Sampled-data based average consensus with measurement noises: convergence analysis and uncertainty principle

In this paper, sampled-data based average-consensus control is considered for networks consisting of continuous-time first-order integrator agents in a noisy distributed communication environment. The impact of the sampling size and the number of network nodes on the system performances is analyzed. The control input of each agent can only use information measured at the sampling instants from its neighborhood rather than the complete continuous process, and the measurements of its neighbors’ states are corrupted by random noises. By probability limit theory and the property of graph Laplacian matrix, it is shown that for a connected network, the static mean square error between the individual state and the average of the initial states of all agents can be made arbitrarily small, provided the sampling size is sufficiently small. Furthermore, by properly choosing the consensus gains, almost sure consensus can be achieved. It is worth pointing out that an uncertainty principle of Gaussian networks is obtained, which implies that in the case of white Gaussian noises, no matter what the sampling size is, the product of the steady-state and transient performance indices is always equal to or larger than a constant depending on the noise intensity, network topology and the number of network nodes.     

基于多维度的新型排名算法

在处理各项指标成绩线性之和相差不多,而要使成绩平均程度高的排名对象排在前面的排名问题时,普通排名算法存在着一定的局限性。基于多维度的新型排名算法,使得各项考核指标成绩越平均的排名对象名次越靠前,该算法科学合理,应用范围广,有较强的实用性。首介绍了该算法的基本原理,分别通过理论和实例论证了这种新型排名算法的优势,最后基于该算法利用Java语言实现了一个简单的排名软件。     

多数据项广播调度策略

多数据项广播是移动计算环境中一种重要的数据访问方式.为减少用户的平均访问时间和响应最多事务请求,提出了一种新的多数据项广播调度策略.调度策略分为两个阶段,第一阶段根据各事务包含的数据项数目和对重复申请数据项的处理选择事务请求;第二阶段对已选择的事务请求用QEM算法进行调度.实验结果表明,它比现有的QEM算法有更高事务调度成功率和更短的平均访问时间.     

索引折半查找算法的研究与设计

当前对有序数列查找常用二分查找,但是二分查找具有一定的约束性和特殊情况下的低效性,为此研究并设计了索引折半查找算法,理论上其平均查找效率优于二分查找的平均查找效率。对比实验验证了索引折半查找算法的良好性能。     

基于类内均值的双投影2DPCA人脸识别方法

在人脸识别问题中,如何提取具有鲁棒性的人脸特征和降低特征维数是两个关键。根据二维主成分分析方法直接利用二维图像来构建方差矩阵的优点,引入了类内均值的思想,首先计算每类训练样本的类内平均脸,并用它对各类样本进行规范化处理,有效扩大了类间样本的差别,缩小了类内样本的差别,进行协方差矩阵的计算并提取最优投影特征向量进行人脸图像的特征提取,通过在水平和垂直两个方向上顺序执行两次提取和投影的操作,极大压缩了特征的维数,克服了传统二维主成分算法的不足。在人脸库ORL和Yale的试验对比结果表明,方法对光照与表情变化有较好的鲁棒性,能实现较高的识别率,因此在实际中具有一定的应用意义。     

Output feedback control for uncertain linear systems with faulty actuators based on a switching method

This paper investigates the problem of output feedback stabilization for a class of uncertain linear systems with faulty actuators via the synergy with a switching strategy. When actuators suffer a ‘destabilizing failure’ and the never‐faulty actuators cannot stabilize the given system, the closed‐loop exponential stability can still be achieved via the average dwell‐time scheme employing an arbitrary switching signal. The prerequisite condition found requires the ratio between the two lapse times, when the system is devoid of faulty actuators and when it is not so, to be less than a certain specified constant. Then the stabilizing output feedback controls are designed via the technique of linear matrix inequalities. The illustrative example and the respective simulation results demonstrate the feasibility and effectiveness of the proposed design synthesis. Copyright © 2008 John Wiley & Sons, Ltd.     

Cyclic moving average control approach to cylinder pressure and its experimental validation

Cyclic variability is a factor adversely affecting engine performance. In this paper a cyclic moving average regulation approach to cylinder pressure at top dead center （TDC） is proposed, where the ignition time is adopted as the control input. The dynamics from ignition time to the moving average index is described by ARMA model. With this model, a one-step ahead prediction-based minimum variance controller （MVC） is developed for regulation. The performance of the proposed controller is illustrated by experiments with a commercial car engine and experimental results show that the controller has a reliable effect on index regulation when the engine works under different fuel injection strategies, load changing and throttle opening disturbance.     

改进的粒子群算法

针对基本粒子群算法容易陷入局部最优点,进化后期速度慢等缺点,设计了一种新的粒子群算法,将基本粒子群算法粒子行为基于个体极值点转化为个体自身极值与其他某一个个体极值的加权平均值,而全局极值点转化为群体中优秀个体极值的加权平均值。数值仿真实验表明,新算法比PSO具有更好的收敛性,能更快地找到问题的最优解。     

基于图像块均值量化的自适应盲水印算法

提出了一种新的基于图像分块DWT的自适应盲水印算法。算法以一幅有意义的二值水印图像为水印信号。同时,利用了Hilbert扫描能很好地保持图像空间局部连接性的特点。在图像块的Hilbert序列中选取相邻的3个分块分别进行一层小波变换,计算各分块对应子带的均值并比较大小,根据较大和较小的两个均值决定的步长,调整另外一个均值对应子带系数的大小,从而完成自适应的嵌入水印信号。而且,水印的提取无需原始图像参与,达到真正的盲水印。实验结果表明,该算法是有效的,水印具有较好的不可见性,对通常的图像处理操作和裁剪、挤压、像素移位等几何攻击有较强的鲁棒性.     

智能公用室内照明系统的设计

分析比较了已有的几种智能照明系统方案,将检测单元阵列引入智能公用室内照明系统的设计中,从而实现了可精确定位使用者位置及检测此位置的自然光水平,进而实现照明灯的精确控制,实现了真正的智能照明。实际应用验证了本文所述方法的可行性,根据室内自然光及使用者情况自动进行智能照明控制可达到节能目的,且方便操作管理,具有很好的应用前景。