非线性摩擦干扰下伺服系统模糊趋近律滑模控制

针对伺服系统由于受非线性摩擦力的影响而产生的"爬行"和"平顶"现象,提出了模糊趋近律方法,设计了基于T-S模糊模型趋近律的滑模控制器,并进行了实验和仿真研究. 实验和仿真结果表明:所设计的控制器能有效地消除低速"爬行"和"平顶"现象,提高伺服系统的跟踪精度;同时该控制器能显著降低常规趋近律滑模控制器的抖振问题,改善控制品质. 该控制器适用于控制品质要求高的伺服系统.     

一类非线性系统的模糊趋近律控制

分析了变结构控制设计方法中趋近律参数的物理意义及参数之间的定性关系 ,根据这些参数的定性和不精确关系 ,提出了基于模糊规则的趋近律控制——模糊趋近律控制 ,即用模糊规则来选择趋近律的参数 ,以达到改善品质控制的目的 .仿真结果表明 ,笔者给出的方法既保留了传统趋近律方法所具有的较强鲁棒性优点 ,又使控制系统的品质控制具有较强的自适应性 ,同时还比传统趋近律方法更有效地削弱变结构控制系统中固有的颤振 .     

基于GA优化趋近律的准滑模控制研究

针对滑模控制(SMC)中的抖振问题,采用了基于指数趋近律的准滑动模态控制,并提出了用改进遗传算法优化趋近律参数,提高系统动态性能的思路.对由PMSM构成的交流伺服系统进行仿真试验,结果表明该方法有效.     

基于饱和函数的机械臂模糊滑模趋近律设计

为了削弱机械臂滑模控制中的抖振现象,提出了模糊趋近律的控制方法.利用模糊控制器实时调整滑模控制的趋近律参数,并将饱和函数引入趋近律的设计中,设计了一种新型趋近律.该方法既保证了控制系统的快速性和鲁棒性,又能够有效地削弱抖振,另外,控制系统设计简单,便于工程应用.仿真结果表明,该控制策略不仅有效地抑制了系统的抖振,而且保...     

航空发动机模糊PID趋近律滑模控制器设计

针对航空发动机是一个强非线性系统,设计了一种基于模糊PID趋近律的航空发动机滑模控制器。模糊理论实现了PID趋近律3个参数的动态自适应调整,在保证控制响应快速性的前提下,还能极大的削弱系统的抖振。通过仿真,模糊PID趋近律控制器的珔nH响应时间较等速趋近律快了0.92s,仅落后固定参数PID趋近律0.11s,且稳态误差较其他两种控制器分别减少了6.89×10-5与1.68×10-5;πT的响应时间较等速趋近律快了0.56s,仅落后固定参数PID趋近律0.23s,且稳态误差分别减少了6.38×10-6与6.11×10-7。通过对比可以看出模糊PID趋近律的航空发动机滑模控制器抑制抖振的效果明显更强,而且对控制的快速性影响不大,证明了该种控制器的有效性。     

工业机器人轨迹跟踪的自适应模糊变结构算法

为提高工业机器人的轨迹跟踪控制性能,提出了一种自适应模糊变结构控制算法,即对滑模区中趋近运动的趋近律进行重新设计,新设计的趋近律能够随着机器人轨迹跟踪误差的改变而做出相应变化,从而使设计后系统的抖振减小,滑模过程中的趋近运动得到改善,控制性能也得到提高.针对该算法设计了自适应模糊变结构控制器,并与其他方法做了实验对比分析,结果表明该算法的响应速度、跟踪精度等更优.     

模糊滑模变结构控制设计

为了削弱滑模控制的颤振现象,提出了模糊趋近律的方法,即利用模糊控制器实时调整滑模控制的趋近律参数．该方法既保证了控制系统的快速性和鲁棒性,又能够有效地削弱颤振．另外,控制系统设计简单,便于工程应用．最后,以实例进行了仿真研究,仿真结果证明了所提出方法的有效性．     

一类非线性不确定系统的自适应模糊滑模控制

针对一类非线性不确定系统提出了一种自适应模糊滑模控制方法，利用趋近律构造理想控制，利用模糊逻辑系统逼近其连续项，用自适应律和非线性补偿保证滑模到达条件成立．该方法综合了自适应模糊控制和滑模控制的优点，既保证了闭环系统的稳定性，又限制了抖振，控制效果良好，仿真结果也说明了这一点．     

过失速机动变指数趋近律UAS-SMC设计

针对常规指数趋近律单向辅助面滑模控制中存在的抖振问题, 提出了一种基于变指数趋近律的单向辅助面滑模控制方法。针对系统控制量变化时飞机模型发生跳变的问题, 进行T-S 模糊建模, 以保证非线性系统在控制区间上的平滑性; 在对UAS-SMC(Unidirectional Auxiliary Surfaces-Sliding Mode Control)方法进行分析的基础
上, 给出了一种变指数的趋近律; 结合飞机模型和变指数趋近律, 设计了基于变指数单向辅助面滑模控制器。仿真实验结果表明, 该控制策略能保证趋近过程快速性的同时在接近滑模面时能有效减少系统的抖振。     

基于改进型指数趋近律的模糊滑模控制

针对传统滑模控制应用在永磁同步电机调速系统中存在转速超调量大、趋近滑模面速度慢、稳定性差、系统抖振等问题,提出一种基于改进型指数趋近律的模糊滑模控制方法。首先,在传统指数趋近律的基础上引入系统状态变量,使系统趋近速度与状态变量的变化相关;其次,通过设置系统状态滑模面与指数项系数的模糊规则,对滑模参数实时整定,使得趋近过程得到动态控制;同时,针对符号函数sgn(s)在切换过程不连续的问题,对其做出改进,使得系统可以平滑切换;最后,仿真结果表明,该方法相比于传统指数趋近律响应速度更快,抗干扰能力更好,动静态性能得到改善,系统的有效性得到验证。     

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.     

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     

Call for Papers

<正>"The Journal of Shanghai Normal University:Mathematics"is published by Shanghai Normal University as regular issues of The Journal of Shanghai Normal University each year from 2014 in English.The editors-in-chief of the issues are professors Yuhao Cong and Maoan Han.The Journal of Shanghai Normal University was started in 1958 with