基于dSPACE的新型双滑模PMSM控制方法

设计一种基于滑模理论的永磁同步电机控制系统,利用滑模控制器代替传统的PID控制器,用滑模观测器代替传统的位置传感器。滑模控制器中针对传统滑模控制的抖振问题,引入准滑模和趋近律的概念,设计一种新的滑模控制器。滑模观测器使用连续饱和函数代替传统的开关函数,有效地减少高频噪声信号,经李亚普诺夫稳定方程证明系统的稳定性。本设计方法充分发挥滑模控制的优势。通过d SPACE实验平台的验证和Control Desk环境的实时观测,证明所设计的新的滑模控制器在消除抖振和抗干扰方面明显优于传统的滑模控制器和PID控制器,滑模观测器能准确地观测位置信号,而且针对具有噪声干扰的场合,加入卡尔曼滤波器,有效地减少了干扰信号。     

基于准滑模观测器的转子位置精确估计

传统的滑模观测器采用开关函数,开关函数在切换过程中的高频抖动使得转子位置的估计出现一定的误差.通过对永磁同步电机的数学模型分析,提出用饱和函数代替开关函数,使得观测器处于准滑动模态,有效抑制高频抖动.同时,用扩展卡尔曼滤波器代替传统的低通滤波器,一方面进一步提高估计精度,另一方面省去低通滤波后的相位补偿.通过自适应的方式选取边界层的厚度,使得控制增益和抖动维持在最优状态.最后采用SIMULINK进行仿真,对方案的有效性进行验证.     

基于滑模观测器的航空发动机信号重构

本文研究航空发动机控制系统中传感器的信号重构问题。针对含有建模误差等未知干扰发动机模型,考虑传感器发生故障情况下,提出了基于滑模观测器的航空发动机信号重构方法。首先通过滤波器将含有传感器故障的系统等效为含有虚拟的执行器故障的系统;然后设计滑模观测器,并设置合适的增益矩阵使得状态估计误差稳定有界、输出估计误差在有限时间内到达滑模面,保证了滑模观测器对传感器故障的精确估计,在此基础上实现航空发动机的信号重构;最后,通过MATLAB/simulink对低压转速传感器发生不同幅度的软硬故障时进行信号重构仿真并与常用的卡尔曼滤波器方法进行对比,结果验证了该方法的有效性。     

改进滑模观测器的永磁同步电机无传感器控制

针对传统滑模观测器由于符号函数在零点处的不连续导致系统发生高频抖振现象,并且引入低通滤波器将获取的不连续反电动势估计值转变为连续反电动势估计值的过程中,产生了一定的相位延迟现象,提出了一种改进的滑模观测器,将新型饱和函数代替符号函数的基础上,同时引入双低通滤波器补偿策略补偿相位延迟造成的角度误差。在Matlab/Simulink中搭建模型进行仿真分析并通过试验台试验验证,结果表明以上改进提高了电机中高速下的转子位置和速度的估算精度,改进后的估计值较传统算法得到的估计值更加接近实际值。改进的滑模观测器提高了永磁同步电机无位置传感器控制系统的性能。     

基于滑模观测器与分数阶锁相环的无传感器PMSM矢量控制(英文)

提出一种基于滑模观测器与分数阶锁相环(FO-PLL)的无传感器永磁同步电机(permanent magnet synchronous motor,PMSM)矢量控制算法.首先用滑模观测器估计出反电势,然后设计FO-PLL对转子位置和速度进行估计.切换函数采用饱和函数代替开关函数,有效地削弱了滑模观测器存在的抖振.所提出的FO-PLL包含一个可调的分数阶次r,因此与传统锁相环(PLL)相比,该FO-PLL具有一个额外的自由度,传统PLL也可以看成是FO-PLL的一个特例.通过选择合适的分数阶次r,能够获得更好的转子位置和速度观测性能.仿真结果证明了所提方法的有效性.     

基于新型滑模观测器的永磁同步电机无位置传感器控制

提出一种新型滑模观测器对永磁同步电机(permanent magnetic synchronous motor,PMSM)转子的位置和速度进行精确的参数估算,该观测器采用变边界层S函数替代传统的正负号函数,S函数的边界层宽度根据永磁同步电机的转速进行调整,有效的克服了正负号函数作为开关函数所带来对电机参数的依赖和抖振的影响。结合永磁同步电机在旋转坐标系的数学模型,推导出观测器的收敛条件,并利用李亚普诺夫理论证明了算法的收敛性。仿真结果表明,该滑模观测器可准确观测转子位置和速度,并且具有良好的动态响应特性和鲁棒性。     

基于改进型滑模观测器的无位置BLDCM控制

永磁无刷直流电机是多变量、强耦合的非线性系统,为进一步深入研究无位置BLDCM控制方法,以解决估算转子位置以及传统滑模观测器的抖振等问题,提出基于改进型滑模观测器的无位置BLDCM控制方法,引入正弦函数的[-π/2,π/2]部分作为滑模观测器的控制函数,以削弱抖振;同时构建反电动势观测器直接提取反电动势信号,并利用李雅普诺夫理论证明其稳定性,引入CORDIC算法以获取电机转子位置和转速.仿真实验结果表明,该控制策略能够准确估计电机转子位置,同时削弱观测器的抖振问题,提高系统精度和可靠性.     

基于滑模变结构控制的有源电力滤波系统研究

针对三相三线制并联有源电力滤波系统中存在时延、负载突变等不确定因素,建立改进的有源电力滤波器离散数学模型,提出直流侧电压控制方案。设计滑模变结构控制器,采用自适应速度函数,提高系统收敛到滑模面上的速度。提出高精度滑模观测器,提高系统的控制精度并减小系统的抖振幅度。分析了控制系统的稳定性,证明了所设计的趋近函数和滑模观测器的收敛性。仿真结果表明,所提出的控制方法有较好的效果,可以提高系统的控制精度。     

基于扩展卡尔曼滤波器的液压驱动器状态估计

本文的液压驱动器属于不可观测的非线性系统,普通的状态观测器难以胜任系统的状态估计,故采用扩展卡尔曼滤波器对液压缸活塞腔和杆腔压力进行估计.建立了液压系统的4阶非线性状态空间模型,用高斯-牛顿法拟合模型参数,用关节角度信号通过扩展卡尔曼滤波器估计液压驱动器状态.仿真结果表明该方法可以精确估计液压缸压力,实验结果显示该方法估计的关节扭矩接近测量值;从而验证了扩展卡尔曼滤波器估计液压系统状态的有效性,为基于状态的故障诊断和液压驱动器控制提供了一定的借鉴.     

基于模糊神经滑模观测器的永磁同步电机无传感器控制

为了解决传统滑模观测器的抖振问题,提出了一种用于永磁同步电机的模糊神经滑模观测器。分析了滑模增益对抖振的影响,并采用模糊神经网络动态调整滑模增益以改善抖振,利用李雅普诺夫函数证明了模糊神经网络观测器的稳定性。利用锁相环方法提取转子位置与速度信息,减小由高频噪声引起的误差。仿真结果表明:改进后的滑模观测器能够对永磁同步电机转子位置进行精确辨识,有效地抑制了抖振,实现了高性能的永磁同步电机无传感器控制。     

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.     

Characterization of Ordovician carbonate reservoirs, southeastern Saskatchewan, Canada

The discovery of the prolific Ordovician Red River reservoirs in 1995 in southeastern Saskatchewan was the catalyst for extensive exploration activity which resulted in the discovery of more than 15 new Red River pools. The best yields of Red River production to date have been from dolomite reservoirs. Understanding the processes of dolomitization is, therefore, crucial for the prediction of the connectivity, spatial distribution and heterogeneity of dolomite reservoirs.The Red River reservoirs in the Midale area consist of 3～4 thin dolomitized zones, with a total thickness of about 20 m, which occur at the top of the Yeoman Formation. Two types of replacement dolomite were recognized in the Red River reservoir: dolomitized burrow infills and dolomitized host matrix. The spatial distribution of dolomite suggests that burrowing organisms played an important role in facilitating the fluid flow in the backfilled sediments. This resulted in penecontemporaneous dolomitization of burrow infills by normal seawater. The dolomite in the host matrix is interpreted as having occurred at shallow burial by evaporitic seawater during precipitation of Lake Almar anhydrite that immediately overlies the Yeoman Formation. However, the low δ18O values of dolomited burrow infills (-5.9‰～ -7.8‰, PDB) and matrix dolomites (-6.6‰～ -8.1‰, avg. -7.4‰ PDB) compared to the estimated values for the late Ordovician marine dolomite could be attributed to modification and alteration of dolomite at higher temperatures during deeper burial, which could also be responsible for its 87Sr/86Sr ratios (0.7084～0.7088) that are higher than suggested for the late Ordovician seawaters (0.7078～0.7080). The trace amounts of saddle dolomite cement in the Red River carbonates are probably related to "cannibalization" of earlier replacement dolomite during the chemical compaction.     

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.     

A computer generator for randomly layered structures

AcomputergeneratorforrandomlylayeredstructuresYUJia shun1,2,HEZhen hua2(1.TheInstituteofGeologicalandNuclearSciences,NewZealand;2.StateKeyLaboratoryofOilandGasReservoirGeologyandExploitation,ChengduUniversityofTechnology,China)Abstract:Analgorithmisintrod…     

An Index mechanism for multi-scale view in spatial databases

There are numerous geometric objects stored in the spatial databases. An importance function in a spatial database is that users can browse the geometric objects as a map efficiently. Thus the spatial database should display the geometric objects users concern about swiftly onto the display window. This process includes two operations:retrieve data from database and then draw them onto screen. Accordingly, to improve the efficiency, we should try to reduce time of both retrieving object and displaying them. The former can be achieved with the aid of spatial index such as R-tree, the latter require to simplify the objects. Simplification means that objects are shown with sufficient but not with unnecessary detail which depend on the scale of browse. So the major problem is how to retrieve data at different detail level efficiently. This paper introduces the implementation of a multi-scale index in the spatial database SISP (Spatial Information Shared Platform) which is generalized from R-tree. The difference between the generalization and the R-tree lies on two facets: One is that every node and geometric object in the generalization is assigned with a importance value which denote the importance of them, and every vertex in the objects are assigned with a importance value,too. The importance value can be use to decide which data should be retrieve from disk in a query. The other difference is that geometric objects in the generalization are divided into one or more sub-blocks, and vertexes are total ordered by their importance value. With the help of the generalized R-tree, one can easily retrieve data at different detail levels.Some experiments are performed on real-life data to evaluate the performance of solutions that separately use normal spatial index and multi-scale spatial index. The results show that the solution using multi-scale index in SISP is satisfying.     

Jane Eyre——A Feminist In The 19th Century

In the 19th century the society was controlled by men, and women were just appendants of them, they had not any rights and freedom. But Jane was an exception, she showed some characteristics of early feminist. Jane showed her characteristics of feminism in three aspects: rebellion, equality, and independence. These characteristics were helpful to her success, and feminism is the only way out for women of that time.     

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-