• 대한기계학회논문집A
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• 제24권8호
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• pp.2131-2142
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• 2000

As recent production facilities are usually operated with unmanned material-handling system, the development of an efficient schedule with deadlock avoidance becomes a critical problem. Related researches on deadlock avoidance usually focus on real-time control of manufacturing system using deadlock avoidance policy. But little off-line optimization of deadlock-free schedule has been reported. This paper presents an optimization method for deadlock-free scheduling for Job-Shop system with no buffer. The deadlock-free schedule is acquired by the procedure that generates candidate lists of waiting operations, and applies a deadlock avoidance policy. To verify the proposed approach, simulation resultsare presented for minimizing makespan in three problem types. According to the simulation results the effect of each deadlock avoidance policy is dependent on the type of problem. When the proposed LOEM (Last Operation Exclusion Method) is employed, computing time for optimization as well as makespan is reduced.

• 대한기계학회논문집A
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• 제25권3호
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• pp.443-451
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• 2001

This paper addresses an on-line scheduling method for track systems in semiconductor fabrication. A track system is a clustered equipment performing photolithography process in semiconductor fabrication. Trends toward high automation and flexibility in the track systems accelerate the necessity of the intelligent controller that can guarantee reliability and optimize productivity of the track systems. This paper proposes an-efficient on-line scheduling method that can avoid deadlock inherent to track systems and optimize the productivity. We employ two procedures for the on-line scheduling. First, we define potential deadlock set to apply deadlock avoidance policy efficiently. After introducing the potential deadlock set, we propose a deadlock avoidance policy using an on-line Gantt chart, which can generate optimal near-optimal schedule without deadlock. The proposed on-line scheduling method is shown to be efficient in handling deadlock inherent to the track systems through simulation.

• 한국시뮬레이션학회논문지
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• 제20권4호
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• pp.59-66
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• 2011

본 연구에서는 시뮬레이티드 어닐링 알고리즘에 기반한 다중 RUN(multi-RUN: m-RUN) 교착 제어 정책 생성 알고리즘 설계에 대해 제안하였다. 이 방법은 단순한 RUN DAP를 m개 생성한 후 이들의 합성에 의해 초기 m-RUN DAP를 정의하고 이를 점차적으로 개선시켜 나가는 것이다. 이 때 이웃(Neighbor) m-RUN은 현재 m-RUN에서 오직 한 개의 성분 RUN만을 랜덤하게 수정하여 생성하는 지역 탐색 기법을 적용하여 선택하였다. 또한 몇 가지 기본적인 시스템 구성을 가정하고 수치 실험을 적용하여 제안된 교착 제어 정책 성능의 우수성을 평가하였다.

• 산업공학
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• 제22권1호
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• pp.10-16
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• 2009

In this paper, we propose an efficient search algorithm for finding an optimal schedule to minimize makespan, while avoiding deadlock situation in Flexible Manufacturing Systems (FMS) with finite capacity, in which each job needs to be processed in several job stages for completion. The proposed algorithm uses a modeling and control method based on Petri-net. Especially, we improve the efficiency of the search algorithm by using a priority rule and an efficient bounding function during the search procedure. The performance of the proposed algorithm is evaluated through a numerical experiment, showing that it holds considerable promise for providing an optimal solution efficiently comparing to past work.