用TMS320LF2407实现无刷直流电机的变结构控制

本文介绍了无刷直流电机的一种变结构控制方法。采用TMS320LF2407芯片,很方便地实现了电机在无刷方式和他控式同步方式之间的切换,发挥了两种方式的优点,有较好的动态和稳态性能     

用TMS320LF2407实现无刷直流电机的变结构控制

本文介绍了无刷直流电机的一种变结构控制方法.采用TMS320LF2407芯片,很方便地实现了电机在无刷方式和他控式同步方式之间的切换,发挥了两种方式的优点,有较好的动态和稳态性能.     

无刷直流电机的设计与仿真研究

无刷直流电机是一种集电机和电力电子一体化的高科技产品,它具有其他电子产品所没有的独特优势,所以被广泛运用在工业生产等多个领域。为了更好地了解掌握无刷直流电机的设计和运作原理以及仿真研究,文章针对无刷直流电机进行了相关的分析与探讨。     

无刷直流电机的设计与仿真研究

无刷直流电机是一种集电机和电力电子一体化的高科技产品，它具有其他电子产品所没有的独特优势，所以被广泛运用在工业生产等多个领域。为了更好地了解掌握无刷直流电机的设计和运作原理以及仿真研究，文章针对无刷直流电机进行了相关的分析与探讨。     

试析优化智能控制器在BLDCM控制系统中的研究现状

随着人工智能技术的不断发展,专家系统、模糊理论、人工神经元网络等智能控制的最新成果开始进入电机控制领域,给进一步提高无刷直流电机的控制性能提供了一条全新的途径。本文结合国内外无刷直流电机控制系统的研究现状,将现代计算机应用中最前沿的最优化与智能控制与传统的PID控制器结合在一起进行研究,针对有非线性复杂特性的控制对象或控制过程,传统控制理论中的PID控制器的难以实现满意的效果。研究利用最优化算法优化智能PID控制如:(fuzzy-PID、BP-PID、自适应PID控制、专家PID、基于遗传算法整定的PID控制器),完善智能控制方法在BLDCM控制系统中的应用。     

无刷直流电机单神经元自适应智能调速系统

本文针对无刷直流电机设计了一种可在线学习的单神经元自适应PID智能控制器,通过有监督的Hebb学习规则来调整权值,每一次采样都直接根据反馈误差对神经元权值进行调整,实现PID三个参数的自适应,采用分段线性化方法建立无刷直流电机反电动势梯形波,采用滞环电流控制器实现电流调节,并在Matlab/Simulink仿真平台上搭建仿真模型,结果表明智能PID控制效果和鲁棒性都优于常规PID,大大提高了系统的跟随性,能满足无刷电机系统对实时性的要求。     

DE优化模糊神经网络算法在无刷直流电机控制系统中的应用

DE优化模糊神经网络算法是一种利用模糊神经网络控制器进行计算的方式,该算法避免了以往DE模糊神经网络连接权值和阈值选择上的随机性缺陷,从而能发挥DE模糊神经网络泛化的映射能力。本文就DE优化模糊神经系统在无刷直流电机控制系统中的应用,进行了系统的研究和探讨。     

基于DSP的无刷直流伺服电机全数字控制系统研究

本文主要介绍了全数字无刷直流电机的伺服系统,该系统主要以DSP为核心,并且采取了IR2130、IPM所组成的功率变换器以及驱动电路,全面的实现了全数字PWM控制体系,该系统结构非常简单,并且具有明显的效果,而经过实验表明,该系统的调整范围也较为广泛,对其性能的相关控制也较好。本文主要内容共分为三个方面,第一部分主要对于无刷直流伺服电机控制系统的相关概念进行了详细的叙述,第二部分则是对于系统的相关硬件配置进行了深入的分析与探讨,最后对控制提出了一定的策略。     

电动车永磁直流无刷电机温度场分析及性能影响

文章以电动车使用的永磁无刷直流电机为研究对象,采用有限元法,利用传热学的理论和方法建立电机的边界条件,利用ANSYS有限元软件分析计算得出电机的温升概况,及温升对电机性能的影响,然后和实际的实验数据进行比对验证。     

国内市场

微电机"十五”优先发展的重点产品 --无刷直流电动机.电机电刷是影响电机可靠运行及寿命的薄弱环节,应用电子技术发展无刷电机,实现高可靠性、长寿命、无须维护的直流电机是今后主要发展方向.     

Development in Information and Communications Technology (ICT) Statistics at the Australian Bureau of Statistics

This paper outlines the ICT statistical developments that the ABS has undertaken over recent years. These developments have been on both the supply side (ICT industry) and the demand side (use of IT by sector). The content of ABS ICT surveys has changed significantly over the last few years and are expected to develop further in line with industry changes and emerging policy needs.
Recent developments in household collections have been the inclusion of IT use questions in the 2001 Census of Population and Housing and in various ABS social surveys such as Children's Participation in Culture and Leisure Activities. Annual business IT use surveys are now conducted and include topics such as Internet commerce and IT security. Biennial ICT industry surveys are conducted to provide data on ICT production, imports and exports, ICT industry employment, performance and structure information. An Internet activity survey is run every six months and provides regional Internet access details and infrastructure details on Internet service providers.
A major development for 2002–03 will be the compilation of an ICT satellite account. ABS intends to produce an ICT Information Development Plan to guide its future statistical development work in the ICT field.     

Value at Risk in the Suburbs: Eminent Domain and the Geographical Politics of the US Foreclosure Crisis

Several US counties and local governments have recently considered a novel solution to the foreclosure crisis. They plan to use eminent domain to compel the owners of mortgage debt—and specifically of private‐label mortgage‐backed securities—to sell the debt to the government at a price reflecting the loan's market value. The government would then restructure the debt and resell it to new investors. The plans are striking because—in contrast to both development‐driven eminent domain and the federal subprime bank bailout—they would force investors to assume asset devaluation and increased long‐term risk. Notably, the plans have emerged as an instance of financialization‐focused politics in suburbs and suburban cities of color, specifically majority‐black and ‐Latino/a suburbs. Local support for the plans, we argue, is rooted in the long‐term disinvestment of these ‘suburbs of exception', which became targets of subprime lending and eventually sites where the ‘financial exception' has been localized. But these demographic shifts, fragmentation and fiscal pressures have at the same time created a suburban political terrain in which the plans have gained their strongest political support.     

Towards a Theory of Serendipity: A Systematic Review and Conceptualization

Serendipity – the notion of making surprising and valuable discoveries – plays a major role in the success of individuals and organizations alike. Previous research has established the importance of serendipity and identified important individual- and organizational-level antecedents. However, the literature has been dispersed and the boundaries of the concept have been blurry, leading to a lack of conceptual clarity and structure, and thus limiting validity and managerial actionability. Based on a systematic literature review, I synthesize existing management-related research on serendipity and explicate the emergence and composition of serendipity in the organizational context. I first identify three necessary conditions that differentiate serendipity from related concepts such as luck or targeted innovation: agency, surprise, and value. Then, I draw from the literature on sensemaking, event-based theorizing, and quantum-based approaches to management to conceptualize the process of cultivating serendipity in the organizational context as a process of enabling potentiality and materialization, and develop a multi-level theory of (cultivating) serendipity. This conceptualization contributes to our collective understanding of how, why, and when (i.e., under what conditions) organizations can leverage the value in the unexpected, which opens up fruitful avenues for further research.     

Accountability of NGOs in Bangladesh A critical overview

NGOs in Bangladesh have been recognized as effective change agents in the socio-economic arena throughout the world. Their contributions in micro credit, non-formal education and primary health care are widely known. NGOs play a significant role in society. NGO accountability, as a result, has become a critical issue. NGO accountability in Bangladesh has been examined here in relation to patrons, clients and themselves. Of the three relationships only accountability to patrons is in a near satisfactory state. Accountability to clients is handicapped by lack of opportunities of beneficiaries to participate meaningfully in NGO policy making. Accountability to themselves is adversely affected due to the adherence to a strictly hierarchical system and the influence of founding and charismatic NGO leaders.     

Towards an Asian model of human resource management? A comparative analysis of China,Japan and South Korea

There has been much discussion regarding the possible decline and weakening of national systems of human resource management (HRM). Yet, culture and institutions are often cited as the major stumbling blocks to this outcome. Such constraints may dissipate in the analysis, particularly if ‘regional clusters’ are considered where geographic and cultural closeness and ‘openness’ to similar economic pressures exist. In such cases, it might be postulated that convergence in HRM will occur. We argue that China, Japan and South Korea represent such a cluster. This article examines these countries, to see if a degree of convergence is taking place and if it is towards an identifiable ‘Asian’ model of HRM. A model of change is presented that distinguishes between levels of occurrence and acceptance. Details of the development and practice of HRM in each country are then set out. The article ends with a discussion and implications section and a brief conclusion.     

The Creation of the Office for National Statistics

A new Office for National Statistics was created in the United Kingdom in 1996 following a series of developments designed to strengthen the relevance and integrity of statistics. This paper describes these fundamental changes and sets out a blueprint for future progress. It also sets current developments in the United Kingdom in an historical and international context.     

What helps? Women engineers' accounts of staying on

We have considerable understanding of the obstacles that women engineers encounter and the reasons that they leave the field, but we know less about what enables them to remain. Adopting an interpretivist approach, this article examines how a group of British women engineers in two FTSE 100 companies account for “staying on” in their male‐dominated work settings. We delineate four specific forms of help that facilitate women's retention in the field. We argue that exposure to help leads to women developing a habitus that enables them to continue working in engineering. To conclude, we draw on our findings to outline HR practices that will facilitate supportive relationships in the workplace and pave the way towards developing more positive organisational climates.     

论现代物流企业的发展观

物流业经过诸多年的发展目前已经成为最热门的行业之一,物流企业的注册数量也与日俱增,达到前所未有的规模。毋庸置疑,任何企业都希望自己迅速做强做大,并成为真正现代物流企业的典型代表,要实现这一目标一个首要问题就是要解决现代物流企业的发展观问题。     

浅谈大体积混凝土裂缝的控制

大体积混凝土的裂缝问题是实际工程中长期困扰工程技术人员的问题,其控制技术的研究是混凝土结构研究的热点问题,具有重大的学术价值和潜伏的工程背景。     

Supply Chain Strategies in the UK Fashion Industry—The Rhetoric of Partnership and Realities of Power

This paper focuses on the fashion industry, one characterised by issues such as dramatic shifts in the scale and power of major retail buyers in the market, the advent of retailer own brands, and the nature of sourcing and supply chain decisions, issues that are increasingly global in nature. The aim of this research is to explore the nature of relationships between UK high street multiple fashion retailers and their contracted suppliers, many of whom are entrepreneurial firms by most definitions of the term. Four core themes emerge from the literature and provide a framework for the research, namely, power, process, partnership, and people. The research approach was qualitative, and conducted over a period of twelve months. The paper ends with an agenda for future research.