• Industrial Engineering and Management Systems
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• 제1권1호
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• pp.10-18
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• 2002

A more comprehensive analytical framework for examining the relative merits of alternative dispatching process policies for nurseries is developed in this paper. The efficiency of the dispatch process of plants in a nursery is analysed using a vehicle routing model. The problem then involves determining in what order each vehicle should visit its locations. The problem is NP-hard. Several heuristic techniques are used to solve a real life nursery sequencing problem. The results obtained by these heuristic techniques are compared with each other and the current sequencing of orders. The model with some minor alterations can be also used to minimise the dispatching and collecting process in different agricultural plants.

• 전기학회논문지
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• 제64권11호
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• pp.1578-1586
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• 2015

Personal rapid transit (PRT) is getting attention as a new form of transportation. It is energy efficient and provides the high level of passenger service. In this study, the dynamic PRT dispatching and routing problem is dealt with. Passengers request transportation service on a complex network, and an operating system monitors passenger arrivals and coordinates vehicles in real time. A new online dispatching and routing algorithm is proposed, which minimizes the total travel distance of vehicles and the waiting time of passengers. The algorithm dispatches vehicles by considering multiple vehicles' state and multiple passengers at the same time. In particular, finding the shortest-time path is attempted by taking into account the future congestion on lanes. Discrete-event simulation is employed to validate the performance of the proposed algorithm. The results show the algorithm in this study outperforms others.

• 산업공학
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• 제13권3호
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• pp.455-461
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• 2000

Logistics systems can be evaluated by how productively distribution center operates, how promptly transportation vehicle dispatches, how efficiently facility layout is, and so on. In this paper, a practical vehicle routing scheme with fixed delivery time and fixed vehicle routes is introduced. The method helps the distribution center reduce logistics cost with respect to dispatching vehicles, and satisfy the customer with pre-determined delivery time window constraints. A case study has shown that the proposed scheme not only generates a feasible schedule with time windows, but also balances material flow in warehouse.

• 한국시뮬레이션학회논문지
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• 제6권1호
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• pp.41-52
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• 1997

It is essential to construct an efficient material flow system for the successful introduction of automated manufacturing systems. Automated Guided Vehicle System (AGVS) plays a significant role more and more in modern manufacturing environments, because of the flexibility and the precision they offer. However, as the size and the complexity of systems increase, the problems of dispatching, routing and scheduling of AGVs become complicated due to their independent and asynchronous demands. In this paper, we review relevant papers, and provide a new and more efficient method for dispatching AGV, named MEVTT (Minimum Empty Vehicle Travel Time) and demonstrate its performance and efficiency using simulation.

• 대한원격탐사학회:학술대회논문집
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• 대한원격탐사학회 2004년도 Proceedings of ISRS 2004
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• pp.249-252
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• 2004

The automatic determination of vehicle operation status as well as continuous tracking of vehicle location with intelligent management is one of major elements to achieve the goals. Especially, vehicle operation status can only be analyzed in terms of expert experiences with real-time location data with scheduling information. However the scheduling information of individual vehicle is very difficult to be interpreted immediately because there are hundreds of thousand vehicles are run at the same time in the national wide range workplace. In this paper, we propose the location-based knowledge management system(LKMs) using the active trajectory analysis method with routing and scheduling information to cope with the problems. This system uses an inference technology with dispatching and geographic information to generate the logistics knowledge that can be furnished to the manager in the central vehicle monitoring and controlling center.

• 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.

• 산업공학
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• 제14권4호
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• pp.365-373
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• 2001

It is discussed how to determine time windows for pickups and deliveries, which have been assumed to be given in all most of previous studies on traveling salesman problems with time window, vehicle routing problems with time window, vehicle scheduling and dispatching problems, and so on. First, time windows are classified into four models (DR, DA, AR, and AA) by customers‘ polices. For each model, it is shown how a time window is related to various cost terms of suppliers and customers. Under the assumption of collaborative supplier-customer relationship, an integrated cost model for both supplier and customer is constructed for determining boundaries of time windows. The cost models in this paper consists of cost terms that depend on waiting time, early arrival time, late arrival time, and rejection of receipt. A numerical example is provided and results of the sensitivity analysis for some parameters are also provided to help intuitive understanding about the characteristics of the suggested models.

• 대한산업공학회지
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• 제23권3호
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• pp.559-580
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• 1997

It is essential to construct on efficient material flow system for the successful introduction of automated manufacturing systems. Automated Guided Vehicle System(AGVS) ploys a significant role more and more in modern manufacturing environments, because of the flexibility and the precision they offer. However, as the size and the complexity of systems increase, the problems of dispatching, routing and scheduling of AGVs became complicated due to their independent and asynchronous demands. In this paper, we review relevant papers, and provide a new and more efficient method for partitioning the AGV system by introducing the concept of Central Path. This method named Central Path design has advantages, since each partitioned workstation group is served by one AGV and the material handling between groups is performed by special AGV that is used for the Central Path. Therefore the congestion problems never occur. Furthermore Central Path Design has a high flexibility for alteration and extension of system. Finally, we demonstrate its efficiency using simulation.

• 산업공학
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• 제10권1호
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• pp.57-65
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• 1997

Less researches on AGV(Automated Guided Vehicle) path configurations have been conducted so far while more studies have been placed in determining AGV guide path directions and pick-up/drop-off station locations, and routing/dispatching/scheduling strategies. In practice plenty of concerns fall in preventing deadlock and simplifying AGV system control through an appropriate AGV path configuration. In order to meet those requirements, a new AGV path configuration, inter-loop stocker type is introduced here. The stocker serves as relaying material between loops as well as stocking material. Automated material handling systems using AGVs play an important role in semiconductor industry including TFT LCD and memory/non-memory chip. A practical example of implementing the inter-loop stocker concept successfully in the TFT LCD fab is presented in this paper.

• 한국시뮬레이션학회논문지
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• 제17권4호
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• pp.29-39
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• 2008

최근 본선작업의 대기시간을 단축할 수 있는 효율적인 이송장비로 ALV(Automated Lifting Vehicle)가 연구되고 있다. 그러나 ALV와 다른 하역장비의 연계에 대한 구체적인 분석을 수행한 후 동적 요소들을 반영한 연구는 미흡하다. ALV의 수행도는 동적 환경하의 자가하역 작업, 차량간 방해, 가용한 작업 공간의 점유에 크게 좌우된다. 그러므로 ALV 시스템이 도입된 컨테이너 터미널의 생산성을 평가하는 것은 매우 어렵다. 따라서ALV시스템에 적합한 운영 규칙을 갖춘 시뮬레이션 모형으로 개발되어야 한다. 또한 모형은 연계작업과 차량 주행의 특성을 고려해야 한다. 본 연구는 수평형 컨테이너 터미널을 가정하고 하역작업 과정을 분석하고 시뮬레이션 모형에 필요한 주요 운영 규칙을 제시하였다. 그리고 객체지향 시뮬레이션 소프트웨어인 Anylogic을 이용하여 ALV 시스템에 기반한 컨테이너 터미널 시뮬레이션 모형을 개발하였다.