Boundedness and Global Stability of a Nonlinear Congestion Control With Delays

This note concerns the global dynamics of a “dual” nonlinear congestion control with time-delays. It has been shown that such control laws are able to maintain local dynamic stability around their unique equilibrium point for networks of arbitrary delay, capacity and topology. We focus here on the case of a single bottleneck network, shared by traffic sources with heterogeneous delays. We first prove that, for any parameter values, an a priori bound can be given on the system state after a certain amount of time. Next, we prove global exponential stability of the delay-differential equations under constraints on its gain parameter and the delays; these are more restrictive than conditions for linear stability, but only mildly so in the homogeneous delay case. The proof is based on a detailed investigation and bounding of the system trajectories.     

Internet拥塞控制及其稳定性分析

随着网络时代的到来,各种资源的传输大量地依赖于网络,造成了网络拥塞日益严重,如何解决拥塞,高效且充分地利用网络资源,成为目前急需解决的问题。研究了TCP拥塞控制算法中的一些问题。重点对TCP协议中拥塞控制算法的策略方案进行了分析和比较。     

时延网络控制系统的稳定性分析

为保证闭环系统的全局渐进稳定性,系统的时延必须是有界的。本文中讨论了具有网络诱导时延的网络控制系统的模型,同时给出了最大允许传输间隔以及一个实际例子。实践证明本文中给出的方法在简单的系统中是十分有效的。接着提出了一个减小网络诱导时延的算法,仿真结果表明了该方法的有效性。     

网络拥塞中的非线性现象与控制

由于Internet通信量的快速增长和爆炸式膨胀,拥塞控制在当今正日益变得重要。Internet拥塞控制又存在着固有的、非常复杂的非线性动态问题。在本文中,我们利用随机早期检测算法(RED)研究了TCP的非线性现象,如RED的分叉、混沌以及鲁棒德定性,同时考虑了线性和非线性的丢包函数。我们还证明了RED和PD-RED算法控制混沌与分叉的稳定性。仿真结果清楚展现以下两个算法结果的有效性。     

具有时延的非线性对偶拥塞控制算法的稳定性*

最近几年来在网络拥塞控制的动力学分析方法上有了很大的进展,尤其是在利用控制与优化理论分析和设计拥塞控制算法方面。首先介绍了基于优化理论提出的对偶控制算法及其一般分析框架,分析了在一种简化了的网络情形下的稳定性,最后指出一些存在的问题和下一步的工作。     

Stability Analysis and Design of Impulsive Control Systems With Time Delay

A class of impulsive control systems with time-varying delays is considered. By establishing an impulsive delay differential inequality, we analyze the global exponential stability of the impulsive delay systems and estimate the exponential convergence rate. On the basis of the analysis, a design procedure of impulsive controller is presented. The designed impulsive controller not only can globally exponentially stabilize the time delay systems, but also can control the exponential convergence rate of the systems. Two numerical examples are given to illustrate the effectiveness of the method.     

互联网络拥塞控制分析与研究

随着互联网业务量的迅猛增长以及新业务的不断涌现,网络拥塞控制问题已成为研究热点。本文在针对拥塞控制问题做了大量研究工作的基础上,讨论了拥塞和拥塞控制算法的概念和技术,重点分析与研究了理想拥塞控制协议及其评价指标。     

Stability Analysis of Constrained Nonlinear Model Predictive Control with Terminal Weighting

This paper investigates stability of model predictive control (MPC) for nonlinear constrained systems. New stability results for the MPC algorithms with terminal weighting are proposed using the dynamic programming method, which gives new criteria for choosing state, control and terminal weighting in the performance index to achieve stability of MPC algorithms. Illustrative examples are given to show that by combining this condition with existing ones, much less conservative results can be generated.     

On Uniform Global Asymptotic Stability of Nonlinear Discrete-Time Systems With Applications

This paper presents new characterizations of uniform global asymptotic stability for nonlinear and time-varying discrete-time systems. Under mild assumptions, it is shown that weak zero-state detectability is equivalent to uniform global asymptotic stability for globally uniformly stable systems. By employing the notion of reduced limiting systems, another characterization of uniform global asymptotic stability is proposed on the basis of the detectability for the reduced limiting systems associated with the original system. As a by-product, we derive a generalized, discrete-time version of the well-known Krasovskii-LaSalle theorem for general time-varying, not necessarily periodic, systems. Furthermore, we apply the obtained stability results to analyze uniform asymptotic stability of cascaded time-varying systems, and show that some technical assumptions in recent papers can be relaxed. Through a practical application, it is shown that our results play a similar role to the classic LaSalle invariance principle in guaranteeing attractivity, noting that reduced limiting systems are used instead of the original system. To validate the conceptual characterizations, we study the problem of sampled-data stabilization for the benchmark example of nonholonomic mobile robots via the exact discrete-time model rather than approximate models. This case study also reveals that in general, sampled-data systems may become non-periodic even though their original continuous-time system is periodic. A novel sampled-data stabilizer design is proposed using the new stability results and is supported via simulation results.     

非线性时延网络控制系统的模糊建模与控制

针对时变网络诱导时延小于一个采样周期的非线性时延网络控制系统,讨论系统的稳定性及控制器的设计方法.利用基于“IF-THEN”规则的模糊模型近似系统中的非线性,将时延的不确定性转化为系统参数的不确定性,从而将此类非线性网络控制系统建模为一类具有参数不确定性的离散Takagi-Sugeno（T-S）模糊模型.基于建立的模型,利用Lyapunov方法和线性矩阵不等式方法,分析了系统的稳定性及模糊状态反馈控制器的设计方法,最后通过仿真实例验证了所提出方法的有效性.     

Tracking Control of Uncertain Nonlinear Systems With Unknown Constant Input Delay

A robust delay compensator has been developed for a class of uncertain nonlinear systems with an unknown constant input delay.The control law consists of feedback terms based on the integral of past control values and a novel filtered tracking error,capable of compensating for input delays.Suitable Lyapunov-Krasovskii functionals are used to prove global uniformly ultimately bounded(GUUB)tracking,provided certain sufficient gain conditions,dependent on the bound of the delay,are satisfied.Simulation results illustrate the performance and robustness of the controller for different values of input delay.     

Stability Analysis of Systems With Time-varying Delay via a Novel Lyapunov Functional

This paper investigates the stability problem for time-varying delay systems. To obtain a larger delay bound, this paper uses the second-order canonical Bessel-Legendre (B-L) inequality. Secondly, using four couples of integral terms in the augmented Lyapunov-Krasovskii function (LKF) to enhance the relationship between integral functionals and other vectors. Furthermore, unlike the construction of the traditional LKF, a novel augmented LKF is constructed with two new delay-product-type terms, which adds more state information and leads to less conservative results. Finally, two numerical examples are provided to demonstrate the effectiveness and the significant improvement of the proposed stability criteria.      

基于价格的拥塞控制模型扩展

基于价格的拥塞控制模型将网络拥塞控制问题抽象为聚合效用最大化的优化问题,已经成为拥塞控制机制设计和分析的一般框架。然而简化的线性模型与现实网络环境有一定差距,不能准确有效地指导新协议的设计与分析。因此,近年来研究人员正试图结合新的技术和应用,扩展完善基于价格的模型,建立更为准确有效的模型来反映现实的网络环境。为了系统地了解该领域研究工作的进展,本文首先简要回顾了基于价格的模型,分析其不足,介绍近年来在模型扩展方面的研究工作,最后指出几个有意义的研究方向。     

互联网端到端拥塞控制研究综述

随着互联网规模的增长,互联网上的用户和应用都在快速地增长,拥塞已经成为一个十分重要的问题.近年来,在拥塞控制领域开展了大量的研究工作.拥塞控制算法可以分为两个主要部分:在端系统上使用的源算法和在网络设备上使用的链路算法.在介绍拥塞控制算法的基本概念以后,在源算法和链路算法两个方面总结了拥塞控制算法的研究现状,并分析了进一步的研究方向.     

网络控制系统中时延的稳定性分析

对时延网络控制系统的稳定性进行研究,针对系统时延中固定时延这种情形,通过对时延黄金分割以及引入改进自由权矩阵,基于李雅普诺夫稳定性理论,给出一种讨论时延网络控制系统稳定性的新方法。     

网络中的拥塞避免控制模型的仿真分析

研究延迟网络中的拥塞避免控制方法.在延迟网络中,随机分配网络资源,造成延迟网络资源的局限性较强,容易造成延迟网络拥塞.传统的拥塞避免控制方法是根据网络链路的反馈回执进行拥塞控制的,但是由于延迟网络的链路均匀性较差,无法建立准确的拥塞反馈回执,造成拥塞避免控制的效果较差.为了避免上述缺陷,提出了一种加权排队控制算法的延迟网络拥塞避免控制模型.对延迟网络参数进行训练,计算延迟网络的带宽,从而为延迟网络的拥塞避免控制提供准确的数据基础.建立加权排队控制模型,能够实现延迟网络的拥塞避免控制.实验结果表明,利用改进算法进行延迟拥塞避免控制,能够有效提高延迟网络的数据传递效率.     

Internet网络的TCP友好控制机制

1.引言随着Internet网络的飞速发展,传统的“尽力”型业务越来越不能满足新的用户和应用的质量要求,网络需要提供更高级的质量保障。同时,对于不同的用户对业务质量(QoS)具有不同的要求,网络也需要区别QoS等级,并采用相应的传输控制机制来保障这些QoS等级。在传统Internet网络中,分别用两种传输协议来传送不同质量要求的业务:TCP(Transmission Control Protrol)和UDP(User Data Protocol)协议。其中,TCP协议适用于突发量较大,需要确保发送而对时延要求不高的业务,如文件传输、数据传送等;UDP协议适用于一些突发较小,对确保发送要求不高而对时延要求高的业务,如话音、视频等多媒体业务。由于两类业务具有不同要求,TCP协议采用窗口机制来进行流量控制,通过每个连接的接收方反馈的信息来改变发送方的发送窗口大小,调整发     

Regional Input-to-State Stability for Nonlinear Model Predictive Control

In this note, regional input-to-state stability (ISS) is introduced and studied in order to analyze the domain of attraction of nonlinear constrained systems with disturbances. ISS is derived by means of a non smooth ISS-Lyapunov function with an upper bound guaranteed only in a sub-region of the domain of attraction. These results are used to study the ISS properties of nonlinear model predictive control (MPC) algorithms.     

互联网拥塞控制算法研究

随着Internet的迅速发展,网络规模、用户数量及业务量呈现爆炸式增长,由此引发的网络拥塞已经成为制约网络发展和应用的瓶颈问题。有效解决拥塞对于提高网络性能具有重要意义,如何更好的预防和控制拥塞成为近年来网络研究领域的重要问题。该文介绍了现有的拥塞控制算法,并分析了进一步的研究方向。