Process hybrid controller based on Petri nets

Given a hierarchical architecture of process control hybrid system, this paper describes a method for constructing a Petri net hybrid controller in its process layer. The process hybrid controller uses PID algorithm for steady state regulation and hybrid switching strategy for large changes. Based on Petri net place invariants the hybrid switching controller (HSC) is implemented by adding control places and arcs in its Petri net structure. Stable switching strategy of HSC can be determined using a Lyapunov approach, which introduces the notion of dynamical invariants. Finally, a class of extended Petri nets called signal interpreted Petri nets is used to synthesize the controller. As an example, we give a practical chemical process to illustrate the detail design procedures.