Knowledge representation for Petri net based PLC stage program of discrete-event control design

In a programmable logic controller of a discrete-event control system, up to 60% of the coding effort is devoted to dealing with interlocking. Stage programming is a new concept by breaking a program into logical stages, making complex systems design easier. The stages can then be programmed individually without concern for how they will affect the rest of the program. To become truly competitive for artificial intelligence semantic implementation in industry, this paper introduces a knowledge representation for the Petri net-based programmable logic controller stage program. The symbolic logic uses a conceptual graph to translate the sensor-based stage Petri nets directly to the predicate calculus with While-Loop expressions. An example is used to illustrate the proposed concept and method.