A hierarchic approach to production planning and scheduling of a flexible manufacturing system

The paper deals with the problem of improving the machine utilization of a flexible manufacturing cell. Limited tool magazine space of the machines turns out to be a relevant bottleneck. A hierarchic approach for this problem is proposed. At the upper level, sets of parts that can be concurrently processed (batches) are determined. At the lower levels, batches are sequenced, linked, and scheduled. Methods taken from the literature are used for the solution of the latter subproblems, and an original mixed integer programming model is formulated to determine batches. The proposed methods are discussed on the basis of computational experience carried out on real instances.     

Production control: Current developments and future trends

Manufacturing industry is going through a period of unprecedented change as a result of the developments in micro-electronic technology. This is bringing about a transformation not only in hardware, in the form of computer-aided manufacturing, but in the manner in which production is organised and controlled.It is in the latter connection that the present paper sets out to review current developments and future trends. In particular the machine readable bar-code is seen as a key element in extending computerised control to cover not only the machines, but tools, materials and parts and their movement in the development of fully integrated manufacturing systems.As the move towards automation gathers pace it is forecast that manufacturing industry will become more process industry like in form, with consequences for the way in which production is organised and controlled.Finally consideration is given to the manner in which these current developments in the field of production are giving rise to a structural alteration in industrial labour requirements in which, in the future, fewer people will be required but on highly enriched work tasks.     

How well does a vanilla loop fit into a frame?

The frame language FRL is compared with some newer object-oriented languages, namely LOOPS, the Flavor System and the Poor Man's Flavor System. The kernel features are investigated in detail and a simulation of FRL in the Flavor System is performed. The conclusion is that in general the object-oriented languages cannot be easily utilized as a substitute for FRL frames because of the different view these languages have of objects, but there are important special cases where object-oriented languages are very similar to FRL.     

传统程序设计语言的面向对象扩充的若干技术

本文论述用转换方式实现传统程序设计语言的面向对象扩充,给出了一组关键技术以解决由子类型多态和动态定连所引出的问题,其基本思想是将类和对象类型分开处理,从而避免转换过程中的重复工作．这些技术具有适用性强、功效高的特点,并且在ＰＡＳＣＡＬ语言的面向对象扩充ＮＤＯＯＰ和ＭＯＤＵＬＡ－２语言的面向对象扩充ＮＤＯＯＭ的实现中被采用,效果令人满意.     

一种命令式风格的面向对象语言语义框架

面向对象语言在软件工程实践中有着广泛的应用。为面向对象语言定义严格的语义有助于理解面向对象语言的本质特征,对验证软件、提高软件系统可靠性等也具有重要意义。给出了一种新的面向对象语言的语义框架,该框架基于命令式的风格,具有操作语义和类型规则;证明了该语义框架的类型安全定理。     

基于物理的三维动画的OOP方法研究

本文阐述了采用用面向对象的方法来开发基于物理的三维动画软件的技术及实现方法，介绍了图形数据结构、类的建立、体素的快速消隐处理、三维几何造型技术和基于物理的动画处理技术。最后，给出尾鳍推进装置三维动画仿真的实例。     

面向对象的柔性设计与控制理论(III)

作者在文犤1犦中提出了面向对象的柔性设计与控制理论。该文在文献犤1犦的基础上,对计算机控制系统的类对象进行了分析、设计;在实现方面,开发了可视化的面向对象的集成开发环境,实现了控制系统的“设计灵活、简捷、方便,控制实时、智能、鲁棒”。     

Production planning and control: A personal philosophy

This paper looks at the author's beliefs, concerning the ways in which Production Planning and Control should be developed in the future. He sees the way forward as one which includes small factories - even if the companies are large - less specialisation; simple materials flow systems; Flexible programming; PBC or Kanban and the development of systems theory.     

A logic-based environment for reactive agents in intelligent CAD systems

This paper is an evolution of a previous article by the authors[1] (Bento, J. P., Feijó, B., Lloyd-Smith, D., Computers and Structures, 1977, 63(5), 1015–1032) motivated by the need to provide computational support to an agent-based implementation of design processes. It presents a new programming environment to support the development of CAD systems based on a hybrid agent architecture in which the symbolic reasoning is carried out by first-order logic. The reactive behaviour of the agents can be achieved through a number of characteristics proposed for the object-oriented environment. This environment is also a general proposal for representing engineering design knowledge in which logic is integrated into an object-oriented paradigm. © 1998 Published by Elsevier Science Limited. All rights reserved.     

Pure cycles in flexible robotic cells

In this study, an m-machine flexible robotic manufacturing cell consisting of CNC machines is considered. The flexibility of the machines leads to a new class of robot move cycles called the pure cycles. We first model the problem of determining the best pure cycle in an m-machine cell as a special travelling salesman problem in which the distance matrix consists of decision variables as well as parameters. We focus on two specific cycles among the huge class of pure cycles. We prove that, in most of the regions, either one of these two cycles is optimal. For the remaining regions we derive worst case performances of these cycles. We also prove that the set of pure cycles dominates the flowshop-type robot move cycles considered in the literature. As a design problem, we consider the number of machines in a cell as a decision variable. We determine the optimal number of machines that minimizes the cycle time for given cell parameters such as the processing times, robot travel times and the loading/unloading times of the machines.     

Job-shop scheduling using neural networks

Job-shop scheduling cannot easily be analytically accomplished, so, it is done by computer simulation using heuristic priority rules. The SLACK rule for calculating the margins of jobs to their due-dates is effective in meeting the due-dates. However, the calculated margins are not precise because the actual margin is shortened due to conflicts with other jobs. The authors propose a method for estimating the margins by using a neural network. It is found that the method is effective for improving the average lateness to due-dates but not the maximum lateness. This paper proposes a method for adding a second neural network for judging the reliability of the estimated margins composed to the first one and for switching to the margins calculated by the SLACK rule when the reliability is low. The proposed method is verified by scheduling simulations to be effective in decreasing the maximum lateness to due-dates as much as the average lateness.     

The state of the art in intelligent real-time FMS control: a comprehensive survey

Flexible manufacturing systems (FMS) have been developed with the hope that they would provide a means to tackle a threefold challenge — better quality, lower cost and shorter lead times — by integrating machine tools, robots, material handling and storage systems, and computers. Control of the integrated system presented a new set of problems as well as challenges, which have been receiving considerable attention from the academic community as well as from industrial system users. Intelligent control, which involves using computers to assist in decision making at various stages of the control process, has been advocated by many researchers as a possible avenue to reach a solution to these problems. This paper provides a review of the state of the art in intelligent control of FMS, in an attempt to supplement earlier general reviews via a more focused perspective. The principles of several techniques, namely simulation, knowledge based, example based, petri nets, and hybrid approaches are briefly introduced, and publications are reviewed, followed by discussions ontheir potential. Suggestions for further research and development are also enumerated.     

Expert' voice: The BabyUML discipline of programming

I want increased confidence in my programs. I want my own and other people's programs to be more readable. I want a new discipline of programming that augments my thought processes. Therefore, I create and explore a new discipline of programming in my BabyUML laboratory. I select, simplify and twist UML and other languages to demonstrate how they help bridge the gap between me as a programmer and the objects running in my computer The focus is on the run time objects; their structure, their interaction, and their individual behaviors. Trygve Reenskaug is professor emeritus of informatics at the University of Oslo. He has 40 years experience in software engineering research and the development of industrial strength software products. He has extensive teaching and speaking experience including keynotes, talks and tutorials. His firsts include the Autokon system for computer aided design of ships with end user programming language, structured programming, and a data base oriented architecture from 1960; object oriented applications and role (collaboration) modeling from 1973; Model-View-Controller, the world's first reusable object oriented framework, from 1979; OOram role modeling method and tool from 1983. Trygve was a member of the UML Core Team and was a contributor to UML 1.4. The goal of his current research is to create a new, high level discipline of programming that lets us reclaim the mastery of software.     

A constraint programming approach to tool allocation and production scheduling in flexible manufacturing systems

This paper presents a constraint programming (CP) methodology to deal with the scheduling of flexible manufacturing systems (FMSs). The proposed approach, which consists of both a model and a search strategy, handles several features found in industrial environments, such as limitations on number of tools in the system, lifetime of tools, as well as tool magazine capacity of machines. In addition, it tackles the problem in a integrated way by considering tool planning and allocation, machine assignment, part routing, and task timing decisions altogether in the approach. The formulation, which is able to take into account a variety of objective functions, has been successfully applied to the solution of test problems of various sizes and degrees of difficulty.