Development of Autonomous Decentralized Scheduling System with Optimization Function

在大多数工厂中，生产指令被下达给由多一个批次单元组成的每个生产部分。通常的情况是，每个生产部门都积累了足够的有关其运作的信息，并有可能制定自己的计划。如果存在一种算法，能够使生产部门在考虑与其他部门的关系的同时创建调度，则可能导致调度系统的快速发展，而没有监控系统来控制整个工厂的调度。从上述观点出发，我们开发了一个自主式的分散式调度系统，其中每个生产部门的调度系统通过以下步骤生成一个调度：1)生成初始调度，2)生产部门之间的数据交换，3)优化调度b…更多地吸收了其他生产部门的信息。通过重复步骤II)和步骤III)，逐步生成整个工厂的合理时间表。由于计划是在每个生产段独立生成的，因此在步骤III)，每个生产段可以使用适合于该段的任何优化方法。在不改变其他生产环节的调度系统的情况下，引入对特定生产环节有效的约束条件也是可能的。为了验证该系统的有效性，将其应用于一个具有复杂流程结构和一些中间储罐的间歇工厂的大规模调度问题。算例结果表明，该系统具有生成满足各种约束条件的可行调度的能力。针对自治分散调度系统，提出了一种新的计算作业开始时间的算法。在该算法中，后一阶段的调度可以更自由地由前一阶段的调度生成，所得到的后一阶段的调度会影响前一阶段的调度。因此，当后面阶段的调度很重要时，所提出的算法是更有效的。实例问题的结果表明，所提出的调度系统能够通过聚焦于对获得整个过程的良好调度至关重要的阶段来生成调度。较少

In most plants, production instructions are given to each production section consisting of one more batch units. It is often the case that each production section has accumulated enough information about its operation and has the potential for creating a schedule of its own. If there exists an algorithm which enables a production section to create a schedule while taking into account the relationships with other sections, it may lead to the speedy development of a scheduling system with no supervisory system controlling the scheduling for the entire plant. Such a scheduling system should also be able to easily and swiftly adjust itself to various requirement changes.From the above viewpoint, we have developed an autonomous decentralized scheduling system, in which an individual scheduling system belonging to each production section generates a schedule in the following steps : 1) Generate an initial schedule, ii) Exchange the data among production sections, iii) Optimize the schedule b … More y incorporating information from other production sections. By repeating steps ii) and iii), a plausible schedule for the entire plant is gradually generated. As the schedule is independently generated at each production section, each production section can use any optimization method which is suitable for that section at step iii). It is also possible to introduce some constraints which are valid to a specific production section without changing the scheduling systems of the other production sections.In order to verify the effectiveness of the proposed system, it is applied to a large scale scheduling problem of a batch plant which has a complicated flow structure and some intermediate storage tanks. The result of the example problem shows that the proposed system has an ability to derive a feasible schedule which satisfies every type of constraints.A new algorithm of calculating the starting times of jobs is proposed for the autonomous decentralized scheduling system. In the proposed algorithm, the latter stages can generate schedules more freely from the schedules of the former stages, and the resulting schedules of the latter stages affect the scheduling of the former stages. Therefore, the proposed algorithem is more effective when the scheduling of the latter stages is important. The result of the example problems shows that the proposed scheduling system has the ability to generate a schedule by focusing on the stage critical for obtaining the good schedule of the entire process. Less