基于遗传-模糊算法的开关磁阻电机位置计算

采用智能方法实现开关磁阻电机的非线性建模及转子位置的精确估算．根据实验测得的开关磁阻电机定子电流、绕组电感和转子位置，得到开关磁阻电动机非线性特性．利用比特性得到模糊规则，实现开关磁阻电机的模糊建模；在此基础上，分别利用神经网络的学习和遗传算法全局优化算法，实现了精确和最优模糊建模．该方法可以实现转子位置的精确估计并具有一定鲁棒性和可靠性，可取代直接的位置传感器．利用智能建模可以避免非线性系统建模的复杂性．仿真结果证明了建模的有效性．     

基于模糊推理规则的开关磁阻电机转子位置估算研究

由于电机间接转子位置角度估计方法中存在一定误差，采用一般的控制策略难以实现电机性能的良好控制。为了提高电机的转速控制精度和抑制转矩脉动，在分析开关磁阻电机的非线性数学模型的基础上，研究了模糊转子位置估算方法，提出了一种新的无位置传感器转子位置估算方法：基于模糊推理规则的转子位置估算，并对此方法的误差信号进行了分析。     

无刷直流电机无位置传感器控制下的转矩波动抑制新策略

永磁无刷直流电机位置传感器和转矩波动的存在限制了它的应用范围．为扩大无刷直流电机在精度较高的伺服系统中的应用，提出在实现无位置传感器控制的同时，减少转矩波动的新策略．无刷直流电机转子位置与电机的电压、电流之间以及电机电流与转子位置、转矩之间都存在着一定的非线性对应关系，通过对两个径向基函数(RBF)神经网络按自适应训练算法进行训练，训练后的两个RBF神经网络分别实现了无刷直流电机转子位置和最大转矩运行时参考电流的在线估计．根据估计的参考电流对绕组的实际电流进行调节，最大限度地抑制了因电流波形不理想引起的转矩波动，为无刷直流电机在高性能伺服系统中的应用提供了保证．实验结果表明了此控制策略的有效性．     

基于SRM非线性电感模型相电流和电磁力的解析计算

在考虑开关磁阻电动机(SRM)的转子位置角和电流对电感曲线影响的基础上,提出一种开关磁阻电动机的非线性电感模型,根据此模型解析计算了电机的相电流、电磁转矩和径向力.计算结果表明,该电感模型在SRM设计阶段,在不降低SRM力能指标的前提下,可减小径向力,从而为抑制振动提供理论依据,对SRM转矩脉动、振动噪声抑制策略的研究具有一定的意义.     

转矩分配策略在SRM中的应用及其优化

转矩脉动较大是开关磁阻电机(SRM)的主要缺点。为了减小转矩脉动,提高电机性能,将转矩分配策略应用到电机中。由于开关磁阻电机的非线性,在转矩分配策略中,传统PID控制器的效果受到了限制。考虑到神经网络对非线性系统的自学习和自适应能力,提出采用RBF神经网络PID控制器进行优化。仿真结果表明,转矩分配策略有效抑制了转矩脉动,优化后的转矩分配策略获得了更好的性能。     

中低速开关磁阻电机转矩优化策略研究

为解决开关磁阻电机因其双凸极结构和严重非线性电感特性所导致的在换相和单相导通时转矩脉动较大的问题,提出了以转速、转矩和电流为控制量的模糊滑模多重闭环控制策略。速度环采用模糊滑模控制,通过积分变换将转速差转化为给定转矩,通过比较电机瞬时转矩与给定转矩,控制开关管的导通关断,实现转矩闭环控制;在电机换相时对同时导通的两相绕组进行转矩分配,建立转矩、电流和转子位置角的解析式,由分配的转矩求得给定的绕组电流进行电流闭环控制,从而达到对电机换相和单相导通时转矩脉动的有效抑制。仿真试验结果表明:在电机中、低速运行时,该控制系统与PID控制下的直接瞬时转矩控制(DITC)系统相比控制效果更好;电机低速运行时转矩波动稳定在±0.3N·m以内,中速运行时转矩波动稍有增大,但仍维持在±0.8N·m以内,实现了对转矩脉动的有效抑制。     

一种改进的DTC策略在SRM上的应用

为了减小开关磁阻电动机转矩脉动,在传统直接转矩控制(DTC)的基础上,对其策略进行了改进,提出了一种改进的DTC的控制策略。通过对开关磁阻电机(SRM)定子绕组电压、电流,以及转子转过的位置角的实时检测,进而得到电机在运行的实时转矩。在MATLAB中构建相关模型,并进行了仿真。仿真结果表明,改进的直接转矩控制方法,使电机获得更好的动静态性能,在很大程度上抑制了SRM的转矩脉动。在控制效果上明显优于常规控制方法,该研究对开关磁阻电机(SRM)调速控制系统的应用有着重要的意义。     

基于单阈值的开关磁阻电机无位置传感器技术

针对位置传感器对开关磁阻电机(Switch Reluctance Motor,SRM)应用范围的限制,研究了一种基于单阈值脉冲注入法的开关磁阻电机无位置传感器控制策略.以三相6/4结构电机为例,讨论在母线电压变化情况下向某一非导通相注入脉冲,通过均值采样方法计算脉冲电流峰值,与预设电流阈值比较实现位置估算.根据相邻阈值的时间间隔计算出电机转速,进一步获得其他相位置信息,并分析了估算位置与实际位置偏差的产生原因.该方法不但降低了脉冲注入带来的负转矩影响,还可实现角度控制,便于电机运行状态的优化.运用所述方法搭建了SRM无位置传感器调速系统的仿真模型,并通过试验证明了其正确性和可行性.     

无位置传感器开关磁阻电机伺服传动系统研究

该文在对比几种无位置传感器方法分析开关磁阻电机伺服传动系统特点的基础上 ,通过相电流和相电流相对转子位置角变化率的研究 ,建立了基于查表法的无位置传感器方法 ,并进行MATLAB仿真研究。结果表明 ,这种无位置传感器方法的实用性     

基于有限元分析的开关磁阻电机调速研究

摘要：本文针对开关磁阻电机定、转子磁极存在显著的端部效应、轴边缘效应和高度的局部饱和特点,采用二维和三维电磁场有限元分析,对开关磁阻电机的磁场分布、静态特性等进行了大量的计算,通过仿真的结果,得出了开关磁阻电机在几个典型转子位置下的磁场分布图、绘制出了开关磁阻电机的磁化曲线族,建立了磁阻电机非线性模型,依据非线性模型构建开关磁阻电机调速系统,采用高速变角度电压斩波控制和低速定角度电流斩波的控制方法,仿真得出好的调速效果。最后,通过样机实验验证了有限元分析数据的合理性及非线性模型的正确性。     

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.     

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-