基于移位继电反馈的模型辨识与控制研究

针对传统继电反馈模型辨识精度较低的问题,介绍了一种新型的移位继电反馈方法,并根据辨识结果设计了基于模型的预测PI控制器。移位继电法采用带滞环的偏置继电器,能够从单次继电反馈测试实验得到模型的三个频率响应点,移位继电法不需要任何模型先验知识,并且辨识精度较高。预测PI控制对于时滞环节具有良好的控制性能,根据移位法与ATV法的辨识结果分别设计了预测PI控制器进行仿真比较,仿真结果验证了移位继电法的实用性。     

基于偏置继电反馈的一种新的频域辨识方法

提出一种新的基于偏置继电反馈的频域辨识算法,能够对包括迟延在内的SISO系统的传递函数参数进行在线辨识。首先利用偏置继电反馈辨识过程的频率响应,一次继电测试可以辨识过程Nyquist曲线上的多点。接着利用最小二乘法估计过程传递函数参数的初值,最后应用非线性共轭梯度法准确的辨识传递函数参数。该方法辨识精度高,同时可以有效避免大多继电反馈辨识方法测试时间过长及只能辨识固定的低阶模型的缺点。仿真结果验证了算法的有效性与准确性。     

基于频域辨识的自整定PID控制器

提出了一种引入继电反馈的自整定ＰＩＤ控制器,在线测出过程对象两点的频率特性,辨识出二阶纯滞后的模型,基于相位,幅值裕度整定出ＰＩＤ参数。还介绍了该方法适应范围,仿真实验及仿真结果。     

基于继电辨识的大时滞对象的内模控制

采用改进的饱和继电反馈实验辨识高精度的过程模型，将内模控制与Smith预估控制器相结合，提出了一种适用于大时滞对象的内模控制结构，并按内模控制结构设计控制器。仿真实验表明该控制结构可获得比Smith预估控制更好的动态性能、鲁棒性和抗干扰性能，为大时滞对象的控制提供了一种新的实用方法。     

流量控制继电反馈参数自整定研究

根据继电反馈理论,通过观测管道流量对象在继电反馈下的极限环振荡,进行比例积分微分(PID)算法和参数自整定技术研究。采用阶跃响应法测试对象的数学模型。管道流量是一阶非线性小惯性过程对象,时间常数小,增益变化大。由于对象的非线性,在不同的流量设定值下,控制参数鲁棒性较差,所以继电反馈振荡应在工艺点附近进行。对单极性PID调节器,通过设置继电输出中心点的方法进行继电输出,而中心点的选择应能使对象工作在工艺点附近。由于对象惯性小、易起振,所以继电输出也应较小,继电幅值d选取5%～10%。对振荡曲线在线辨识,用变量参数归一化的方法计算继电振荡时的临界增益,再根据Ziegler-Nichols公式自动计算PID控制器参数。控制过程超调量小于10%,稳态误差小于1%。通过对试验结果的分析比较可知,带滞环继电反馈参数整定方法和微分先行PID算法适用于流量控制。采用微分先行,可以防止设定值阶跃时对流量小惯性对象的冲击而产生振荡。     

串级控制系统模型矩量辨识方法

针对现代工业过程串级控制系统的对象模型辨识问题,提出一种新的基于系统正常运行数据的闭环矩量辨识方法。该方法仅需得到一次设定值变化的正常运行数据,采用梯形积分的方法计算得到传递函数两次求导的值,再运用极小化误差方法和最小二乘法对数据拟合,从而解得二阶含滞后模型的四个未知参数,进而辨识出串级控制系统的内环和外环模型。最后,通过MATLAB进行多次仿真实验。仿真结果表明,该辨识方法不仅具有普适性和极高的辨识精度,而且对噪声信号不敏感,具备良好的鲁棒性。     

基于继电反馈自整定PID控制器研究及应用

研究控制器优化问题,提出了一种改进型的继电反馈自整定PID,用来控制自衡过程.改进型的继电环节是由一个标准的继电环节串联一个比例积分控制器组成,比例积分控制器的比例系数设定为单位增益,积分时间由保持最小相角裕度为π/6来确定.自整定PID控制器的参数是根据改进型的继电环节产生的极限环的输出数据确定的,微分时间常数需保持上述提到的相角裕度.积分时间常数等于改进型继电环节中的比例积分控制器的积分时间,进行仿真.结果PID控制器可用到造纸机的热泵供汽控制中,并收到了明显效果.     

复杂多变量过程模型的闭环频域辨识

针对模型预测控制中模型辨识存在的问题,提出一种多变量过程闭环辨识方法.首先通过对多变量闭环系统正常运行产生的输入输出信号进行信号分解和频谱分析,得出多变量过程对象在重要频率段上的频率响应特性矩阵;然后采用最小二乘法,在幅值和相位两方面拟合一个二阶加纯滞后模型结构;最终获得一个多变量传递函数模型矩阵.仿真实验表明,该闭环辨识方法适用于广泛的多变量过程对象,具有很好的鲁棒性和精确性.     

基于尺度滤波与小波去噪的PID继电整定

针对PID参数继电整定法存在继电环节对噪声敏感和受噪声污染的输出波形无法提取出特征参数等缺陷,提出一种利用小波技术的解决方法.该方法以尺度函数为低通滤波器在线滤除反馈信号中的高频干扰,并用小波阈值去噪法离线去除输出波形中的噪声,恢复真实波形以提取出精确的特征参数.从理论上证明了尺度滤波与小波去噪的正确性,并给出了实用算法.仿真实例验证了该方法的有效性.     

基于选择性自校正的模糊动态矩阵控制

针对实际系统模型失配不确定性及其难以控制的问题,提出了一种基于选择性自校正的模糊动态矩阵控制方法。在模型失配较大,基础动态矩阵控制自身的反馈校正无法实现理想的控制时引入最小二乘法在线辨识对象模型。同时为了得到更准确的模型,辨识过程尽可能避开了扰动的影响,对反馈校正参数采用模糊调节的方法。仿真研究结果表明,即使对于纯滞后非最小相位且有扰动的系统,在其参数与结构发生变化时,该控制方法保证了较好的鲁棒性和抗扰性。     

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.