Consideration of machine breakdown in the control of flexible production systems

Control of operational production systems requires a reaction to disturbances. In this paper, the authors present a Petri net model describing a decision-making mechanism induced by the breakdown of a machine. The aim of such a proposal is to reassign the operations to the workshop's resources. A decision-making aid methodology is essential to consider the disturbances according to several criteria. Therefore, the authors propose a Petri net model composed of Deterministic and Stochastic Petri nets (DSPN) and Object Petri nets (OPN). The decision-making process is based on the introduced concept of ‘potential’ associated with each machine. This potential is evaluated by means of several criteria to take the ‘right’ decision. In this study, the three following criteria are retained: Time, Cost, and machine reliability. A state of the art survey about the multicriteria decision aid methods has led to the choice of a method called AHP (Analytic Hierarchy Process). The authors thus present a multicriteria algorithm, based on the AHP method, developed for the reassignment of the operations that are blocked following a machine breakdown. The reassignment of the blocked operation is carried out on the machine providing ‘the best’ compromise between the three criteria.