Study On Rules Based Re-entrant Lines Scheduling

Re-entrant line is a class of complex manufacturing system with semiconductor manufacturing system being its typical. Semiconductor industry is the basic foundation of the age of information, characterized with dense capital and technologies. It develops very quickly and the updating of semiconductor product is very quickly. Under the pressure of business and complexities of the system, re-entrant lines' scheduling becomes the focus of the industry and the academe. Practical method is fewer among the large number of literatures due to the complexities of the system. Scheduling rules act as an important role in dispatching practice and this paper is based on scheduling rules. Aims to provide much more applied techniques, this paper focuses on modeling re-entrant line, optimized scheduling strategy and to schedule bottleneck devices. The main works are as follows:1. A class of extended timed colored stochastic petri net (ETCSPN) is introduced and employed to model re-entrant lines since ETCSPN shows great advantages in modeling discrete event dynamic system (DEDS). The proposed ETCSPN model of re-entrant lines is composed by two sub-models: process flow model and transportation model. Workpieces' complex maching process are embodied in process flow model, the complex working procedure of workpieces are embodied in transportation model. In process flow model, some modules includes batch devices in different situations, a kind of equivalent model for semi-batch processing device defined in this paper, and rule based scheduling modules are given. Through ECTSPN model, all possible behaviors of the re-entrant lines, such as WIP status and machine status could be tracked down by the reach-ability graph of the net. The model enables one to perform both qualitative and quantitative analysis.2. On the basis of scheduling rules in common use, a class of buffer-time (B-T) rules according to the characteristics of re-entrant line is brought forward, then a scheduling strategy which is the combination of buffer-time rules based on grouping devices and separated scheduling period is proposed. Genetic algorithm is employed in this paper to optimize the combination of buffer-time rules strategy. The simulation results based on a TFT manufacturing system proved the superiority of the proposed strategy.3. Aims to make full use of bottleneck workstation, a class of Longest Cycle Time First Serve (LCTFS) dispatching rule is proposed according to characteristics of re-entrant line. The rule is easy to be applied in practice and the simulation of re-entrant line testified the performance of the rules. On the basis of decomposeing of the re-entrant, a class of strategy defined as bottleneck analyzing based strategy is proposed in the paper.The simulation results proved the superiority of the stragety on the condition of low WIP levels.4. At last, on the basis of the methods mentioned above, with one TFT manufacturing...