Supervisory Control of Reconfigurable Manufacturing Systems based on NCESs

Abstract

This work proposes a supervisory control method for reconfigurable manufacturing systems (RMSs) based on net condition/event systems (NCESs) under the firing rule ‘maximal single spontaneous transition steps’. It is assumed that the occurrence of a reconfiguration event changes the system configuration immediately and a reconfiguration requirement is triggered randomly in the current work. For the safety of an RMS, the implementation of system reconfigurations is only permitted at some specific plant states. However, it is unreasonable to execute a system reconfiguration immediately at a reconfigurable state, when current on-going manufacturing tasks are not finished. In order to keep the continuity of production process and to avoid confusion of an RMS, a novel reconfiguration control structure based on NCESs is proposed, where a reconfiguration controller (RC) performs the implementation of reconfigurations and a task supervisor (TS) monitors the execution status of tasks. The applicability of the method is illustrated by using a simple RMS.