Modeling, safety verification and optimization of operating procedures in process systems using hybrid Petri nets

In this paper, a hybrid Petri net-based hierarchical control and modeling framework for real-time process procedural control is introduced. The new modeling tool, called as hybrid predicate Petri net, is an extension of hybrid Petri net and Predicate/Transition net, in which the firing speeds of its continuous transitions are changeable and controlled by upper level and continuous mathematical model. Predicates are introduced to discrete transitions to represent the various constraints possibly existing in process systems. Definition of net structure and running rules of the hybrid predicate Petri net are provided. On the basis of supervisory model, the issues of safety verification, optimization of control parameters and scheduling of operating sequences are discussed. At last, a distillation column is used as an example for modeling and analysis.