弱通信条件下多机器人编队控制及稳定性分析

为消除弱通信因素给多机器人编队控制系统带来的影响,基于一致性理论,提出了一种时延依赖的分布式编队控制算法.利用编队图描述机器人群体内部的网络拓扑结构,通过图的矩阵表示,基于矩阵论和控制理论研究具有通信时延的多机器人系统形成稳定的期望编队的条件.根据Lyapunov稳定性定理,得到了线性矩阵不等式(LMI)形式的时延独立和时延依赖的稳定条件,并在此基础上进一步证明采用的控制方法能够保证多机器人系统全局渐近地收敛至期望队形和期望速度.最后,通过一个多机器人编队实例对控制算法和结论进行验证.结果表明在满足系统稳定条件下,所采用的编队控制算法能够保证多机器人系统形成稳定的期望编队.     

基于仿生鱼群优化方法的非完整机器人队形控制(英文)

利用人工鱼群优化(AFSO)方法研究了多机器人的队形控制问题。机器人编队可视为寻迹问题,而编队寻迹是不断减小机器人与其期望编队位置之间的平移和角度误差的优化过程。每一个机器人的控制指令可看做是人工鱼群,通过一系列的控制实现期望队形。队形控制策略中包含机器人间的冲突规避行为。利用Matlab中的多机器人仿真器MRsim工具进行了仿真,结果表明,提出的方法具有很高的有效性和效率,适用于各种形式的队形,可以被广泛应用在没有精确系统模型的无线传感器网络中。     

基于仿生鱼群优化方法的机器人队形控制

本文利用人工鱼群优化（AFSO）方法研究了多机器人的队形控制问题。机器人编队可视为寻迹问题,而编队寻迹是不断减小机器人与其期望编队位置之间的平移和角度误差的优化过程。每一个机器人的控制指令可看做是人工鱼群,通过一系列的控制实现期望队形。队形控制策略中包含机器人间的冲突规避行为。本文利用Matlab中的多机器人仿真器MRsim工具进行了仿真,结果表明本文提出的方法具有很高的有效性和效率,适用于各种形式的队形,可以被广泛应用在没有精确系统模型的无线传感器网络中。     

基于传感探测系统的多自治水下机器人编队协调控制

针对自治水下机器人(AUV)编队协调控制问题,研究了基于传感探测系统的主从式编队协调控制方法.该方法能够避免AUV编队之间依靠水声通信而造成的通信延迟和数据丢失的问题,提高编队控制的可靠性以及生存能力.首先根据领航者位置信息和期望的编队队形得到跟随者的参考路径,跟随者可以实时测得领航者的距离和航向信息并与参考路径相对比.其次为了使跟随者轨迹在短时间内收敛于参考路径从而得到期望的队形,利用Lyapunov函数设计了反演控制器.最后对设计进行了编队控制的仿真.结果表明,AUV编队队形保持良好,所采用的方法具有很好的可行性.     

基于行为的多机器人编队控制的仿真研究

多机器人的编队问题是多机器人协作中的一个典型问题,编队包括队形形成和编队控制。针对多机器人的编队控制问题,本文采用基于行为法和基于leader的协调策略相结合的方法。首先根据Motor Schema的反应式控制结构,设计了五种基本行为,即奔向目标行为（move-to-goal）,保持队形行为（keep-formation）,躲避静态障碍物行为（avoid-stastic-obstacle）,躲避机器人行为（avoid-robot）和随机行为（random）,对各行为进行加权形成局部控制器来控制机器人的局部行为。然后利用基于leader的协调策略来协调各个机器人的行为,形成全局控制器来控制机器人的最终的行为。通过仿真,验证了该方法的可行性和有效性。     

基于领航跟随法和星系动力学的多机器人编队控制

针对机器人常规编队控制方法编队精度低、机器人易掉队,且当队形进行大角度变换时跟随者不能快速适应的问题,提出了一种基于领航跟随和星系动力学(LF-GD)机器人编队控制方法.该方法结合了领航跟随法控制简单、编队快速和星系动力学法编队稳定和动态均衡的优点.实现了机器人快速编队和动态避障的性能要求,避免了队形大角度变换时机器人相互之间的碰撞和掉队问题,提高了整个编队系统的智能性和环境适应性.通过仿真验证了该方法的可行性和有效性.     

一种基于局部感知的多机器人编队控制方法

针对未知环境下多机器人难以实现灵活、稳定的编队控制的情况,在分析领队-跟随法、基于行为方法以及虚拟结构法的编队控制方法基础上,提出了一种模拟人类社会中方队形成与变化的思想,将其应用在多机器人的编队中,进行多机器人的编队控制.机器人存储不同编队队形的相对位置信息,通过领航者发布队形控制信息,跟随者查找并匹配预先存储的队形...     

基于反步法的多移载工装协同作业编队控制策略

研究了一种基于反步法的多移载工装协同作业控制策略，提出了基于改进人工势场法和纯轨迹跟踪法的期望运动状态规划方案，并根据自适应蒙特卡洛定位方法确定了实际运动状态的估计值，设计了反步法与虚拟领航跟随法结合的队列控制器.构建了基于机器人操作系统(ROS)环境的仿真模型，并开展仿真验证.结果表明：提出的队形误差计算方法能够提高误差估计精度，该编队控制策略能够使得队形误差在6.2 s内收敛，所设计的队形控制器能够满足多移载工装的作业要求.     

基于领导者的群体机器人编队及导航控制

介绍了基于领导者的群体机器人一致性方法,在此基础上提出一种群体机器人编队及导航控制方法。该方法采用分层控制策略,即控制系统分为目标层、领导层和跟随层。将目标层中目标点的位置信息发送给领导者,采用位置一致性算法使领导者朝目标运动;与此同时,领导者将其状态信息发送给跟随层中的跟随者,采用基于领导者的群体机器人编队控制方法,使跟随者与领导者保持一定的队形朝着目标运动。该方法可针对由多个子集构成的群体机器人系统进行导航。通过计算机仿真和群体机器人实验平台验证了所提方法的有效性。     

基于MAPSO的混合式多机器人编队控制

为了解决目前编队控制中队形不稳及复杂环境适应性差等问题,针对全局环境中含有动/静态障碍物的复杂环境,提出一种将Leasder-Follower法及人工势场法改进结合的混合式多机器人编队控制新方法;同时,引入多智能体粒子群优化(MAPSO)算法对多机器人编队控制相关参数进行在线优化,能有效避免机器人陷入局部最优,增强其抗干扰能力.对该方法进行仿真分析,并和Leasder-Following法与基于行为法相结合的混合编队控制方法进行比较.结果表明:MAPSO的混合式多机器人编队控制方法能更好地完成多机器人在复杂环境下的编队控制任务,验证了其有效性和可行性.     

An Index mechanism for multi-scale view in spatial databases

There are numerous geometric objects stored in the spatial databases. An importance function in a spatial database is that users can browse the geometric objects as a map efficiently. Thus the spatial database should display the geometric objects users concern about swiftly onto the display window. This process includes two operations:retrieve data from database and then draw them onto screen. Accordingly, to improve the efficiency, we should try to reduce time of both retrieving object and displaying them. The former can be achieved with the aid of spatial index such as R-tree, the latter require to simplify the objects. Simplification means that objects are shown with sufficient but not with unnecessary detail which depend on the scale of browse. So the major problem is how to retrieve data at different detail level efficiently. This paper introduces the implementation of a multi-scale index in the spatial database SISP (Spatial Information Shared Platform) which is generalized from R-tree. The difference between the generalization and the R-tree lies on two facets: One is that every node and geometric object in the generalization is assigned with a importance value which denote the importance of them, and every vertex in the objects are assigned with a importance value,too. The importance value can be use to decide which data should be retrieve from disk in a query. The other difference is that geometric objects in the generalization are divided into one or more sub-blocks, and vertexes are total ordered by their importance value. With the help of the generalized R-tree, one can easily retrieve data at different detail levels.Some experiments are performed on real-life data to evaluate the performance of solutions that separately use normal spatial index and multi-scale spatial index. The results show that the solution using multi-scale index in SISP is satisfying.     

Wuhan University Journal of Natural Sciences TOTAL CONTENTS

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Advances in broadband wireless communications under high-mobility scenarios

Future mobile communication systems aim at providing very high data transmission rates, even in high-mobility scenarios such as high-speed wheel-track trains, maglev trains, highway vehicles, airplanes, guided missiles or spacecraft. A particularly important commercial application is the strong and increasing worldwide demand for high- speed broadband wireless communications （up to 574.8 km/ h test speeds or 380 km/h commercial speeds） in railways, providing data, voice and video services for applications such as onboard entertainment services to passengers, train control, train dispatch, train sensor status handling and sur- veillance. In such high-mobility scenarios, there are a number of communication challenges, including fast hand- over, location updating, high-speed channel modeling, estimation and equalization, anti-Doppler spreading tech- niques, fast power control, and dedicated network architec- ture. Because signal transmission in very high-speed scenarios will inevitably experience serious deterioration, it is imperative to develop key broadband mobile communi- cation techniques for such high-speed vehicles.     

Perspherical Approaches for Electrons in Atoms and Charged Excitons in Quantum Wells

Instead of following Fock’s expansion,we solve the Schrodinger equation for some quantum mechanical manybody systems such as electrons in atoms and charged excitons in quantum wells in a similar way in hyperspherical coordinates by expanding the wave functions into orthonormal complete basis sets of the hyperspherical hannonics(HHs)of hyperangles and generalized Laguerre polynomials(GLPs)of the hyperradius.This leads the equation to     

Scale-based spatial data model for GIS

Being the primary media of geographical information and the elementary objects manipulated, almost all of maps adopt the layer-based model to represent geographic information in the existent GIS. However, it is difficult to extend the map represented in layer-based model. Furthermore, in Web-Based GIS, It is slow to transmit the spatial data for map viewing. In this paper, for solving the questions above, we have proposed a new method for representing the spatial data. That is scale-based model. In this model we represent maps in three levels: scale-view, block, and spatial object, and organize the maps in a set of map layers, named Scale-View, which associates some given scales.Lastly, a prototype Web-Based GIS using the proposed spatial data representation is described briefly.     

英文诗歌中的喻类修辞

为了有助于提高英文爱好者的个人情操、文化素养和学习兴趣,以及专业人员对英语学习和研究进行多途径的探索,本文通过一些精选诗歌的引证和分析,着重论述了喻类修辞法在英文诗歌中的运用其及效果。     

Man Is Unable to Change the Miserable Life——Analysis of the Arrangement of Four Characters in The Glass Menagerie

Tennessee Williams is considered as one of the most important American playwrights since World War II.The Glass Menagerie is his first successful drama,which describes a tragic situation of family and means to say that Man is unable to change the miserable life,no matter whatever means he try,This essay focuses on the analysis of the arrangement of the four main characters:Laura.Amanda,Jim and Tom to reveal the theme.Laura is fragile.Amanda is brave.Jim is vital.Tom is sensible.And all of them develop and try the different means to struggle against life,but fail tragically.With the evidence,the paper comes to conclusion naturally that Man is unable to change the miserable life,and he dooms to fail.     

Characterization of root-nodulating bacteria on Retama raetam in arid Tunisian soils

The aim of this study is to investigate the diversity of Retama raetam root-nodule bacteria isolated from arid regions of Tunisia. Twelve isolates, chosen as representative for different 16S rRNA gene patterns, were characterized by 16S rRNA gene sequencing and phenotypic analysis. Isolates were assigned to Sinorhizobium, Rhizobium and Agrobacterium. Symbiotic properties of Sinorhizobium and Rhizobium isolates showed a large diversity in their capacity to infect their host plant and fix atmospheric nitrogen. Strain RK 22 identified as Rhizobium was the most effective isolate.     

An Affordable Accurate Evaluation of the Binding Conformations Predicted by Molecular Docking Studies in Bio-System

正Recently,docking has been widely used to predict the binding-modes of protein-inhibitors,when the crystal complexes structure was absent.Most docking algorithms are able to generate a large number of probable conformations,it,however,is difficult to effectively evaluate these docking poses and identify the most reasonable bindingmode.In the present study,on the basis of the crystallographic data of human 3-hydroxy-3-methylglutaryl coenzyme     

WIMAX与WI-FI技术分析及联合组网

介绍了WiMAX与Wi-Fi两种无线宽带接入技术,并对两者之间的关系及相互之间的影响做了对比及分析,并对WiMAX的关键技术进行了详细说明,最后对两者的联合组网方式做了简单的探讨。