不确定系统鲁棒容错H_∞控制的LMI设计方法

针对不确定线性系统.研究了执行器失效情况下鲁棒容错H∞控制问题.基于连续增益故障模式.利用线性矩阵不等式LMI推导了系统H∞指标约束下鲁棒容错镇定的充要条件.分别给出了输出反馈和状态反馈H∞控制器的设计方法.通过引入变量代换.将求解输出反馈H∞指标约束的鲁棒容错控制器的可解条件转化为标准的LMI.所获得的控制器不仅能使故障系统鲁棒稳定,并且能达到给定的H∞性能指标.仿真实例验证了所提出设计方法的有效性.     

容错控制系统鲁棒H∞和自适应补偿设计

通过设计动态输出反馈控制策略研究线性时不变系统执行器故障下的鲁棒自适应容错H∞控制问题. 结合自适应技术和线性矩阵不等式(Linear matrix inequalities, LMI)技术, 设计一个控制策略同时实现系统的故障补偿控制和性能优化控制. 在设计中, 提出由自适应律在线调节控制增益方程补偿未知执行器故障和摄动; 并设计一个基于模式依赖李亚普诺夫方程的LMI条件解出控制参数及次优H∞性能. 所设计的动态输出反馈控制器可以处理一般执行器卡死故障, 并得到更少保守性的H∞性能指标. 此外, 一个更具挑战性的问题, 即通过自适应机构补偿故障致使系统多少性能退化得到论证. 所提方法的有效性由一个解耦线性化动态飞行器系统仿真验证.     

一类不确定系统鲁棒容错D-稳定性分析

研究不确定系统D-稳定鲁棒容错H_∞控制问题.基于连续型执行器故障模式,利用线性矩阵不等式(LMI),给出了系统D-稳定的鲁棒容错输出反馈控制器存在的充分条件,并将动态输出反馈控制器设计方法归结为求解一族线性矩阵不等式组.仿真示例表明,无论执行器是否发生故障,所得到的动态输出反馈控制器不仅保证闭环系统是D-稳定的,而且满足给定的H_∞干扰指标,从而验证了所提出的控制器设计方法的有效性.     

基于输出反馈的鲁棒容错D-稳定性分析

研究线性不确定系统基于输出反馈的鲁棒容错控制问题.基于连续型执行器故障模式,利用线性矩阵不等式LMI,给出了系统基于输出反馈的鲁棒容错D-稳定的充分条件,并把控制器的设计方法归结为求解一族线性矩阵不等式组.与常规的方法相比,给出的控制器不仅保证闭环系统对执行器故障具有完整性,并且使闭环系统的极点配置在指定区域D中.通过仿真示例表明,无论执行器发生故障与否,得到的基于输出反馈的鲁棒容错控制器均保证闭环系统是D-稳定的,从而验证了所提出设计方法的有效性.     

不确定广义模糊系统的鲁棒模糊H∞控制器设计

研究了不确定广义模糊系统鲁棒H∞状态反馈控制器和动态输出反馈控制器设计问题。在E确定其它系数矩阵均存在不确定性情况下，给出鲁棒模糊H∞状态反馈控制器和动态输出反馈控制器存在的充分条件。鲁棒H∞状态反馈控制律的设计可能通过求解线性矩阵不等式得到，而动态输出反馈鲁棒H∞控制器可通过定义新变量得到，所求控制器使闭环系统对所有的不确定性稳定且满足H∞性能指标γ。     

一类不确定系统鲁棒容错D-稳定性分析

研究不确定系统D-稳定鲁棒容错H_∞控制问题.基于连续型执行器故障模式,利用线性矩阵不等式(LMI),给出了系统D-稳定的鲁棒容错输出反馈控制器存在的充分条件,并将动态输出反馈控制器设计方法归结为求解一族线性矩阵不等式组.仿真示例表明,无论执行器是否发生故障,所得到的动态输出反馈控制器不仅保证闭环系统是D-稳定的,而且满足给定的H_∞干扰指标,从而验证了所提出的控制器设计方法的有效性.

     

不确定时滞系统的保代价H∞鲁棒可靠控制

针对一类不确定时滞受扰系统,研究了在执行器发生故障情况下系统具有保代价的H_∞鲁棒可靠控制器设计问题。根据Lyapunov稳定性理论,得到了系统存在保代价H_∞鲁棒可靠控制器应满足的一个矩阵不等式,进一步将这个矩阵不等式转化为线性矩阵不等式（LMI）,并给出了系统状态反馈控制器的设计方法。利用论文方法设计的鲁棒可靠控制器能够使得时滞系统对于任意允许的不确定量以及一个预先指定执行器子集中任意执行器失效不仅具有鲁棒容错性,并且使系统存在保成本上界以及具有指定H∞范数的干扰抑制能力。仿真结果表明了该可靠控制器设计方法的有效性。     

一类不确定Lurie时滞奇异系统的鲁棒H∞控制

研究一类具有不确定性的Lurie时滞奇异系统的鲁棒稳定性分析和H∞状态反馈控 制器设计方法.针对一类具有参数不确定性、未知时滞的奇异系统,得出了系统鲁棒稳定和 鲁棒H∞状态反馈控制器存在的充分条件,它能使得不确定Lurie时滞奇异系统的解在所容 许的范围内是正则的、无摄动的和稳定的;而且还得出了基于线性矩阵不等式(LMI)的鲁棒 H∞状态反馈控制器的设计方法,使得闭环系统具有鲁棒稳定性和H∞性能.     

具有时变不确定性的线性时滞系统的鲁棒H_∞控制

研究具有一般形式的不确定线性时滞系统的鲁棒 H∞ 状态反馈控制器设计问题 .基于二次 H∞ 性能概念 ,首先证明了若存在鲁棒 H∞ 动态状态反馈控制器 ,则必存在鲁棒 H∞ 静态状态反馈控制器 ,然后利用线性矩阵不等式给出了鲁棒 H∞ 静态状态反馈控制器存在的充分条件和构造方法 ,最后给出一个算例验证本文方法的有效性     

数值界不确定关联大系统分散鲁棒H∞控制

针对一类状态矩阵、控制矩阵及关联矩阵存在数值界不确定性的关联大系统,研究其分散鲁棒H∞状态反馈控制器设计问题.基于有界实引理将存在鲁棒分散H∞状态反馈控制器的条件归结为一个非线性矩阵不等式求解问题,采用同伦迭代线性矩阵不等式方法求解分散控制器,使闭环大系统鲁棒稳定,并且满足给定的H∞性能指标.最后通过一个数值例子来说明该设计方法的有效性.     

European Community policy and the market

Abstract This paper starts with some reflections on the policy considerations and priorities which are shaping European Commission (EC) research programmes. Then it attempts to position the current projects which seek to capitalise on information and communications technologies for learning in relation to these priorities and the apparent realities of the marketplace. It concludes that while there are grounds to be optimistic about the contribution EC programmes can make to the efficiency and standard of education and training, they are still too technology driven.     

一种自适应子融合集成多分类器方法

融合集成方法已经广泛应用在模式识别领域,然而一些基分类器实时性能稳定性较差,导致多分类器融合性能差,针对上述问题本文提出了一种新的基于多分类器的子融合集成分类器系统。该方法考虑在度量层融合层次之上通过对各类基多分类器进行动态选择,票数最多的类别作为融合系统中对特征向量识别的类别,构成一种新的自适应子融合集成分类器方法。实验表明,该方法比传统的分类器以及分类融合方法识别准确率明显更高,具有更好的鲁棒性。     

Explanation and prediction: an architecture for default and abductive reasoning

Although there are many arguments that logic is an appropriate tool for artificial intelligence, there has been a perceived problem with the monotonicity of classical logic. This paper elaborates on the idea that reasoning should be viewed as theory formation where logic tells us the consequences of our assumptions. The two activities of predicting what is expected to be true and explaining observations are considered in a simple theory formation framework. Properties of each activity are discussed, along with a number of proposals as to what should be predicted or accepted as reasonable explanations. An architecture is proposed to combine explanation and prediction into one coherent framework. Algorithms used to implement the system as well as examples from a running implementation are given.     

Three Process Perspectives: Organizations, Teams, and People

This paper provides the author's personal views and perspectives on software process improvement. Starting with his first work on technology assessment in IBM over 20 years ago, Watts Humphrey describes the process improvement work he has been directly involved in. This includes the development of the early process assessment methods, the original design of the CMM, and the introduction of the Personal Software Process (PSP)^SM and Team Software Process (TSP){^SM}. In addition to describing the original motivation for this work, the author also reviews many of the problems he and his associates encountered and why they solved them the way they did. He also comments on the outstanding issues and likely directions for future work. Finally, this work has built on the experiences and contributions of many people. Mr. Humphrey only describes work that he was personally involved in and he names many of the key contributors. However, so many people have been involved in this work that a full list of the important participants would be impractical.     

基于复小波噪声方差显著修正的SAR图像去噪

提出了一种基于复小波域统计建模与噪声方差估计显著性修正相结合的合成孔径雷达(Synthetic Aperture Radar,SAR)图像斑点噪声滤波方法。该方法首先通过对数变换将乘性噪声模型转化为加性噪声模型,然后对变换后的图像进行双树复小波变换(Dualtree Complex Wavelet Transform,DCWT),并对复数小波系数的统计分布进行建模。在此先验分布的基础上,通过运用贝叶斯估计方法从含噪系数中恢复原始系数,达到滤除噪声的目的。实验结果表明该方法在去除噪声的同时保留了图像的细节信息,取得了很好的降噪效果。     

How do children do mathematics with LOGO?

Abstract  This paper considers some results of a study designed to investigate the kinds of mathematical activity undertaken by children (aged between 8 and 11) as they learned to program in LOGO. A model of learning modes is proposed, which attempts to describe the ways in which children used and acquired understanding of the programming/mathematical concepts involved. The remainder of the paper is concerned with discussing the validity and limitations of the model, and its implications for further research and curriculum development.     

Editorial: Special issue on recent advances in hybrid control theory and applications

正The demands of a rapidly advancing technology for faster and more accurate controllers have always had a strong influence on the progress of automatic control theory.In recent years control problems have been arising with increasing frequency in widely different areas,which cannot be addressed using conventional control techniques.The principal reason for this is the fact that a highly competitive economy is forcing systems to operate in regimes where     

Information for Authors

正Aim The Journals of Zhejiang University-SCIENCE(A/B/C)areedited by the international board of distinguished Chinese andforeign scientists,and are aimed to present the latest devel-opments and achievements in scientific research in China andoverseas to the world’s scientific circles,especially to stimulateand promote academic exchange between Chinese and for-eign scientists everywhere.     

Enhancing a leaf radiative transfer model to estimate concentrations and in vivo specific absorption coefficients of total carotenoids and chlorophylls a and b from single-needle reflectance and transmittance

The relative concentrations of different pigments within a leaf have significant physiological and spectral consequences. Photosynthesis, light use efficiency, mass and energy exchange, and stress response are dependent on relationships among an ensemble of pigments. This ensemble also determines the visible characteristics of a leaf, which can be measured remotely and used to quantify leaf biochemistry and structure. But current remote sensing approaches are limited in their ability to resolve individual pigments. This paper focuses on the incorporation of three pigments—chlorophyll a, chlorophyll b, and total carotenoids—into the LIBERTY leaf radiative transfer model to better understand relationships between leaf biochemical, biophysical, and spectral properties.Pinus ponderosa and Pinus jeffreyi needles were collected from three sites in the California Sierra Nevada. Hemispheric single-leaf visible reflectance and transmittance and concentrations of chlorophylls a and b and total carotenoids of fresh needles were measured. These data were input to the enhanced LIBERTY model to estimate optical and biochemical properties of pine needles. The enhanced model successfully estimated reflectance (RMSE = 0.0255, BIAS = 0.00477, RMS%E = 16.7%), had variable success estimating transmittance (RMSE = 0.0442, BIAS = 0.0294, RMS%E = 181%), and generated very good estimates of carotenoid concentrations (RMSE = 2.48 µg/cm², BIAS = 0.143 µg/cm², RMS%E = 20.4%), good estimates of chlorophyll a concentrations (RMSE = 10.7 µg/cm², BIAS = − 0.992 µg/cm², RMS%E = 21.1%), and fair estimates of chlorophyll b concentrations (RMSE = 7.49 µg/cm², BIAS = − 2.12 µg/cm², RMS%E = 43.7%). Overall root mean squared errors of reflectance, transmittance, and pigment concentration estimates were lower for the three-pigment model than for the single-pigment model. The algorithm to estimate three in vivo specific absorption coefficients is robust, although estimated values are distorted by inconsistencies in model biophysics. The capacity to invert the model from single-leaf reflectance and transmittance was added to the model so it could be coupled with vegetation canopy models to estimate canopy biochemistry from remotely sensed data.     

Mr. Twinn’s bombes

This article discusses the history and design of the special versions of the bombe key-finding machines used by Britain’s Government Code & Cypher School (GC&CS) during World War II to attack the Enigma traffic of the Abwehr (the German military intelligence service). These special bombes were based on the design of their more numerous counterparts used against the traffic of the German armed services, but differed from them in important ways that highlight the adaptability of the British bombe design, and the power and flexibility of the diagonal board. Also discussed are the changes in the Abwehr indicating system that drove the development of these machines, the ingenious ways in which they were used, and some related developments involving the bombes used by the U.S. Navy’s cryptanalytic unit (OP-20-G).