力反馈电液伺服阀优化

研究力反馈电液伺服阀的初步设计问题,伺服阀的各个参数往往不是最佳的.针对动态性能(包括超调、调节时间、峰值时间及频宽)进行优化.为了优化系统性能,建立了力反馈式电液伺眼阀线性及非线性模型,根据喷嘴流量最优及非线性有约束多变量的优化函数对其静态结构参数进行优化,在保证了伺服阀的最优流量和综合控制性能的前提下,提高了伺服阀的频宽.对非性模型进行仿真计算,结果验证了改进方法优化系统的品质特性,为设计提供了可靠的参考.     

微型直线旋转音圈电机的设计与分析

针对光电子封装设备对高精度、小体积、多维运动电机的需求,设计了一种微型单定子直线旋转两自由度音圈电机.介绍了电机的结构特点和运行原理,以输出推力和转矩特性为优化目标,利用有限元仿真对其结构参数进行了优化.根据优化的结构参数制造样机进行实验,实验结果表明:电机输出推力、扭矩幅值大,推力波动、扭矩波动在0.5％以下,验证了电机设计和优化仿真的有效性.     

气液联合驱动式冲击器换向系统参数研究

为了研究换向系统结构参数对液压冲击器工作性能的影响,根据气液联合驱动式液压冲击器,采用高速开关电磁阀作为先导阀和二通插装阀作为主阀的配流换向组合,替代了传统液压换向阀配流换向系统,构建了配流换向系统数学模型,在多领域建模仿真软件AMESim平台下,构建液压冲击器的整体仿真模型,获得了不同主阀芯质量、弹簧刚度下的活塞的速度和位移曲线.结果表明:主阀芯质量越轻,弹簧刚度越大,冲击活塞到达最大冲击速度和最大位移所需的时间越短,冲击效率越高.仿真结果对提升冲击器的品质有一定的指导.     

液压制动螺纹插装集成阀动态特性仿真与研究

研究单个螺纹插装结构参数对集成阀系统的综合动态影响,为明确液压制动系统动态响应特性,采用功率键合图法建立了履带底盘液压制动螺纹插装集成阀控制系统的键图模型,根据图元之间的关系,选定状态变量,导出了系统数学模型,MATLAB软件上仿真求解系统状态方程组.对比试验曲线与仿真数据,结果相吻合,验证了系统模型和仿真算法的正确性.分析仿真结果,得到螺纹插式梭动阀阀芯球直径、进出油口直径和螺纹插式减压阀复位弹簧刚度、进出油口直径对系统的压力稳定值和稳定时间的综合影响规律.     

过渡目标值的非线性PID对自治水下机器人变深运动的稳定控制

针对传统PID在控制自治水下机器人(autonomous underwater vehicle,AUV)变深运动时易出现超调、大幅波动等问题,提出一种具有过渡目标值过程来调节误差反馈的非线性PID控制器.在分析传统PID控制下系统出现超调原因的基础上,对系统目标值安排过渡过程,利用系统输出跟踪过渡后的目标值进行误差反馈控制.通过赫尔维兹判据证明了系统稳定性,仿真验证了控制的可行性.最后通过湖上试验验证其工程可行性与实用性,得出在非线性过渡目标值的PID控制下,系统的动态响应特性得以优化,变深超调和波动问题明显改善,可实现AUV平稳地变深运动控制.     

冲击环境下航天器电磁自锁阀锁闭特性研究

电磁自锁阀广泛应用于卫星、运载火箭、飞船等航天器中,在发动机点火、火工装置爆炸、星箭分离等强冲击环境下,可能发生锁闭失效,影响航天器的安全运行.本文针对冲击载荷作用下电磁自锁阀的锁闭可靠性问题,研究了自锁阀锁闭失效机理,建立了工装-自锁阀有限元模型,并通过模态试验验证模型的正确性.基于模态叠加理论,研究自锁阀的冲击响应特性,根据冲击响应结果和阀芯能量分析,判断阀芯锁闭状态.为了验证分析结果的准确性,使用摆锤式冲击台开展冲击试验,得到的阀芯锁闭状态与理论分析结果吻合良好,说明了分析方法的有效性.本文的研究可为电磁式自锁阀的抗冲击设计提供理论基础和技术支撑.     

Terfenol-D高频磁滞特性测试与分析

目前对超磁致伸缩材料Terfenol-D的研究,主要集中于静态或准静态条件下的磁滞特性的测试和分析.为了更好的探究材料的高频磁滞特性,将Terfenol-D制成方形环状薄片样品,在不同驱动磁场频率和磁密幅值的条件下,测量其动态磁滞回线,分析磁损耗的数值和变化趋势,探究剩磁和矫顽力等磁特性参数随频率和磁密幅值的变化规律.测试结果表明:当驱动磁场频率或磁密幅值增加时,动态磁滞回线横向变宽、面积增大,剩磁、矫顽力和损耗也都随之增大.此项研究为超磁致伸缩材料Terfenol-D高频磁滞特性和电磁损耗的理论分析提供了实验数据基础.     

路面激扰与电磁激扰下电动轮车辆系统非线性全局动态特性研究

为研究电动轮车辆系统在路面 电磁联合激励下的非线性振动特性,并挖掘参数与初始条件协同作用下系统全局动力学信息,建立了计及悬架系统和轮胎的非线性弹簧力和阻尼力的电动轮车辆系统两自由度1/4垂向振动非光滑非线性时变动力学模型,考虑外部激励的谐波性和随机性以及电磁激励的分段周期性,得到了含谐波性、随机性和周期性的复杂外激励模型,分析了驱动电机转速与多初值的关联性对系统动力学共存行为及其分岔的影响规律,研究了共存运动的多样性及其吸引域的拓扑构型,揭示了转速对系统全局动力学稳定性的影响机理.结果表明：电机转速与多初值协同作用诱发系统出现多样性的共存运动,共存运动吸引域的拓扑结构复杂多样,部分共存运动的振动幅值可能较大亦可能很小,其全局动力学稳定性差异较大.电机转速与初值的协同作用对电动轮车辆系统非线性振动和全局动态特性的影响不予忽视.本文研究对电动轮车辆系统的动态性能改善和结构优化具有重要的理论意义和工程价值.     

电磁驱动燃气阀动态响应特性仿真分析

为了对电磁驱动燃气阀的动态响应特性问题进行研究,建立了燃气阀的非线性数学模型,研究了不同阀门参数对燃气阀开-关过程各阶段响应时间的影响规律,并利用Matlab/Simulink平台的电磁、机械和气动耦合的一体化仿真框图,进行了燃气阀动态过程仿真.仿真结果表明:分阶段响应时间分析方法为阀门响应特性研究提供了新的思路;驱动电压、预紧力、线圈电阻和匝数是影响响应时间的重要因素;阀门参数变化对各响应时间影响程度不同,对总响应时间to、tc的作用效果相反;响应时间tt1、tt1数值较小,且基本保持不变.     

比例伺服阀静动态特性仿真建模

建立准确的比例伺服阀静动态特性仿真模型,对研究液压伺服系统具有重要的意义。由于比例伺服阀的静动态特性随输入信号的幅值变化而变化,难以用单一数学公式准确表达,而且样本所提供的性能数据往往有限,给比例伺服阀准确的仿真建模带来不便。以产品样本为依据,利用比例伺服阀仿真建模的方法,首先建立了比例伺服阀详细的数学模型,通过对产品样本的分析,分析了比例伺服阀静动特性的组成形式;利用MATLAB软件,建立了仿真模型;将仿真结果性能曲线数据化,并运用仿真模型中相关参数进行了辨识。仿真结果表明,模型的幅相频曲线和流量曲线与产品样本上的性能参数基本一致;说明仿真建模的方法是可行的。     

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。     

基于QTE的蒙古文显示机制研究与实现

蒙古语言是中国蒙古族使用的通用语言,由于蒙古文区别于其他文字的书写方式和其自身变形机制等特点,在很多通用的文字处理引擎中都不被支持。在嵌入式产品开发与应用领域中Linux加QTE已经成为流行方式。该文给出了一种在QTE环境上实现基于标准Unicode的蒙古文点阵显示和变形算法, 并自定义了支持蒙古文的QTE组件,扩展了QTE功能,为在Linux加QTE方式的嵌入式体系结构中处理蒙古文提供了一种解决方法。