摘要:

The objective of this study is to use the knowledge acquisition model of inductive learning to establish a selection system for coordinate measuring machines. In this paper, an example knowledge base for the selection of a coordinate measuring machine was induced and analyzed from the diffusive information in the example. The goal is to reduce the amount of knowledge related to the event so as to represent the knowledge in the knowledge base with the fewest number of rules possible. Then the concise decision tree is established by means of the knowledge acquisition model to describe the entire selection problem of coordinate measuring machines.

ISSN:0740-817X    

DOI:10.1080/07408170008967417

出版商:Taylor & Francis Group    

年代:2000

数据来源: Taylor

摘要:

In this paper we develop an optimal and a heuristic algorithm for the problem of designing a flexible assembly line when several equipment alternatives are available. The design problem addresses the questions of selecting the equipment and assigning tasks to workstations, when precedence constraints exist among tasks. The objective is to minimize total equipment costs, given a predetermined cycle time (derived from the required production rate). We develop an exact branch and bound algorithm which is capable of solving practical problems of moderate size. The algorithm's efficiency is enhanced due to the development of good lower bounds, as well as the use of some dominance rules to reduce the size of the branch and bound tree. We also suggest the use of a branch-and-bound-based heuristic procedure for large problems, and analyze the design and performance of this heuristic.

ISSN:0740-817X    

DOI:10.1080/07408170008967418

出版商:Taylor & Francis Group    

年代:2000

数据来源: Taylor

摘要:

This paper addresses the production control problems created in the scheduling of a flexible manufacturing cell consisting of groups of identical machines. An actual manufacturing system, drawn from Sikorsky Aircraft Corporation, was used as a prototype for modeling the cell to study its optimal behavior. The model, stated in the form of optimal production flow control combines classical machine-part scheduling and scheduling of part fixtures. Such an extension induces three problem formulations comprising practical production issues important for many modern plants other than Sikorsky. These formulations are related to three production cases covering different degrees of fixture availability. With the aid of the maximum principle, a numerical scheduling method is constructed for all three problem formulations, and case studies are presented.

ISSN:0740-817X    

DOI:10.1080/07408170008967419

出版商:Taylor & Francis Group    

年代:2000

数据来源: Taylor

摘要:

Landmark navigation is a common positioning method of material handling vehicles operating in industrial environments. The position is calculated based on relative measurements to landmarks, the locations of which are known in advance. This paper presents a nonlinear optimization model used to determine the position of the minimum number of beacons required by a shop floor to guarantee accurate and reliable performance of AGVs. This position is based on guidelines developed by a previous error analysis study. The model is later converted to a binary linear programming model which is used as a lower bound to a heuristic solution procedure. Finally, two examples are used to illustrate the procedure.

ISSN:0740-817X    

DOI:10.1080/07408170008967420

出版商:Taylor & Francis Group    

年代:2000

数据来源: Taylor

摘要:

Three sources of variability in task completion times are identified: the task itself, the worker performing the task, and the environment where the task is performed. Although all three sources might play a role, for practical purposes researchers seek a parsimonious model of variability in task completion times which identifies the most significant source. It is typically assumed that the most significant sources are the task itself or the environment where the task is performed. In this paper we investigate the notion that the worker performing the task may be the most significant source of variability in task completion times, and propose a modeling approach for this situation. We also present the results of a field experiment that support the proposed modeling approach.

ISSN:0740-817X    

DOI:10.1080/07408170008967421

出版商:Taylor & Francis Group    

年代:2000

数据来源: Taylor

摘要:

The achievement of lower product cycle times requires the use of a multidimensional agility measure. In addition to quantifying a manufacturers ability to respond quickly and cost effectively to sudden unexpected changes in customer demands, this measure should be able to guide the concurrent engineering effort. Such a measure is described in this paper. This model utilizes state variable based performance metrics, which account for the hierarchy among design activities. Also, to address the subjectivity that is inherent in this process and provide confidence interval estimates for the resulting agility measures, simulation modeling is used.

ISSN:0740-817X    

DOI:10.1080/07408170008967422

出版商:Taylor & Francis Group    

年代:2000

数据来源: Taylor

摘要:

Currently, conflict-free routing in AGV systems is established by means of one of the following three approaches: (i) the problem elimination through the adoption of a segmented path flow or tandem queue configuration; (ii) the identification of imminent collisions through forward sensing and their aversion through vehicle backtracking and/or rerouting; or (iii) the imposition of zone control and extensive route pre-planning, typically based on deterministic timing of the vehicle traveling and docking stages. Among these three approaches, the segmented path flow-based approach presents the highest robustness to the system stochas-ticities/randomness, but at the cost of restricted vehicle routings and the need for complicated handling operations. This paper proposes an alternative conflict resolution strategy that will ensure robust AGV conflict resolution, while maintaining the operational flexibility provided by free vehicle travel on arbitrarily structured guidepath networks. Specifically, the approach advocated in this paper also employs zone control, but it determines vehicle routes incrementally, one zone at a time. Routing decisions are the result of a sequence of safety and performance considerations, with the former being primarily based on structural/logical rather than timing aspects of the system behavior. The resulting control problem is characterized as the AGV structural control. After defining the notion of AGV structural control, the paper proceeds to the formal characterization and analysis of the problem, and to the development of a structural control policy appropriate for the class of AGV resource allocation systems. The paper concludes with some discussion on the accommodation of emerging AGV operational features in the proposed modeling and analysis framework, and the integration of AGV structural control with the broader control of material-flow among the shop-floor workstations.

ISSN:0740-817X    

DOI:10.1080/07408170008967423

出版商:Taylor & Francis Group    

年代:2000

数据来源: Taylor

摘要:

Existing commercial CAD/CAM systems allow the user to generate the cutter-path for machining a 2-1/2D pocket by using only a single cutting-tool size. Therefore, to avoid potential problems, such as gouging and unmachined areas, the user tends to choose the size of the cutting-tool in a conservative manner. This can result in longer processing time and higher production cost than those that can be achieved by using multiple cutting-tool sizes to machine a given pocket. The key to cutter-path generation using multiple cutting-tool sizes lies in having an efficient mechanism for representing the material volumes that can be removed by a specified cutting-tool size and the unmachined material volumes that will remain after its use. In this paper, we develop a novel concept called the Voronoi mountain and describe its application to cutter-path generation using multiple cutting-tool sizes. The theoretical significance of this approach stems from its ability to: (i) to create a Voronoi mountain representation of unmachined material volumes without having to construct the corresponding Voronoi diagram; and (ii) to accommodate generalized pocket geometries.

ISSN:0740-817X    

DOI:10.1080/07408170008967424

出版商:Taylor & Francis Group    

年代:2000

数据来源: Taylor

ISSN:0740-817X    

DOI:10.1080/07408170008967425

出版商:Taylor & Francis Group    

年代:2000

数据来源: Taylor