• 제어로봇시스템학회:학술대회논문집
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• 1991.10b
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• pp.1564-1569
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• 1991

In this paper we describe Flexible Manufacturing Systems (FMS) using Petri nets, since Petri nets provide a powerful tool for modeling dynamical behavior of discrete concurrent processes. We deal with off-Line and on-Line rule-based scheduling of FMS. The role of the rule-base is to generate appropriate priority rule for resolving conflicts, that is, for selecting one of enabled transitions to be fired in a conflict set of the Petri nets. This corresponds to select a part type to be processed in the FMS. Towards developing more Intelligent Manufacturing Systems (IMS) we propose a conceptual framework of a futuristic intelligent scheduling system.

• The Transactions of the Korean Institute of Electrical Engineers D
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• v.51 no.7
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• pp.294-301
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• 2002

A new dynamic scheduling algorithm is proposed for CAN-based real-time system in this paper. The proposed algorithm is extended from an existing EDS(Earliest Deadline Scheduling) approach having a solution to the priority inversion. Using the proposed algorithm, the available bandwidth of network media can be checked dynamically, and consequently arbitration delay causing the miss of deadline can be avoided. Also, non-real time messages can be processed with their bandwidth allocation. Full network utilization and real-time transmission feasibility can be achieved through the algorithm. To evaluate the performance of algorithm, two simulation tests are performed. The first one is transmission data measurement per minute for periodic messages and the second one is feasibility in the system with both periodic messages and non-real time message.

• 제어로봇시스템학회:학술대회논문집
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• 1993.10a
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• pp.1111-1116
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• 1993

In this study, we discuss the design of the expert system for the scheduling of the FMC(Flexible Manufacturing Cell) consisting of the several versatile machines. Due to the NP property, the scheduling problem of several machine FMC is very complex task. Thus we proposed the two heuritstic shceduling algorithms for solving the problem and constituted the algorithm based of solving the problem and constituted the algorithm base of ISS(Intelligent Scheduling System) using them. By the rules in the rule base, the best alternative among various algorithms in algorithm base is selected and applied in controlling the FMC. To show the efficiency of ISS, the scheduling output of ISS and the existent dynamic dispatching rule were tested and compared. The results indicate that the ISS is superior to the existent dynamic dispatching rules in various performance indexes.

• Proceedings of the Korea Society for Simulation Conference
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• 2000.11a
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• pp.28-33
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• 2000

This article describes the application of discrete event simulation in a process industry (coffee manufacturing) as a daily production-scheduling tool. A large number of end products (around 300), sporadic demand, and limited shelf life of coffee (90 days) make it difficult to generate feasible production schedules manually. To solve this problem an integrated system was developed incorporating discrete event simulation methodology into scheduling process. The integrated system is comprised of two components: a scheduling program and a simulation model. The scheduling program is used to generate daily schedules for roasting, grinding, and packing coffee. The simulation model uses the generated schedules to simulate the production of coffee and regenerates a modified production schedule. In this paper, each of the components will be described in detail, evaluated in terms of performance factors, and validated with a set of real production data. Although this article focuses on a specific system, we will share our experiences and intuitions gained and encourage other process industries to develop simulation-based scheduling tools.

• Journal of Korean Society of Industrial and Systems Engineering
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• v.27 no.2
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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.

• Journal of Korean Society of Industrial and Systems Engineering
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• v.23 no.59
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• pp.21-36
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• 2000

The drum-buffer-rope(DBR) system is a finite scheduling mechanism that balances the flow of the production system. DBR controls the flow of materials through the plant in order to produce products in accordance with market demand, with a minimum of manufacturing lead time, inventory, and operating expenses. This paper integrates the best of MRP push system and JIT pull system with DBR system, efficiently adapts these logics to capacity constraint resources, and contributes to the evolution of synchronous manufacturing. The purpose of this paper is, thus, threefold. The first objective is to identify the frame of theory of constraints(TOC) and the logic of DBR scheduling. The second objective is to formulate the DBR constraint scheduling problems(DBRCSP) in a job shop environments. Finally, the paper is to suggest the solution procedure of DBRCSP for embedding TOC into MRP/JIT along with an numerical expression. In addition, illustrative numerical example is given.

• Proceedings of the Korea Society for Simulation Conference
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• 1999.10a
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• pp.100-107
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• 1999

무인 운반차량 시스템 (AGV System) 의 이용도가 날로 증가함에 따라 시스템의 최적화 및 운영 방법에 관한 많은 연구가 진행되고 있다. 이에 본 연구에서는 AGV System에서 사용하는 Routing 및 Scheduling 정책들을 연구하고 이를 개선할 수 있는 새로운 방안을 모색한 후, 컴퓨터 모델링 기법을 이용한 보다 객관적인 시뮬레이션을 수행하여 최적의 AGV System과 그에 적합한 운영 정책을 제시하는데 그 목적이 있다. 따라서 본 논문은 크게 AGV Routing 과 Scheduling에 관한 연구로 나누어진다. AGV Routing은 AGV의 이동경로를 설정하는 것으로서 충돌 방지 (Collision Avoidance)와 최단경로 탐색 (Minimal Cost Path Find) 이라는 두 개의 주요 알고리즘으로 이루어진다. AGV Scheduling 은 장비의 공정시간과 AGV의 Loading/Unloading, Charging 시간으로 인해 불규칙한 Event 가 일어났을 경우 AGV 각각의 Jop을 알맞게 선정해주는 정책을 말하며 일반적으로 AGV Selection Rule, Charging Rule이 여기에 속한다. 본 연구에서는 이러한 알고리즘들이 반영된 AGV System을 컴퓨터 모델로 구축하여, 기존 시스템에서 사용되고 있는 여러 운영 정책들의 문제점들을 분석하였으며, Multiple AGV System을 최적화 시키는 운영 정책이 보다 객관적으로 제시되었다.

• Journal of Korean Society of Industrial and Systems Engineering
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• v.33 no.4
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• pp.153-158
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• 2010

This study presents a single machine scheduling algorithm to minimize total cost(lateness cost, earliness cost and failure cost) by controlling machining speed. Generally, production scheduling uses the information of process planning and machining speed is not changed at production scheduling. And failure cost is not consider for scheduling algorithm. Therefore, the purpose of this study is to consider the change of machining speed for efficient production scheduling. And performance criteria for algorithm considers total cost. Especially, failure cost of product by increasing machining speed is considered.

• The Transactions of The Korean Institute of Electrical Engineers
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• v.56 no.10
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• pp.1721-1730
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• 2007

SThis paper proposes a new dispatch scheduling algorithm in interconnected regional system operations. The dispatch scheduling formulated as mixed integer non-linear programming (MINLP) problem can efficiently be computed by generalized Benders decomposition (GBD) algorithm. GBD guarantees adequate computation speed and solution convergency since it decomposes a primal problem into a master problem and subproblems for simplicity. In addition, the inter-temporal optimal power flow (OPF) subproblem of the dispatch scheduling problem is comprised of various variables and constraints considering time-continuity and it makes the inter-temporal OPF complex due to increased dimensions of the optimization problem. In this paper, regional decomposition technique based on auxiliary problem principle (APP) algorithm is introduced to obtain efficient inter-temporal OPF solution through the parallel implementation. In addition, it can find the most economic dispatch schedule incorporating power transaction without private information open. Therefore, it can be expanded as an efficient dispatch scheduling model for interconnected system operation.

• Journal of Computing Science and Engineering
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• v.9 no.2
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• pp.108-117
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• 2015

Interrupt handling is generally separated from process scheduling. This can lead to a scheduling anomaly and priority inversion. The processor can interrupt a higher priority process that is currently executing, in order to handle a network packet reception interruption on behalf of its intended lower priority receiver process. We propose a new network interrupt handling scheme that combines interrupt handling with process scheduling and the priority of the process. The proposed scheme employs techniques to identify the intended receiver process of an incoming packet at an earlier phase. We implement a prototype system of the proposed scheme on Linux 2.6, and our experiment results show that the prototype system supports the predictable real-time behavior of higher priority processes even when excessive traffic is sent to lower priority processes.