倾转旋翼飞行器配平及仿真分析

倾转旋翼飞行器是一种特殊的飞行器,在操纵方式上既有直升机的旋翼操纵,又有定翼机的舵面操纵,在过渡段何时完全退出旋翼周期变距操纵是一个很有研究意义的问题.在进行仿真特性分析之前,首先需要对倾转旋翼飞行器过渡段进行数学建模,利用统一的数学模型对倾转旋翼飞行器过渡段进行描述.考虑倾转旋翼飞行器XV-15的复杂空气动力学,加入旋翼尾流对机翼、垂尾以及平尾的气动干扰,建立了该飞行器的数学模型.利用Maltab仿真软件搭建了XV-15的simulink仿真模型,分别对直升机模式、定翼机模式以及过渡模式进行了配平,并对配平结果进行了分析,分析了不同飞行模式下的操纵特性规律,并给出了何时完全退出旋翼周期变距操纵量的建议.     

一种多旋翼飞行器的设计及实验验证

传统多旋翼机具有欠驱动特性,且平移、旋转运动均存在强耦合,极大地限制了飞行器的机动性能．为此本文设计了一种具备全向运动、推力矢量控制飞行、倾转悬停功能的多旋翼飞行器．该飞行器结构为正四面体,4个倾转旋翼模组分别固定于该四面体的4个顶点．每个倾转旋翼模组能够提供矢量推力,从结构上实现了飞行器姿态控制和位置控制的解耦,使得飞行器能够实现3维空间中全姿态的轨迹跟踪．为避免欧拉角控制产生的奇异性,设计了基于四元数的姿态控制器．利用可控性原理分析了旋翼发生故障时飞行器的可控性,证明了相比传统飞行器它具有更高的容错性．样机实验测试了该飞行器的大角度复杂机动动作以及推力矢量控制飞行能力,可实现最大70°的倾转悬停．实验结果表明,该飞行器相比于传统的四旋翼飞行器具备更高的机动性．     

基于Adams与Matlab的四旋翼飞行器控制仿真

为了避免推导四旋翼飞行器动力学方程的繁琐过程,提高其机械系统与控制系统的设计效率,在三维绘图软件Solidworks中建立四旋翼飞行器的实体模型,然后通过动力学仿真软件Adams的接口模块Adams/control与Matlab进行数据交换,利用Matlab/Simulink搭建了四旋翼飞行器控制系统的仿真平台,最终实现基于Matlab与Adams的四旋翼飞行器的联合动态仿真。同时验证了该系统具有良好的响应特性与跟踪特性,体现了Adams与Matlab联合仿真的可行性与优越性。     

旋翼模型操纵系统设计与实现

倾转旋翼模型实验台用于倾转旋翼飞行器模型的地面悬停试验及风洞试验研究,通过对倾转旋翼模型实验台旋翼模型操纵系统的研究,建立和分析了旋翼模型操纵系统的数学模型,采用永磁同步直线电机作为执行元件,运用常规PID控制方法,实现了对旋翼模型作总距操纵和横向、纵向周期变距操纵,设计了操纵系统的测控软件;试验结果显示所设计的系统能很好地跟踪输入信号,系统具有较好的静态和动态性能,满足倾转旋翼模型实验台的要求.     

四倾转旋翼无人机无源控制与飞行实验

倾转旋翼无人机以低速悬停以及快速巡航能力得到了大量的关注,但是其变化的飞行器结构(旋翼的倾转)以及较强的非线性特性(飞行速度的大范围变化)都增大了飞行控制的难度.针对一种四倾转旋翼无人机的飞行控制问题,本文中的研究内容主要基于无源性概念,改进了互联和阻尼分配无源控制以提出此飞行器的姿态与高度控制方法.通过对于飞行器动力学模型的公式化,其姿态与位置模型均可表示为端口受控哈密尔顿算子模型形式,模型中的旋翼倾转角度被格外关注以实现对于飞行模式过渡时动力学特性的分析与简化.根据上述模型简化,改进且包含积分作用的互联和阻尼分配无源控制被用于进行姿态与高度控制器设计,基于无源性概念可进行进一步的稳定性分析.最终,仿真对比实验与包含飞行模式过渡的巡航飞行实验验证了所提出控制方法的有效性.     

双桨倾转旋翼飞行器的最优飞行控制

对最新发展的双发倾转旋翼飞行器进行了研究,建立了旋翼飞行器推力矢量控制系统的数学模型,得到了两个最优飞行控制定理.由这两个定理建立了最优起飞巡航飞行轨迹.分析结果表明,该飞行器具有节约动力能源,机动性好和多用途等优点.计算机仿真证实了飞行控制系统的最优性和有效性.     

城轨塞拉门虚拟样机建立方法研究

基于Recur Dyn和Matlab/Simulink的机电联合仿真分析功能,模拟了城轨塞拉门的开关门过程,提出了一种城轨塞拉门虚拟样机建立方法。首先建立机械系统仿真模型,然后采用速度、电流双闭环控制建立控制系统仿真模型,再将机械系统与控制系统相结合建立机电联合仿真模型。对仿真模型进行仿真分析,将仿真结果和实验结果进行对比,根据对比结果对机械系统和控制系统的仿真模型进行修正。最后对塞拉门的部分亚健康工况进行了仿真模拟,进一步验证了机电联合虚拟样机的正确性。     

倾转旋翼机平均驻留时间切换鲁棒H∞跟踪控制

针对倾转旋翼飞行器模态转换阶段的飞行控制问题,本文给出了倾转旋翼机纵向运动飞行控制系统模型和一种基于参考模型的鲁棒跟踪控制方法.为了保证闭环系统在切换过程中稳定并同时满足指定的鲁棒H∞性能指标,利用状态观测器对系统不可观测状态进行估计,结合模型依赖平均驻留时间方法提出了一种倾转旋翼机切换鲁棒H∞跟踪控制方法,通过求解线性矩阵不等式得到控制器增益,并分析了系统的鲁棒稳定性.仿真结果表明,所提出的方法能够使飞行器系统准确跟踪指令,且对于控制器切换具有鲁棒性.     

倾转旋翼飞行器最优推力矢量控制

最优控制中的线性状态调节器对于一个易受外界扰动的系统来说具有十分重要的作用。飞行器在飞行过程中经常会受到风之类的外界扰动,使其偏离正常运行轨道,因此在设计飞行器的时候,考虑滚动通道和偏行通道的状态反馈调节器对于飞行器的正常飞行来说具有十分重要的意义。基于此,该文对最新发展的双发倾转旋翼飞行器进行了研究,通过建立其数学模型,分析设计了旋翼飞行器的滚动通道和偏行通道的线性状态控制器,最优飞行控制给出了倾转旋翼飞行器的最优矢茸推力控制。分析结果表明：该飞行器具有节省动力能源,机动性能好以及抗干扰能力强等优点。计算机仿真证实丁飞行控制系统的最优性和有效性。     

基于舵面平衡的五旋翼飞行器建模及飞行验证

在四旋翼飞行器基础上,增加了一个位于几何中心位置的主升力旋翼,并使用平衡舵面平衡该旋翼产生的扭矩.建立五旋翼飞行器的三维模型;推导出五旋翼飞行器的数学模型,并制成原理样机.通过飞行测试验证了机型的可行性以及数学模型的准确性.将五旋翼的中间升力电机用汽油发动机替代,即为混合动力多旋翼飞行器.研究为混合动力多旋翼飞行器开发积累了经验和数据.     

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.