On rescheduling in holonic manufacturing systems

Abstract

This paper treats a topical issue for present manufacturing systems, which is the needed adaptability when manufacturing orders are received in an unpredictable way and/or a perturbation appears with respect to the used resources. To face such cases, a rescheduling mechanism is necessary and such a possibility is investigated for a holonic system that materializes its coordination through a combination between the Contract Net Protocol and Distributed Constraint Satisfaction Problem. The analysis is carried out for two of the most used distributed algorithms – Asynchronous Backtracking and Weak Commitment Search. Moreover, the improvement of searching through a learning process is also examined. The proposed method is investigated for a case study, by doing simulation experiments with the system colored Petri net model. The results are analyzed for cases when a new command received during execution is more or less important than the ongoing ones and for situations when a resource becomes unavailable.