冗余式高压直流无刷电机控制系统设计

在冗余式高压直流无刷电机基本结构的基础上,研究了冗余式高压直流无刷电机的控制策略,设计了一套基于DSP的冗余式高压直流无刷电机控制系统;该系统主要分为控制电路、隔离电路、驱动电路、主功率电路、故障检测与保护电路和系统供电电源模块等;系统采用专用电机控制集成芯片TMS320F2812为控制核心,实现了总线控制、电机余度工作模式的切换、正/反转运行、故障检测与保护等功能;系统采用转速闭环控制策略,实验结果表明系统动态响应快,稳速精度高,并在两个余度同时工作时实现了电流的均衡.     

基于DSP平台高性能控制系统与方法研究

基于DSP平台的高性能控制系统由DSP主控板,电机驱动电路板和电源板三个主要部分组成.文中详细说明了系统结构图,叙述了数字输入数字输出电路的组成,给出了模拟输入电路设计原理以及模拟量输入通道控制电路图.在基于DSP的控制系统设计中考虑了故障处理电路.故障处理电路包括过流保护电路和三相不平衡保护电路.阐述了光电编码器接口电路设计思想和接口电路图.实现了对于给定转速的电机运行状态显示.解决了获取转速信息,通过A／D检测电压电流,实现控制算法等关键问题.     

基于F28335的小型化无刷直流电机伺服控制器的开发

介绍了一种小型化高性能无刷直流电机伺服控制器的软硬件设计及实现.硬件上采用TMS320F28335型DSP为核心处理器,设计了三相全控桥式功率驱动电路和完成欠压、过流检测等检测保护电路.能通过CAN总线实现与上位机的高速通信并进行实时数据交换,应用PID算法实现电机的位置闭环和转速闭环数字调节.实验结果表明控制器基本满足200W以内的中小型无刷直流电机驱动控制需求.     

工业机器人交流伺服驱动系统设计

针对工业机器人系统应用和高性能国产化伺服系统开发,研究了基于DSP控制器的全数字交流伺服控制系统的设计与实现。实现了基于DSP控制器TMS320F28335的交流伺服控制系统的电机控制电路。论述了整流电路、功率驱动电路、信号采集电路及保护电路等模块的设计原理。设计实现了各个闭环实时控制算法的DSP控制器软件模块。运动控制采用了面向插补控制的位置环给定端控制。     

基于DSP的交流电机伺服控制器设计

对基于DSP交流异步电机伺服控制系统进行硬件设计,介绍了双闭环伺服电机硬件电路的设计,并主要介绍DSP外围电路的设计及器件选型,包括整流逆变电路、能耗制动电路、电流检测电路、光电编码电路、温度检测电路以及电流保护电路.通过温度和电流检测电路对电机的运行状态进行实时保护;通过光电编码电路可以对增量式光电编码器信号进行信号变换;DSP对光电编码器的信号进行解码,并通过换算关系进行电机转速和位置的计算.本系统在基于电流环、速度环检测的基础上对交流电机进行精确的转速控制.     

一种新型矿用高压保护器综合测试台设计

设计了一种新型矿用高压保护器综合测试台,介绍了该测试台的总体结构及软、硬件设计方案。该测试台以S7-300系列PLC为控制器,可以产生短路、过流、欠压、过压、零序过压、零序过流等故障信号,并将故障信息、试验项目及相关硬件运行状态显示在上位机监控界面上,从而快速检测高压保护器的性能。以ZBT-11高压保护器电流保护功能测试为例进行了测试台功能检测,结果表明该测试台能够快速、准确地检测出高压保护器故障。实际应用验证了该测试台效果良好。     

医用仪器绝缘性检测的直流高压电源的设计

长期以来,由于医用设备绝缘性故障造成的医疗事故屡见不鲜。然而,国内直流高压电源技术在绝缘检测仪的研究处于空白状态。基于此,设计一种医用仪器绝缘性检测的直流高压电源。本文中的直流高压电源由DC-AC逆变电路、AC-AC升压变压电路、AC-DC倍压整流电路、过压保护电路和反馈调节电路五部分组成。实验表明,此直流高压电源工作稳定,为医用绝缘检测仪的开发提供了参考。     

基于储能Crowbar的直驱风电系统低压穿越控制策略

随着风力发电装机占比的提升,对其安全可靠性要求也越来越高。低压穿越(LVRT)能力是直驱式风力发电系统性能的重要评估指标。针对因为电网故障产生电压跌落、风电系统不脱网稳定运行的要求,提出了一种新的基于电容储能装置的Crowbar卸荷电路实现LVRT的方法。该方法利用滞环控制以及输入信号互锁控制Crowbar电路切入切出,实现了精准控制系统开关元器件,以防止开关频繁动作导致的系统失稳。仿真对比结果表明,该方法能够安全、稳定运行,并能够有效降低系统网侧有功功率的输出,以防止过电压对直流母线侧的冲击。与传统的低压穿越控制策略相比,基于储能的Crowbar方法可以有效地补偿直流母线电压的欠压状态,从而显著提高系统的低电压穿越能力。     

基于DSP的小型直流风扇自动化测试系统

针对目前我国小型直流风扇产品出厂检测设备落后的现状,采用现代微处理器检测与控制技术开发了基于DSP控制器TMS320F2812A的新型直流风扇自动化测试系统。该系统实现了直流风扇的一站式测试,大大提高了测试效率。给出了该系统的设计和实现方法,介绍了其主要硬件电路结构和软件流程。实际应用表明,该系统在性价比、测试速度和可维护性等方面均有明显的优势。     

一种过电压欠电压保护提示电路的设计

本文设计了一种直流电源供电的过压欠压告警保护电路。当电网中出现过电压和欠电压时,该保护电路能够及时的切断用电器的供电以保护电路并且点亮LED灯进行警示。经过仿真验证,该保护电路检验灵敏及时,具有很好的实用价值。     

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).