无人机毫米波信道建模进展和挑战

无人机毫米波通信技术结合无人机和毫米波的优势,提供高速数据传输和广域网络覆盖能力,在军用通信系统中拥有广阔的应用前景。精确的信道模型是无人机毫米波系统设计和性能评估的重要理论基础。不同于传统移动通信场景,无人机通信信道具有明显的三维传播特征,构建模型需要考虑包括三维散射空间、三维飞行轨迹及姿态、三维阵列天线和三维窄波束等多种因素。本文首先总结了无人机毫米波信道建模的新需求和挑战,并详细阐述了无线信道建模方法以及现有信道模型的研究进展,最后给出了信道建模的发展方向及关键技术,旨在为无人机毫米波信道模型的科学构建和标准化等研究提供参考。     

基于序贯无迹卡尔曼滤波的雷达目标跟踪方法

提出一种基于序贯无迹卡尔曼滤波的雷达目标跟踪方法。雷达跟踪系统为离散非线性系统,传统的解决方法是使用扩展卡尔曼滤波。无迹卡尔曼滤波用少量采样点表示随机变量的分布,通过非线性系统传播,能以三阶精度获得非线性变换的均值和方差的估计。为了提高无迹卡尔曼滤波的精度,用序贯无迹卡尔曼滤波方法依次处理方位角、俯仰角和距离,来进行雷达目标跟踪。通过Monte Carlo仿真,验证了该滤波算法比传统的扩展卡尔曼滤波具有更高的滤波精度和更高的计算效率。     

基于双目视觉的无人机悬停精度测量研究

为评测悬停状态无人机的稳定性,设计了一套基于双目立体视觉的无人机悬停状态评测系统。首先结合双目相机标定对视频图像校正,并利用提出的邻域灰度改进分级匹配策略,获取匹配特征点;然后根据重建原理计算求得视野中无人机三维坐标数据;最后利用悬停精度测量函数评测无人机的稳定程度。实验证明系统有效匹配目标的特征点,计算出目标三维坐标,同时根据其相对控制精度的浮动,对无人机悬停状态进行评测。     

基于加性无迹卡尔曼滤波的雷达目标跟踪方法

提出一种基于加性无迹卡尔曼滤波的雷达目标跟踪方法。雷达跟踪系统为离散非线性系统,传统的解决方法是使用扩展卡尔曼滤波。无迹卡尔曼滤波用少量采样点表示随机变量的分布,通过非线性系统传播,能以三阶精度获得非线性变换的均值和方差的估计。用无迹卡尔曼滤波进行雷达目标跟踪。通过Monte Carlo仿真,验证了该滤波算法比传统的扩展卡尔曼滤波具有更高的滤波精度。     

控制约束下的多AUV编队路径跟踪

对水下航行器路径跟踪优化控制问题,研究了控制约束下的多AUV编队路径跟踪问题.由于滚动时域控制能够有效处理约束的优势,为提高系统稳定性,提出了一种分布式控制方法.各AUV在每个控制更新时域,根据自身状态向量与控制向量的实际值与其邻居状态向量的预测值,令给定的带有末端项的性能指标最优计算出作用于下一个控制时域的控制输入,并计算出预测控制,向其邻居发送.从理论上证明了算法的稳定性.仿真结果表明,所设计的控制方法能够在功率消耗较小的情况下实现多AUV的编队路径跟踪.     

基于点的造型中如何计算采样点的法向量

随着三维扫描技术的迅速发展,以及大量采样点数达百万数量级的高精度模型的产生,使得基于点的绘制技术逐渐成为热点。文章介绍了一种在基于点的造型中不必经过三角化,由采样点直接计算法向量的方法。该方法首先找到当前点周围的临近采样点;然后,根据最小二乘法由这些临近点近似计算当前点所在位置的切平面;最后,将切平面的法向量作为当前采样点的近似法向量。试验表明,该方法可以快速有效地计算采样点的法向量。     

基于指纹库更新补偿的波束跟踪算法研究

针对拒止、复杂电磁环境下,高动态无人节点定向通信面临的坐标信息不精确、飞行姿态和轨迹变化剧烈等问题,为保持可靠的波束对准与跟踪,提出了一种基于卡尔曼滤波的指纹库更新补偿算法。首先,利用卡尔曼滤波算法对自身姿态进行预测更新,建立新的载体坐标系;利用改进的算法对波束指向进行预测更新,并利用指纹库对状态向量均值和协方差矩阵进行更新补偿,调节采样比例,并将新的数据存入指纹库对指纹库数据更新,然后进行二次状态信息预测,完成最终波束指向。整体设计的波束跟踪算法流程更加符合实际应用场景,满足无人机自组网的需求。仿真结果表明,在半波束宽度为3°,100个通信时隙中,维持正常通信的成功率有92%以上,相比传统跟踪算法提高了8%,具有更加稳定的通信质量。     

一种基于SR-UKF的FastSLAM算法

标准FastSLAM算法存在着粒子集退化和线性化误差累积的缺陷。针对上述问题,提出了基于平方根无迹卡尔曼滤波(SR-UKF)的FastSLAM算法。SR-UKF选取一组能够代表状态向量统计特性的代表点带入非线性函数处理后重新构建出新的统计特性;使用SR-UFK取代EKF来估计每个粒子的后验位姿提议分布,可以提高粒子采样精度,减缓粒子集的退化;同时SR-UKF可以确保协方差矩阵的非负定,保证了SLAM算法的稳定性。仿真实验结果表明,基于SR-UKF的FastSLAM算法在估计精度和鲁棒性两方面均优于FastSLAM 2.0算法。     

基于在线增量小波LS-SVM的垂直陀螺仪残差故障检测研究

垂直陀螺仪是无人机重要的飞行姿态传感器,其在飞行过程中实时获取无人机的飞行姿态信息,因而其故障检测对在线性有着很高的要求;最小二乘支持向量机(Least Squares Support Vector Machine,LS-SVM)相比于支持向量机的具有训练速度快、计算复杂度和需要内存少的特点,且能够扩展为自回归的形式来处理动态问题;因此文章采用基于在线增量小波LS-SVM建立无人机垂直陀螺仪动态模型,实时获得实际值与模型预测值之间的残差,并依据残差对陀螺仪进行在线故障检测;实验结果表明,该方法能够对陀螺仪实现快速精确的在线检测。     

基于激光和视觉信息的机器人目标跟踪方法

文中介绍了一种利用移动机器人的激光信息和摄像头信息实时跟踪目标的方法。实现了对人的准确迅速的跟踪。通过大量提取照到人的双脚的激光特征作为样本集,描述了一种基于条件随机场（CRF）模型的Rao—Blackwellized particle filter（RBPF）算法,CRF的observation potential可以直接从样本数据中获得。采用类似栅格滤波方法计算样本的后验概率。RBPF算法根据后验概率进行权值的更新和采样实现对激光特征的实时跟踪,从而实现人的跟踪。根据人的位置信息可以确定人在摄像头图像窗口中的大概位置,提取该位置的SURF特征,从而获得人在图像中的精确位置。     

Only connect: teaching, technology and telesis

Abstract This paper describes an approach to the design of interactive multimedia materials being developed in a European Community project. The developmental process is seen as a dialogue between technologists and teachers. This dialogue is often problematic because of the differences in training, experience and culture between them. Conditions needed for fruitful dialogue are described and the generic model for learning design used in the project is explained.     

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。     

Avoiding semantic and temporal gaps in developing software intensive systems

Development of software intensive systems (systems) in practice involves a series of self-contained phases for the lifecycle of a system. Semantic and temporal gaps, which occur among phases and among developer disciplines within and across phases, hinder the ongoing development of a system because of the interdependencies among phases and among disciplines. Such gaps are magnified among systems that are developed at different times by different development teams, which may limit reuse of artifacts of systems development and interoperability among the systems. This article discusses such gaps and a systems development process for avoiding them.     

Designing economic np control charts: A programmed simulation approach

This paper presents control charts models and the necessary simulation software for the location of economic values of the control parameters. The simulation program is written in FORTRAN, requires only 10K of main storage, and can run on most mini and micro computers. Two models are presented - one describes the process when it is operating at full capacity and the other when the process is operating under capacity. The models allow the product quality to deteriorate to a further level before an existing out-of-control state is detected, and they can also be used in situations where no prior knowledge exists of the out-of-control causes and the resulting proportion defectives.     

The development of robot art

Going through a few examples of robot artists who are recognized worldwide, we try to analyze the deepest meaning of what is called “robot art” and the related art field definition. We also try to highlight its well-marked borders, such as kinetic sculptures, kinetic art, cyber art, and cyberpunk. A brief excursion into the importance of the context, the message, and its semiotics is also provided, case by case, together with a few hints on the history of this discipline in the light of an artistic perspective. Therefore, the aim of this article is to try to summarize the main characteristics that might classify robot art as a unique and innovative discipline, and to track down some of the principles by which a robotic artifact can or cannot be considered an art piece in terms of social, cultural, and strictly artistic interest. This work was presented in part at the 13th International Symposium on Artificial Life and Robotics, Oita, Japan, January 31–February 2, 2008     

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.