Compact disc standards: an introductory overview

The success of the compact disc (CD) as a storage medium for digital audio has, over the last ten years, resulted in a number of initiatives to use the CD for other applications as well, e.g., as read-only memory for computers, as a storage medium for audio-visual material for multimedia applications, and as a storage medium for photographs. Each of these applications poses additional requirements on how the corresponding information is stored and retrieved, resulting in a range of different CD standards. The functional specifications of these standards are each given a specific color for ease of reference: the Red Book for CD-DA, the Yellow Book for CD-ROM, the Green Book for CD-I, etc. This paper aims at giving an overview of the various CD standards by explaining what is specified in each of the colored books and by indicating how they relate to one another.     

Stability of pull production control methods for systems with significant setups

In manufacturing, a pull production control method is a method of authorizing production based on replenishing current and past consumption, as opposed to forecasts or orders for future consumption. We consider special classes of pull systems for operations that involve significant setup times. In particular, we present a model for variations of the signal Kanban method and the pattern production method, each of which is used in industry when conventional Kanban methods are inappropriate. The paper examines such systems under demands with unpredictable load content but an upper bound on the total load. It is shown that, under appropriate conditions, such systems are stable in the sense that cumulative production at any time trails cumulative demand by no more than a constant. We determine buffer parameters under each protocol (including reorder points in the signal Kanban case) such that the backorder queue will clear to zero and remain empty thereafter. The results are then extended to consider multiple machines fulfilling production authorizations in parallel.     

非最小相位系统跟踪控制综述

非最小相位系统是指包含不稳定零动态的系统.经典的跟踪控制理论,特别是非线性系统跟踪控制理论,是以最小相位系统为基础建立的,不能直接用于非最小相位系统.研究非最小相位系统跟踪控制理论,是对经典控制理论的扩展和补充,具有重要的意义.本文对目前非最小相位系统跟踪控制领域取得的成果进行综述.首先梳理各种非最小相位系统跟踪控制方法的基本思想,并按照近似跟踪和精确跟踪进行归类,建立非最小相位系统跟踪控制的基本框架.然后围绕该框架对各种方法进行详细介绍.接着讨论非最小相位系统的跟踪性能限制.最后总结现有研究存在的一些问题及对今后的发展方向进行展望.本文的目的在于使控制工作者对非最小相位系统的跟踪控制有一个较为清晰的认识.     

Optimal control of pull manufacturing systems

We consider the problem of optimal control of pull manufacturing systems. We study a fluid model of a flow shop, with buffer holding costs nondecreasing along the route. The system is subject to a constant exogenous demand, thus incurring additional shortfall/inventory costs. The objective is to determine the optimal control for the production rate at each machine in the system. We exhibit a decomposition of the flow shop into “sections” of contiguous machines, where, in each section, the head machine is the bottleneck for the downstream system. We exhibit the form of an optimal control and show that it is characterized by a set of “deferral times”, one for each head machine. Machines which are upstream of a head machine simply adopt a “just-in-time” production policy. The head machines initially stay idle for a period equal to their deferral time and thereafter produce as fast as possible, until the initial shortfall is eliminated. The optimal values of these deferral times are simply obtained by solving a set of quadratic programming problems. We also exhibit special cases of re-entrant lines, for which the optimal control is similarly computable     

Development and evaluation of a Basestock-CONWIP pull production control strategy in balanced assembly systems

In this study, a new pull production control strategy called Basestock-Constant Work-in-Process (B-CONWIP) is proposed. It is used to control the flow of materials and information in balanced assembly production systems. This proposed control strategy uses one type of authorization cards called CONWIP card that limits the work-in-process (WIP) in the whole system. It has been applied in a single-product and a mixed-product assembly system balanced by two efficient Genetic algorithms introduced in literature. The performance of this control strategy is compared with another pull production control strategy called Basestock Kanban CONWIP (BK-CONWIP), which is a very promising production control strategy found in literature. The proposed strategy has two control parameters, CONWIP authorization cards and basestock levels while BK-CONWIP has three control parameters Kanban authorization cards, CONWIP authorization cards and basestock levels. The comparison is based on three performance measures average system WIP, percentage of satisfied customer demand (service level) and WIP variation between workstations. The performance of the proposed strategy B-CONWIP and BK-CONWIP is mainly similar in both types of assembly systems when mean demand rates are low with respect to mean service rates with the proposed strategy being easier to control and optimize. On the other hand, when mean demand rates are high with respect to mean service rates; B-CONWIP is preferable if service level is more important, while BK-CONWIP is preferable if WIP level is more important. Regarding WIP variation, it mainly depends on the efficiency of the balancing approach. The more efficient the balancing approach, the less WIP variation. Treating demand as lost instead of backordered results in decreased average system WIP and does not affect service levels in both PCSs. It is also shown that S-KDP is more flexible in dealing with situations of variable product mixes than d-KDP because control parameters can be used by any product which minimizes the effect of the unbalanced systems.     

并行计算机中基于令牌的许可证管理

提出一种适用于并行计算机系统的基于令牌的许可证管理模型。该模型将软件许可证的使用显式分开为申请与检出两步,许可证的释放分开为检入和回收两步,并由资源管理系统代理软件进行许可证资源的申请和回收。在此模型中,软件许可证的使用将由资源管理系统完全控制与调度,避免了现有模型中存在的资源管理系统外作业使用许可证、作业错误指定许可证信息、应用进程残留等情景下,出现用户作业因许可证不可用而造成的运行失败或资源浪费。设计了两种在现存遗留应用软件和许可证管理软件上实现基于令牌的许可证管理模型的方法,充分表明了此模型的现实意义。     

Intelligent tutoring systems: an overview

This is a non-expert overview of Intelligent Tutoring Systems (ITSs), a way in which Artificial Intelligence (AI) techniques are being applied to education. It introduces ITSs and the motivation for them. It looks at its history: its evolution from Computer-Assisted Instruction (CAI). After looking at the structure of a typical ITS, the paper further examines and discusses some other architectures. Several classic ITSs are reviewed, mainly due to their historical significance or because they best demonstrate some of the principles of intelligent tutoring. A reasonably representative list of ITSs is also provided in order to provide a better appreciation of this vibrant field as well as reveal the scope of existing tutors. The paper concludes, perhaps more appropriately, with some of the author's viewpoints on a couple of controversial issues in the intelligent tutoring domain.     

On the search of workstations arrangement in pull production systems

This research presents a model to determine the workstation arrangement and kanban number for pull production systems. Several practical production line characters are considered, and evolutionary algorithms are utilized to obtain the optimal/near-optimal result. The proposed system is a flow-shop, pull production line with N unreliable workstations and N ? 1 inter-stage buffers. Workstations may be allocated to any stage in the production line and have a different processing rate at each stage. Workstations will breakdown/recover at fixed rates, and the operating-breakdown-recovery process is formulated as a Markov process in this model. The size of the inter-stage buffers varies according to the arrangements of workstations. A model is established on the objective of minimizing the total production cost per item of the finished product. The costs considered in the system contain the allocation of workstations, operations, inventory, and production shortage costs. An evolutionary algorithm, genetic algorithm, is used to obtain the allocation of workstations in the production line.     

Main memory database systems: an overview

Main memory database systems (MMDBs) store their data in main physical memory and provide very high-speed access. Conventional database systems are optimized for the particular characteristics of disk storage mechanisms. Memory resident systems, on the other hand, use different optimizations to structure and organize data, as well as to make it reliable. The authors survey the major memory residence optimizations and briefly discuss some of the MMDBs that have been designed or implemented     

Production control of a pull system with production and demanduncertainty

We consider a continuous material-flow manufacturing system with an unreliable production system and a variable demand source which switches randomly between zero and a maximum level. The failure and repair times of the production system and the switching times of the demand source are assumed to be exponentially distributed random variables. The optimal production flow control policy that minimizes the expected average inventory carrying and backlog costs is characterized as a double-hedging policy. The optimal hedging levels are determined analytically by minimizing the closed-form expression of the cost function. We investigate two approximate single hedging policies. It is empirically shown that an approximate policy that uses a single hedging level which is the sum of a production uncertainty term and a demand uncertainty term gives accurate results for the expected average cost     

网络控制系统的发展现状及展望

探讨了网络控制系统存在的基本问题, 介绍了网络控制系统的代表性应用实例, 并从控制理论研究、网络调度协议研究以及兼顾二者的综合研究3个方面重点综述了网络控制系统的研究成果. 最后, 讨论并指出了这一领域下一步的发展方向和有待解决的新课题.     

Walsh transform theory and its application to systems analysis and control: an overview

The purpose of this paper is to provide an overview of the works dealing with the application and utilization of Walsh function series and transforms to a variety of systems and control applications. The works reviewed are classified in the following groups: 1. Walsh signal definition and generation, 2. Walsh transform Computation, 3. System analysis using Walsh functions, 4. System identification via Walsh functions, 5. Optimal control via Walsh functions, 6. Block-pulse functions, 7. Miscellaneous properties of Walsh functions, 8. Walsh-to-Fourier transform conversion, and 9. Walsh transform applications.     

Testing hybrid control systems with TTCN-3: an overview on continuous TTCN-3

TTCN-3 has gained increasing significance in recent years. It was originally developed to fit the needs of testing software-based applications and systems in the telecommunication industry and has shown its applicability to a wide range of other industrial domains in the mean time. TTCN-3 provides platform-independent, universal and powerful concepts to describe tests, especially for discrete, interactive systems. However, TTCN-3 addresses systems with discrete input and output characteristics only. The lack of powerful means that reasonably allow specifying and evaluating continuous data flow makes TTCN-3 sufficient neither for the automotive industry nor for other industries that deal with highly complex software-based control systems. This paper introduces the notion of streams, stream ports and stream templates to TTCN-3. It revises the initial design of continuous TTCN-3, a TTCN-3 extension for testing continuous or hybrid systems [20,21] and demonstrates the applicability for a case study that is typical for testing embedded control systems in the automotive industry.     

基于令牌的无线工业控制网络的信道接入控制

针对无线工业控制网络(WICN)的实时性和可靠性要求,在分析了几种常见的无线局域网的MAC协议(MACA、MA-CAW和IEEE802.11)的不足后,提出了一种基于令牌控制的MAC协议.并且还详细介绍了该协议中的令牌恢复机制、优先级机制和数据帧确认机制,并利用离散事件仿真平台OMNeT 对该协议和CSMA/CA协议进行了仿真对比试验.仿真结果表明,该协议保证了信道接入的公平性,减少了数据传输时延,增强了数据传输的可靠性,适用于无线工业控制网络.     

Type-2 fuzzy sets and systems: an overview

This paper provides an introduction to and an overview of type-2 fuzzy sets (T2 FS) and systems. It does this by answering the following questions: What is a T2 FS and how is it different from a T1 FS? Is there new terminology for a T2 FS? Are there important representations of a T2 FS and, if so, why are they important? How and why are T2 FSs used in a rule-based system? What are the detailed computations for an interval T2 fuzzy logic system (IT2 FLS) and are they easy to understand? Is it possible to have an IT2 FLS without type reduction? How do we wrap this up and where can we go to learn more?     

Digital paint systems: an anecdotal and historical overview

The history of digital paint systems derives from many things-chance meetings, coincidences and boredom, artistic license, brilliant researchers, a wealthy benefactor, and, of course, lawsuits. The author tells the fascinating story-facts first, then anecdotes-in his own words     

Co-simulation platforms for co-design of networked control systems: An overview

This paper gives an overview of the existing co-simulation platforms for co-design of networked control systems (NCSs). NCSs contain coupled control and communication perspectives. However, the existing simulators focus either on control systems or communication networks. In order to analyse the coupling effect from both sides, co-simulation method is under consideration as one of the most promising solutions. This paper briefly introduces the commonly used individual control and communication simulators. Then the existing co-simulation platforms have been reviewed and discussed. Synchronization technique is the key point toward co-simulation, thus different synchronization methods have also been summarized. Two sample case studies with results are provided to show the beneficial of co-simulations.     

Interpolation methods in model predictive control: an overview

Interpolation methods are one means of tackling the classical performance versus feasibility compromise in model predictive control (MPC). However, although some details are available in various conferences, very little has appeared in the published journals and also there is no paper pulling all the various algorithms together. Hence this article seeks to give a brief but insightful survey of existing proposals along with their strengths and weaknesses, before proposing useful avenues for future studies.     

Adaptive smart card-based pull control systems in context-aware manufacturing systems: Training a neural network through multi-objective simulation optimization

Nowadays, context aware manufacturing systems offer interesting capabilities to improve the performance of pull controlled production systems. Smart Kanbans can be used instead of physical cards, and the information become available about the production context, collected for example through sensors and RFID. Such information can be exploited by intelligent pull control strategies so as to dynamically adapt the number of cards. This is particularly useful for production systems that are subjected to unpredictable changes in the customers’ demand, and need to react quickly to preserve a high level of performance. For this reason, we aim, in this article, at proposing an intelligent system, which can communicate with the information system, whose purpose is to autonomously decide or to help managers in adding or removing cards. In this respect, we propose an approach that uses a neural network which is trained offline, directly from simulation, to decide when it is relevant to change the number of cards, and at what production stage. The learning process, based on multi-objective simulation optimization, aims at reducing the production costs as well as the number of changes to avoid nervousness. The use of stochastic simulation, allows various types of complex problems, related to manufacturing systems, to be addressed and fluctuating demand phenomena to be taken into account. The relevance of our approach is illustrated using six published adaptive ConWIP and Kanban systems. Comparisons with adaptive Kanban and ConWIP systems show that the neural network can automatically learn very relevant knowledge. Good results are obtained in terms of performance, with fewer changes in the number of cards. Several possible future research directions are pointed out.     

Distributed control of production systems

This editorial introduces the special issue of the Elsevier journal, Engineering Application of Artificial Intelligence, on Distributed control of production systems. The current technology in communication and embedded systems allows products and production resources to play a more active role in the production process. This new active capacity will generate major changes in organizations and information systems (e.g., Enterprise Resource Planning (ERP) and Manufacturing Execution Systems (MES)). New approaches are now required for modelling, testing and assessing the features made possible by the decisional and informational capabilities of these new active entities. One among the many possibilities is to use agents and holons, since agent and holon-based approaches assume interaction between intelligent entities to facilitate the emergence of a global behavior. This special issue thus focuses on the possible applications of distributed approaches for the design, evaluation and implementation of new control architectures for production systems. Both fundamental and applied research papers are presented.