SLIDING MODE CONTROL SYNTHESIS OF UNCERTAIN TIME‐DELAY SYSTEMS

Sliding mode control synthesis is developed for a class of uncertain time‐delay systems with nonlinear disturbances and unknown delay values whose unperturbed dynamics is linear. The synthesis is based on a new delay‐dependent stability criterion. The controller constructed proves to be robust against sufficiently small delay variations and external disturbances. An admissible upperbound such that the corresponding closedloop system remains globally asymptotically stable for each delay value less than this up‐perbound is derived. Performance issues of the controller are illustrated in a simulation study.     

ESTIMATION OF AMPLITUDE OF OSCILLATIONS IN SLIDING MODE SYSTEMS CAUSED BY TIME DELAY

Time delay does not allow realizing ideal sliding mode but implies oscillations in the state variable space. An estimation technique is developed for an upper bound of oscillation amplitude induced by bounded uncertain time delay presence.     

“灵活”的滑动窗口算法及其计算量的估计

通过对预存储空间的充分利用,首先给出了一种"灵活"的滑动窗口算法,然后对该算法所涉及的整数表示方法的汉明重量进行了仔细的估计.通过与原有滑动窗口算法、m-ary算法的平均模乘次数的比较,最后得出"灵活"的滑动窗口算法在基本保持原有滑动窗口算法计算复杂度的同时,克服了原有算法中对预存储空间的限制.     

SLIDING MODES, Δ‐MODULATORS,AND GENERALIZED PROPORTIONAL INTEGRAL CONTROL OF LINEAR SYSTEMS

In this article, we attempt a reapproachment between sliding mode control of linear systems and classical control through the possibilities of evading state measurements and circumventing the use of asymptotic state observers in the sliding surface synthesis. This is shown to be possible thanks to the use of integral state reconstructors combined with iterated integral output error compensation. The proposed scheme is also robust with respect to unmatched perturbation inputs. A connection between sliding modes and classical analog Δ‐modulators, and their natural generalization, is also brought to attention as a tool for the realization of integral reconstructor based sliding mode control schemes.     

高速以太网技术和交换式以太网技术剖析

高速以太网和交换式以太网技术是解决传统以太网的带宽危机的两项重要技术。本文中，首先对高速以太网和交换式以太网技术进行了深入，全面地分析，最后，针对结合这两项技术的产品ＦａｓｔＳｗｉｔｃｈ１０／１００利用对等通信性能的测试程序，对这现代项技术所带来的性能改进进行了定量分析。     

MODEL‐REFERENCE OUTPUT‐FEEDBACK SLIDING MODE CONTROLLER FOR A CLASS OF MULTIVARIABLE NONLINEAR SYSTEMS

This paper proposes an output‐feedback sliding mode control design for a class of uncertain multivariable plants with nonlinear disturbances. The approach used here is based on the control parameterization employed in model‐reference adaptive control. The disturbances are allowed to be unmatched and to depend not only on the plant output but also on its unmeas‐urable state. A less restrictive condition on the uncertainty of the high frequency gain matrix is also obtained.     

企业数据备份系统分析与研究

通过分析企业信息系统对数据备份的需求,给出了大中型企业建立层次化数据备份系统时一般需要考虑备份软件,大容量的磁带库,SAN存储网络,数据库在线备份,无人职守备份管理等,必要时还应该建立异地容灾中心.     

ROBUST STABILIZATION OF A CLASS OF UNCERTAIN TIME DELAY SYSTEMS IN SLIDING MODE

This paper addresses the problem of robust stabilization of a class of uncertain systems subject to internal (i.e., in the state) point delays, external (i.e., in the input) point delays and nonlinear disturbances by using sliding mode control. Methods for the design of sliding mode controllers based on state feedback, static output feedback and dynamic output feedback, respectively, are proposed. Sufficient conditions for the asymptotic stability and robustnesss of the closed–loop systems are given under a wide class of admissible nonlinear disturbances. © 1997 by John Wiley & Sons, Ltd.     

基于模糊逻辑的安全苛求系统失效模式与影响分析研究

针对传统RPN(风险优先数)方法在安全苛求系统FEMA(失效模式与影响分析)过程中的不足,提出一种基于FRPN(模糊风险优先数)的新方案,即运用模糊逻辑理论进行定量的FMEA。通过运用模糊加权几何平均计算失效模式的FRPN,据此对失效模式的风险程度排序,寻找影响系统安全性的主要因素,并将其作为改善对象。最后将该方法应用到高速铁路列控系统的FMEA过程中,结果表明,所提出的FRPN方法比传统RPN更加科学严谨,更能紧密联系应用环境,具有较高的科学性和实用价值。     

快速求取临界增益及周期的数值分析方法

详细介绍了一种应用临界比例度法的思想,并结合计算机快速数据处理能力,智能地分析辨别过渡过程曲线,找出临界增益及周期的数值方法,并进而整定PID参数.整定效果证明了此法的有效性.     

PERFORMANCE FUNCTIONS AND SUBLEVEL SETS FOR FREQUENCY DOMAIN DESIGN OF SINGLE LOOP FEEDBACK CONTROL SYSTEMS WITH PLANT UNCERTAINTY

The frequency domain design of control systems involves the fitting of a designable complex function of frequency (e.g., loop transfer function, compensator transfer function) to specification derived constraints in the design space ℂ×ℝ. In the classical Bode approach and its recent modifications the designable function is the loop transfer function, the specifications lead to constraints on the magnitude of the loop transfer function and the constraints have circular cross-sections in ℂ. In more recent design procedures (e.g., H _∞ optimization or QFT) the specifications lead to more complex constraint surfaces in ℂ×ℝ and the design procedure must fit the designable function to these constraints. In this paper we develop explicit representations of some important ℂ×ℝ constraint surfaces encountered in the design of SISO control systems with both non-parametric (unstructured) and parametric plant uncertainty and study the characteristics of their frequency axis cross-sections or level sets: important information use in the fitting process. The results are presented in two systems of co-ordinates (i.e., designable functions): nominal closed loop transfer function T_o(jω) and and nominal open loop transfer function L_o(jω). While the results in T_o co-ordinates are more useful when using mathematical optimization (e.g., H _∞ optimization techniques), the results in L_o co-ordinates have significant advantages of insight and ease of graphical manipulation as demonstrated in QFT. The inclusion of results in both sets of co-ordinates increases their utility for workers in both areas and also reveals some links between these two different approaches. © 1997 by John Wiley & Sons, Ltd.     

马尔科夫链在域名信息探测中的应用

域名信息探测是企业网络安全评估和渗透测试的重要内容。针对当前蛮力扫描和DNSenum等基于字典的探测方法普遍存在获取信息不全、过度依赖数据字典的问题,建立了基于Markov链的域名结构模型,提取出域名起始字符集合与分布、状态转移矩阵等域名统计与分布特征,提出了一种新域名的生成算法。对.com、.net和.org三类通用域名进行抽样探测,实验结果表明,该算法在探测域名数量、探测域名集的区分度和探测效率上优于现有方法 DNSenum。     

ON STABILITY AND PERFORMANCE OF INDUCTION MOTOR SPEED DRIVES WITH SLIDING MODE CURRENT CONTROL

A novel inner loop sliding mode current control scheme for induction motor speed drives is proposed in this paper. The controller design is based on the nonlinear mathematical model of an induction motor in a coordinate system oriented along the rotor flux. The parameters of the PI speed controller are taken into consideration in the inner loop sliding mode current control. Rigorous stability verification for the overall system is provided in this paper. The chattering in sliding mode control is attenuated using the reaching law design method. The experimental results show that the proposed approach exhibits robust tracking performance in the presence of motor parameter variations and load disturbances.     

网络环境下高校自动排课系统中教室安排算法的设计与分析

自动排课系统在高校教学管理中处于重要位置，也是一个难题。本文设计了一种高校自动排课系统中教室安排算法，对算法中四类不同的教室安排方式结果的合理性和效率进行了详细地比较和分析，设计并实现了高校教室安排与管理系统。     

基于网络划分和并行运算的P/G布线网络快速分析算法

提出了一个基于网络划分和分布式并行运算的P/G网快速验证方法.对于各子网运算,采用带加速子网运算策略的Cholesky分解法;并根据各个子网运算相互独立的特点,采用基于MPI(Message Passing Interface)的并行结构对子网络运算进行分布式并行运算.实验证明,该快速验证方法在运算时间和内存占用上效果十分良好.     

OpenLDAP性能测试分析与优化

OpenLDAP是开源的LDAP服务器,在分布式目录服务中得到了广泛应用.详细分析了OpenLDAP目前所采用的独特"线程池"模式.通过比较OpenLDAP在不同模式下的性能差异,发现原模式对LDAP操作存在较大的响应延迟.进一步给出了改进的"线程池"模式,该改进模式能够降低LDAP操作响应延迟.最后通过仿真实验,表明改进模式可以明显改善OpenLDAP的性能.     

分布系统中多米诺效应的分析与消除

分布系统中发生故障后,错误信息在进程间的传播,以及由此引起的系统恢复过程中的多米诺效应是分布系统容错恢复技术所面临的最重要与最困难的问题.目前各种研究工作偏重于具体的系统动态恢复技术.本文的研究重点在于首次揭示多米诺效应本身固有的数量特征及其与分布系统技术参数间的联系,给出多米诺效应动态消除技术,引入系统额外开销的下限,并针对动态技术的缺点,探讨多米诺效应的静态消除技术,为解决困难开辟新途径.     

几种主流大规模并行计算机实现技术的对比分析

本文主要分析了ＣＭ－５３、ＫＳＲ２、Ｐａｒａｇｏｎ ＸＰ／Ｓ和曙光１０００这几种当前国内外典型的大规模并行计算机的系统结构、互连网络等方面的一些基本情况，着重比较了它们各自的互连网络的实现技术及特点。     

多指标系统分析及应用

为了得到多指标系统合理的指标权值,本文建立了一个组合赋权模型,该模型综合主观赋权法和客观赋权法的优点,计算出系统的指标权值,此权值优于单纯用一类方法得到的结果,本文综合运用组合赋权模型和ＩＳＭ法对系统进行结构分析,准确而直观地反映了系统的内部结构。