两相交错并联双向DC-DC变换器研究

对一种两相交错并联双向DC-DC变换器进行i了研li究，变换器由两个半桥拓扑交错并联构成，采用电压、电流双闭环控制。首先介绍变换器电路结构和工作原理，然后通过MATLAB/Smu变换器可以实现稳定的能量转换，交错并联能有效减小纹波，变换器在双闭环控制下均流效果好响应速度快、抗干扰性强，对于实现稳定可靠双向DC-DC变换的相关领域具有研究意义。     

基于主电流控制的并联DC-DC升压变换器改进

并联DC-DC升压变换器之间的负载电流分配关系到系统可靠性;针对并联DC-DC升压变换器,提出了一种基于主电流控制的改进下垂方法;该方法利用并联DC-DC升压变换器的算法,根据下垂法的负载调节特性自适应地调整每个变换器的参考电压;与传统的下垂法不同,在所有变换器的内环控制器中使用其中一个并联变换器的电流反馈信号,以避免并联变换器控制回路的时延差异;研究结果显示,该算法保证了负载均流与下垂法的负载调节特性一致,在并联变换器参数失配的情况下对该算法进行了测试,通过Matlab/Simulink仿真验证了该算法的有效性。     

电动汽车车载充电系统的设计和仿真

在电动汽车控制系统的研究中,针对满足电动汽车高功率因数的充电要求,设计了一种具有功率因数校正(PFC)功能的电动汽车车载充电系统.重点研究了充电系统PFC级平均电流控制的Boost变换器的电压、电流双闭环控制回路的设计方法和DC-DC级双管正激电路恒流回路恒压充电控制的设计方法.利用saber软件对整体充电系统模型进行仿真,并对其性能做出分析,充电系统功率因数相比传统无功率校正功能的充电系统得到显著提高.试验表明,充电系统PFC级很好地实现了功率因数校正和输出电压的预稳,DC-DC级也能够很好地实现恒流恒压充电.方案可以满足电动汽车充电的性能要求,并具有实际应用价值.     

基于单片机的电流比任意可调并联电源设计与实现

开关电源并联系统中往往存在两个并联电源性能参数不同甚至差异较大的情况,因此不能采用传统的并联均流方案来平均分摊电流,这就需要按各个电源模块的输出能力分担输出功率。基于这种灵活性的需要,本设计在采用主从设置法设计并联均流开关电源的基础上新增加了单片机控制模块,实现了分流比可任意调节、各模块电流可实时监控的半智能化并联开关电源系统。实测结果表明,该并联开关电源系统分流比设置误差小于0.5%,具有总过流和单路过流保护功能。     

用于电动汽车的多重化软开关双向DC/DC变换器的研究

针对典型的半桥式双向DC/DC变换器拓扑结构特点,利用DCM模式下电感电流反向的特征,采用一种不额外添加半导体器件的软开关技术,减小开关损耗;采用多重化拓扑结构弥补DCM模式下电压、电流纹波大的缺陷;在控制方式上采用电压电流双闭环形式,将共用电压环的输出作为每个基本单元的给定电流,解决了并联结构的均流问题。     

并联变换器均流控制策略研究

将模糊控制引入并联变换器均流控制技术中,对模糊控制规则以及选择模糊控制器输入变量的量化因子和输出控制量的比例因子进行了分析。提出了一种按中间电流自主均流方法。该方法减小了各相电流调节幅度,使得各相电流很快均衡。仿真实验结果表明,均流控制策略能够使得并联变换器具有良好的动态均流与负载均分特性,能够在大负载变化内良好运行。     

电动汽车新型超级电容能量管理系统设计

设计了一种应用于电动汽车的新型能量管理系统,分析了基于超级电容的双向DC-DC变换器原理.在分析电动汽车运行特性的基础上设计了该能量管理系统的控制策略.系统在电机控制部分采用相电流闭环控制,在双向DC-DC变换器部分采用电压、电流双闭环控制.     

基于电流分解的逆变器无连线并联控制

针对基本 PQ 控制法对非线性负载均流性能较差的缺点,采用了基于电流分解的方法对逆变器进行无连线并联控制。给出了功率均分和电流分解原理,提出了逆变器并联控制的实现方案和 DSP 在并联控制中的应用。实验表明,该方案对于非线性负载也具有很好的均流性能。     

并联DC-DC变换器系统的固定时间分布式协同控制

针对负载为超级电容的并联DC-DC变换器系统,为了在固定时间内实现电流输出均衡目标,提出固定时间分布式协同控制方法.将耦合子系统之间的通信拓扑,利用无向图进行刻画.借助输入输出反馈线性化技术,将并联DC-DC变换器系统的电流均衡控制设计难题转化为固定时间内一阶多智能体系统的一致性跟踪问题.借助符号函数、拉普拉斯矩阵、牵制增益矩阵,基于最近邻原则,设计参数可调的固定时间电流均衡分布式协同控制律.利用李亚谱诺夫函数严格证明整个闭环系统的稳定性,并推导出收敛时间的上界.所提出的固定时间电流均衡分布式协同控制方法,可以克服有限时间协同控制方法对初始状态依赖性强的缺点,同时改善了系统的收敛性.借助仿真,验证了所提出方法的有效性和可行性.     

新型交错并联反激变换器的稳定性研究

新型交错并联反激变换器具有电路结构简单,开关管电压尖峰小且无漏感能量损耗等优点,且其输入、输出电流脉动为开关频率的两倍,大大减小了输入与输出滤波器的体积。本文介绍了采用连续建模的状态空间平均法,建立了新型交错并联反激式DC-DC变换器在连续导电模式下的稳态及小信号数学模型,并利用控制理论,对单电压环反馈控制方式下的新型交错并联反激变换器系统进行了稳定性分析及校正设计,并通过MATLAB软件仿真及实验验证了以上理论分析的正确性。     

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.