Fuzzy supervisory control of manufacturing systems

A supervisory controller is derived for scheduling (single/multiple-part-type, reentrant) production networks. The supervisory controller is used to tune a set of lower level distributed fuzzy control modules that reduce work-in-process (WIP) and synchronize the production system´s operation. The overall production-control system is viewed as a two-level surplus-based system with the overall control objective to keep the WIP and cycle time as low as possible, while maintaining quality of service by keeping backlog to acceptable levels. The production rate in each production stage is controlled to satisfy demand, avoid overloading, and eliminate machine starvation or blocking. The system´s improvement is demonstrated using a set of performance measures. Extensive simulation results show that the supervisory controller, when compared with the single-level distributed fuzzy controllers reduces WIP and cycle time while keeping backlog to acceptable levels.