MODELLING AND SCHEDULING OF FMSS BASED ON OBJECT ORIENTED CTPN AND HEURISTICS

Abstract

The motivation for this work is on the dynamic scheduling of flexible manufacturing systems. Though there has been much research effort towards the scheduling and dispatching of FMSs, dynamic scheduling is one of the less studied areas and remains a major gap in the implementation of manufacturing systems. This research introduces an object-oriented hierarchical approach to build the dynamic model of an FMS. The integrated model in the proposed Petri Net is flexible and can be extended to fit different production system layouts and tasks. It can be viewed as an integrated platform to support the development of scheduling, dispatching and control of FMSs. In this work, a mixed - weighted heuristic (MWH) approach is carried out to assign different dispatching rules to a colored time Petri Net (CTPN) model of an FMS. Once the complete model of the system is structured, the MWH rules are selected to control appropriate transitions according to given performance criteria. An experimental study of the efficiency of the MWH rules is conducted. A system based on above has been developed and shown to work. The system can handle real-time factors such as concurrent operations, choices (conflicts), shared resources and unexpected interruptions.