提高编码器长时间定位精度的研究

1引言编码器是一种位置传感器,它是将位移信号转换为数字脉冲信号的一种装置。编码器可以测量物体所转过的角度、所经过的位移,被广泛应用于各种伺服控制中。自动化立体仓库中最重要的设备是堆垛机。对于堆垛机来说最重要的是速度和位置控制,在北京物资学院校博物馆的自动化立体仓库中,安装的是增量式编码器,这种编码器有时候会产生丢码现象,特别是货叉     

基于PLC的电梯控制系统的研究

PLC控制系统由于运行可靠,使用维修方便,抗干扰强,设计和调试周期短等,已成为电梯控制系统中常用方式。本设计基于PLC和变频器实现电梯常规控制的基础上,利用旋转编码器发出的脉冲信号构成位置反馈,连在电梯电机轴头的旋转编码器用来检测电梯的运行速度和运行方向,实现电梯精确位移控制。     

自动控制一体化系统的设计与实现

当前通过PLC来实现生产线的自动化控制应用已经非常成熟,以PLC为中心,加上光电传感检测及变频驱动或伺服驱动,构建自动化控制的一体化系统,能提高自动化控制的精度,从而提高生产效率和产品质量。文章基于PLC设计了一套工艺较复杂的自动控制一体化系统,从设计思路到系统实现两个方面进行阐述,用PLC分段多级控制各工序,用光电技术进行检测,用气动机械手及机器人进行驱动,实现一套小型生产线的上料、灌装、分拣、检测、分类、包装和入库等全智能自动化控制过程,并通过实物组建、安装及调试运行。     

基于LabVIEW的步进电机测控系统设计

文章采用虚拟仪器控制技术,用2M656驱动器驱动一步进电机,通过NI公司的USB-6251数据采集卡采集增量式编码器的转速信号,上位机运用LabVIEW图形编程语言设计步进电机的测控系统。文章的设计为步进电机测控系统寻找了一种方便灵活的设计思路,也使得步进电机的测控系统变得结构简单、运行高效。     

基于LabVIEW的步进电机测控系统设计

文章采用虚拟仪器控制技术,用2M656驱动器驱动一步进电机,通过NI公司的USB-6251数据采集卡采集增量式编码器的转速信号,上位机运用LabVIEW图形编程语言设计步进电机的测控系统。文章的设计为步进电机测控系统寻找了一种方便灵活的设计思路,也使得步进电机的测控系统变得结构简单、运行高效。     

基于西门子840D系统的数控轧辊车床的设计

轧辊作为生产工艺过程中的一个重要环节,决定了轧机的效率和轧材的质量,轧辊车床是用于生产轧辊的设备,由于普通轧辊车床采用继电器控制,需要大量人力和物力,效率较低,数控轧辊车床能够解决这一问题。文章首先对数控轧辊车床的基本原理进行了阐述,在此基础上对数控轧辊车床进行了硬件设计,数控系统采用西门子公司的840D系统,选用S7-300 PLC实现外部数字量控制,主轴驱动系统采用模数转换器ADI4和直流伺服驱动器6RA70组合,刀架和托板系统采用611D数字驱动模块和IFT6交流伺服电机。软件上通过对于MMC软件系统、NC软件系统、PLC软件系统和通信及驱动接口软件进行设置,运用STEP 7-Micro/WIN软件对PLC进行梯形图的编程,通过PC/PPI通信电缆将程序下载到PLC中,最终完成了系统的控制要求。     

基于LabVIEW的步进电机测控系统设计

文章采用虚拟仪器控制技术,用2M656驱动器驱动一步进电机,通过NI公司的USB-6251数据采集卡采集增量式编码器的转速信号,上位机运用LabVIEW图形编程语言设计步进电机的测控系统.文章的设计为步进电机测控系统寻找了一种方便灵活的设计思路,也使得步进电机的测控系统变得结构简单、运行高效.     

双电机伺服驱动系统的建模与仿真

精密测量雷达伺服系统通常采用典型的三环控制,从外到内依次是位置环、速度环、电流环,伺服驱动系统指的是速度环以内的部分,是伺服系统的基础。利用MATLAB/Simulink的辅助设计和强大仿真功能,对某雷达所采用的双电机伺服驱动系统进行了环路分析和建模,并进行了仿真试验,得到了系统动态的响应效果。该仿真方法为不同状态和参数下的伺服系统性能分析提供了科学的依据。     

异形件加工中步进电机的控制研究

加工异形件时最主要的工作就是对步进电机的控制,我们在加工异形件时选用AT89C51单片机对步进电机进行控制。在实验中单片机主要控制换相顺序、步进电机的速度及步进电机的位置。本文通过介绍在异形件加工过程中使用步进电机带动执行机构运行,设计出异形件加工时的硬件驱动和软件驱动,保证加工异形件是的质量和效率。在实际应用中,该系统运行稳定、可靠,设计简单实用。     

阀门的执行机构以及选用

一种能提供直线或旋转运动的驱动装置,它利用某种驱动能源并在某种控制信号作用下工作,这是对于执行机构最广泛的定义。执行机构使用液体、气体、电力或其它能源并通过电机、气缸或其它装置将其转化成驱动作用,基本的执行机构用于把阀门驱动至全开或全关的位置。用与控制阀的执行机构能够精确的使阀门走到任何位置。因为越来越多的工厂采用了自动化控制,人工操作被机械或自动化设备所替代,人们要求执行机构能够起到控制系统与阀门机械运动之间的界面作用,更要求执行机构增强工作安全性能和环境保护性能。在本文就阀门的执行机构及其选用做简单的介绍。     

浅谈增量型编码器在侧式刮板取料机中的应用

编码器是电感元件,具有精度高、测量准确、抗干扰能力强等特点。侧式刮板取料机中应用了编码器,使得取料量恒定这一工艺要求得到完美实现。     

变频器内建PLC在上料机改造中的应用

结合青海百通公司的高炉情况,设计出了上料机改造方案。介绍了台达变频器在高炉卷扬调速系统中的应用情况,给出了电气原理图、注意事项和常见故障处理。实际应用的良好效果验证了该系统的稳定性和可靠性。     

S7-200系列PLC在龙门吊自动纠偏控制系统中的应用

近几年来,随着造船业在我国的快速兴起,造船龙门起重机的应用越来越广泛。对于跨度大于40 m的龙门吊来说,在实际使用中,由于众多因素的影响,如,大车轨道高低和平行偏差造成运行阻力的不同,行走轮直径的偏差,电动机转速的偏差,刚、柔腿运行一段时间后会产生速度不一致的现象,导致大车啃轨,影响生产,并带来一定的隐患。文章把S7-200系列PLC与增量编码器相结合,通过变频器调速,以解决这些问题。     

无线遥控系统的分析与应用

无线遥控系统主要包括发射系统和接收系统两大部分。发射系统的主要功能是将主控信号的指令代码或电平通过编码器编码后送入发射器,通过其内部的调制电路完成对高频载波信号的控制,将携带控制信息的载波信号通过天线转化成电磁波发出;而接收系统则是将发射的电磁波接收,去除高频载波信号并解码,还原出控制信号后再对相应的电路进行控制。     

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.     

Ansätze und Ergebnisse anglo-amerikanischer M&A-Forschung

Based on a review of established U.S. management journals (1995–2003), six schools of thought are identified within the Anglo-American M&;A research: “Capital Market”, “Principal/Agent”, “Industrial Organization”, “Organizational Behavior”, “Human Resources” and “Strategic Management”. The literature review shows that the definition of M&;A success, the methods applied, and insights from empirical research differ according to the respective school of thought. Empirical studies focus on the resource combinations of merger partners, the specific circumstances of merger negotiations, and on integration management as antecedents of merger performance. Unfortunately, empirical findings have not yet provided reliable explanations for M&;A success. Based on the current state of Anglo-American M&;A research, the authors discuss implications for business practice, identify research gaps, and propose areas for future research.