Vibration analysis of cable-driven parallel manipulators

A cable-driven parallel manipulator is a manipulator whose end-effector is driven by a number of parallel cables instead of rigid links. Since cables always have more flexibility than rigid links, a cable manipulator bears a concern of possible vibration. Thus, investigation of vibration of cable manipulators caused by cable flexibility is important for applications requiring high system stiffness or bandwidth. This paper provides a vibration analysis of general 6-DOF cable-driven parallel manipulators. Based on the analysis of the natural frequencies of the multibody system, the study demonstrates that a cable manipulator can be designed stiff enough for special applications like the cable-manipulator based hardware-in-the-loop simulation of contact dynamics. Moreover, under an excitation, a cable may vibrate not only in its axial direction, but also in its transversal direction. The paper also analyzes the vibration of cable manipulators caused by cable flexibilities in both axial and transversal directions. It is shown that the vibration of a cable manipulator due to the transversal vibration of cables can be ignored comparing to that due to the axial flexibility of cables.     

Broadcasting scheme with low client buffers and bandwidths for video-on-demand applications

Efficient data broadcasting is independent of request arrivals, and is thus highly promising when transmitting popular videos. A conventionally adopted broadcasting method is periodic broadcasting, which divides a popular video into segments, which are then simultaneously broadcast on different data channels. Once clients want to watch the video, they download the segments from these channels. The skyscraper broadcasting (SkB) scheme supports clients with small bandwidths. An SkB client requires only two-channel bandwidths to receive video segments. This work proposes a reverse SkB (RSkB) scheme, which extends SkB by reducing buffering spaces. The RSkB is mathematically shown to achieve on-time video delivery and two-channel client bandwidths. A formula for determining the maximum number of segments buffered by an RSkB client is presented. Finally, an analysis of RSkB reveals that its client buffer requirements are usually 25–37% lower than SkB. Extensive simulations of RSkB further demonstrate that RSkB yields lower client buffer demand than other proposed systems.

振弦式力传感器一带二接线技术试验研究

大坝安全监测所用的振弦式测力监测仪器一般采用四芯屏蔽电缆实现信号输入和输出。”一带二”技术是在实际工作中根据施工现场的需要总结出来的一种应急补救措施。当振弦式仪器的信号电缆在埋设施工后,发生电缆故障时可以采取该技术措施来进行补救处理。试验结果表明监测信号完整且相互之间无干扰。     

广电宽带数据业务用户常见故障及排除

利用有线电视网络资源开展数据增值业务已是大势所趋，而作为广电宽带数据网络运营商，在业务发展的同时，也面临用户故障维护的新挑战。本文结合广电宽带数据网络的运营维护实践，总结了采用以太网和Cable Modem两种接入方式，在运营过程中的常见用户故障及排除。     

三种主流宽带小区接入方式的比较与研究

通过对ADSL、LAN、HFC三种宽带接入方式原理及实际应用范围,并从运营商和用户两个角度对宽带小区接入方式的优劣予以阐述.     

带有连接电缆的"NTN"校准技术

在利用“NTN”校准技术对取样示波器进行校准时，为保证校准精度，要求两台取样示波器的输入端直接对接。但在实际运用中，为方便起见，常常将两台取样示波器的输入端用电缆连接在一起。显然，电缆的接入。将对“kick-out”脉冲的响应波形产生影响，这就要求在数据处理中扣除电缆的影响。详细介绍了带有电缆的“NTN”校准技术的实验设置、数据预处理算法(包括去时基抖动处理、消除取样电路的非对称性的方法等)、“kick-out”脉冲的反卷积分离以及扣除电缆影响的算法。最后，给出取样示波器阶跃响应的波形并进行了评价。     

电缆故障指示器及其使用情况评析

本文通过介绍近年来在广州供电分公司配网中使用较为广泛的三种电缆故障指示器,分析论述了其在查找故障点等方面的优势,同时也指出了其在使用过程中存在的问题,并提出了解决问题的方法。     

斜拉桥张拉索张力的测定

基于斜拉桥拉索的受力特点,提出一种索张力测定的新方法.文中研究了索张力传感器的测试机理,导出了传感器测力信号与索张力的关系.研究结果表明:该测试方法能有效地消除支座条件、拉索自重及索抗弯刚度等因素对测力信号的影响,可实现斜拉桥张拉索受力的精确、快捷测量.     

有线电视业务收入结算摊分初探

讨论有线电视业务收入结算摊分的定义及分类 ,详细分析收视费结算摊分的项目、结算原则和计算模型 ,简要介绍结算摊分的计算机管理     

有线电视网络的经营发展方向

在信息社会,人们迫切希望计算机能以人类习惯的方式提供信息服务,多媒体技术应运而生。三网融合己经开始,广电借助三网融合之机遇,有了涉足电信互联网业务的条件,如何推动广电业务加速向电信领域渗透,正成为广电产业经营思考的问题。