Design of Multi-stage Production System Robust to Variance

本研究考虑一种方法，利用多任务工人（MTW）在多级生产过程。在设计生产系统时，重要的是通过有效地使用工人和生产设备来提高生产率。然而，操作时间的变化和不平衡的工作负载通常会降低系统的性能。本研究提出一个MTW分配规则，其中MTW被转移到前一站的最小工作量，使用一个时间缓冲区。MTW能够有效地吸收操作时间的变化和不平衡的工作负载，最近提出了一种结合时间缓冲器概念的流量控制系统。它与看板系统的不同之处在于，时间缓冲系统使用剩余的加工时间来评估在制品（Work-in-Process，简称WIP）;然而，这些系统并不使用多阶段生产过程中的所有库存信息。也就是说，当库存处于特定状态时发出生产指令。流量控制系统的性能根据库存的各种状态而提高。在这项研究中，我们设计了一个最佳的流量控制系统，利用所有可用的库存信息在多级生产过程。通过将在制品的状态空间视为库存的控制域来实现详细的流程控制。

This research considers a method for utilizing multitasking workers (MTWs) in multistage production processes. In designing a production system, it is important to raise productivity by using workers and production facilities effectively. However, the variation in operation time and the unbalanced workloads generally decreases the system's performance. This study proposes a MTW assignment rule in which the MTW is shifted to the previous station of the minimum workload, using a time-buffer. It is clarified that the MTW can absorb the variation in operation time and the unbalanced workloads effectively.A flow-control system incorporating the concept of time buffer was proposed recently. It differs from the Kanban system in that a time-buffer system evaluates work-in-process (WIP) using the remaining processing time; however, these systems do not use all the inventory information in multistage production processes. That is, a production instruction is issued when the inventory is in a specific state. The performance of the flow-control system improves depending on the various states of inventories. In this study, we designed an optimal flow-control system that utilizes all the available inventory information in multistage production processes. Detailed flow control is achieved by treating the state space of WIP as a control domain of the inventory.