• 산업경영시스템학회지
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• 제27권2호
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• pp.17-23
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• 2004

Changes in manufacturing system are those that occur during production and cause the systems to behave unpredictably. So scheduling problem in this dynamic Industrial environments is very complex. The main concept of this dissertation is to continuously monitor a manufacturing system status(Rate of Prior Job, Rate of Large Job, Rate of Shortest due date Job, Job Interval Time) and detect or predict a change so that scheduling system will react by modifying production schedule(dispaching rule) to lessen the effects of this change.

• 제어로봇시스템학회논문지
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• 제8권8호
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• pp.706-712
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• 2002

In general, a deadlock in flexible manufacturing systems (FMSs) is caused by a resource limitation and the diversity of routings. However, the deadlock of industrial controllers such as programmable logic controllers (PLCs) can occur from different causes compared with those in general FMSs. The deadlock of PLCs is usually caused by an error signal between PLCs and manufacturing systems. In this paper, we propose a deadlock detection and recovery (DDR) algorithm to resolve the deadlock problem of PLCs at design stage. This paper employs the MAPN (modified automation Petri net), MTPL (modified token passing logic), and ECC (efficient code conversion) algorithm to model manufacturing systems and to convert a Petri net model into a desired LD (ladder diagram). Finally, an example of manufacturing systems is provided to illustrate the proposed DDR algorithm.

• 한국경영과학회지
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• 제22권2호
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• pp.79-97
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• 1997

Many dispatching rules have been developed for the on-line control of product flow in a job shop. The introduction of a flexible manufacturing system (FMS) has added a new requirement to classical job shop control problem : the selection of machines by parts of different types. An FMS can keep a great deal of information on the status of the system, such as information on what is scheduled in the near future, with great accuracy. For example, the knowledge of the time when the next part will arrive at each machine can be neneficial for the routing. This paper tests the effects of the use of this knowledge for part routing on the parts flow time (sum of the time for waiting and service) under a simple routing procedure- a look-ahead routing procedure. A test under many operating conditions shows that the reduction of part flow time from the cases without using this information is between 1% and 11%, which justifies more study on this routing procedure at real production sites when machine capacity is a critical issue. The test results of this paper are also valid for other highly automated systems such as the semi-conductor fabrication plants for routing when the arrivals of parts in the near future are known.

• 기계저널
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• 제27권3호
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• pp.198-202
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• 1987

PLC의 도입이 10여년 남짓된 지금, 자동화의 추세는 기능의 다양함과, 빠른 제어 속도, 높은 신뢰도가 요구되어 전기적인 제어에서 전자적인 제어로 전환되어 가고 있다. 특히 주 컴퓨터와 연결하여 생산 및 판매, 관리 부시 등에 정보를 신속히 제공할 수 있어 여러모로 편리하다. 이와 같은 흐름은 전문적인 지식을 필요로 하지 않고 프로그램의 작성 및 수정이 용이하며 시스템고 장수리시 PLC의 기능에 의해 간단히 해결되고 새로운 전자제품의 개발로 점점 더 가격이 싸지 고 있다는 점을 감안할 때 FMS(flexible manufacturing system)를 실현하고자 하는 모든 기업에 그 응용이 예상된다.

• 한국시뮬레이션학회:학술대회논문집
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• 한국시뮬레이션학회 2000년도 춘계학술대회 논문집
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• pp.131-136
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• 2000

FMS(Flexible Manufacturing System, 유연생산 시스템)는 1960년대 최초로 소개된 이후, 뛰어난 Throughput과 Flexibility로 지금까지 다양한 생산 현장에서 널리 활용되고 있다. 하지만 복잡한 Part의 흐름, 충분하지 못한 AGV(Automated Guided Vehicle) 등으로 인한 성능 저하는 가장 큰 장애물이라 할 수 있다. 이에 대한 대비책으로 시스템 내에 설치하는 버버는 일시적인 WIP(Work In Process, 재공재고)의 저장공간으로써 Blocking, Starving 등의 발생을 최소화하는 역할을 수행한다. 따라서 이러한 버퍼의 적절한 배치는 시스템 성능에 큰 영향을 미치게 되며, 이에 본 연구에서는 각 Workstation의 Workload를 고려해 각 버퍼의 적절한 Capacity를 결정하는 과정을 소개하며, 제시된 방법론의 실효성을 시뮬레이션을 통해 검증하고자 한다.

• 산업공학
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• 제1권2호
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• pp.1-12
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• 1988

A justification methodology which evaluates the tactical aspects of an FMS project is proposed. For evaluation of quantifiable tactical costs/savings a method of internal rate of return on incremental investment is developed while for the tactical ones which are difficult to quantify a weighted factor scoring model is proposed.

• 한국시뮬레이션학회:학술대회논문집
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• 한국시뮬레이션학회 1994년도 추계학술발표회 및 정기총회
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• pp.9-9
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• 1994

FMS를 비롯한 대부분의 제조시스템의 운용을 위해서는 크게 전략적 의사결저오가 전술적 읫사결저이 필요하며, 이 중 전술적 의사결증은 부품 선택, 생산율 결정, 부하할당, 부품 투입, 일정계획 문제등과 관련되어 있다. 본 연구에서는 부품투입시점과 부품투입순서에 의해 결정된 부품투입 정책이 시스템 성능에 미치는 영향을 알아보기 위해서, 서울대학교부설 자동화시스템공동연구소(ASRI)내의 FMS/CIM Center를 대상으로 시뮬레이션을 수행하였다. ASRI-FMS /CIM Center 는 기계가공과 조립이 동시에 이루어지는 FMAS(Flexible Mauufacturing & Assembly System) 형태의 모형공장이며, 현재 세 종류의 모터 등을 생산할 수 있다. 본 연구에서는 고려한 부품투입시점 전략으로는 고정 WIP(Work-in-process)유지전략 , 병목기계 전략, 일정비율 투입전략 등이며, 부품 투입순서 전략으로는 크게 주기적 투입전략과 비주기적 투입전략을 고려하였다. 또한 이러한 부품 투입정책들이 시스템 내에서 적용할 수 있는 여러 가지 우선순위규칙 등과 함께 사용될 때, 나타나는 상호관계를 파악하기 위한 연구가 수행되었다. 아울러 병목기계 추가도입, 물류운반시간의 감소 등과 같이 가능한 범위에서 현재의 시스템 조건이 바뀐 상황에 대해서도 시뮬레이션을 수행함으로써, 추후 변경된 시스템에서도 본 연구의 결과가 적응될 수 있도록 하였다.

• 대한전기학회:학술대회논문집
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• 대한전기학회 1991년도 하계학술대회 논문집
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• pp.713-716
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• 1991

This paper describes a methodology of mobile robot navigation which is designed to carry heavy payloads at high speeds to be used in FMS(Flexible Manufacturing System) without human control. Intelligent control scheme using fuzzy logic is applied to the navigation control. It analyzes sensor readings from multi-sensor system, which is composed of ultrasonic sensors, infrared sensors and odometer, for environment learning, planning, landmark detecting and system control. And it is implemented on a physical robot, AGV(Autonomous Guided Vehicle) which is a two-wheeled, indoor robot. An on-board control software is composed of two subsystems, i.e., AGV control subsystem and Sensor control subsystem. The results show that the navigation of the AGV is robust and flexible, and a real-time control is possible.

• 산업경영시스템학회지
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• 제20권43호
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• pp.249-263
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• 1997

This paper addresses the parts route selection and economic design in flexible manufactuirng system (FMS). Parts are processed through several stage workstations according to operation sequences. The machine of each workstation can do multiple operation functions. And the operation stage of a part can be processed in several workstations, which are non-identical in functional performance. The objective of this paper is to determine the processing routes of parts, number of machine at each workstation, number of vehicle and makespan time. Two models are suggested. One is assumed that the operation stage of parts can be processed at the only one among several available workstations. Other is assumed that the operation stage of parts is allowed to be processed at several workstations. Parts are transported by automated guided vehicles (AGVs). The decision criteria is to minimize the sum of processing cost, travel cost, setup cost and overhead cost. The formulation of models is represented. A solution algorithm is suggested, and a numerical example is shown.

• 대한산업공학회지
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• 제16권2호
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• pp.51-62
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• 1990

One of the important scheduling and control problems that must be solved for the efficient operation of FMS could be the "part ordering problem" which is finding optimal sequence of parts to be released into a manufacturing system. In this paper an approach which solves the problem using simulation-optimization technique will be presented. Currently available heuristic approaches for dispatching rules can only get the near optimum at the local level because of the complexities of the system and the dependencies of its components whereas the proposed approach will try to get the global optimum for a given criterion.