四旋翼无人机姿态系统复合连续快速非奇异终端滑模控制EI北大核心CSCD

本文针对受多源干扰影响的四旋翼无人机姿态系统,基于复合连续快速非奇异终端滑模算法,研究了姿态指令变化率未知情况下的连续有限时间姿态跟踪控制问题.首先,基于四旋翼无人机姿态回路动力学模型,通过引入虚拟控制量实现姿态跟踪误差动态的三通道解耦;其次,分别针对各通道跟踪误差动态设计高阶滑模观测器,实现跟踪误差变化率和集总干扰的有限时间估计;最后,结合姿态跟踪误差变化率的估计信息,构建动态快速非奇异终端滑模面,并在控制设计中用指数幂函数代替符号函数以保证控制量连续.并且基于Lyapunov分析方法给出了姿态跟踪误差有限时间收敛的严格证明,仿真结果验证了所提方法的有效性.     

时变终端滑模自适应有限时间控制算法

为实现非线性系统输出对期望轨迹的有限时间内精确跟踪，提出一种有限时间鲁棒控制算法。通过设计一种无到达过程的时变终端滑模面，在保证有限时间收敛的基础上，消除了传统滑模控制中固有的稳态误差，实现系统输出对期望轨迹的精确跟踪。设计了自适应更新律补偿由参数摄动导致的系统扰动，增强系统对内部未知参数摄动的鲁棒性。对比仿真结果表明：时变终端滑模控制比线性滑模控制的轨迹跟踪时间快41.5%；线性滑模控制器下的轨迹跟踪稳态误差为0.005，时变滑模控制器使轨迹跟踪的稳态误差降为0，实现精确跟踪。     

改进滑模面的自适应终端滑模混沌同步控制

为了提高混沌同步误差在滑模面上的收敛速度,提出了一种改进的终端滑模面,并设计了自适应终端滑模控制律,改善了混沌同步控制性能。在终端滑模面中引入系统状态量的幂指函数积分项,提高了误差沿滑模面的收敛速度。针对同时考虑系统中存在未知参数、不确定项及外部扰动的混沌系统的同步控制问题,设计了自适应终端滑模控制律,实现了混沌同步系统的滑模控制,并对系统的稳定性进行了证明。将所设计的滑模控制方法应用于混沌同步控制系统中,相比于传统终端滑模控制方法,改进方法能够明显提高误差的收敛速度。仿真实验验证了所提方法的有效性。     

仿生假手抓握力控制策略

为了使仿生假手完成各种精细作业,提出一种抓握力控制策略.在自由空间和约束空间中分别使用基于位置的阻抗控制和力跟踪阻抗控制.在过渡过程中使用模糊观测器切换控制模式.两种控制模式采用同一个基于位置的阻抗控制器,在约束空间向阻抗控制器中引入参考力,以满足约束空间的抓握力控制要求.这种方法可以使关节在自由空间和约束空间中分别实现良好的轨迹跟踪和力矩跟踪,在过渡过程中实现控制模式的可靠切换和系统的稳定过渡.提出一种自适应滑模摩擦力补偿方法,利用终端滑模思想设计了滑模函数,使得系统跟踪误差在有限时间内收敛,避免了传统线性滑模面状态跟踪误差无法在有限时间内收敛至0的问题.根据指数形式摩擦力的特点,利用终端滑模控制思想获得包含摩擦力参数估计的滑模控制律,并基于李亚普诺夫稳定性定理推导了估计参数的在线自适应律.对该抓握力控制策略在HIT假手上进行了抓取实验,实验结果证明了控制策略的有效性.     

基于非线性增益递归滑模的船舶轨迹跟踪动态面自适应控制

针对三自由度全驱动船舶存在模型不确定和未知外部环境扰动的情况,设计出一种基于非线性增益递归滑模的船舶轨迹跟踪动态面自适应神经网络控制方法.该方法综合考虑船舶位置和速度误差之间关系设计递归滑模面,引入神经网络对船舶模型不确定部分进行逼近,设计带σ-修正泄露项的自适应律对神经网络逼近误差与外界环境扰动总和的界进行估计,并应用一种非线性增益函数构造动态面控制律,选取李雅普诺夫函数证明了该控制律能够保证轨迹跟踪闭环系统内所有信号的一致最终有界性.最后,基于一艘供给船进行仿真验证,结果表明,船舶轨迹跟踪响应速度快、精度高,所设计控制器对系统模型参数摄动及外界扰动具有较强的鲁棒性.     

基于观测器的机器人鲁棒跟踪控制

基于滑模控制原理设计稳定的状态观测器，在此基础上。研究了仅有关节角位移可测量的机器人轨迹跟踪控制问题。运用反推设计方法提出一种机器人鲁棒跟踪控制新方案。通过引入用于抑制观测误差的阻尼项和调制参数。加快了输出跟踪误差的收敛速度。利用李亚普诺夫方法分析了闭环控制系统的全局稳定性，证明了系统所有状态信号有界，跟踪误差收敛到零。仿真结果进一步表明，提出的控制方案具有较强的鲁棒性和良好的跟踪性能。     

基于扰动观测器补偿的机械臂非奇异快速终端滑模控制

针对机械臂系统在实际应用中存在的建模误差及未知扰动问题, 设计了一种基于扰动观测器的改进型非 奇异快速终端滑模控制策略. 通过扰动观测器准确估计系统存在的总扰动, 并设计恰当的非线性增益函数使扰动观 测误差指数收敛, 实现了对控制器的前馈补偿. 考虑到终端滑模存在的奇异性问题, 结合扰动观测器设计了非奇异 快速终端滑模控制器, 在保证跟踪误差有限时间收敛的同时抑制了滑模控制固有的抖振现象. 同时在控制器设计过 程中, 用fal函数代替sig函数有利于削弱滑模控制抖振, 提高系统稳定性及跟踪精度. 最后, 利用MATLAB软件进行 实验仿真, 验证了所设计控制器的有效性.     

基于时变终端滑模的任意迭代初态抑制控制EI北大核心CSCD

为解决迭代学习过程中的任意迭代初值和迭代收敛理论证明难的问题,本文构造了一种轨迹跟踪误差初值恒位于滑模面内的时变终端滑模面,将轨迹跟踪误差初值不为零的轨迹跟踪控制问题转换为滑模面初值恒为零的滑模面跟踪控制问题,建立了任意迭代初值与相同迭代初值的迭代学习控制理论连接桥梁.本文提出一种基于时变滑模面的比例–积分–微分(PID)型闭环迭代学习控制策略,基于压缩映射原理证明了迭代学习的收敛性,给出了迭代收敛条件.时变终端滑模面经有限次迭代学习收敛到零,达到轨迹跟踪误差最终稳定在时变滑模面内的目的;Lyapunov稳定理论证明了位于滑模面内的轨迹跟踪误差在有限时间内收敛到原点,达到轨迹局部精确跟踪目的.随机初态下的工业机器人轨迹跟踪控制数值仿真验证了本文方法的有效性和系统对外部强干扰的鲁棒性.     

基于神经网络观测器的反推终端滑模位置控制

为了提高永磁直线同步电机(PMLSM)的位置跟踪精度,本文提出了一种基于神经网络自适应观测器的反推终端滑模控制(TSMC)方法.首先,建立PMLSM的动力学模型.然后,利用RBF神经网络的万能逼近特性去逼近系统中不确定性,并将逼近后的输出信号输入给自适应观测器进行跟踪目标位置和速度的估计,补偿由不确定性所导致的跟踪误差,进而获得高精度的跟踪性能.同时反推TSMC方法能够保证系统状态在有限时间内收敛,有效改善了系统响应速度和鲁棒性能.此外,设计出一种新型饱和函数来改善系统抖振,并利用Lyapunov稳定性定理进行了闭环系统稳定性分析.最后,通过空载和负载实验证实了该控制方案的有效性.     

基于云模型的船舶航迹跟踪滑模控制

为解决船舶路径跟踪控制中存在的非线性问题,引入滑模控制实现船舶的轨迹跟踪。采用云模型与指数趋近律结合的方法,设计基于云模型的轨迹跟踪智能滑模控制器,以减少滑模控制中的抖振。仿真结果表明,通过云模型的不确定性推理,智能滑模控制器能够动态调整滑模控制的趋近速度,抑制抖振的产生,船舶动态轨迹跟踪性能良好,能够精确控制航迹。     

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.