Colored Timed Petri Net Model Research Articles

Petri-net and GA-based approach to modeling, scheduling, and performance evaluation for wafer fabrication

A genetic algorithm (GA) embedded search strategy over a colored timed Petri net (CTPN) for wafer fabrication is proposed. Through the CTPN model, all possible behaviors of the wafer manufacturing systems, such as WIP status and machine status, can be completely tracked down by the reachability graph of the net. The chromosome representation of the search nodes in GA is constructed directly from the CTPN model, recording information about the appropriate scheduling policy for each workstation in the fabrication. A better chromosome found by GA is received by the CTPN based schedule builder, and a near-optimal schedule is then generated.

System Modeling and Real-Time Simulator for Highly Model-Mixed Assembly Systems

In recent years, the automobile industry is facing more challenge than ever due to rapid model change requirements and demand fluctuations. Traditional fixed-type production systems are less capable in coping with the rapid change, while flexible production systems can better meet the requirement of low-volume production with model variations. Flexible machines integrated with model-mixed assembly lines form flexible assembly systems (FASs). In this paper, Colored Timed Petri Net (CTPN) is used to model a highly model-mixed automobile assembly system. Based on this CTPN model, a real-time simulator was developed along with different dispatching rules. Besides, the algorithm of balanced budget work standard (BWS) for a small batch production is developed for adjusting the loading balance of the operators in the highly model-mixed assembly lines. The simulator can be used as an effective tool for developing scheduling strategies.

Modeling and emulation of a furnace in IC fab based on colored-timed Petri net

In integrated circuit (IC) manufacturing, the wafer processing takes more time in furnaces than other equipment. How to effectively integrate furnaces with other automated machines is very important. In particular, using the real furnace for testing not only introduces trouble but also wastes time. This paper aims to model and construct an emulation environment for the furnace. The colored timed Petri net (CTPN) is used to model the furnace. Based on CTPN, the dynamic behaviors of the furnace, such as loading, processing, unloading and wafer count mismatching, can be emulated. The proposed CTPN model is hierarchical and modular. The hierarchical architecture is built by dividing the behaviors of the furnace to make the model more compact and the modular modeling makes the model flexible and easy to use. On the other hand, the furnace emulator provides a quasi environment for testing so that potential problems of the system can be detected in advance and the testing time can be economized.

A CTPN‐based scheduler for a flexible manufacturing cell

Abstract This paper first presents hierarchical scheduling and control architecture for a flexible manufacturing cell (FMC) that is currently set up at the Mechanical Industrial Research Laboratories of the Industrial Technology Research Institute at Hsinchu, Taiwan. With this architecture, we focus on the scheduling problem of the FMC and present a scheduling mechanism based on a colored timed Petri net (CTPN) model. The CTPN model has three functions in the proposed mechanism: the first one is to formally describe pallet flows and resource constraints in the FMC by the event‐condition relation; the second one is to analyze conflict points among the pallet flows; the third one is to evaluate the used dispatching rules concerned with the selection of machine routings, the selection of work‐in‐process pallets in inter‐medium buffers and the assignment of the commonly used material‐handling device. Using the CTPN‐based scheduler, an appropriate combination of dispatching rules for each given batch can be se...