一类有色噪声干扰下的随机时变系统学习辨识

讨论由一类时变ARMAX模型描述的动态系统学习辨识问题,提出用于估计有限区间上重复运行时变系统时变参数的学习算法.文中给出最小二乘学习算法的具体形式及实现步骤,并分析所提出学习算法的收敛性.分析结果表明,当重复持续激励条件成立且满足严格正实条件时,提出的学习算法具有重复一致性,即参数估值完全收敛于真值.文中还将结果推广到一类周期时变系统.通过数值仿真,进一步对所提学习算法的有效性进行了验证.     

非线性时变时滞FAST TCP系统低保守全局稳定性

研究了非线性、时变时滞的快速传输控制协议(FAST TCP)系统的全局稳定性. 首先, 利用其时滞变化与源端发送窗口变化成比例关系和其非线性函数是严格单调递减函数这两个特性, 计算每个振荡周期的解轨迹界, 建立计算轨迹界的改进型迭代公式, 得到了比已有结论更低保守的全局稳定性条件. 最后, 通过网络模拟器2(NS-2)仿真实例验证了改进的全局稳定性条件的有效性.     

混合编码和声搜索算法在动态优化中的应用

采用混合双重编码方法,提出一种混合编码二进制和声搜索算法HBHSA,用以求解动态位匹配问题和时变背包问题。仿真结果表明,与DS_BPSO、HBDE和PDGA算法相比,HBHSA具有更好的鲁棒性和通用性,在动态环境中的搜索能力和对最优解的跟踪能力更优。     

A new approach to adaptive control: no nonlinearities

In adaptive control the goal is to design a controller to control an uncertain system whose parameters may be changing with time. Typically the controller consists of an identifier (or tuner) which is used to adjust the parameters of a linear time-invariant (LTI) compensator, and under suitable assumptions on the plant model uncertainty it is proven that good asymptotic behaviour is achieved, such as model matching (for minimum phase systems) or stability. However, a typical adaptive controller does not track time-varying parameters very well, and it is often highly nonlinear, which can result in undesirable behaviour, such as large transients or a large control signal. Furthermore, most adaptive controllers provide only asymptotic tracking, with no ability to design for a pre-specified settling time.Here we propose an alternative approach, which yields a linear periodic controller. Rather than estimating the plant or compensator parameters, instead we estimate what the control signal would be if the plant parameters were known. In this paper we argue the utility of this approach and then examine the first order case in detail, including a simulation. We also explore the benefits and limitations of the approach.     

一类时变非线性系统自适应控制

针对非线性时变系统提出一种间接自适应方法。利用时尺变量函数，将非线性系统划分为若干子系统，间接自适应方法对任意信号都具有稳定性。仿真结果表明了，此法的有效性。     

一种新的时变系统极点配置自适应控制方法*

本文针对连续快时变系统，提出不要求系统参数未知部分上界的先验信息的自适应算法，得到间接自适应控制方案并且证明闭环系统稳定，仿真结果说明本文的方法有效．     

连续时间时变参数系统的指数稳定性和Lp指数稳定性

本文给出具有慢时变参数的连续时间线性齐次系统指数稳定的一个一般性条件，并给出具有随机时变参数的连续时间线性齐次系统Ｌｐ指数稳定的一个充分条件。这些结果可用来分析带有未建模动态，确定性噪声或随机噪声及慢时变参数的自适应控制系统的稳定性问题。     

基于观测器的不确定动态时滞系统鲁棒镇定的Riccati方程方法

本文给出了一类不确定动态时滞系统基于观测器的鲁棒镇定方法，该类系统的状态、输人和输出矩阵均含有不确定性，且不确定性需满足给定的匹配条件，系统不仅有状态时滞，还有控制时滞，该方法通过求解两个代数Riccati方程实现，本文比较全面地解决了满足匹配条件的不确定动态时滞系统的鲁棒镇定问题．     

Designing Efficient and Robust Caching Algorithms for Streaming-on-Demand Services on the Internet

Content Delivery Networks (CDN) have been used on the Internet to cache media content so as to reduce the load on the original media server, network congestion, and latency. Due to the large size of media content compared to normal web objects, current caching algorithms used in the Internet are no longer suitable. This paper presents a high-performance prefetch system that accommodates user time-varying behavior. A hybrid caching technique, which combines prefetch and replacement algorithms, is also introduced. The robustness of the cache system against imperfect user request information is evaluated using three request noise models. Two prefetch performance indices are also presented to help content administrators in deciding when to update the user request profile for caching algorithms.     

基于系统输出的时变特征参数辨识

在子空间辨识方法的基础上给出时变特征参数辨识的新方法。将特征阻尼修正与数字滤波相结合，由输出信号估计特征频率和阻尼比。对于系统输出，假定其具有短时平稳特性，通过对响应信号在局部时问段上建模得到时变特征。使用分量能量指标指示信号中各振动分量的强弱，并通过能量指标在时频面上建立一种时频表示，以此反映系统的时频特性。对Hankel矩阵使用QR分解，在提高运算速度的同时不降低参数估计的精度。