基于滑模观测器的卫星姿态控制系统滑模容错控制

针对卫星姿态控制系统执行机构故障,设计了基于滑模观测器的滑模容错控制律.采用迭代学习算法在线调节观测器滑模项切换增益,设计滑模观测器估计卫星姿态和角速度.在此基础上,将执行机构故障作为系统的未知动态,提出一种对卫星姿态控制系统执行机构故障不敏感的滑模容错控制方法.该方法利用系统输入和状态信息,结合动力学特性实现未知动态估计,以此设计滑模控制律.通过数字仿真验证了该容错控制方法的有效性.     

具有状态约束的机电伺服系统自适应鲁棒控制

针对执行器动态及其状态受限、状态中存在测量噪声的问题,为伺服系统设计了一种基于非线性高增益观测器的自适应非线性鲁棒跟踪方法.基于系统位置测量值设计高增益观测器,利用滤波器消除噪声对观测器精度的影响,采用自适应律估计观测器增益,以保证观测器的鲁棒性.在设计过程中,引入一种新的障碍Lyapunov函数,以限制中间控制信号的幅值而满足系统对状态变量的约束要求,并通过Lyapunov方法验证了闭环系统的一致有界稳定性.结果表明,所提出的方法能够准确估算负载位置和速度.与传统的控制方法相比,其所观测的信息量较充分、估计精度较高、抗干扰能力及参数变化的鲁棒性较强.     

交流伺服系统永磁同步电机电流及位置二级状态观测器设计

为了提高交流伺服控制系统的反馈精度,并消除反馈信号的滞后问题,针对永磁同步电机电压控制模型及其运动学控制模型进行深入分析,并在此基础上对控制系统反馈环节的工作时序进行分析,得到了电流及位置反馈环节的滞后周期数,提出电流及位置一级状态观测器。通过当前控制周期反馈位置及电流值,对下一个控制周期的电流及反馈位置值进行精确估计,并将一级状态观测器的观测输出值作为二级状态观测器的输入,进一步抑制电流及位置反馈信号的高频振荡及时滞。结果表明:二级电流及位置状态观测器对反馈信号的高频噪声起到明显的抑制作用,并对反馈值进行了准确的预计观测;二级位置观测误差小于0.005rad,并消除了反馈中夹杂的高频噪声。将该方法应用于交流伺服控制系统中,进行高速高响应定位控制,响应频率达到200Hz,加速度达到62 831rad/s2,此时系统相电流稳定,定位精度达到1.5°,从而实现了电流及位置的精确观测。     

定子磁链全阶观测器增益矩阵的确定方法

为了提高异步电机定子磁链观测精度,减小观测误差受其运行过程中温度、频率和磁路等因素的影响,使用定子磁链全阶观测器观测定子磁链.利用静止坐标系下的异步电机数学模型,分析当电机参数改变时,高速运行状态下定子磁链观测器u-i模型和低速运行状态下i-n模型的观测误差变化情况,然后给出定子磁链全阶观测器增益矩阵的确定方法.在Matlab/Simulink仿真环境下,进行了仿真验证.研究结果表明:定子磁链观测精度主要是随着电机在运行过程中转速和转矩的变化而变化;采用此方法在保证观测器稳定的前提下,依据不同的转速区间,选择合适的观测器极点配置,可以提高异步电机全速运行状态下定子磁链的观测精度;采用此方法有效地提高了全速范围内定子磁链的观测精度,并且实现简单.     

具有边界扰动的变系数多维波动方程的稳定性

应用自抗扰控制方法研究了具有边界扰动的变系数多维波动方程的稳定性.首先,使用时变高增益观测器代替常数高增益观测器很好地解决了峰值问题;其次,应用半群理论得到了加变系数多维波动方程解的存在性和唯一性;最后,设计时变高增益观测器估计出边界扰动,并通过状态反馈将其抵消使得系统稳定.     

机器人角速度两种软测量方法的PD控制对比

对比分析了用LPP差分方法和高增益观测器方法估计机器人角速度的有效性,并用这两种角速度估计方法分别形成了机器人两种不同的PD输出反馈控制器·在机器人仿真实验中,对这两种方法产生的动态和稳态估计误差以及闭环系统的动态和稳态跟踪误差进行了对比分析·从这两种方法产生的估计误差及闭环系统跟踪误差的对比结果表明,当角位置测量精确度较高时,利用差分方法估计机器人角速度较理想,而较低时采用观测器方法估计机器人角速度较理想·     

伺服驱动系统高增益速度环的振动抑制方法

为解决速度控制器增益过大和负载扰动等因素引起伺服系统振动,导致系统不稳定的问题,提出伺服驱动系统高增益速度环的振动抑制方法.首先,采用速度振动信号反馈补偿的方法,设计滤波器提取振动速度信号作为速度反馈补偿;然后,采用内模控制(IMC)观测器进行负载扰动补偿,将观测出的扰动转换成对应的电流量,对电流环指令信号进行前馈补偿.仿真结果表明:与比例积分(PI)控制和传统的观测器补偿法相比,文中方法能有效地提高系统的响应和抗扰动性.     

四旋翼无人机滑模自抗扰控制

针对四旋翼无人机易受到非线性、多目标以及控制量受限和其他不确定性因素干扰的影响,本文基于自抗扰控制和滑模控制设计了一种滑模自抗扰控制器。在被控对象姿态角速度未知的情况下,该控制器采用扩张状态观测器对无人机的姿态角速度和未知干扰进行观测;再将估计的姿态角速度和干扰用于控制器的反馈和控制量的补偿;最后利用Lyapunov理论证明控制系统的稳定性。仿真结果表明,本文设计的滑模自抗扰控制器可以保证观测误差的快速收敛,实现被观测量的高精度估计;在姿态角速度未知的情况下,仍可保持稳定的姿态控制。     

基于Luenberger观测器的降阶H∞控制器的设计

本文主要研究了基于Luenberger观测器的H∞降阶控制器的设计问题,该观测器是干扰解耦的。首先利用LMI方法提出了求解H∞状态反馈增益的充要条件,然后对该控制器进行渐近降阶观测,基于sylvester矩阵方程的显示通解的参数化设计方法,实现了线性系统的降阶H∞控制器的设计,最后给出了相应的降阶H∞控制器设计算法。     

基于反馈线性化的整车振动状态观测算法

针对整车振动状态观测器设计中的整车悬架系统高维非线性特性,提出了反馈线性化卡尔曼滤波算法.基于微分几何理论,通过求解坐标变换,将车辆非线性振动模型变换成一个可观测的标准型,实现系统的精确反馈线性化,进而采用线性卡尔曼滤波算法,针对变换后的线性系统设计观测器,最后通过坐标逆变换获得原非线性系统的状态观测值.仿真结果表明,相比扩展卡尔曼滤波算法,该算法能够提高车辆振动状态观测精度和运算效率.      

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.     

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     

On the Thermodynamic Limit for Responses to Static Electromagnetic Fields

For molecular systems,the quantum-mechanical treatment of their responses to static electromagnetic fields usually employs a scalar-potential treatment of the electric field and a vector-potential treatment of the magnetic field.Although the potential for each field separately is associated with the choice of an(unphysical)origin,the precise choice of the origin for the electrostatic field has little consequences for the results.This is different for the     

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     

Journal of Donghua University ( English Edition) Contents of Volume 31

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