• 대한산업공학회지
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• 제21권1호
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• pp.137-151
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• 1995

A difficult problem in operating Flexible Manufacturing Systems (FMS) is to control the system in real-time by coordinating heterogeneous machines and integrating distributed information. The objective of the paper is to present the models and methodologies useful to resolve the difficult problem. The detailed objectives can be described in three folds. First, a hierarchical Colored and Timed Petri-Net (CTPN) is designed to control an FMS in real-time. The concerned FMS consists of a loading station, several machining cells, a material handling system, and an unloading station. Timed-transitions are used to represent the timed-events such as AGV movements between stations and cells, part machining activities in the cells. Signal places are also used to represent communication status between the host and the cell controllers. To resolve the event conflicts and scheduling problems, dispatching rules are introduced and applied. Second, an implementation methodology used to monitor and diagnose the errors occurring on the machines during system operation is proposed. Third, a Petri-Net simulator is developed to experiment with the designed control logic.

• 산업공학
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• 제11권3호
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• pp.181-191
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• 1998

In the make-to-order (MTO) manufacturing environment, one of the important issues is setting attainable delivery dates for customer orders, which significantly affects the performance of the MTO manufacturing. Although this topic has received considerable attention in the literature, most of the efforts took a lower level approach that is concerned primarily with the effect of various delivery date assignment methods on the relative performance of some dispatching rules. This paper proposes the delivery date decision support system which takes a higher level approach of integrating the marketing and production planning functions with the consideration of the current capacity and the workload smoothing. The proposed system has been implemented in a Rotating Machinery Shop and the results of the implementation showed good performance.

• Industrial Engineering and Management Systems
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• 제6권2호
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• pp.125-135
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• 2007

An automated guided vehicle (AGV) system is a group of collaborating unmanned vehicles which is commonly used for transporting materials within manufacturing, warehousing, or distribution systems. The performance of an AGV system depends on the dispatching rules used to assign vehicles to pickup requests, the vehicle routing protocols, and the home location of idle vehicles, which are called dwell points. In manufacturing and distribution environments which emphasize just-in-time principles, performance measures for material handling are based on response times for pickup requests and equipment utilization. In an AGV system, the response time for a pickup request is the time that it takes for the vehicle to travel from its dwell point to the pickup station. In this article, an exact dynamic programming algorithm for selecting dwell points in a tandem-loop multiple-vehicle AGV system is presented. The objective of the model is to minimize the maximum response time for all pickup requests in a given shift. The recursive algorithm considers time restrictions on the availability of vehicles during the shift.

• 한국경영과학회지
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• 제26권2호
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• pp.69-83
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• 2001

The problem of minimizing total tardiness on a batch processing machine with incompatible job families when there are sequence independent setup times between families is studied where all jobs of the same family have identical processing times and jobs of different families cannot be processed together. A batch processing machine can process a number of jobs, within a maximal batch size, simultaneously as a batch. The processing time required of each batch is equal to the one of jobs. A dynamic programming algorithm which gives the optimal solution, and several heuristics are presented. Performance of simple dispatching rules based on due dates are compared, and the best of them is used as an initial solution for the decomposition algorithm, which is shown to give good schedules in relatively short computational time.

• 산업공학
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• 제12권1호
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• pp.121-131
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• 1999

In this article, a simulation model of a microwave oven assembly line is developed to identify system parameters to improve the system performances such as work-in-process inventories, production lead time, mean earliness, mean tardiness and in-time completion rate. System parameters investigated include dispatching rules, lot sizing, setup time reduction, demand increase, productivity improvement, production scheduling, hardware characteristics, etc. The model has been developed using SIMAN simulation language which has been demonstrated to be a powerful tool to simulate complex manufacturing systems. We have suggested the results obtained to improve the system performances of an existing production line.

• 산업경영시스템학회지
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• 제22권53호
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• pp.23-35
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• 1999

Since on-time delivery is becoming increasingly important in today's competitive markets, the development of effective scheduling methodologies to meet customer needs through on time delivery is of vital importance for the well-being of companies. The objective of this study is to develope a general heuristic algorithm for scheduling both the static and dynamic problems under certain on-time delivery criteria. For the problems with due-date related, we present insights for minimizing the number of tardy jobs and propose a heuristic scheduling algorithm. Experimental results show that the proposed algorithm performs significantly better than other dispatching rules within reasonable computation time, specially in the environment of strong competition for resources.

• 대한산업공학회지
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• 제25권2호
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• pp.192-203
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• 1999

This paper deals with the order release problem for minimizing weighted earliness and tardiness as well as Work In Process (WIP) in dynamic job shop environments. A newly designed hierarchical order release mechanism is developed for efficient real-time control of the earliness/tardiness and WIP. The hierarchical order release mechanism consists of the order release plan and the order release control which is composed of two procedures. The experimental results show that the proposed order release mechanism is superior to other four order release mechanisms under overall simulation conditions of utilization rate, due-date allowances, and earliness/tardiness cost structures. In addition, the difference of total cost among the four dispatching rules is much more reduced in the proposed order release mechanism than in other release mechanisms.

• 한국시뮬레이션학회논문지
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• 제19권4호
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• pp.99-109
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• 2010

기존의 반도체 생산 공장에서 운용되는 공정설비의 자동화된 웨이퍼 이송을 위한 스케줄링 운용전략에 대한 연구는 일반적으로 특정 공정 환경과 시스템 형태에서 운용되는 이송패턴에 최적화시킨 규칙기반으로 진행되어 왔다. 그러나 이러한 방식은 시스템이나 공정이 달라지면 새로운 규칙이 필요하거나 전체 운용 전략을 변경해야 하는 문제가 발생할 수 있다. 또한, 규칙이 추가될수록 확장, 유지 보수 시에 추가된 규칙들의 상호 연관 작용에 대한 고려가 부족한 경우 예기치 않은 문제를 유발할 시킬 수 있는 위험성을 내포하고 있다. 따라서 본 논문에서는 이러한 문제점을 개선하기 위해 이송패턴이나 설비의 형태에 일반적으로 적용 가능한 동적 우선순위 기반의 기본 이송작업 선택 알고리즘을 제시하였다. 또한 특수한 요구 사항에 대해서는 범용성을 저하시키지 않는 범위 내에서의 최소한의 규칙 처리부를 별도로 관리하는 방식으로 운용 환경 변화에 일관된 스케줄링 정책을 유지하고 확장 시의 안정성 저하를 최소화하여 생산성 향상을 이끌 수 있는 범용 스케줄링 알고리즘을 제안하였다. 이에 대한 검증을 위하여 트윈 슬롯 형태의 반도체 공정설비를 대상으로 모델링 및 시뮬레이션 환경을 구축하였고, 시뮬레이션을 통해 타당성을 검증하였다.

• 한국산학기술학회논문지
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• 제12권5호
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• pp.2038-2047
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• 2011

본 논문에서는 TFT-LCD(Thin Film Transistor-Liquid Crystal Display) 제조 공정 중 Module 공정의 Slim MES(Manufacturing Execution System)를 위한 생산계획 프레임워크(framework)개발에 관해 연구한다. TFT-LCD 제조 공정 중 Module 공정의 라인 구성 및 기능은 각 제조 현장마다 차이가 있다. 본 논문은 이러한 차이를 반영하는 제조현장 맞춤형 MES를 위한 생산계획 프레임워크를 제시한다. 먼저 TFT-LCD Module 공정의 분석을 통해 생산계획 프로세스를 파악한다. 그런 다음 현장 상황 제약조건을 반영한 수리적 모델링을 제시하고 이에 대한 최적 스케줄의 도출을 사례를 통해 제시한다. 또한 현장 상황을 반영한 디스패칭(dispatching) 룰에 의한 스케줄 생성 과정을 제시하고 성능실험 결과를 제시한다. 마지막으로 Slim MES를 위한 생산계획 프레임워크 설계 과정을 제시한다.

• 산업경영시스템학회지
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• 제41권3호
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• pp.120-128
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• 2018

OLED Display fabrication system is one of the most complicated discrete processing systems in the world. As the glass size grows from $550{\times}650mm$ to $1,500{\times}1,850mm$ in recent years, the efficiency of Automated Material Handling System (AMHS) has become very important and OLED glass manufacturers are trying to improve the overall efficiency of AMHS. Aiming to meet the demand for high efficiency of transportation, various kind of approaches have been applied for improving dispatching rules and facility layout, while simultaneously considering the system parameters such as glass cassettes due date, waiting time, and stocker buffer status. However, these works did not suggest the operational policy and conditions of distribution systems, especially for handling unnecessary material flows such as detour. Based on this motivation, in this paper, we proposed an efficient algorithm for improving detour transportation in OLED FAB. Specifically, we considered an OLED FAB simplifying OLED production environment in a Korean company, where four stockers are constructed for the delivery of Lot in a bay and linked to processing equipments. We developed a simulation model using Automod and performed a numerical experiment using real operational data to test the performance of three operation policies under considerations. We showed that a competitive policy for assigning alternative stocker in case of detour was superior to the current dedicated policy using a specified stocker and other considered policies.