Dynamic scheduling of elevator systems over hybrid Petri net/rule modeling

A hybrid model of a multiple elevator system is proposed, consisting of a timed place Petri net (TPPN) model and a set of control rules implemented via the so-called control places in the TPPN model. The Petri net model is a highly modulized structure, whose constituent modules can be classified into four types: basic movement module, loading/unloading module, direction reversing module, and call management module. The whole complete model is a combination of the copies of the above four modules. Since the firing sequences of the TPPN equate the evolution of the modeled system, they can be regarded as a schedule. A dynamic scheduling strategy is proposed to obtain the desirable schedule. A new concept of control places is also introduced in the proposed model so as to make the modeling more precise and to reduce the reachability graph more efficiently. To show the feasibility of the proposed method, an emulator of the elevator system is constructed for demonstration.