未知环境下移动机器人地图构建仿真研究

未知环境的地图构建是移动机器人研究领域的一个研究热点.为了研究在未知环境下移动机器人地图构建,基于微软机器人开发工作室(MRDS),对虚拟环境中移动机器人进行了仿真建模,通过激光测距仪获取未知环境信息,应用迭代最近点(ICP)算法处理未知环境信息实现了移动机器人对未知环境地图构建.对移动机器人地图构建仿真实验结果表明,文中的方法能够有效地实现未知环境地图构建,可为移动机器人运动提供导向作用,具有一定的理论和现实意义.     

动态环境中移动机器人地图构建的研究进展

大部分现有的移动机器人地图构建方法都是基于静态环境的假设,而实际应用中移动机器人的工作环境是随时间变化的.综述了动态环境中移动机器人地图构建的最新研究进展,介绍了基于地图、基于运动和基于跟踪的检测动态障碍物的各种方法,分析比较了动态环境中移动机器人过滤运动障碍物传感器观测信息和结合运动障碍物传感器观测信息构建环境地图的主要方法,并总结了各种方法的优缺点.探讨了动态环境中移动机器人地图构建存在的难点问题,并展望了该领域的研究方向.     

基于人机交互的移动服务机器人导航系统

针对目前全自主移动机器人尚难实现的问题,基于人机结合的思想研制了由操作者、人机交互平台和移动机器人组成的“人—机—环境”一体化移动机器人导航系统．介绍了该系统的结构组成,阐述了系统导航策略,详细分析了人机交互、人机协作、移动机器人位姿预测及基于扩展卡尔曼滤波的位姿校正方法．设计了导航系统界面,通过在室内真实环境下的导航实验,验证了该“人—机—环境”一体化移动机器人导航系统的有效性．     

基于模糊控制器的机器人路径规划研究

针对复杂环境下移动机器人路径规划实际问题,提出了一种基于行为的移动机器人控制体系结构,设计了一种基于模糊控制器的移动机器人实时路径规划算法,为移动机器人在未知环境中的导航提出了一种新的思路.仿真结果表明,移动机器人能够克服环境中的不确定性,可靠地完成复杂任务,该算法有计算量小,效率高,鲁棒性好等优点.     

基于3D-NDT的移动机器人定位算法研究北大核心CSCD

移动机器人定位是移动机器人自主导航的基本问题,在室外环境,GPS作为成熟方案被广泛使用,但在存在遮挡、有强电磁干扰等环境下,GPS定位的精度、稳定性及可靠性受到很大影响。本文详细阐述了三维激光点云3D-NDT匹配方法,在此基础上提出了融合里程计与3D-NDT点云匹配方法的移动机器人实时定位方法,解决了移动机器人在室外弱GPS环境下定位精度无法保证的问题。利用自主研发的移动机器人平台,在大范围室外环境中进行了测试,实验结果验证了本文所提算法的有效性。     

基于EPOS的激光导航移动机器人运动控制研究

为了提高移动机器人运动控制精度,满足移动机器人精确运动的需要,研制了一种以EPOS运动控制器为核心、采用激光导航的移动机器人运动控制系统。为验证运动控制系统的正确性和有效性,采用Lyapunov函数设计出一种速度跟踪控制算法。移动机器人轨迹跟踪实验结果表明,该控制系统精度高、实时性好、可以满足移动机器人在各种环境中的行走需要。     

具有友好人机界面遥操作移动机器人的合作控制

文章针对遥操作移动机器人的人机界面、远程通讯和合作控制问题进行研究,以促进遥操作移动机器人在现实环境中的应用为目的,设计和实现了一个具有友好的人机界面、方便的通讯方式和控制灵活稳定的遥操作移动机器人。实验证明,该系统运行平稳可靠,控制灵活,可用于危险环境下的任务执行。     

基于ROS的移动机器人平台系统设计

ROS是一个开源机器人操作系统。通过对机器人操作系统的研究,首先介绍了ROS系统框架和结构特点,其次提出了在ROS环境下搭建移动机器人平台的方法,并介绍了移动机器人系统的硬件平台,最后阐述了移动机器人各个功能模块。该移动机器人可以根据事先确定的任务自主进行全局路径规划,同时不断感知周围的局部环境信息,对ROS的应用有着重要的意义。     

基于模糊控制的超声波避障方法的研究

依据移动机器人上超声波传感器的布置和分组情况,将反映移动机器人当前感知环境的期望类别进行了概括。在此基础上分析了移动机器人的模糊避障原理,并建立了一种基于人的驾驶经验的模糊逻辑控制的路障躲避方法。通过对人的驾驶经验的分析,针对移动机器人建立了路障躲避的模糊规则,并给出了输入与输出变量的隶属度函数。在Simulink中模拟机器人行驶的环境,建立相应的模型对系统进行仿真,结果表明移动机器人能实现自主行驶。     

履带腿式非结构环境移动机器人特性分析

针对非结构环境的特点,提出一种适用于非结构环境的新型履带腿移动机器人.这种移动机器人结构简洁,实用,具有很好的环境适应能力.本文主要分析该移动机器人在非结构环境下的斜坡行走、越障、跨沟、阶梯地形行走、自动复位等功能.􀁱 􀁽     

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).