带时延补偿的图像雅可比矩阵在线估计方法

传统的在线估计图像雅可比矩阵的方法没有考虑时延因素,因此具有较大的估计误差。为了补偿时间延迟,提出一种新的带时延补偿的图像雅可比矩阵估计方法。该方法利用卡尔曼滤波估计特征点在图像空间中当前时刻的位置和速度,进而计算当前时刻较为准确的图像雅可比矩阵估计值。仿真和实验结果表明,该方法显著地提高了系统的性能,从而验证了提出的带时延补偿的图像雅可比矩阵在线估计方法的可行性和优越性。     

带时延补偿的视觉跟踪控制

在实际的视觉伺服系统中, 由于摄像机到图像处理设备的传输延迟和图像处理本身占用的时间, 视觉信息的获取会产生时延. 对此, 给出了一个带有时延补偿的视觉跟踪控制方法. 通过实时拟合图像雅可比矩阵, 实现了对机械手末端执行器图像特征信息的实时预测, 从而减小了估计误差. 在此基础上, 设计了一个带有时延补偿的控制方案. 通过对运动目标进行跟踪的仿真实验, 验证了本文时延补偿方法的有效性.     

图像雅可比矩阵伪逆估计在视觉伺服中的应用

在一般无标定视觉伺服算法的基础上,提出了一种基于递推最小二乘法估计图像雅可比矩阵伪逆的无标定视觉伺服算法．这种方法无需计算雅可比矩阵伪逆．针对固定目标,文中给出了比例控制算法的稳定性条件．针对运动目标,推导了基于图像雅可比矩阵伪逆估计的伪高斯—牛顿视觉伺服算法和信任区视觉伺服算法．最后,仿真验证了三种视觉伺服算法的有效性．     

基于图像雅可比矩阵的智能机器人视觉跟踪

根据智能机器人视觉伺服的要求,建立了固定眼结构的MOTOMAN-SV3XL型工业机器人无标定视觉伺服系统.研究了目前在机器人视觉伺服研究领域中使用最为广泛的一类方法,即基于图像雅可比矩阵的方法.针对图像雅可比矩阵的特点,设计了一种基于简化Sage-Husa自适应滤波的图像雅可比矩阵在线估计算法,并将其应用于机器人视觉反馈控制任务中,实现了对二维平面上运动目标的跟踪,实验结果表明了该算法的有效性.     

一种新的双环结构机器人无标定自抗扰视觉伺服控制方法

在研究基于自抗扰控制器的机器人无标定视觉伺服方法的基础上，提出了一种新的双环结构机器人无标定自抗扰视觉伺服控制方法．内环采用Kalman滤波算法进行图像雅可比矩阵的在线辨识，可较好地逼近真实模型；外环采用自抗扰控制器，利用非线性观测器实时估计系统相对于当前估计模型的总扰动，并在控制中加以动态补偿．针对六自由度工业机器人进行了二维运动目标的跟踪实验，实验结果表明了该方法的可行性和有效性．     

鲁棒卡尔曼滤波下的图像雅可比矩阵带时延补偿的估计

传统的图像雅可比矩阵估计的方法没有考虑时延因素,因此具有较大的估计误差.为补偿时延带来的影响,提出一种鲁棒卡尔曼滤波的方法,实现时延情况下当前时刻特征点在图像空间中位置和速度的估计,进而得到时延情况下较为准确的图像雅可比矩阵的估值.具体说,特征点在图像空间中当前时刻位置和速度是首先用卡尔曼滤波的方法估计的,但观测噪声的描述却采用了马尔科夫链模型,由此产生了过程噪声和观测噪声的互相关,传统卡尔曼滤波受限.为此,我们引入滤波修正向量并重新定义过程方程及观测方程,结合卡尔曼滤波中噪声的数学特性,得到滤波修正向量消除互相关性,从而构建出鲁棒卡尔曼滤波模型;其次,针对鲁棒卡尔曼滤波模型中存在的无法获得时延期间的观测向量的问题,提出利用多项式拟合出这部分观测向量,该多项式的选取综合考虑了特征点的位置、速度、加速度、加速度的变化率对于特征点轨迹的影响,与实际情况相符;最后,由预测出的当前时刻特征点在图像空间中的位置和速度,实现时延情况下图像雅可比矩阵较为准确的估计.仿真和实验结果验证了本文方法的可行性和优越性.     

基于无极卡尔曼滤波算法的雅可比矩阵估计

在基于图像的机器人视觉伺服中,采用在线估计图像雅可比的方法,不需事先知道系统的精确模型,可以避免复杂的系统标定过程。为了有效改善图像雅可比矩阵的在线估计精度,进而提高机器人的跟踪精度,针对机器人跟踪运动目标的应用背景,提出了利用无极卡尔曼滤波算法在线估计总雅可比矩阵。在二自由度的机器人视觉伺服仿真平台上,分别用卡尔曼滤波器（KF）、粒子滤波器（PF）和无极卡尔曼滤波器（UKF）三种算法进行总雅可比矩阵的在线估计。实验结果证明,使用UKF算法的跟踪精度优于其他两种算法,时间耗费仅次于KF算法。     

基于雅可比预测的机器人无模型视觉伺服定位控制

针对未知相机标定及目标3D几何模型,研究机器人无模型视觉伺服定位方法.引入状态空间,建立机器人“视觉空间-运动空间”雅可比非线性映射的状态方程和观测方程,提出神经网络联合卡尔曼滤波雅可比预测算法,网络在线动态补偿系统近似误差与参数估计误差,实现最小均方差条件下的雅可比预测;以李雅普诺夫稳定性准则构建雅可比预测的无模型图像视觉伺服控制方案,避免了相机标定和目标建模.“眼在手”六自由度机器人定位比较实验表明,图像空间特征轨迹平滑稳定在相机视场中,笛卡尔空间机器人末端运动平稳,无震荡回退,定位精度在10个像素范围内.     

摄像机参数标定实验的设计与实现

在基于位置的视觉伺服中,需要建立将二维图像信息转换为三维坐标信息的图像雅可比矩阵。为了获取高精度的雅可比矩阵本文设计了CCD摄像机参数标定的实验。首先介绍了摄像机标定原理,然后设计了标定实验,最后给出了标定的具体步骤以及实验结果。     

摄像机参数标定实验的设计与实现

在基于位置的视觉伺服中，需要建立将二维图像信息转换为三维坐标信息的图像雅可比矩阵。为了获取高精度的雅可比矩阵本文设计了CCD摄像机参数标定的实验。首先介绍了摄像机标定原理，然后设计了标定实验，最后给出了标定的具体步骤以及实验结果。     

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).