• Journal of Korean Society of Transportation
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• v.25 no.3
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• pp.137-144
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• 2007

This study involves an analytical approach to determine transit dispatching schedules (headways) Determining a time schedule is an important process in transit system planning. In general, the transit headway should be shorter during the peak hour than at non-peak hours for demand-responsive service. It allows passengers to minimize their waiting time under inelastic, fixed demand conditions. The transit headway should be longer as operating costs increase, and shorter as demand and waiting time increase. Optimal headway depends on the amount of ridership. and each individual vehicle dispatching time depends on the distribution of the ridership. This study provides a theoretical foundation for the dispatching scheme consistent with common sense. Previous research suggested a dispatching scheme with even headway. However, according to this research, that is valid for a specific case when the demand pattern is uniform. This study is a general analysis expanding that previous research. This study suggests an easy method to set a time table without a complex and difficult calculation. Further. if the time axis is changed to the space axis instead, this study could be expanded to address the spacing problems of some facilities such as roads. stations, routes and others.

• Proceedings of the Korean Operations and Management Science Society Conference
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• 2000.04a
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• pp.151-151
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• 2000

• Industrial Engineering and Management Systems
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• v.6 no.2
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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.

• IE interfaces
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• v.17 no.2
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• pp.233-241
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• 2004

The main subject to become a hub port is automation. The automated container terminal has already operated in advanced ports and it has been planned for the basic planning and operation design in domestic case. The key of automated container terminal is effective operation of both ATC(automated transfer crane) and AGV(automated guided vehicle) which is automated handling equipments. This is essential to productivity of automated container terminal. This study suggests the most optimal method of equipment operation in order to minimize loading time using each three types of effective ATC operation methods and AGV dispatching rules in automated container terminals. As the automated equipment operation causes unexpected deadlocks or interferences, it should be proceeded on event-based real time. Therefore we propose the most effective ATC operation methods and AGV dispatching rules in this paper. The various states occurred in real automated container terminals are simulated to evaluate these methods. This experiment will show the most robust automated equipment operation method on various parameters(the degree of yard re-marshaling, the number of containers and AGV)

• Journal of Korean Society of Transportation
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• v.13 no.1
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• pp.83-94
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• 1995

Many taxis called "Mobum" in Seoul are empty and waiting along the curb during the day time. However, it is almost impossible for elderly and handicapped people, and women carrying babies to use them .It is because they can not serve passengers who request services by phone. If taxis, expecially "Mobum" taxis which offer high quality services, can be dispatched based on requests by phone, not only elderly and handicapped people but also auto commuters will easily call and use them. This paper shows a taxi dispatching system. The system minimizes the total empty vehicle hours under given number of empty vehicles and passengers and their locations. As a result, the system maximizes number of services and revenue under given number of taxis. The system adopts a well -known linear programming model and the model can fast and easily be solved by PC level linear programming packages. Also, practical solutions of the system's constraints such as size and travel time forecast are discussed.ecast are discussed.

• Industrial Engineering and Management Systems
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• v.9 no.2
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• pp.178-194
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• 2010

To improve the ship operation in automated container terminals, it is important to schedule different types of handling equipment to operate synchronously. For example, a vehicle with container receiving and lifting capabilities is used to transport containers from a storage yard to a vessel and vice versa, while a triple quay crane (QC) can handle up to three 40-ft containers simultaneously. This paper discusses the manner in which vehicles should be assigned to containers to support such multi-lifts of QCs by using information about the locations and times of deliveries. A mixed-integer programming model is introduced to optimally assign delivery tasks to vehicles. This model considers the constraint imposed by the limited buffer space under each QC. A procedure for converting buffer-space constraints into time window constraints and a heuristic algorithmfor overcoming the excessive computational time required for solving the mathematical model are suggested. A numerical experiment is conducted to compare the objective values and computational times of the heuristic algorithm with those of the optimizing method to evaluate the performance of the heuristic algorithm.

• IE interfaces
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• v.11 no.1
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• pp.119-129
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• 1998

The relative importance of Logistics in steelworks industry is rather higher among other business activities. The objective of the paper is to propose the methodology for real-time vehicle scheduling for scrap disposal in the steelworks industry. Currently, the rule necessary to assign vehicles to a specific job is strictly fixed. The paper adopts the multi-pass rule selector (MPRS) that suggests a promising rule used for vehicle dispatching for a period of time. The MPRS is regularly invoked if necessary and then evaluates a set of rule candidates to select the best rule with respect to the system performance criteria. The experiment shows that the proposed approach outperforms the current single-pass strategy.

• Proceedings of the Korean Institute of Navigation and Port Research Conference
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• 2002.11a
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• pp.63-70
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• 2002

The main subject to become a hub pen is automation The automated container terminal has already operated in advanced pons and it bas been planned for the basic planning and operation design in domestic case. The key of automated container terminal is effective operation of both ATC(automated transfer crane) and AGV(automated guided vehicle) which is automated handling equipments. This is essential to productivity of automated container terminal. This study suggests the moat optimal method of equipment operation in order to minimize loading time using each three types of effective AT operation methods and AGV dispatching rules in automated container terminals. As the automated equipment operation causes unexpected deadlocks or interferences, it should be proceeded on event-based real tine. Therefore we propose the most effective ATC operation methods and AGV dispatching rules in this paper. The various states occurred in real automated container terminals are simulated to evaluate these methods. This experiment will show the most robust automated equipment operation method on various parameters(the degree of yard re-marshaling, the number of containers and the number of AGVs).

• Journal of Korean Society of Industrial and Systems Engineering
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• v.23 no.58
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• pp.29-39
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• 2000

This paper concerns the location of the transit point between adjacent loops and guide direction of loops in the tandem configuration manufacturing system. The tandem configuration has been used to solve control problems like the vehicle dispatching and traffic control. The transit point between loops needs to deliver the parts from one loop to another. The location of transit point between adjacent loops and direction of loops must be determined to minimize the total travel time of parts in the manufacturing system. The model formulation is developed, a numerical example is shown.

• Journal of Korean Institute of Industrial Engineers
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• v.23 no.2
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• pp.343-357
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• 1997

This paper proposes a new AGV dispatching algorithm which is suitable for heterarchical manufacturing control structure. It is developed on the basis of bidding concept utilizing the information of work-in-process in incoming and outgoing buffers of workstation, and travel time of AGV. Since the bidding functions are functions of two parameters, sensitivity test is performed to find their appropriate values. The performance of the algorithm is compared with those of well-known existing rules in terms of system throughput through simulation on a hypothetical job shop type manufacturing system.