基于GPS/SINS紧耦合系统的新息外推法

在GPS/SINS紧耦合系统中,完好性是一个极其重要的指标。为缩短卫星故障检测时间,在新息检测法的基础上提出一种新息外推法,该算法通过对外推过程中产生的新息进行处理,形成检验统计量来检测卫星故障。结合GPS/SINS紧耦合系统,仿真结果表明,新息外推法比新息检测法能更快地检测慢变故障,且能在一定程度上削弱野值对故障检测的影响。     

导航系统全球完好性仿真分析的设计与实现

完好性分析是导航系统分析的重要组成部分,完好性的仿真验证和测试可以降低系统研制的技术风险,是导航领域仿真的一个重要问题.提出了基于用户接收机格网的完好性仿真分析涉及的PAlM算法和RAIM可用性算法等相关算法模型,基于此,设计和实现了导航系统完好性仿真分析系统,最后针对格网分辨率为10°×10°的中国区域格网(24个网格点)进行了完好性的仿真试验分析,验证了相关RAIM算法,讨论了失效卫星对导航系统完好性的影响和基于保护级别概念的完好性计算的不足.     

基于完好性与连续性风险的最优垂直保护门限计算

为降低飞行器精密垂直引导进近过程中的完好性风险和连续性风险,使接收机自主完好性监测(RAIM)算法能提供水平方向和垂直方向上的完好性保障,提出一种基于多假设解分离的RAIM算法来求解最优垂直保护门限(VPL)。在满足全球导航卫星系统(GNSS)完好性和连续性的前提下,优化GNSS系统对各假设故障模式的完好性风险和连续性风险分配,得到最优VPL。仿真结果表明,与传统基于斜率的RAIM算法相比,该算法能够提供更精确的VPL值,提高了系统可用性,并且随着卫星故障先验概率不断增大仍具有较好的鲁棒性。     

基于优选几何分组增强的假设检验RAIM方法

针对传统接收机自主完好性监测(RAIM)算法对15~50m级较小故障检测和排除率低,不易满足多测距故障场景应用问题,建立4种典型卫星分布几何结构模型,通过研究各模型对含偏差测距带来的定位误差与检测统计值间耦合性的影响,提出了一种基于几何优选分组增强的RAIM方法。该方法在假设检验方法基础上,利用分组间残差矢量建立新型检测统计量与门限值,通过检验子集一致性来检测和排除含有偏差的测距。仿真表明:该方法能够提升较小故障检测和排除率,增强接收机自主完好性性能水平,且支持联合导航系统单、多测距故障场景假设,有效降低定位估计误差,保证了定位解的精度。     

基于自适应策略的权值修正累积历元RAIM算法

传统的接收机自主完好性监测(RAIM)算法对微小慢变故障的检测延迟较长,漏检率较高,不利于故障检测。针对这一问题,在奇偶矢量RAIM算法基础上,提出了一种基于自适应策略的权值修正累积历元的RAIM新方法。该算法根据单历元故障程度确定权值因子,进而调整选定“窗口”内各历元所占比例,以构造更有效的检测统计量,其中“窗口”的大小依据多次仿真实验确定。仿真结果表明,该算法相对于累积历元和传统RAIM方法检测延迟时间分别缩短了16.67%和56.52%,能更好地检测微小慢变故障。     

用于检测双星故障的RAIM算法分析与研究*

随着GPS等卫星导航技术的广泛应用,在实际导航中对接收机的导航定位精度,尤其对定位的有效性提出了越来越高的要求。目前对此较为有效的方法就是利用接收机自主完好性监视(RAIM, Receiver Autonomous Integrity Monitoring)进行保障,而且该方法日益凸显出其优越性,但目前对该方法的研究多基于单星故障的假设。随着新一代导航系统的完善以及组合导航技术的发展,双星甚至多星同时出现故障成为不可避免的话题。本文分析和比较了用于检测两颗卫星故障的偏差完好性风险(BIT, Bias Integrity Threat)法和保护限值(PL, Protection Level)法两种RAIM算法。通过数据仿真,对用不同方法检测卫星故障的可用性及故障检测率进行比较,并分析了两种方法存在差异的理论依据。通过分析比较,说明在未来接收机处理多颗卫星同时出现故障的情况时,如何更精确地描述统计检测量与定位偏差的关系以及如何处理不同测量噪声的影响是RAIM算法可用性及有效性的关键。     

GPS+BD双模接收机自主完好性监测算法研究

在高动态导航中,卫星接收机自主完好性监测(RAIM)越来越受到重视.假如在单一模式下监测,RAIM系统至少需要接收到5颗卫星的信息才能监测出异常卫星,而如果需要辨识出故障卫星,则至少需要接收到6颗卫星的信息,这就使得单一的接收模式很难保证在全球范围内进行全天候的完整性检测.而随着北斗(BD)系统的迅速发展,使得采用GPS+BD导航模式进行监测成为可能.文中讨论了GPS和BD组合接收机中,在某时刻假设只有一颗卫星出现故障的情况下,怎样使用加权方法进行自主完好性监测.并通过仿真GPS、BD单模式和GPS+BD模式下的故障识别率和RAIM完好性可用率,证明了GPS+BD模式RAIM算法要优于任何一种单系统模式的RAIM算法.     

基于多假设解分离算法的BDS/SINS紧组合完好性监视

完好性是民航基于性能的导航（PBN）运行的关键性能要求,是导航安全性的重要支撑。北斗导航系统（BDS）/惯性导航系统（SINS）紧组合导航系统将SINS信息加入到完好性监视中,增加了冗余信息,通过多假设解分离算法进行故障卫星的检测与隔离,满足民航特定飞行阶段高完好性要求。论文利用BDS接收机接收到的BDS卫星数据,通过设置飞行轨迹,模拟卫星故障,对BDS/SINS组合导航系统的完好性算法进行测试验证。实验结果表明,基于多假设解分离方法的BDS/SINS紧组合导航系统可以较好地实现故障卫星的检测与隔离,保护限计算符合预期。     

GPS+BD双模接收机自主完好性监测算法研究

在高动态导航中,卫星接收机自主完好性监测(RAIM)越来越受到重视。假如在单一模式下监测,RAIM系统至少需要接收到5颗卫星的信息才能监测出异常卫星,而如果需要辨识出故障卫星,则至少需要接收到6颗卫星的信息,这就使得单一的接收模式很难保证在全球范围内进行全天候的完整性检测。而随着北斗(BD)系统的迅速发展,使得采用GPS+BD导航模式进行监测成为可能。文中讨论了GPS和BD组合接收机中,在某时刻假设只有一颗卫星出现故障的情况下,怎样使用加权方法进行自主完好性监测。并通过仿真GPS、BD单模式和GPS+BD模式下的故障识别率和RAIM完好性可用率,证明了GPS+BD模式RAIM算法要优于任何一种单系统模式的RAIM算法。     

基于子集p值检验的惯性/ 卫星紧组合多星故障识别方法

传统的 RAIM 算法对多颗卫星同时发生故障的识别能力较差,鉴于此,提出一种基于子集 值检验的多卫星故障检测与识别方法.该方法在惯导信息辅助的基础上,采用 值检验对观测量子集进行显著性水平分析,通过决策得到各卫星观测量质量值,并进行故障识别和系统重构.仿真结果表明,该方法在可见星数?5时即可进行故障识别,且对于多颗卫星同时发生故障的情况具有较好的识别效果,提高了紧组合导航系统容错性和精度.     

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.