Control logic design with Petri nets for integrated manufacturing systems

The authors present a Petri net approach to designing supervisory control logic (SCL) for integrated manufacturing systems and its application to design of the Laserlite Workstation Control System. Explicit representation of SCL is obtained by using Petri nets. Thus concurrency, choices, and precedence relations can be graphically visualized. Mathematical analysis can be conducted for both qualitative and quantitative properties of the control systems. Inconsistency errors and deadlock situations can be detected. The temporal properties can be derived by incorporating timing information into the net representation if needed. Based on the net representation of the system, control code in C or C++ can be systematically derived. Related control system components and their description using the Manufacturing Information Systems Toolkit for Building Integrated Control Systems are useful in specifying a practical implementation. New schemes can be exploited by modifying the net structure or changing the initial condition