自适应评价设计的执行依赖方法

自适应评价设计(ACD)是一种适用于非线性系统的近似最优控制方法。介绍了自适应评价设计的执行依赖启发式动态规划(ADHDP)和执行依赖双启发式动态规划(ADDHP)方法,该方法可以解决由对象非线性或者系统建模不良所造成的不确定性问题,适于处理时变的复杂系统和动态变化的复杂任务。阐述了两种方法的结构、计算和评价网络输出上的不同,并通过仿真分析了两种方法各自的学习能力、控制效果。     

近似动态规划在双容水箱预测控制中的应用

在双容水箱液位优化控制的研究中,由于双容水箱液位控制系统是一个典型的具有大滞后、非线性特征的难控系统,造成系统液位控制不稳定.为解决上述问题,提出一种近似动态规划的预测控制算法,建立反映系统预测时域内参考轨迹与预测输出偏差的性能指标函数J.将函数J的优化问题看作动态规划问题,为了避免“维数灾”,采用近似动态规划求解J的近似值,获得最(次)优控制策略.算法包括评价网络、模型网络和执行网络三部分.评价网络近似性能指标函数,模型网络近似系统输入输出关系,执行网络给出相应控制策略.通过不断在线调整各网络参数,使系统输出逼近参考液位.仿真结果表明,与经典PID算法相比,改进算法表现出更好的控制效果.     

基于迭代神经动态规划的数据驱动非线性近似最优调节

利用数据驱动控制思想,建立一种设计离散时间非线性系统近似最优调节器的迭代神经动态规划方法.提出针对离散时间一般非线性系统的迭代自适应动态规划算法并且证明其收敛性与最优性.通过构建三种神经网络,给出全局二次启发式动态规划技术及其详细的实现过程,其中执行网络是在神经动态规划的框架下进行训练.这种新颖的结构可以近似代价函数及其导函数,同时在不依赖系统动态的情况下自适应地学习近似最优控制律.值得注意的是,这在降低对于控制矩阵或者其神经网络表示的要求方面,明显地改进了迭代自适应动态规划算法的现有结果,能够促进复杂非线性系统基于数据的优化与控制设计的发展.通过两个仿真实验,验证本文提出的数据驱动最优调节方法的有效性.     

基于改进粒子群算法的永磁同步电机PID控制器

为提高永磁同步电机系统的控制精度,提出一种使用改进粒子群算法优化的永磁同步电机PID控制器。首先建立永磁同步电机数学模型,然后采用改进粒子群算法对PID控制器参数进行优化,实现永磁同步电机参数在线辨识,最后采用仿真实验对其性能进行测试。仿真结果表明,相对于传统的永磁同步电机PID控制器,本文方法优化的永磁同步电机PID控制器改善了系统响应性能,能够使永磁同步电机获得良好的稳定性、鲁棒性和动态性能。     

PMSM调速系统CMAC网络PID并行优化控制

针对永磁同步电机调速系统存在多变量、非线性和强耦合的控制特点,提出了基于混沌优化策略与自适应CMAC网络PID并行控制相结合的控制方法,并将其应用于永磁同步电机调速系统的参数设计中.该方法首先通过混沌搜索,得到PID控制器参数的次优值,然后再利用变尺度的方法在次优值附近找出PID控制器参数的全局最优值.与传统CMAC网络PID并行控制以及单纯PID控制相比较的仿真结果表明.该方法可以更好地提高永磁同步电机调速系统的控制精度和响应速度.     

改进TD3算法在电机PID控制器中的应用

本文针对永磁同步电机(PMSM)在工业领域中的多变量、非线性和强耦合特性以及传统PID控制在应对其变化时可能导致参数调整困难、响应延迟、鲁棒性差以及适应性问题,提出一种结合双延迟深度确定性策略梯度(TD3)算法和PID控制的创新方案,以优化PID参数调整,实现更精确的电机速度控制.在本文的方法中,融合双向长短期记忆网络(BiLSTM)到Actor和Critic网络中,极大增强了对PMSM动态行为的时间序列数据处理能力,使得系统不仅能够准确捕捉当前状态,还能预测未来趋势,从而实现对PID参数更精确和适应性强的自整定.此外,通过整合熵正则化和好奇心驱动的探索方法进一步增强策略的多样性,避免过早收敛到次优策略,并鼓励模型对未知环境进行深入探索.为验证方法的有效性,设计了一个永磁同步电机的仿真模型,并将本文提出的方法BiLSTM-TD3-ICE与传统的TD3以及经典的Ziegler-Nichols (Z-N)方法进行对比.实验结果充分证明了本文提出的策略在控制性能上具有显著的优势.     

基于自适应PID的永磁同步电机转速控制研究

介绍了一种基于自适应PID算法的永磁同步电机转速控制,提出了一种简化型自适应策略,对PID参数进行在线自校正,与传统PID控制器相比,增强了控制器对电机非线性、时变性及扰动的响应性能。且该自适应策略结构简单,更易于工程实现,具有一定的工程实用价值。系统仿真结果表明,与传统PID控制效果对比,响应过渡时间更短,超调量更小。     

BP神经网络在永磁同步电机中的应用

永磁同步电机是一个多变量、非线性、强耦合的系统,传统PID速度控制效果不理想.在分析永磁同步电机数学模型的基础上,采用改进型BP神经网络与传统PID控制相结合作为速度控制器,应用于永磁同步电机调速系统中.在电机初始运行阶段采用传统PID控制,网络学习一段时间后,切换到经过改进的BP神经网络在线自整定PID控制,实现了电机速度的自适应控制.仿真结果表明:应用这种新型控制方式的永磁同步电机调速系统具有良好的动态性能和稳态精度.     

机器人永磁同步电机控制器的控制策略设计

研究具有自主知识产权的高性能交流伺服控制技术,尤其是针对具有广阔应用前景的永磁同步电动机的伺服控制技术,具有重大的理论意义和经济利益。在分析永磁同步电机的近似动态结构的基础上,分别对电流环控制器、速度环控制器、位置控制器进行设计。电流环采用常规的PI控制器,速度环采用基于遗传算法的参数自整定PI控制器,位置环采用简单的P控制器。针对选用的三相Y型连接永磁同步电机求得控制参数。应用该设计策略进行永磁同步电机数学模型的设计,可以实现对同步电机的稳定控制。     

基于自适应粒子群优化算法的永磁同步电机参数辨识

永磁同步电机广泛应用于工业驱动系统中,开展永磁同步电机参数在线辨识对实现电机高性能控制和可靠状态监测具有重要意义.针对永磁同步电机动态数学模型具有非线性、多参数、强耦合等特点,从电气系统和机械系统两方面建立了永磁同步电机数学模型,针对参数辨识问题的特点,提出了一个惯性因子的自适应公式,在此基础上,建立了以粒子群算法为框架的自适应粒子群优化算法,对永磁同步电机定子电阻Rs和负载转矩TLd进行了在线辨识,并基于实验平台验证了辨识结果.研究结果表明:自适应粒子群优化算法通过不超过20次迭代就可以发现最优参数,模型参数的估计值和测量值匹配良好,该算法可在其他类型电机的参数辨识中推广应用.     

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。     

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.     

Editorial: Special issue on recent advances in hybrid control theory and applications

正The demands of a rapidly advancing technology for faster and more accurate controllers have always had a strong influence on the progress of automatic control theory.In recent years control problems have been arising with increasing frequency in widely different areas,which cannot be addressed using conventional control techniques.The principal reason for this is the fact that a highly competitive economy is forcing systems to operate in regimes where     

Information for Authors

正Aim The Journals of Zhejiang University-SCIENCE(A/B/C)areedited by the international board of distinguished Chinese andforeign scientists,and are aimed to present the latest devel-opments and achievements in scientific research in China andoverseas to the world’s scientific circles,especially to stimulateand promote academic exchange between Chinese and for-eign scientists everywhere.     

Enhancing a leaf radiative transfer model to estimate concentrations and in vivo specific absorption coefficients of total carotenoids and chlorophylls a and b from single-needle reflectance and transmittance

The relative concentrations of different pigments within a leaf have significant physiological and spectral consequences. Photosynthesis, light use efficiency, mass and energy exchange, and stress response are dependent on relationships among an ensemble of pigments. This ensemble also determines the visible characteristics of a leaf, which can be measured remotely and used to quantify leaf biochemistry and structure. But current remote sensing approaches are limited in their ability to resolve individual pigments. This paper focuses on the incorporation of three pigments—chlorophyll a, chlorophyll b, and total carotenoids—into the LIBERTY leaf radiative transfer model to better understand relationships between leaf biochemical, biophysical, and spectral properties.Pinus ponderosa and Pinus jeffreyi needles were collected from three sites in the California Sierra Nevada. Hemispheric single-leaf visible reflectance and transmittance and concentrations of chlorophylls a and b and total carotenoids of fresh needles were measured. These data were input to the enhanced LIBERTY model to estimate optical and biochemical properties of pine needles. The enhanced model successfully estimated reflectance (RMSE = 0.0255, BIAS = 0.00477, RMS%E = 16.7%), had variable success estimating transmittance (RMSE = 0.0442, BIAS = 0.0294, RMS%E = 181%), and generated very good estimates of carotenoid concentrations (RMSE = 2.48 µg/cm², BIAS = 0.143 µg/cm², RMS%E = 20.4%), good estimates of chlorophyll a concentrations (RMSE = 10.7 µg/cm², BIAS = − 0.992 µg/cm², RMS%E = 21.1%), and fair estimates of chlorophyll b concentrations (RMSE = 7.49 µg/cm², BIAS = − 2.12 µg/cm², RMS%E = 43.7%). Overall root mean squared errors of reflectance, transmittance, and pigment concentration estimates were lower for the three-pigment model than for the single-pigment model. The algorithm to estimate three in vivo specific absorption coefficients is robust, although estimated values are distorted by inconsistencies in model biophysics. The capacity to invert the model from single-leaf reflectance and transmittance was added to the model so it could be coupled with vegetation canopy models to estimate canopy biochemistry from remotely sensed data.     

Mr. Twinn’s bombes

This article discusses the history and design of the special versions of the bombe key-finding machines used by Britain’s Government Code & Cypher School (GC&CS) during World War II to attack the Enigma traffic of the Abwehr (the German military intelligence service). These special bombes were based on the design of their more numerous counterparts used against the traffic of the German armed services, but differed from them in important ways that highlight the adaptability of the British bombe design, and the power and flexibility of the diagonal board. Also discussed are the changes in the Abwehr indicating system that drove the development of these machines, the ingenious ways in which they were used, and some related developments involving the bombes used by the U.S. Navy’s cryptanalytic unit (OP-20-G).