Browsing by Author "Liu, FH"

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Bilevel hysteretic service rate control for bulk arrival queue
(1999-10-01)
Liu, FH
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Tseng, JW
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工業工程與管理學系
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Department of Industrial Engineering and Management
This paper concerns M-[X] / M / 1 queue. The number of customers in each arriving unit is a random variable. There is two control threshold values K and N, K is smaller than N. Service rate is switched from u to tu whenever the system size increases to N. The tu rate is switched to u when the system size drops to the value K. We derive the steady-state probabilities of the number of customers in system and the expected number of customers in system. A cost model is introduced for the service cost, queuing cost, and switching cost. (C) 1999 Elsevier Science Ltd. All rights reserved.
Real-time deadlock-free control strategy for single multi-load automated guided vehicle on a job shop manufacturing system
(2001-05-01)
Liu, FH
;
Hung, PC
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工業工程與管理學系
;
Department of Industrial Engineering and Management
An unmanned automated job shop manufacturing system with a single multi-load automated guided vehicle, which traverses around a single-loop guidepath, is considered in this work. This type of shop design is often used as an independent sector of some complex AGV layouts, such as tandem, segmented bi-directional single-loop and divided configurations. The type of multi-load vehicle is a good alternative against using more single-load vehicles to serve a higher transportation demand. To an unmanned automated manufacturing system, the management of finite system resources, e.g. finite input/output queuing space and transporting carriers, plays a vital role in avoiding system deadlocks and machine blockages. The proposed control strategy for a single multi-load vehicle uses global shop real-time information to achieve the objectives: avoid shop deadlocks caused by inappropriate job movement as well as satisfy the system transport requirement. The efficiency of the proposed vehicle control strategy and the other two expanded strategies under various parameter designs are verified by computer simulation.
The fleet size and mix vehicle routing problem with time windows
(1999-07-01)
Liu, FH
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Shen, SY
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工業工程與管理學系
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Department of Industrial Engineering and Management
This paper describes several insertion-based savings heuristics for the fleet size and mix vehicle routing problem with time window constraints. A certain number of candidate fleet compositions are recorded in the construction phase, followed by applying a composite improvement scheme on them to enhance the solution quality. Computational results on 168 sample problems are reported. We found that heuristics with the consideration of a sequential route construction parameter yielded very good results. In addition, results on the 20 benchmarking problems for the fleet and mix vehicle routing problem with no time window constraints also demonstrate the effectiveness of our heuristics.