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The stochastic economic lot scheduling problem: heavy traffic analysis of dynamic cyclic policies
, 2000
"... We consider two queueing control problems that are stochastic versions of the economic lot scheduling problem: A single server processes N customer classes, and completed units enter a finished goods inventory that services exogenous customer demand. Unsatisfied demand is backordered, and each class ..."
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Cited by 13 (2 self)
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We consider two queueing control problems that are stochastic versions of the economic lot scheduling problem: A single server processes N customer classes, and completed units enter a finished goods inventory that services exogenous customer demand. Unsatisfied demand is backordered, and each class has its own general service time distribution, renewal demand process, and holding and backordering cost rates. In the first problem, a setup cost is incurred when the server switches class, and the setup cost is replaced by a setup time in the second problem. In both problems we employ a longrun average cost criterion and restrict ourselves to a class of dynamic cyclic policies, where idle periods and lot sizes are statedependent, but the N classes must be served in a fixed sequence. Motivated by existing heavy traffic limit theorems, we make a time scale decomposition assumption that allows us to approximate these scheduling problems by diffusion control problems. Our analysis of the approximating setup cost problem yields a closedform dynamic lotsizing policy and a computational procedure for an idling threshold. We derive structural results and an algorithmic procedure for the setup time problem. A computational study compares the proposed policy and several alternative policies to the numerically computed optimal policy.
Simulation Optimization for the Stochastic Economic Lot Scheduling Problem with SequenceDependent Setup Times
"... We consider the stochastic economic lot scheduling problem (SELSP) with lost sales and random demand, where switching between products is subject to sequencedependent setup times. We propose a solution based on simulation optimization using an iterative twostep procedure which combines global poli ..."
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We consider the stochastic economic lot scheduling problem (SELSP) with lost sales and random demand, where switching between products is subject to sequencedependent setup times. We propose a solution based on simulation optimization using an iterative twostep procedure which combines global policy search with local search heuristics for the traveling salesman sequencing subproblem. To optimize the production cycle, we compare two criteria: minimizing total setup times and evenly distributing setups to obtain a more regular production cycle. Based on a numerical study, we find that a policy with a balanced production cycle outperforms other policies with unbalanced cycles.
Lead Time Minimization of MultiProduct, SingleProcessor System: A Comparison of Cyclic Policies
, 2005
"... Lead time minimization of a multiproduct, singleprocessor system: A comparison of cyclic policies ..."
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Lead time minimization of a multiproduct, singleprocessor system: A comparison of cyclic policies
Production Scheduling of Continuous Flow Lines: Multiple Products with Setup Times and Costs
"... The Problem Of... this paper. The facility can only produce one product at a time. A setup is required when the production switches from one type of product to another. Both setup times and setup costs are considered. The objective is to determine the setup schedule and production rate for each prod ..."
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The Problem Of... this paper. The facility can only produce one product at a time. A setup is required when the production switches from one type of product to another. Both setup times and setup costs are considered. The objective is to determine the setup schedule and production rate for each product that minimize the average total costs, which include the inventory, backlog and setup costs. Under the assumption of a constant production rate, we obtain the optimal cyclic rotation schedule for the multiple products system. Besides the decision variables studied in the classical Economic Lot Scheduling Problem (ELSP), the production rate is also a decision variable in our model. We prove that our solutions improve the results of the classical ELSP.
©2005 INFORMS Recovering Cyclic Schedules Using Dynamic ProduceUpTo Policies
"... We consider facilities that follow a cyclic schedule to replenish the inventory of a set of items through production by a shared resource. We introduce a dynamic produceupto policy that recovers the target cyclic schedule after a single disruption, and is also shown to be effective when disruption ..."
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We consider facilities that follow a cyclic schedule to replenish the inventory of a set of items through production by a shared resource. We introduce a dynamic produceupto policy that recovers the target cyclic schedule after a single disruption, and is also shown to be effective when disruptions are more frequent. Our policy is more flexible than traditional recovery policies in that our policy is able to adjust the amount of idle time observed during recovery in response to disruptions, and yet reestablish the target idle time as the schedule recovers. This results in a policy that not only saves cost and time, but provides better schedule stability than other recovery procedures. Furthermore, unlike simple produceupto policies, our policy is anticipatory—replenishments will be speeded up or delayed, whichever is necessary, to help avoid congestion at the shared resource. In addition, recovery is controlled by a single “knob ” or parameter that can tune recovery to be fast and aggressive (frequent setups and small batches) or slow and methodical (few setups and larger batches). Finally, our policy is easy to implement, augmenting a traditional produceupto policy with a simple set of counters that control replenishment decisions. Subject classifications: production/scheduling: recovering cyclic schedules, bucket brigades; mathematics: discrete dynamical systems.
The Stochastic Economic Lot Scheduling Problem: A Survey
, 2005
"... We consider the production of multiple standardized products on a single machine with limited capacity and setup times under random demands and random production times, i.e., the socalled stochastic economic lot scheduling problem (SELSP). The main task for the production manager in this setting i ..."
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We consider the production of multiple standardized products on a single machine with limited capacity and setup times under random demands and random production times, i.e., the socalled stochastic economic lot scheduling problem (SELSP). The main task for the production manager in this setting is the construction of a production plan for the machine that minimizes the total costs, i.e., the sum of holding, backlogging and setup costs. Based on the critical elements of such a production plan, we give a classification and extensive overview of the research on the SELSP together with an indication of open research areas.
MANAGING QUALITY AND LEAD TIME UNCERTAINTIES USING COMPONENT COMMONALITY IN A PRODUCTION ENVIRONMENT
"... Uncertainty is inevitable in manufacturing. Uncertainties like quality and lead time extensively affect the competitive outcomes of the system. For their statistically unpredictable nature and due to complex interrelationships between resources and operations, they have varied effects in manufacturi ..."
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Uncertainty is inevitable in manufacturing. Uncertainties like quality and lead time extensively affect the competitive outcomes of the system. For their statistically unpredictable nature and due to complex interrelationships between resources and operations, they have varied effects in manufacturing. Many factors of uncertainty have been reported in literatures. Component commonality is the use of same type of components in different levels of product structure. In different manufacturing settings, parts commonalities occur in their own ways or can be planned for their preferred occurrences. The main objectives of this article are: i) to augment the understanding of uncertainty factors and commonality, (ii) to explore the commonality indices and pertinent measuring tools in manufacturing resource planning, and (iii) to instigate fruitful solutions for managing cutthroat outputs under quality and lead time uncertainties in production/manufacturing system where component commonality is applied. This paper is based on a comprehensive and uptodate review of the recent literatures on uncertainty and commonality in manufacturing resource planning models. It is observed that the use of common components for different products and in different levels in production/ manufacturing environment can dampen quality and lead time uncertainties to some extent.
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, 2008
"... do^ar^qb=p`elli=lc=_rpfkbpp=C=mr_if`=mlif`v= k^s^i=mlpqdo^ar^qb=p`elli= Approved for public release, distribution is unlimited. ..."
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do^ar^qb=p`elli=lc=_rpfkbpp=C=mr_if`=mlif`v= k^s^i=mlpqdo^ar^qb=p`elli= Approved for public release, distribution is unlimited.
THE STOCHASTIC ECONOMIC LOT SCHEDULING PROBLEM: HEAVY TRAFFIC ANALYSIS OF DYNAMIC CYCLIC POLICIES
"... We consider two queueing control problems that are stochastic versions of the economic lot scheduling problem: a single server processes A ^ customer classes, and completed units enter a finished goods inventory that services exogenous customer demand. Unsatisfied demand is backordered, and each c ..."
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We consider two queueing control problems that are stochastic versions of the economic lot scheduling problem: a single server processes A ^ customer classes, and completed units enter a finished goods inventory that services exogenous customer demand. Unsatisfied demand is backordered, and each class has its own general service time distribution, renewal demand process, and holding and backordering cost rates. In the first problem, a setup cost is incurred when the server switches class, and the objective is to minimize the long run e.xpected average costs of holding and backordering inventory and incurring setups. The setup cost is replaced by a setup time in the second problem, where the objective is to minimize average holding and backordering costs. In both problems we restrict ourselves to a class of dynamic cyclic policies, where idle periods and lot sizes are statedependent, but the N classes must be served in a fixed sequence. Under standard heavy traffic conditions, these scheduling problems are approximated by diffusion control problems. The approximating setup cost])roblem is solved exactly, and the optimal dynamic lot sizing policy is found in closed form. Structural results and an algorithmic procedure are derived for the setup time problem. A computational study is undertaken to compare the proposed policy and several straw policies to the numerically computed optimal policy.
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, 2008
"... Approved for public release; distribution is unlimited. ..."