一种基于FPGA的SPWM波的实时生成方法

文中基于FPGA设计了一种新型的三相SPWM波的实时生成方法。该方法以Xilinx公司的Spartan-3E系列FP-GA芯片XC3S500E作为控制核心,结合直接数字频率合成技术（DDS）,利用VHDL语言实时生成三相SPWM波形。通过三个相位互差120°的正弦调制波与一个三角载波进行比较来产生三相SPWM脉冲信号,由两者的交点来确定逆变器开关时刻,其中载波频率、载波比以及死区时间可变,使生成的三相SPWM波适应性强。通过Modesim和数字示波器验证了利用FPGA实时生成三相SPWM波的可行性,为该方法进一步应用提供了一个良好的开放平台。     

基于FPGA的高精度数字化正弦信号生成的新方法

提出了一种基于FPGA的高精度数字化正弦调制信号生成的新方法;该方法利用查表和线性插值相结合的办法,实时生成高精度正弦调制信号;首先介绍了新方法的基本原理及FPGA实现方案,然后对该方法进行了模型误差和量化误差分析,给出系统设计参考依据;最后,利用新方法产生500Hz的正弦调制信号对频率为13.552kHz三角载波进行调制生成SPWM波形,给出实验结果.     

基于面积等效法的SPWM发生器的设计

依据冲量效果不变理论,本文提出了采用直接面积等效法计算三相SPWM波的方法,并基于FPGA设计了SPWM发生器.电路简单可靠,编程方便.仿真结果表明用该方法所产生的PWM波形精度高,并且输出波形的频率可变,能很好地满足变频调速系统的要求.     

基于DSP28335的三相SPWM波的实现

针对传统的逆变电路,介绍了利用TI公司的DSP专用芯片TMS320F28335,通过不对称规则采样法来采样来输出三相SPWM波,并给出了部分源代码和实验结果。实验结果表明,该方法生成的SPWM波能满足逆变系统的需要,具有高效、简洁、实时性强等优点。     

基于Verilog HDL的SPWM全数字算法的FPGA实现

在详细阐述正弦脉宽调制算法的基础上,结合DDS技术,以Actel FPGA作为控制核心,通过自然采样法比较1个三角载波和3个相位差为1200的正弦波,利用Verilog HDL语言实现死区时间可调的SPWM全数字算法,并在Fushion StartKit开发板上实现SPWM全数字算法。通过逻辑分析仪和数字存储示波器得到了验证,为该技术进一步应用和推广提供了一个良好的开放平台。     

基于DSP+FPGA的载波移相算法的研究与实现

本文介绍了载波移相技术的SPWM算法,由于级联型高压变频器产生的SPWM控制信号至少15路以上,显然一块DSP是不可能实现的,本文利用DSP与FPGA相配合来产生SPWM。通过变频器带电机实验,验证了该方法的可行性。     

基于FPGA的交流电动机伺服控制系统的设计

提出了一个基于FPGA的交流电动机伺服控制系统的设计方案.该伺服控制系统利用SPWM原理进行控制,通过驱动三相逆变器,从而达到控制三相交流电动机转速的目的.实验结果验证了该交流电动机伺服控制系统的可行性.     

基于不对称规则法SPWM矩阵式变换器研究

本文把不对称规则采样SPWM法应用于三相AC/AC矩阵式变换器.详细推导出了应用不对称规则采样SPWM法三相AC/AC矩阵式变换器各种条件下的开关组合、各开关组合的通断时序和通断时间计算公式.并在把结论应用于三相交流电机进行了仿真实验,通过对仿真结果的分析,证明了把不对称规则采样法SPWM调制应用于三相AC/AC矩阵式变换器是可行的,应用本文的推导结论可生成相位、幅值、频率均可调的三相SPWM调制波.     

三相SPWM波的软件生成及应用研究

提出了一种软件生成三相SPWM波的新方法，首先，阐述了对称规则采样法和基准正弦函数法；然后，介绍了一个通用变频器的应用实例及生成三相SPWM的程序，实验结果显示，该变频器能满足实际应用的要求。     

基于FPGA的SPWM实现研究

分析了不对称规则法产生SPWM波的基本原理,在此基础上研究了利用FPGA器件得到SPWM波输出的实现方法,给出了工作流程模块,通过实验验证了该方案的可行性。     

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.