一种BLDCM反电动势过零检测方法

针对传统直流无刷电动机控制系统电动机转子位置检测准确度不高的状况,介绍了一种基于DSP的无位置传感器直流无刷电动机控制系统的硬件电路组成和软件结构.通过对无刷直流电机转子位置检测研究,提出了以TMS320F2812芯片为内核的综合转子位置检测方法,通过软件算法来得到电机转子位置信息,从而在改善系统调速性能的情况下降低系统成本.     

基于硬件滤波电路的无刷直流电机转子位置辨识

反电动势过零检测是无刷直流电机无位置传感器控制中转子位置检测的主要方法之一,为消除PWM因素的影响,需要对转子位置检测电路进行滤波处理。本文采用硬件滤波器对反电动势过零检测电路进行滤波,既要考虑深度滤波带来的相移问题又要兼顾消除噪声的影响,分析滤波器的幅频特性和相频特性,根据反电动势过零检测指标要求设计滤波器参数,并用于无刷直流电机转子位置辨识和无位置传感器控制中。仿真结果和实验结果表明,所采用的滤波器及其参数能较好地检测出转子位置,可以明显提高无位置传感器无刷直流电机驱动系统的控制性能。     

一种无刷直流电机转子位置检测方法的研究

位置检测和换相准确与否,对无刷直流电机的运行有非常关键的影响。通过分析无刷直流电机间接位置检测原理,本文提出了一种新的方法来实现转子位置的检测。该方法构建一个以相磁通和相电流为输入,转子位置为输出的小波神经网络模型,并采用遗传算法来训练网络参数。经仿真验证该模型能有效地控制电机换相。     

基于高频信号注入法的永磁同步电机无传感器控制

介绍了一种基于永磁同步电机空间凸极追踪的转子位置无传感器自检测的方法.该方法采用高频电压载波注入法,通过采用外差法的转子位置跟踪观测器完成了转子位置信息的提取,实现无机械位置传感器的电机转子位置的检测.并通过仿真证明了这种方法的可行性.     

反电动势法无刷直流电动机位置检测误差分析及补偿

目前,无刷直流电动机无位盖传感器研究正受到越来越广泛的关注,而反电动势过零检测法是转子位置检测方法中技术最成熟应用最广泛的转子位置检测方法之一。但是这种方法也存在各种缺点。本文分析了反电动势过零检测法产生转子位置误差的原因,对传统的眨电动势过零检测法做了改进,并且提出了相应的补偿方法。     

IRMCF341的无位置传感器PMSM控制系统设计

针对频率自控式永磁同步电动机的转子位置检测问题,提出一种基于IRMCF341的无位置传感器PMSM控制系统,同时采用了通过测量电机定子电流来估算转子位置的方法和PID控制策略。本系统经研究与开发后,在实验样机上做了测试。结果表明,该系统的硬件和软件设计方案及无位置传感器检测方法是可行的,系统不仅获得了良好性能和高可靠性,而且减小了电路体积和噪声。     

基于ML4428的无刷直流电机无传感器的控制

介绍了目前常用的无位置传感器无刷直流电动机的控制策略,分析了反电势检测换相原理以及ML4428的功能、参数设定及应用.ML4428无传感器平滑启动无刷直流电机PWM控制器是一种较理想的无刷直流电机驱动器件.     

基于ML4428的无刷直流电机无传感器的控制

介绍了目前常用的无位置传感器无刷直流电动机的控制策略,分析了反电势检测换相原理以及ML4428的功能、参数设定及应用。ML4428无传感器平滑启动无刷直流电机PWM控制器是一种较理想的无刷直流电机驱动器件。     

基于ST7的无传感器BLDCM控制系统设计

介绍了基于ST7FMC1K2单片机控制的无位置传感器无刷直流电机控制系统的设计。该系统通过反电动势法实现位置检测,同时给出了系统的硬件的构成。阐述了利用ST7FMC1K2芯片实现无位置传感器无刷直流电机的三段式起动方法;最后通过实验证明该系统具有较宽的凋速范围、优越的静态和动态特性。此方案电路简单、可靠性高,具有较高的应用价值。     

无刷直流电动机的反电势积分法位置检测技术研究

文章提出了一种无位置传感器无刷直流电动机的控制方案。该方案采用反电势积分法获取转子位置信号,对不同转速下反电势检测电路的相位偏移进行补偿控制,并通过升频升压法实现无刷直流电动机的外同步开环启动,从而实现了无刷直流电动机的无位置传感器控制。实验结果验证了该方案的正确性。     

微机监测与铁道信号设备安全

目前我们铁路运输事业快速发展,全国各地都新建了高铁铁路。速度是提升了,安全问题也不能忽视。列车在运行过程中要想保证安全,就需要铁道各处的信号信息正确。控制台通过相关的信号设备将运行的指令传递给列车,以保证铁路的整体运行情况。在新的时期,需要能够全天候检测铁路安全的方法,以便维修人员能够及时了解问题并处理。本文通过对TJWX-2006型信号设备监测系统进行研究,来分析在铁路上使用微机来检测铁路的运行情况。这对研究信号设备安全有着积极的意义。     

防火墙在组建局域网中的应用

防火墙作为网络安全设备越来越多地应用于局域网络与公用网络的互联中,具有服务代理、包过滤、入侵检测等功能。防火墙作为一个网络互连设备,在组建网络中还有着局域网与Internet互联、隐藏防火墙外网IP地址、隐藏内部网络、IP地址重定向、安全访问控制以及构建VPN等应用。文中结合某单位的局域网规划设计就防火墙的应用作了重要的阐述。     

Would I lie to you? Self-serving lies and other-oriented lies told across different media

This study set out to investigate the type of media individuals are more likely to tell self-serving and other-oriented lies, and whether this varied according to the target of the lie. One hundred and fifty participants rated on a likert-point scale how likely they would tell a lie. Participants were more likely to tell self-serving lies to people not well-known to them. They were more likely to tell self-serving lies in email, followed by phone, and finally face-to-face. Participants were more likely to tell other-oriented lies to individuals they felt close to and this did not vary according to the type media. Participants were more likely to tell harsh truths to people not well-known to them via email.     

IPv6协议下域名系统的扩展与实现

为了实现对IPv6协议的支持，需要对现有IPv4协议下的域名系统进行相应的扩展，以使其能在IPv6协议下正确地进行IP地址与域名的正向或反向解析。域名系统的扩展主要包括以下两方面：一是增加了两个新的资源记录AAAA和A6来存储IPv6地址，以实现域名到IPv6地址的正向解析；二是增加了两个新域：ip6.int和ip6．arpa，以实现IPv6地址到域名的反向解析。文中以著名的域名系统软件BIND为对象，以Linux操作系统Redhat9作为实验平台，详细介绍了基于Linux平台的域名系统对IPv6协议的扩展与实现，从而为实现IPv4到IPv6的平稳过渡打下了坚实基础。     

From remote maintenance to MAS-based e-maintenance of an industrial process

One of the main consequences of the extended enterprise is the emergence of new forms of relationships between the customer and the supplier in order to ensure the quality of service of the object throughout the life cycle. Innovative communication and co-operation methods are needed to support these new relationships. The combination of modern information processing and communication tools, commonly referred to as tele-service, offers the technical support required to access remote information. Indeed, it is easier to transfer information and knowledge to different actors than to move an actor to the site. However, even if this technical support is necessary for information communication, it is insufficient to develop a co-operation-based working situation that involves many self-motivated customers and suppliers sharing a common goal. This synergy is an emergent property of the system as a whole, and it is not expected to be obtained as a simple sum of its components. For example, a challenging problem in the field of product manufacturing is to assist the operator in its decision-making, when the system functioning is degraded, to preserve the system under service at maximum (anticipation of the failure) while remaining it in a space of allowed operation (to avoid consequences of an error in judgement). That means an evolution from tele-service to e-work and e-maintenance in particular where the assistance to operator results from collaboration of maintenance processes and experts. Consequently, this paper examines some issues and challenges involved in the evolution from the tele-maintenance of an industrial platform to the e-maintenance, and then proposes a multi-agent system-based collaboration as a solution to implement the e-maintenance experiments.     

基于P2P覆盖树网络的流媒体传输技术优化研究

PeerCast是一个基于P2P网络的流媒体传输系统,各节点被组织成树状来进行数据的分发.但没有一个有效的机制来维护树的平衡和保证所选取的父节点是最佳的节点.在此基础上,对该系统进行优化,在媒体数据包上加一个字节用来标识当前节点与根节点的距离,并对节点间响应消息进行优化.实验结果表明,这些优化措施能够有效的维护树的平衡和降底数据传输时延.     

Naturalistic decision-making in expert badminton players

This paper reports on a study of naturalistic decision-making in expert badminton players. These decisions are frequently taken under time-pressured conditions, yet normally lead to successful performance. Two male badminton teams participated in this study. Self-confrontation interviews were used to collect data. Inductive data analysis revealed three types of intentions during a rally: to maintain the rally; to take the advantage; and to finish the point. It also revealed eight types of decision taken in this situation: to ensure an action; to observe the opponent's response to an action; to realize a limited choice; to influence the opponent's decision; to put pressure on an opponent; to surprise the opponent; to reproduce an efficient action; and to play wide. A frequent decision was to put pressure on the opponent. Different information and knowledge was linked to specific decisions. The results are discussed in relation to research that has considered naturalistic decision-making.     

A two-layered interface architecture

The problems of interfacing to external subsystems and using multiple paradigms in a single software system center on resolving the impedance mismatch (the differences in the data models and thought patterns of each paradigm) and how to reflect the differences across the language boundary. One technique is to build an interface between the two paradigms. The interface should strive to resolve the mismatches while providing access to those language features valuable to the problem solution. This means that semantic issues as well as syntactic issues must be addressed. Features of the implementation languages that contribute to the mismatch need to be identified and examined in order to develop a solution. This paper describes a two-layer architecture based upon the idea of abstract interfaces. This architecture appears to provide a basis for interfacing programming languages to object databases which addresses the semantic gap, or impedance mismatch, between the two as well as the syntactic differences.     

在教育中加强网络意识

随着当代信息技术向中小学教育的扩展,校园网络的建设已成为许多学校的议事日程。计算机网络应用到教育中,不但有利于激发学生产生主动学习的兴趣,而且还有利于学生综合能力的培养,同时计算机网络的便捷性也有利于提高远程教学质量。所以我们要依托校园网,营造数字化的校园环境,综合利用各种教学方式,充分发挥网络教学的优势,以获得最佳的教学效果。     

网络时代拓展高校图书馆学习空间的思考

随着网络时代的到来,到图书馆的到访读者非减而增,阅览座位需求缺口极大。为此,笔者走访调查,根据高校图书馆学习空间现状,研究网络时代如何拓展高校图书馆学习空间,从图书馆规划设计、利用网络优势建立自动化系统、加强读者自律等方面进行探讨,大胆创新图书馆阅览室管理模式,提高阅览室利用效率和服务质量。为拓展高校图书馆学习空间探索新途径。