无速度传感器矢量控制系统转速辨识方法研究

转速辨识是无速度传感器矢量控制系统的关键问题之一.介绍了当前研究的具有代表性的异步电动机无速度传感器矢量控制系统速度辨识方法,利用MATLAB/SIMULINK建立了异步电动机无速度传感器矢量控制系统模型,对动态速度估计器、模型参考自适应、滑模观测器等几种速度辨识方法进行了仿真、比较和分析.     

基于MRAS变参数无速度传感器矢量控制系统的研究

利用电动机定子电压方程和电流方程得到电动机转速的模型参考自适应（MRAS）辨识算法，在此基础上建立了一个改进的变参数MRAS速度辨识数学模型，并在无速度传感器异步电动机矢量控制系统中对该速度辨识模型进行了研究，仿真结果验证了该变参数MRAS速度辨识模型具有满意的辨识精度和动态性能．     

用自适应神经网络辨识异步电机转速

根据观测异步电机磁链的电压模型和电流模型 ,利用电机易于检测到的定子电压和电流 ,通过Simulink模块和S函数建立了自适应神经网络模型对异步电机转速进行辨识。该方法简单直观 ,仿真结果表明 ,观测模型可达到 1%的精度 ,可为无速度传感器矢量控制系统提供一种速度观测方法。     

基于神经网络的速度估计方法

为解决无速度传感器感应电动机矢量控制系统的速度估计问题,以神经网络模式识别的理论为基础,结合神经网络在自动控制领域中的典型应用经验,提出了两种基于神经网络的速度估计方案,分析比较了各自的优点,并通过Matlab仿真,证明了所提方案的估计精度高,估计转速能很好地跟踪实际转速(即使负载发生变化或转速发生阶跃变化),而且对电机参数变化具有很强的鲁棒性,对考虑铁耗后所产生的影响也不太敏感,使相应的无速度传感器矢量控制系统具有良好的静、动态性能.     

基于观测器的无速度传感器感应电机控制

为了辨识感应电机的转速,提出了一种模型参考自适应观测器.该观测器基于模型参考自适应系统(model reference adaptive system,MRAS),将感应电机和全阶观测器分别作为参考模型和可调模型,基于两模型输出之间的误差构造了一个自适应律,通过自适应律不断调整观测器的参数,全阶观测器的输出将实现对实际系统输出的跟踪,并用李雅普诺夫稳定性定理验证了系统的稳定性.理论分析和仿真结果表明,所提出的感应电机无速度传感器矢量控制系统的转速辨识方法具有令人满意的动静态性能.     

无速度传感器的PMSM最优转矩控制系统研究

针对无速度传感器控制系统模型,采用PMSM的数学模型和最优转矩矢量控制方案,建立了基于模型参考自适应的观测器,解决了转子速度位置的估计问题。理论分析和仿真结果表明,所提出的永磁同步电机无速度传感器矢量控制系统的转速辨识方法具有较强的鲁棒性和较好的动静态性能。     

用波波夫超稳定性理论设计交流调速系统

根据模型参考自适应原理，针对无速度传感器交流调速控制系统中速度辨识算法的收敛性问题，采用波波夫超稳定性理论设计了异步电机无速度传感器的直接转矩控制系统。理论分析证明，所提供的方法能保证速度辨识算法的全局渐进稳定性，仿真结果证明了这种方法的有效性。     

无速度传感器直接转矩控制系统的仿真研究

在深入研究异步电机直接转矩控制的基础上，提出了基于模型参考自适应方法的速度辨识器，并将之改进。仿真结果证明，应用该速度辨识器的无速度传感器的直接转矩控制系统具有较好的动态性能。     

粒子群算法优化神经网络的异步电机转速估计

在异步电机的矢量控制系统中,电机的转速检测是必不可少的,并且转速检测的精度直接影响磁场定向的准确性。讨论了各种无传感器速度辨识方法的特点,利用BP神经网络对异步电机转子转速进行辨识,通过粒子群算法优化使BP神经网络获得更好的网络初始权值和阀值,在此基础上利用Matlab/Simulink建立一个异步电机矢量控制系统,仿真结果表明这种方法能较好地辨识异步电机转子转速,系统具有良好的动态性能,对系统参数变化具有较强的鲁棒性。     

MRAC异步电动机直接转矩控制系统转速辨识研究

针对异步电动机直接转矩交流调速系统的转子转速辨识问题,文章分析和研究了模型参考自适应控制(MRAC)速度辨识算法.在对异步电动机转子转速和磁链观测深入研究的基础上,基于超稳定性理论证明了该算法的稳定性,构建了模型参考自适应速度辨识系统并设计了该算法的自适应率;在MATLAB7.04软件平台上,建立了无速度传感器直接转矩控制系统的仿真模型并进行了仿真,仿真试验结果表明,该系统控制性能和精度良好,验证了算法的正确性和可实践性.     

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