开关磁阻电机光栅编码器的研究

开关磁阻电机作为一种新型的高性能变速传动系统,速度与位置信号的反馈是必不可少的.本文旨在研制一种适用于12/8极开关磁阻电机的经济型光栅编码器,以完善并优化开关磁阻电机控制系统.首先设计了光电信号采集电路,对速度与位置的检测方法做了分析、比较等研究,确定了一种变M/T法测速方案,并且进行了测试实验以及误差分析.     

一种提高转速测量范围与精度的新方法

一、M/T法测速原理 在电机测试中,经常要进行位置（或转角）和转速的测试,光电编码器由于既可作速度信号传感器。又可作位置信号传感器,且精度高,无疑是这类传感器的优选者。采用编码器测速目前主要以M/T法、V/F法为代表,且采用前者较多,这是由于计算机的高速与高精度导致的。M/T法光电式数字测速在计数器与微机软件的配合下,可实现高精度的数字式测量。     

基于FPGA的变M/T归一化测速算法研究

针对永磁同步电机的测速问题,提出关于增量编码器的变M/T归一化测速算法,并基于Xilinx FPGA板级系统完成算法设计与实现。通过分析M/T算法在低速范围的局限性,添加速度预测单元实时指导计数脉冲个数选取。为便于算法移植,在算法中引入归一化的设计思想。针对算法中使用较多的乘法器,引入Booth算法降低整体算法设计对FPGA片内DSP的依赖性。仿真结果表明,基于FPGA的变M/T归一化测速算法转速测量误差在±0.4 r/min内,测速响应时间不超过3 ms。     

基于8098单片机控制的电动机转速实时检测系统

介绍了一种利用INTEL8098单片机和旋转式光电编码器构成的数字实时转速检测系统.给出了系统的硬件实现途径和软件设计方法,对系统的性能作了分析和评估.结果表明,系统将M/T法和T法相结合,可在全速范围内获得高分辨率.使用脉冲频率1024/r的光电测速器时,可获得±0.03%的检测精度,用于标准的电机驱动系统和自动调速系统可获较好的控制精度.     

基于正交编码器高精度测速方法的研究

根据正交光电编码器测速原理,在分析了M法测速的测量误差和分辨率的基础上,提出了一种改进的转速高精度测量方法——变M法,即同时测量正交的两组脉冲序列的上升沿和下降沿,极大的减小了转速和转角测量误差,提高了分辨率。还提供了一种适用于工业现场环境条件的,基于正交编码器测速算法的虚拟仪器软硬件设计方案及其实验效果。     

基于LabWindows/CVI的电机转速稳定性测试系统设计

电机转速由于齿槽转矩的存在会产生波动,重点阐述了一种新的电机转速稳定性的测试方法.利用光电编码器作为角度传感器,转子位置信号由单片机系统采集、处理并经串口发送给上位机,基于LabWindows/CVl的上位机设计实现了电机转速的图形化、实时显示功能.测试结果可直观地反映和分析电机转速的变化规律,为电机转速测试,尤其是低速稳定性的研究提供了一种新的有效途径.     

一种光电编码器精度自动检测系统

随着光电编码器的广泛应用,市场对其需求也逐渐增大。利用自准直仪－金属多面棱体对光电编码器精度检测的传 统手动检测方法具有检测效率低的缺点,严重制约了光电编码器生产效率的提高。针对上述问题,设计了一种光电编码器精度自动检测系统,MATLAB程序控制电机带动待测光电编码器同步旋转,通过对比待测光电编码器及电机运动角度的数据计算待测光电编码器的精度,实现光电编码器精度自动检测。系统采用沿面检测算法减小测量结果的分辨率误差,采用傅里叶谐波分析方法对电机转角误差进行修正,进而提高了检测精度,使用该系统对某型号的 16位光电编码器进行检测.实验结果显示该系统检测精度不大于±２″,该系统具有结构简单,检测精度高的优点,可提高光电编码器的生产和检测效率。     

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.     

基于STM32的步进电机PID速度环控制系统设计

设计了一种步进电机驱动控制系统,该设计以STM32F103VET6作为主控制器,采用PID算法进行闭环控制,旋转编码器作为反馈通道,负责收集步进电机转子在单位采样时间内的实际执行的步数,系统将实际步数转换为转速并与目标转速进行比较然后计算出偏差,偏差值输入到PID控制器中,控制器输出经过修正的期望转速,最后交由步进电机执行。当步进电机在运动过程中发生丢步,会出现实际转速偏离目标转速,编码器将实际转速反馈给系统,控制器就能及时做出偏差修正。利用该方法,可稳定、精准地进行步进电机的速度环闭环控制。     

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).