ISSN:1246-0125    

DOI:10.1080/12460125.1996.10511669

出版商:Taylor & Francis Group    

年代:1996

数据来源: Taylor

ISSN:1246-0125    

DOI:10.1080/12460125.1996.10511670

出版商:Taylor & Francis Group    

年代:1996

数据来源: Taylor

ISSN:1246-0125    

DOI:10.1080/12460125.1996.10511671

出版商:Taylor & Francis Group    

年代:1996

数据来源: Taylor

摘要:

In hierarchical planning systems, up to three different kinds of abstraction hierarchies can be used: consistent aggregation and disaggregation are based on aggregation hierarchies. By representation hierarchies, general rules can be represented, and different levels of granularity can be integrated consistently. Finally, problem—solving hierarchies are exploited to solve complex search problems efficiently. While structure and properties of its components impose fixed, distinct levels for aggregation and representation hierarchies (e.g. a “type”, “family”, and “item” level), problem—solving hierarchies are derived from user—defined criticalities of its components and, therefore, are continuous. In order to combine efficient support of interactive, hierarchical search for solutions of complex planning problems with overall consistency control, a database—oriented planning system should comprise not only fixed—level aggregation and representation hierarchies, but also continuous problem—solving hierarchies. In this paper, traditional approaches to computer- based production planning and hierarchical planning are examined with regard to their abstraction capabilities. Based on that evaluation, a hierarchical search concept for supporting complex planning decisions is proposed. Design guidelines, application examples, derivation methods, and consistency requirements for all three types of abstraction hierarchies are presented. Conceptual modeling and implementation of an appropriate database-oriented, hierarchical planning system are discussed. Being an application of our concept to a make-to-order and make-to-stock balancing problem in mechanical engineering, the PLASIM system is presented.

ISSN:1246-0125    

DOI:10.1080/12460125.1996.10511672

出版商:Taylor & Francis Group    

年代:1996

数据来源: Taylor

摘要:

In this paper, a multi—product multi-stage planning problem is addressed by means of a two level hierarchical approach. The decision structure is based on an aggregation of time: the upper (aggregate) level involves macro—periods while elementary periods are considered at the lower (detailed) level. Thus, the detailed level refines (disaggregates) the higer level decisions i.e. distributes the production volume defined for each macro-period, over the relevant elementary periods. In such a framework, the global consistency of the decisions is investigated, leading to the basic concept of aggregate consistency. Analytical aggregate consistency conditions are obtained; they rely on a graph modeling of the disaggregation problem and on the analysis of a flow problem within the relevant network. Introduced as additional constraints in the aggregate model, they ensure that the selected aggregate decisions can be further disaggregated in order to provide feasible detailed production plans. In order to reduce the complexity brought about by these constraints a computational structure based on heuristics is proposed. In this context, numerical experiments are carried out to evaluate the quality of this decisional structure.

ISSN:1246-0125    

DOI:10.1080/12460125.1996.10511673

出版商:Taylor & Francis Group    

年代:1996

数据来源: Taylor

摘要:

Current industrial trends favor distributed manufacturing with extensive use of subcontracting. In this context we present a two—level decision support system for operations scheduling where a set of firms (subcontractors) is competing for the realization of the manufacturing operations pertaining to a product. We consider the case where operation precedences are given in form of an assembly tree. Each firm bidding for an operation specifies a start time, a processing time, a production cost together with a storage cost for storing the work-in-process resulting from that operation beyond its completion time. At the first level, IBIS, an information support system is used for bid preparation based on resource usage, production requirements and production operations costs. At the second level, given the bids we present a procedure for finding the assignment of operations to firms that minimizes production and storage costs.

ISSN:1246-0125    

DOI:10.1080/12460125.1996.10511674

出版商:Taylor & Francis Group    

年代:1996

数据来源: Taylor

摘要:

This paper presents a temporal decomposition approach for the one—machine scheduling problem, with ready times, due dates and fixed processing times. We aim at characterizing feasible schedules of the problem and deriving benefit from the temporal properties pointed out, in order to generate a solution which minimizes the maximum lateness. The set of feasible schedules is characterized by means of constraint—based analysis rules. They permit the determination of the feasible locations of each task in a sequence, represented by the rank interval. A solving heuristic procedure is described; it decomposes the set of tasks according to their rank intervals and applicates upon each subproblem a priority rule. Computational results are reported, so that the characterization method as well as the solving procedure can be evaluated.

ISSN:1246-0125    

DOI:10.1080/12460125.1996.10511675

出版商:Taylor & Francis Group    

年代:1996

数据来源: Taylor

摘要:

For real time scheduling, a decision aid approach, based on the characterization of a set of schedules compatible with the problem constraints, is proposed. This set is specified in terms of sequences of permutable operations on the resources. Generating such a group sequence is described for the scheduling problem where products have to be performed according to a specified routeing with release times and due dates. Each product operation requires a set of resources, each of them being selected inside a pool of several resources.

ISSN:1246-0125    

DOI:10.1080/12460125.1996.10511676

出版商:Taylor & Francis Group    

年代:1996

数据来源: Taylor

摘要:

This paper presents an optimization methodology based on lagrangean relaxation to solve the problem of scheduling jobs with due date. Each job consists of a distinct number of operations to be processed in a specified order. We obtain an efficient near—optimal algorithm with guaranteed bounds for the non—preemptive job shop scheduling problem. The method is investigated for scheduling jobs on possibly different sets of identical parallel machines for different operations of a job. By relaxing the coupling capacity constraints with nonnegative Lagrange multipliers and forming the langrangean, we decompose the problem according to jobs, which may be solved independently. The multipliers are adjusted at each step by a subgradient procedure. A list—scheduling heuristic then derives a feasible schedule from this solution.

ISSN:1246-0125    

DOI:10.1080/12460125.1996.10511677

出版商:Taylor & Francis Group    

年代:1996

数据来源: Taylor

摘要:

The paper presents heuristics for two types of resource—constrained project-scheduling problems: the problem of levelling the resources consumption and the minimum project—duration problem. Both minimal and maximal time lags between the start of successive activities of the project in question are permitted. Such a project can be modelled by an activity-on-node network containing cycles. For the resource—levelling problem with maximal time lags, neither exact algorithms nor heuristic procedures have been proposed so far. Two different heuristic procedures are presented. The sequential or direct method processes the nodes or respectively activities of the cyclic project network successively without scheduling the strong components of the network separately. The contraction method firstly finds a feasible subschedule for each strong component of the cyclic network and secondly replaces each strong component by a single node. The resulting (contracted) acyclic network is treated by the direct method. An empirical analysis shows that for the minimum project—duration problem, the contraction method is markedly superior to the direct method. For the resource—levelling problem, both approaches behave similarly.

ISSN:1246-0125    

DOI:10.1080/12460125.1996.10511678

出版商:Taylor & Francis Group    

年代:1996

数据来源: Taylor