Equilibria, Stability, Oscillations, Chaos, and Transients in Re-entrant Lines

本研究课题主要针对半导体制造业中广泛使用的生产系统--可重入生产线进行性能分析和改进。人们普遍认为，可重入式生产线的特点是生产能力（TP）和在制品（WIP）的波动性大。这会导致性能下降以及生产周期长且不可预测。目前，对这些现象没有严格的解释，打击这些现象的努力也远未成功。这项研究旨在发展一种理论，解释这些现象的根本原因，并提供缓解这些现象的技术。该方法是基于非线性动力学的方法。具体来说，该项目将研究再入线的稳态，其（李雅普诺夫）稳定性，周期性和混沌振荡，以及瞬态行为（即，机器故障后收敛到稳定状态的过程）。因此，该项目将提供分析工具，用于调查可重入生产线的性能，包括TP和TMPs的变化，并提供定量方法和定性见解，可供生产人员使用，以减轻不良的动态现象。该研究的更广泛影响将通过PI在半导体制造工厂提供的工业短期课程来实现。这些课程将以适合工厂现场应用的形式展示这项研究的结果。PI已经在汽车行业提供类似的课程超过十年，其中已经提出了先前NSF支持的串行线和装配系统研究的结果。结果，其中一些结果已被纳入几个汽车厂的标准操作程序，并导致了显着的性能改善。预计半导体行业也将获得类似的结果。

This research project is devoted to performance analysis and improvement of production systems widely used in semiconductor manufacturing - the re-entrant lines. It is universally accepted that performance of re-entrant lines is characterized by large variability and oscillations of the throughput (TP) and work-in-process (WIP). This leads to performance degradation and long and unpredictable production cycle time. At present, no rigorous explanations of these phenomena are available, and the attempts to combat them are far from being successful. The research is intended to develop a theory that explains fundamental reasons for these phenomena and provide techniques for their alleviation. The approach is based on the methods of nonlinear dynamics. Specifically, the project will investigate steady states of re-entrant lines, their (Lyapunov) stability properties, periodic and chaotic oscillations, and transient behavior (i.e., the processes of convergence to steady states after machine breakdowns). As a result, the project will provide analytical tools for investigating the performance of re-entrant lines, including TP and WIP variability, and offer quantitative methods and qualitative insights that can be used by production personnel to mitigate the undesirable dynamic phenomena.The broader impact of this research will be attained through industrial short courses to be offered by the PI at semiconductor manufacturing plants. These courses will present the results of this research in the format appropriate for factory floor applications. The PI has been offering similar courses in the automotive industry for over ten years, where the results of prior NSF-supported research on serial lines and assembly systems have been presented. As an outcome, some of these results have been incorporated in standard operating procedures at several automotive plants and led to a substantial performance improvement. Similar outcomes are expected to be obtained in the semiconductor industry as well.