Design and analysis of sequential function charts using sensor-based stage Petri Nets

Sequential function chart (SFC) is currently one of the design diagrams for automated control systems to capture the sequence of operations executed by the system´s control software. This method grows so complex that locating the cause when a problem is detected becomes extremely difficult. Researchers are constantly pursuing to develop tools that eliminate the limitations and increase the design performance using SFCs. Petri nets are among the most widely used tools to model and evaluate the behaviour of automated control systems. Petri net control of real-worlds systems is achieved by mapping sensor signals and actuator commands to Petri net transitions. Being a well-defined and well-developed tool based on a mathematical formulation, PN models are used to analyze and implement real-time control for discrete industrial systems. This paper discusses a methodology to convert the SFC of an automated control system for design and analysis using the sensor-based stage Petri nets (SBSPN). Appropriate rules are suggested to convert all the I/O sensors of SFC into stages Petri net picture. A pneumatic control system is illustrated as an example to demonstrate the practical use of this technique.