基于观测器的闭环系统故障检测及其在飞控系统中的应用

通过在闭环系统中加观测器,并基于实际飞行控制系统中控制器经常饱和的考虑,对执行器、反馈传感器故障进行了Matlab仿真研究.通过结果分析,提出了一种获取残差的新方法:即把控制器的输出残差和观测器的输出残差结合起来检测故障.该方法对于实际系统可能发生的各种故障更为有效,可以提高系统检测故障的性能,减小漏报率.针对一个飞行控制系统的仿真结果表明:新提出的诊断方案是有效的.     

基于神经网络预测的网络控制系统故障检测

考虑一类长时延网络控制系统,假定其存在输出时延,对其进行故障检测。通过对网络控制系统时延采样值进行神经网络预测,使之成为无延迟的控制系统。在此基础上,建立了基于神经网络预测的故障观测器误差方程,并证明了该观测器稳定的条件。当系统正常时,只要给定的不等式条件成立,该观测器系统就是稳定的。当系统发生故障时,观测器残差能够迅速发生跳变,从而检测出故障的发生。最后通过仿真示例说明该文方法能够较好预测网络时延,发现系统故障。     

基于多级观测器的液压伺服系统自适应故障检测与隔离

针对传统的基于固定阈值的故障检测及诊断方法虚警率高,无法有效实现液压伺服系统的故障检测与隔离,提出了一套基于多级观测器的液压伺服系统自适应故障检测与隔离方法。首先,采用第1级RBF网络作为液压伺服系统观测器,通过比较观测器估计输出值与实际系统输出得到残差信号。其次,采用第2级RBF神经网络产生自适应阈值,实现了液压伺服系统自适应故障检测。最后,采用小波包分析提取残差信号特征,利用第3级RBF神经网络实现系统的典型故障隔离。实验结果表明,利用多级观测器模型能够有效实现液压伺服系统的自适应故障检测及隔离。     

无线传感器网络控制系统故障检测

为了确保无线网络控制系统运行的可靠性,该文针对由无线传感器网络组成的网络控制系统,设计了基于离散切换系统的故障观测器.假定其可能发生故障,对其进行故障检测研究.通过研究无线传感器网络数据的传输特性,构建了增广故障观测器.将该观测器等效为离散切换系统.利用李雅普诺夫稳定性理论将观测器稳定条件归结为1个线性矩阵不等式,给出了稳定性证明.该观测器能在1s内跟踪上原系统的状态.当系统发生故障时,观测器残差能够迅速发生跳变,从而检测故障.仿真示例验证了该文方法的有效性.     

基于滑模观测器的非线性系统故障检测与重构

 为提高控制系统的安全性和可靠性,针对非线性系统传感器的故障诊断问题,提出一种利用滑模观测器进行故障检测和重构的方法。首先引入积分变量将传感器故障转化为执行器故障,通过对执行器故障的诊断间接诊断传感器故障。针对转化后的系统构造滑模观测器,进而实现传感器故障重构。采用Lyapunov稳定性理论,证明设计的滑模观测器的稳定性。对于构造的滑模观测器,给出一种用线性矩阵不等式方法求解的简便算法。最后,对于文献中给出的非线性系统,就不同的故障类型作用在传感器上的几种情形进行仿真。仿真结果表明,所设计的滑模观测器能够准确地重构非线性系统中传感器的缓变故障和突变故障;当系统存在未知扰动时,所设计的滑模观测器也能准确地重构故障。该方法从开始就对故障进行重构,避免了产生和评价残差信号的复杂性。     

多包传输机制下航空发动机分布式控制系统故障检测

考虑航空发动机分布式控制系统中,传感器与控制器间采用多包传输机制,传感器节点将测量数据封装为多个数据包发送给控制器,在每一采样时刻,同时产生的多个数据包只有一个能够发送,不能发送的数据包则被数据总线丢弃,针对这种情况,设计了神经网络预估器,用预估值来更新未被传输的数据包,使多包传输分布式控制系统"变为"单包传输分布式控制系统,建立了基于状态预估的多包传输分布式控制系统模型,构建了相应的故障观测器,将观测器误差系统看成一个离散周期系统,并应用周期系统稳定性理论推导了神经网络预估器和故障观测器能够稳定工作的条件。最后,给出了具体的故障检测步骤,仿真结果验证了所提出的故障检测算法的有效性。     

传感器饱和约束下网络控制系统丢包故障检测

研究了一类网络控制系统丢包情况下传感器输出饱和的故障检测问题.首先假设网络控制系统丢包存在于传感器到控制器之间,并用两个独立的伯努利分布序列来描述.然后在传感器输出饱和约束条件下设计了一个故障检测观测器,用来加大故障对残差的敏感性并减小干扰对故障的影响.最后基于线性矩阵不等式技术,得到一个鲁棒故障检测系统有界均方稳定的充分条件,并满足了H∞性能指标.数值算例表明了在丢包和传感器饱和约束情况下所提方法的有效性.     

具有固定拓扑结构的无线网络控制系统故障检测

为了提高无线网络控制系统对故障的灵敏度,该文根据鲁棒控制理论,对一类具有固定拓扑结构的无线网络控制系统的故障检测进行了研究。由于网络中节点的状态受到其它节点的影响,因此该文为每个节点对之间设计了故障观测器来对系统的故障进行检测。通过构建Lyapunov函数,以线性矩阵不等式的方式给出了使误差系统渐进稳定的充分条件,更进一步得到了系统的观测器增益。仿真结果表明,当系统出现故障时,故障观测器能够迅速检测到系统残差的跳变,验证了所提方法的有效性。     

电动车辆锂离子电池传感器故障诊断方法

为降低锂离子电池传感器故障对电动车辆安全与性能的影响,提出了一种基于观测器的电池传感器故障诊断方法。结合锂离子电池电热耦合动态模型,构建2个扩展卡尔曼滤波(extended Kalman filter, EKF)观测器,估计电池单体的状态量,对比状态量估计值与传感器测量值以生成残差,并使用累计和(cumulative sum, CUSUM)测试方法进行残差评价,根据残差组合的不同响应情况实现锂离子电池电流传感器、电压传感器以及表面温度传感器故障的诊断与分离(fault diagnosis and isolation, FDI)。在不同的传感器故障情况下对诊断方法进行测试,结果表明,该方法能够及时准确地对锂离子电池单体3种传感器故障进行诊断与定位,性能表现优异且易于实施。     

基于LS-SVM软传感器的容错控制方法及应用

针对一类非线性系统中传感器卡死、恒增益和恒偏差失效等易发故障,考虑控制系统多存在耦合、非线性、时变、滞后等难以建立精确的解析模型,基于数据驱动技术提出一种软传感器容错控制方法.基于LS-SVM构建了系统软传感器,并利用软传感器的预测输出与实际传感器输出之差获取残差信号;采用SPRT算法进行故障检测,当传感器发生故障时,用LS-SVM软传感器预测输出代替物理传感器的实际输出,从而以软闭环方式实现对传感器故障的容错控制.将所提出的方法应用于一阶水箱液位控制系统,实验结果表明,基于LS-SVM软传感器与SPRT的结合能够可靠及时检测非线性系统中各类传感器故障,而借助于软闭环切换还可对传感器故障实现安全容错.     

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