Modeling and scheduling methods for batch production systems based on petri nets and heuristic search

Abstract

An approach is proposed for modeling and scheduling batch production systems based on Petri nets. First, a group of jobs to be carried out by a batch production system is modeled by a transition-timed Petri net according to logical relations between operations and time requirements on operations. Second, conflict relations between operations are obtained by operation-resource diagrams that describe how operations compete for resources, and are formally expressed by linear constraints. Third, monitor places are designed to enforce linear constraints on the transition-timed Petri net, and a plant net is consequently built and made free of conflicts between operations, which can well emulate a real batch production system. Fourth, an optimal schedule problem, where the optimization performance index is to minimize a makespan, is formalized based on a plant net. Finally, a new variant of filtered beam search method is proposed to solve the problem based on an ad hoc function and a dynamical timed extended reachability graph of a plant net. A typical chemical production plant illustrates the theoretic results.