Petri net-based closed-loop control and online scheduling of the batch process plant

The paper discusses the Petri net (PN) modelling of a multiproduct batch process plant with uncertain processing time intervals. A closed loop control strategy is outlined in which the PN model functions as a reference input and is compared with the batch output time sequence of events and states. The effect of processing time interval disturbances on the batch makespan are considered and the resulting errors used in an algorithm, which utilises a critical path analysis, to initiate online time-scheduling of the batch sequence of events in order to correct plant disturbances and retain constant batch makespan. Results are presented, in the form of Gantt charts, when the theory is applied to a simple batch process plant