• Journal of Korean Society of Industrial and Systems Engineering
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• v.25 no.4
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• pp.40-45
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• 2002

An AS/RS construction cost minimization model under throughput rate requirement constraint has been developed, whose objective function includes S/R machine cost, storage rack cost, and interrace conveyor cost. S/R machine cost is a function of the storage rack height, the unit load weight, and the control logic used by the system, while storage rack cost is a function of the storage rack height, the weight and the volume of the unit load. Since the model is a nonlinear integer programming problem which is very hard to solve exactly with large problem size, a solution procedure is developed to determine the height and the length of the storage rack with a fixed number of S/R machines, while increasing the number of S/R machines one by one to meet the throughput rate requirement.

• Journal of Korean Society of Industrial and Systems Engineering
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• v.28 no.4
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• pp.134-141
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• 2005

Due to the complexity and stochastic nature of automated warehousing system, items are usually queued up at I/O point. We introduce a storage/retrieval policy : dual-command. We present quick approximations to queueing phenomena under these policies. It is assumed that the storage and retrieval arrival pattern follow the same poisson process. We also assumed that storage queue and retrieval queue being operated separately. The approximation attempts are performed under the proposed storage/retrieval policies after we derive S/R machine travel time distributions.

• Journal of Korean Society of Industrial and Systems Engineering
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• v.21 no.46
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• pp.137-146
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• 1998

Most studies related to AS/RS are about operation policies or system designs. However, the studies on operation policy could not deal with various products using the single unit load system. In this paper, two different sized units are introduced and six different AS/RS operation policies are developed to process the different sized items. Computer simulation is used to evaluate AS/RS performances on various operation policies and to find the most effective operation policy for each case. The simulation model is developed using GPSS/PC and operation policies include COL-FIFO-SP, SIL-FIFO-SP, COL-RN-SP, COL-FIFO-LP, SIL-FIFO-LP and COL-RN-LP. The policies are evaluated based on the criteria of crane utilization, rack utilization, crane moving time, throughput and waiting time.

• IE interfaces
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• v.12 no.2
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• pp.237-246
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• 1999

The Automated Storage/Retrieval System(AS/RS) is very expensive to be built. But there are few tools available which can be used to design the storage systems optimally considering overall system building costs and constraints. In this paper, we propose a design support system for optimal design of AS/RS which includes different sized cells using expert systems and mathematical models considering customer's demands. The optimization models are to be used to minimize the total cost including building, equipment and operation costs. Expert system technique is utilized for using the experiences of skilled designers. By using the proposed system, AS/RS can be designed accurately, economically and efficiently.

• Journal of Korean Society of Industrial and Systems Engineering
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• v.22 no.49
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• pp.1-10
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• 1999

A cost minimization model for designing AS/RS (Automated Storage/Retrieval Systems) has been developed, whose objective function includes penalty cost caused by the incapability of meeting throughput rate requirements as well as S/R machine cost, storage rack cost, and interface conveyor cost. Since the model is a nonlinear integer programming problem which is very hard to solve with large problem size the problem is divided into four cases according to the ratio of horizontal S/R machine speed to its vertical speed and the existence of the penalty cost. A solution procedure is developed which solves each problem exactly under the different number of S/R machines.

• Journal of the Korean Institute of Illuminating and Electrical Installation Engineers
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• v.12 no.1
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• pp.85-92
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• 1998

In this paper, we design a sequential system controller, which is capable of processing parallel sequence, on the basis of analysis of control specification described by Petri Net with incidence matrix. The sequential system controller consists of input conditioning unit and petri net control unit which is composed of the token control unit and firing unit. The firing unit determines the firing condition of the transfer signal on the basis of the token status of token control unit. By the proposed scheme, we can easily develop and implement the sequential system controller of automated warehousing system, automated transportation system, elevator system, and so on, as it is possible to modify control specification by changing simply the content of incidence matrix ROM and to expand easily functional capacity as the result of modular design.design.

• Proceedings of the Korean Operations and Management Science Society Conference
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• 1993.04a
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• pp.382-389
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• 1993

공장자동화를 추진하기 위한 중요한 구성요소는 설비기기들이다. 작업관련 설비기기들의 관리를 효율적으로 함으로 현장에서의 작업이 원활하게 이루어질 수 있다. 이러한 설비기기들의 현 상황을 지금까지는 대부분 작업자에 전적으로 의존하여왔는데 작업자가 일일이 확인하고 관리하기에는 시간적 낭비와 관리의 일괄성이 없어 효율적 관리가 힘들다. 본 연구에서는 자동창고, 무인반송차등 물류설비와 수평형, 수직형 Machining Center와 같은 공작기계들의 정지, 가동, Set Up상태등 기기 현황정보를 수신받아 컴퓨터 화면으로 항상 확인하므로써 보다 편리한 상태감시를 할 수 있다. 또한 컴퓨터 그래픽을 이용해 외부 정보데이타를 시각적으로 나타내고 관리하기 때문에 컴퓨터에 대한 전문적 지식이 없는 작업자라도 기기상태를 용이하게 파악할 수 있고 설비기기들의 수리 및 교체상황등 이력관리를 데이타베이스화하여 정확하고 체계적으로 관리한다.

• Proceedings of the Korean Operations and Management Science Society Conference
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• 2000.04a
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• pp.1-4
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• 2000

In general, under the concept of unit load, Automated Storage/Retrieval Systems (AS/RS) have the rack of equal sized cells. However, they are inadequate and inefficient meeting the various sizes of customers' demands in today's business environment. Higher utilization and flexibility of warehouse storage can be achieved by using AS/RS with tile rack of modularized cell. In this paper, the model of AS/RS with the rack of modularized cell is proposed, and the effectiveness of proposed model is presented by way of numerical examples. The model developed in this research, as one type of AS/RS that is more flexible to the size and has higher space utilization than those of existing rack structure, could every useful for the storage of heterogeneous unit load sizes.

• Proceedings of the Korean Operations and Management Science Society Conference
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• 2000.04a
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• pp.253-256
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• 2000

In general, Automated Storage/Retrieval Systems (AS/RS ) have racks of equal sized cells to utilize the concept of unit-load. Most of the techniques for the performance estimation of a unit-load AS/RS are a static model or computer simulation. Especially, their models were developed under assumption that the Storage/Retrieval (S/R) machine performs only single command (SC) or dual command (DC). In reality, defending on the operating policy and the status of the system at a particular time, the S/B machine performs a SC or a DC, or becomes .: idle. In order to resolve these weak points, we propose a stochastic model for the performance estimation of unit-load AS/RS by using a single-server queueing model. Expected numbers of waiting storage and retrieval commands are found

• Journal of Industrial Technology
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• v.16
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• pp.217-230
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• 1996

This paper deals with storage and retrieval policies for S/R machine with capacity constraints in Man-On-Board AS/RS. It is assumed that storage sequence is based on SFC(spacefilling curve) routine and that storage layout is dedicated by storage policies. We present several heuristic algorithms for storage and retrieval policies which minimize total distance travelled by the S/R machine. These algorithms are based on COI, group COI, frequency of order, similarity between items and capacity of S/R machine. Experimental results of 24 combinastorial policies are provided to illustrate the performance of the heuristics under various rack utilization ratios. In storage policies, the results show that algorithms considering both similarity and frequency are better than those with COI as rack utilization is increasing. And algorithm using group COI is superior to others. In retrieval policies, the method with revision expression is shown to be better than others.