低频大幅隔振器设计及实验

为了突破传统隔振器刚度和承载能力之间的矛盾,需要隔振器具有高的静态刚度,低动态刚度的特性.如今的准零刚度隔振器技术可以实现低频微幅隔振,但是对于大幅振动,隔振效果并不明显甚至失效,因此突破宽幅隔振成为隔振领域亟待解决的问题.为此,我们利用多稳态折纸通过并联装配的方式,构造具有宽幅零刚度区间的折纸型隔振器,以解决传统隔振器振动抑制幅值较低的问题.本文建立了宽零刚度隔振器模型,提出宽幅零刚度的设计方法,并通过动力学分析分析了模型的隔振效果.最后搭建试验样机,验证了理论的正确性.这种设计打破了传统准零刚度隔振器单点准零的设计准则,能够在一个大幅范围内保证稳定性,同时实现零刚度,极大拓宽了隔振器的适用范围.这种设计理念能够被用在新隔振材料设计和航空、船舶等大幅低频动态环境中.     

基于准零刚度隔振器的自适应模糊控制

准零刚度隔振器兼具高承载力和低固有频率,对于隔离地面的振动具有良好的效果.但准零刚度隔振器在平衡位置处刚度较低,这会使负载对低频的直接扰动力具有很强的敏感性并且隔振器的工作位置很容易出现偏差；其次,准零刚度隔振器的负载受到的扰动越大则表现出的非线性越强,这种非线性又会导致振幅放大和幅值跳跃.针对以上问题,提出了一种基于非线性准零刚度隔振器的自适应模糊控制方法,该方法在天棚阻尼的基础上增加了位置反馈量,并以负载的振动频率作为自适应系数,以Sigmoid函数建立自适应系数和振动频率之间的关系,控制方法采用模糊控制.首先建立了准零刚度隔振器的物理模型,之后利用Matlab/Simulink对系统动力学特性和控制系统进行仿真,最后搭建了主动隔振试验系统对所提方法的有效性进行验证.结果表明,所提方法对于作用在负载上的复杂且时变的直接扰动具有良好的抑制效果,同时对负载具有精准定位的作用.     

基于弹性关节的二维宽频隔振结构的设计及优化

为了得到具有隔振功能的新型材料,本文对带有弹性关节的新型二维隔振结构的形状、尺寸及材料的选取进行了研究.探究了负泊松比结构实现宽频的带隙功能的作用,分析其在低频处的隔振性能.首先,文章建立了基于弹性关节单元的有限元模型,并以弹性关节的角度作为设计变量,确定角度与单元模型前三阶模态频率之间的关系,获得了最优的结构参数及单元构型.其次,对单元结构进行了动力学分析,给出了结构的动力学响应曲线,得到了隔振频带与结构参数的关系,并且确定了最优角度下的带隙深度和宽度.最后,建立了二维隔振结构有限元模型,对此二维结构进行了动力学分析,得到了在不同方向激励下的动力学响应曲线.结果表明,该二维隔振结构在低频处具有宽而深的频率带隙,实现了将弹性关节与二维隔振结构相结合的低频宽频隔振,为隔振领域的结构和材料设计提供了新思路.     

X型准零刚度隔振器动力学设计及分析

结合准零刚度(quasi-zero stiffness,QZS)结构和X型结构,设计了一种新型X型准零刚度隔振器(X-QZS).通过准零刚度弹簧组替换X型结构中的线性弹簧,达到超低频隔振的效果.利用拉格朗日方程建立了动力学方程,通过谐波平衡法和弧长法得到了系统响应的近似解析解并通过数值法验证了解析解的正确性.研究了系统的动力学响应和隔振性能.分析结果表明X-QZS结构在超低频范围的隔振效果能够比QZS更好,共振频率更低,隔振频带更宽.     

隔振对象重量变化对准零刚度隔振器隔振性能的影响

本文主要研究隔振对象重量变化对一类准零刚度隔振器隔振性能的影响,并给出了新的研究结果.文中使用欧拉屈曲梁构建负刚度调节结构并设计了隔振系统的平衡位置可调机构.假设系统有轻微的过载和超载,推导了系统的动力学方程并进行求解,定义了非线性隔振系统的力传递率及位移传递率来评价系统的隔振性能.对线性隔振系统,超载会让隔振频率略微降低,共振放大峰略微增大.对于准零刚度隔振系统,力传递率和线性系统类似,但是对于位移传递率,过载会导致系统固有频率和共振放大峰均升高,反而不利于隔振.研究结果可以对此类隔振系统的使用场合以及对过载和轻载的选择有工程指导意义.     

一种基于电磁—空气弹簧的非线性隔振器理论与实验研究

本文提出一种主要由空气弹簧和永磁体所组成的具有准零刚度特性的非线性隔振器.首先,通过分析空气弹簧和磁体的受力特性,建立隔振器力-位移关系和刚度-位移关系,揭示隔振器静态力学特性,并分析隔振器参数对系统刚度的影响规律.然后,采用谐波平衡法计算隔振器力传递率特性.结果表明,通过在适当范围内调节系统阻尼比或激励幅值,所提出的非线性隔振器在隔振频率范围内优于普通空气弹簧隔振器.最后,通过实验验证隔振器的隔振性能.该研究可为小振幅甚至微振动系统的振动隔离提供新的参考.     

Stewart并联机构主动隔振平台的非线性L2鲁棒控制

以Stewart并联机构主动隔振平台为研究对象,提出一种非线性L2鲁棒主动隔振控制方法．应用牛顿—欧拉方法建立了由直线音圈电机驱动的隔振平台的完整动力学模型．在模型非匹配不确定性的上界未知的情况下,充分考虑动力学模型的非线性特性、参数摄动以及未建模动态等因素对隔振控制的影响,设计了模型非匹配不确定性上界估计的调节律并推导出鲁棒主动隔振控制律．通过构造合适的存储函数,在理论上证明了系统的稳定性和满足L2性能准则的隔振性能．仿真结果表明,该方法能有效地抑制6个方向的低频振动,得到满意的隔振性能．     

基于自适应滑模控制的主动磁悬浮隔振系统

该文研究了一套电磁悬浮主动隔振系统,并设计了相应的自适应滑模隔振算法。考虑该主动隔振系统的复杂特性,采用有限元法对其进行磁路分析,将计算结果与理论模型进行比较,并通过引入不确定项获取更加准确的改进模型。在此基础上设计了自适应滑模隔振控制律,该控制律具有较强的鲁棒性,有效地抑制了模型的强非线性以及参数不确定性所带来的影响,且设计中无需预知振源的振动形式。仿真表明了整套隔振系统具有较强的低频隔振能力。     

带柔性天线卫星机动过程动力学分析

基于刚柔耦合动力学模型仿真分析卫星机动过程的动力学特性.模型将天线上的柔性金属网近似成阻尼弹簧模型,将径向肋刚化并等效其柔性为径向肋根部的扭簧转角;利用该简化模型研究了卫星机动过程中径向肋和金属网的柔性对卫星姿态的影响.通过仿真分析天线卫星系统在不同结构参数情况以及不同驱动力作用下的卫星机动过程动力学特性,对比分析得出：提高径向肋的固有频率,增加金属网以及增大径向肋扭簧的阻尼能有效降低刚柔耦合问题对卫星本体姿态的影响.     

试验台测控仪器隔振装置振动传递特性分析

试验台精密测控仪器在工作过程中会受到振动设备的干扰,从而对其正常工作产生影响,因此需要采用隔振装置进行振动保护.本文以双层隔振装置为研究对象,结合有限元法和阻抗综合法建立了多点多维柔性动力学模型,分析了不同仪器质量、系统结构型式和隔振器参数对隔振装置振动传递特性的影响,结果表明所设计的双层隔振装置可以满足使用需求,增加上台面厚度和减小隔振器刚度可显著提高隔振效率.     

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。