tables describing interlocks.