三相交流异步电机矢量控制系统仿真建模

分析了三相交流异步电机的数学模型,介绍了三相交流异步电机的矢量控制原理.采用模块式设计方法和结构化设计方法,开发了基于MATILAB/SIMULINKV参数化三相交流异步电机矢量控制仿真模型.该模型的输入参数为电机转子目标转速和转子实时转速,输出参数为电机输出转矩.基于建立的仿真模型开展了电机空载变速过程和恒速加载过程仿真.仿真结果表明,所设计的仿真模型能够实现电机运动过程中转速和转矩的准确计算;所设计的参数化仿真模型可用于三相交流异步电机矢量控制系统仿真研究.     

纯电动汽车坡道自适应起步控制策略

以一款三相交流异步电机为动力源的纯电动汽车为研究对象,搭建了三相交流异步电机动力传动系统试验台,研究了三相交流异步电机在转速控制模式下的堵转特性,得到了不同转速偏差下的电机转矩响应规律。建立了纯电动汽车坡道识别模型和起步过程中各控制量的计算模型,提出了一种基于电机堵转特性的纯电动汽车坡道自适应起步控制策略,通过Matlab/Simulink软件建立了仿真模型,对不同坡道的上坡起步和下坡起步进行了仿真研究,结果表明,提出的起步控制策略能够较好地适应纯电动汽车的坡道起步。     

基于ELM神经网络的采煤机截割载荷软测量建模方法

采煤机是煤矿综采工作面的关键设备,由于煤层结构复杂,导致截割载荷复杂多变,并且截割载荷难以直接测量。因此,针对采煤机截割载荷难以直接检测难题,研究了采煤机交流异步电机的机械特性,提出了基于软测量建模技术的截割载荷预测方法。首先,通过分析采煤机交流异步电机的机械特性,得出截割载荷与截割电机的转速、电流符合非线性关系,运用软测量建模方法可以预测截割载荷。然后,以截割电机的转速和电流作为输入变量,运用ELM神经网络的软测量建模方法建立采煤机截割载荷软测量模型。最后,运用ELM,BP,RBF3种神经网络软测量建模方法对采煤机电机载荷进行预测,以均方误差和相关系数作为预测评价指标,结果表明:ELM神经网络软测量建模方法在预测精度和预测速度方面都优于BP神经网络和RBF神经网络软测量建模方法。运用ELM神经网络软测量建模方法能够准确、快速预测采煤机截割载荷,为采煤机恒功率截割和牵引智能调速提供了理论基础。     

动车组用异步牵引电机转速的估计方法

总结了动车组已有的异步电机转速估计方法,简要分析了增量型转速编码器的3种测速方法.在T法测速的基础上,提出了一种实现电动车组用异步牵引电机转速估计的方法.该方法在低速区和转速调节的动态过程中效果显著,并且转速估计的准确性不受牵引电机参数变化的影响.通过对转速的估计,间接矢量控制中转子磁场定向的准确度也大大提高.以国产先锋号电动车组为例,在Matlab/Simulink下进行了仿真研究,仿真结果证明了该方法的正确性.     

基于单片机的低速旋转机械转速测量系统设计

针对低速旋转机械转速测量系统由于硬件电路设计原因造成的测速精度较低及需要拆卸、安装方可测速引起的操作不便问题,设计了一套低速旋转机械测速系统．该系统由硬件电路和软件程序组成,以单片机AT89C52为核心,通过霍尔传感器采集转速信号,经过光电耦合器隔离后整形,然后信号被送入单片机系统进行计数运算,所得转速测量结果显示在LCD屏上．该转速测量系统精度高,调试方便,可广泛应用于各种控制系统中对低速旋转机械的转速进行测量．     

卡尔曼滤波在异步电机中的应用研究

为提高异步电机转速环的动态性能,提出了一种新型转速控制器设计方案。该控制器采用简化的卡尔曼滤波方法以观测电机的转速,通过对测量转速的滤波处理以提高转速环的动态响应。     

基于转速测量的电机保护器的设计

通过霍尔开关,将电机的转速信号变换为脉冲信号,以AT89S51单片机为控制器,采用同步法对电机的转速信号进行频率测量,使测量频率的相对误差与被测信号频率的大小无关,提高了被测信号频率的测量精度.通过测量电机转速实现了电机保护,此方法具有可靠性高、抗干扰能力强、测量速度快、测量精度高,电路简单、成本低,安装、使用方便等特点.     

基于单片机的转速测量系统设计

为了设计简单可靠的直流电机测速装置,提出基于单片机为核心的电机速带测量系统。整个系统的构架包括转速信号的采集,转速信号的处理,转速的计算与显示。信号处理电路主要是将传感器输出的带有外界噪声的不稳定的电信号转化成理想的方波;转速的计算利用单片机AT89C51的定时器和计数器。根据系统编写源程序,并通过运行试验证明,该系统结构简单,测量结果稳定可靠,满足电机的测速要求。     

三相鼠笼异步电动机无传感器转速检测技术及其适应性（英文）

针对三相鼠笼异步电机无位置传感器快速傅立叶变换(fast Fourier transformation, FFT)测速方法需要预先知道转子槽数,且测试精度易受噪声干扰和采集时长等因素的影响,提出一种基于奇异值分解-Prony(singular value decomposition-Prony, SVD-Prony)算法的无位置传感器高精度转速测量技术。运用电机学相关理论,研究转子槽谐波测速机理,并给出整数倍率转子槽数的计算方法。在分析并明确定子电流噪声影响和FFT法存在检测精度受采样时长限制等问题的基础上,研究基于奇异值增长率的SVD滤波方法和用于辨识转子槽谐波的Prony算法,并以Y160M-4型电机为研究对象,在不同运行状态下对该技术的适应性进行分析。在此基础上,构建相关物理测试平台,对YE90S-2型电机进行实测。结果表明,在相同采集情况下,所提方法测试绝对误差仅为FFT测速方法的几分之一,检测精度大幅提高。     

基于自适应滤波法的静电传感器转速测量

为解决使用静电传感器进行信号自(互)相关转速测量中,因信号干扰大导致相关法时延计算易出错的问题,采用自适应滤波算法对相邻传感器的时延信息进行提取,从而达到测速的目的。实验结果表明,该方法能有效得出测速结果,并对叠加了强噪声的静电信号也有良好的表现。对异步电机转轴进行测试,转速测量的线性度达到1.29%,具备一定的应用价值。     

Markedness and its Interpretation in Language Use

Language markedness is a common phenomenon in languages, and is reflected from hearing, vision and sense, i.e. the variation in the three aspects such as phonology, morphology and semantics. This paper focuses on the interpretation of markedness in language use following the three perspectives, i.e. pragmatic interpretation, psychological interpretation and cognitive interpretation, with an aim to define the function of markedness.     

Features of Women's language

Language is a means of verbal communication. People use language to communicate with each other. In the society, no two speakers are exactly alike in the way of speaking. Some differences are due to age, gender, statue and personality. Above all, gender is one of the obvious reasons. The writer of this paper tries to describe the features of women＇s language from these perspectives： pronunciation, intonation, diction, subjects, grammar and discourse. From the discussion of the features of women＇s language, more attention should be paid to language use in social context. What＇s more, the linguistic phenomena in a speaking community can be understood more thoroughly.     

An Analysis of Catherine＇s Character——Wuthering Heights

Wuthering Heights, Emily Bronte＇s only novel, was published in December of 1847 under the pseudonym Ellis Bell. The book did not gain immediate success, but it is now thought one of the finest novels in the English language. Catherine is the key character of this masterpiece, because everybody and everything center on her though she had a short life. We can understand this masterpiece better if we know Catherine well.     

Lower Paleozoic oil relationships within Williston Basin, Canada

The Williston Basin is a significant petroleum province, containing oil production zones that include the Middle Cambrian to Lower Ordovician, Upper Ordovician, Middle Devonian, Upper Devonian and Mississippian and within the Jurassic and Cretaceous. The oils of the Williston Basin exhibit a wide range of geochemical characteristics defined as "oil families", although the geochemical signature of the Cambrian Deadwood Formation and Lower Ordovician Winnipeg reservoired oils does not match any "oil family". Despite their close stratigraphic proximity, it is evident that the oils of the Lower Palaeozoic within the Williston Basin are distinct. This suggests the presence of a new "oil family" within the Williston Basin. Diagnostic geochemical signatures occur in the gasoline range chromatograms, within saturate fraction gas chromatograms and biomarker fingerprints. However, some of the established criteria and cross-plots that are currently used to segregate oils into distinct genetic families within the basin do not always meet with success, particularly when applied to the Lower Palaeozoic oils of the Deadwood and Winnipeg Formation.     

低渗透非均质砂岩油藏启动压力梯度研究

理论推导与室内实验相结合,建立了低渗透非均质砂岩油藏启动压力梯度确定方法。首先借助油藏流场与电场相似的原理,推导了非均质砂岩油藏启动压力梯度计算公式。其次基于稳定流实验方法,建立了非均质砂岩油藏启动压力梯度测试方法。结果表明:低渗透非均质砂岩油藏的启动压力梯度确定遵循两个等效原则。平面非均质油藏的启动压力梯度等于各级渗透率段的启动压力梯度关于长度的加权平均;纵向非均质油藏的启动压力梯度等于各渗透率层的启动压力梯度关于渗透率与渗流面积乘积的加权平均。研究成果可用于有效指导低渗透非均质砂岩油藏的合理井距确定,促进该类油藏的高效开发。     

On Tragic Consciousness In The Works By Ernest Hemingway

As an American modern novelist who were famous in the literary world, Hemingway was not a person who always followed the trend but a sharp observer. At the same time, he was a tragedy maestro, he paid great attention on existence, fate and end-result. The dramatis personae's tragedy of his works was an extreme limit by all means tragedy on the meaning of fearless challenge that failed. The beauty of tragedy was not produced on the destruction of life, but now this kind of value was in the impact activity. They performed for the reader about the tragedy on challenging for the limit and the death.     

Design and analysis of generic LBS application developing platform

Location based services is promising due to its novel working style and contents.A software platform is proposed to provide application programs of typical location based services and support new applications developing efficiently. The analysis shows that this scheme is easy implemented, low cost and adapt to all kinds of mobile nework system.     

Achieving Unusual States of Matter Under High Pressure

正The periodicity of the elements and the non-reactivity of the inner-shell electrons are two related principles of chemistry,rooted in the atomic shell structure.Within compounds,Group I elements,for example,invariably assume the+1 oxidation state,and their chemical properties differ completely from those of the p-block elements.These general rules govern our understanding of chemical structures and reactions.Using first principles calcula-     

Exchange-Correlation and Electronic Excitation Energies from Pairing Matrix Fluctuations

We have developed an adiabatic connection to formulate the ground-state exchange-correlation energy in terms of pairing matrix linear fluctuations.This formulation of the exchange-correlation energy opens a new channel for density functional approximations based on the many-body perturbation theory.We illustrate the potential of such approaches with an approximation based on the particle-particle Random Phase Approximation(pp-RPA).This re-     

Density Functional Theory for the Response of Periodic Systems to Electric Fields Based on the Vector Potential Approach

正The electronic and nuclear(structural/vibrational)response of 1D-3D nanoscale systems to electric fields gives rise to a host of optical,mechanical,spectral,etc.properties that are of high theoretical and applied interest.Due to the computational difficulty of treating such large systems it is convenient to model them as infinite and periodic(at least,in first approximation).The fundamental theoretical/computational problem in doing so is that