Article Abstract:
A problem of structure optimization of a series-parallel production system is considered where redundant producing elements (machines) and in-process buffers are included in order to provide a desired level of reliability. A procedure which determines the minimal cost system configuration is proposed. In this procedure, producing elements and buffers are chosen from a list of products available in the market. The elements are characterized by their cost, estimated average up and down times and productivity (machines) or capacity (buffers). System reliability is defined as the ability to satisfy consumer demand which is represented by a piecewise cumulative load curve. A genetic algorithm is used as an optimization technique. An example of the redundancy optimization of a power station coal feeding system is presented. [C] 2001 Elsevier Science B.V. All rights reserved. Keywords: Series-parallel production system; Buffers; Genetic algorithm; Reliability
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Article Abstract:
The concept of limited flexibility, originally applied to production planning, has shown that many benefits of totally flexible systems can be obtained by less flexible systems. This concept is here applied to shop floor control. Limited flexibility is considered as a particular routing flexibility that allows system resources to process some products according to a logic chain, as an intermediate configuration between a totally flexible system (where every resource can process every product) and a non-flexible system (dedicated resources). A simulation study is carried out to measure the system performance such as the lead time and work-in-process for different system configurations, with variable demand, setup times and processing times. [C] 2001 Elsevier Science B.V. All rights reserved. Keywords: Limited flexibility; Batch production; Performance; Simulation
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Article Abstract:
This paper aims at describing methods for the coherence analysis in production systems. This coherence between the various objectives of the decision system is analysed in order to ensure that the achievement of local performances allows the achievement of the global ones, assigned to the whole enterprise. The coherence analysis methods are usable for quantitative objectives, whatever the kinds of performance which is concerned (cost, quality, lead time, flexibility, etc.). The coherence analysis is based on the aggregation and comparison of expected performances (objectives) between the various decision levels. Various methods are developed in the frame of the concepts of the GRAI Model. [C] 2001 Elsevier Science B.V. All rights reserved. Keywords: Performance; GRAI Model; Coherence; Objectives; Aggregation
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