基于T-S模糊神经网络的飞机防滑刹车系统研究

航空业的发展对飞机防滑刹车系统提出了更高的要求,而传统PID+PBM控制器存在着低速打滑、刹车效率较低等问题;针对刹车过程中的不确定性和非线性问题,提出采用T-S模糊神经网络来进行防滑刹车控制器设计;在MATLAB/SIMULINK平台建立飞机刹车总体仿真模型,将设计的控制器与传统控制器进行对比仿真试验;仿真结果表明,基于T-S模糊神经网络的控制器解决了传统PID+PBM系统存在的问题,具有良好的控制效果,系统具有鲁棒性,能够适应变化的跑道情况,为飞机防滑刹车控制提供了一种新的方法。     

基于RBF神经网络的电动负载模拟器摩擦与间隙补偿方法研究

为提高电动负载模拟器系统的动态性能和信号跟踪准确度,提出针对系统摩擦和间隙进行补偿的方法。采用基RBF波神经网络的PID 控制器实现摩擦非线性补偿,同时利用间隙逆模型针对间隙非线性进行补偿。利用Matlab 软件对补偿结果进行仿真验证,仿真结果显示经过补偿后系统正弦响应曲线跟随性能变好,跟踪误差明显减小,准确度得到很大改善。仿真结果证明：基于RBF神经网络的PID 控制器和间隙逆模型分别对摩擦和间隙有明显的抑制效果,系统动态性能得到提高。     

DVD光学头的RBF神经网络自适应PID控制器设计

为了使三维光存储技术的应用水平得到提高,以DVD伺服技术、双光子吸收技术为基础组建了一套信息存储系统。针对DVD光学读取头系统,采用RBF神经网络自适应PID控制器进行控制,充分利用RBF神经网络的自学习和全局非线性逼近能力,在线调整修正PID控制器的3个参数,使其达到一种最优控制,并通过MATLAB软件进行了计算机仿真。由仿真结果可以得出:通过应用RBF神经网络自适应PID控制算法,系统单位阶跃响应的调整时间为0.25 s,并使系统的超调量降低到几乎为零。     

基于遗传算法的统一混沌系统比例-积分-微分神经网络解耦控制研究

提出了采用改进的遗传算法优化比例-积分-微分(PID)神经网络解耦控制器的连接权值，从而实现PID控制器参数的优化及非线性多变量系统的解耦控制. 改进的遗传算法优于基本遗传算法，它使寻优过程中的计算量减少，计算效率提高，收敛速度加快. 将优化后的PID神经网络解耦控制器应用于统一混沌系统的控制中，仿真实验收到良好的控制效果，证明了PID控制器应用于统一混沌系统控制的有效性. 关键词： 混沌系统 遗传算法 比例-积分-微分 神经网络     

定向战斗部随动系统新型模糊-PID复合控制

针对随动定向战斗部随动系统工作中存在的非线性与随机干扰问题,普通的PID控制器和模糊控制器不能满足快速性与适应性的要求,基于模糊自整定PID参数控制器与模糊-PID切换控制器,提出了一种新型模糊-PID复合控制算法,控制前段利用模糊控制加快控制速度,后段利用模糊逻辑整定PID参数提高精度与自适应能力;仿真结果表明,采用这种新型模糊-PID复合控制算法能够保持跟踪精度,减少调节时间,加快系统跟踪速度,减小切换冲击,提高抗干扰能力。     

Fuzzy-PID分级控制变水量空调系统温度的研究

针对变水量空调系统温度控制的时变、大滞后、非线性特点,结合模糊控制和PID控制,设计了基于模糊规则切换的Fuzzy-PID分级控制器,并在Matlab/Simulink软件上进行了仿真。仿真结果表明,控制器同时具有模糊控制超调量小、鲁棒性好和PID控制精度高、响应速度快的优点。     

基于模糊控制的自适应光学校正技术

自适应光学中普遍采用的比例-积分-微分(PID)控制严格依赖于变形镜的响应模型,响应模型的标定非常繁琐且性能容易随时间和温度而漂移.采用模糊控制摆脱了对变形镜响应模型的依赖,通过波面的快速重构,从波面中提取波面评价指标,将该评价指标及其微分作为模糊PID控制器的输入.选择模糊输入和输出论域的隶属度函数,设计出模糊规则库,通过模糊推理、解模糊等过程,对PID控制器的3个参数即比例kp、积分ki和微分kd进行模糊自整定,实现了自适应控制.采用高速数字信号处理器(DSP)设计了硬件验证测试平台,通过该平台的测试,证明该方法有效可行,在不需要变形镜响应矩阵的前提下,能够将光斑的衍射极限倍增因子β值从10—12校正到3—4,与传统的PID控制基本一致,但稳定性更好.因无需标定,故降低了变形镜的安装要求.     

基于感知模糊自适应蚁群算法的非线性PID控制

随着系统复杂度的提高和对象不确定性因素的增加,为克服线性PID动态性能和稳态性能差的缺陷,分析了非线性PID控制器各控制参数对误差的理想变化过程,构造非线性PID控制器。由于增益参数大量增加,传统参数优化方法不再适用,在分析蚁群算法的基础上,提出了基于感知自适应蚁群算法,并加入模糊自适应信息素更新机制,用于优化非线性PID控制器的设计方法。通过仿真实验将该控制器与基于蚁群算法的非线性PID控制器和基于蚁群算法、Z-N法的PID控制器进行对比,并对控制性能和收敛性能进行了分析,结果表明该算法有效克服了传统蚁群算法收敛速度较慢、容易陷入局部最优而停滞的缺陷,该控制器具有更好的动态性能和稳态性能。     

基于相关测量法的电动舵机系统频率特性测试分析

为解决频率特性分析仪对舵机频率特性分析容易产生时间延迟及Simulink仿真分析中无法求出非线性舵机系统的Bode图的问题,针对某型舵机,采用相关测量法得到舵机的频率特性;首先介绍了相关测量法原理,其次建立了电动舵机的非线性模型,最后应用相关测量法进行仿真分析和实验验证;仿真结果表明相关分析法可以得到非线性舵机系统的Bode图,实验结果为采用相关测量法计算得到的舵机的带宽为31.824,谐振峰值为1.398 dB,频率特性分析仪得到的带宽为31.818,谐振峰值为和1.402 dB,二者结果一致;仿真分析和实验证明了该方法的可行性,大大降低了硬件、仪器对系统响应的影响。     

模糊自抗扰控制在永磁同步电机调速系统的应用

针对直接转矩调速系统中PID控制器参数鲁棒性差,调速过程中磁链和转矩脉动大的问题,设计了一种基于模糊的改进自抗扰转速控制器;自抗扰策略代替传统的PID控制方法,模糊规则对自抗扰控制算法进行简化,减少待整定参数;与传统的PID控制方法相比,模糊自抗扰控制能提高调速系统的误差估计补偿和抗干扰能力;对比仿真结果,模糊自抗扰控制响应速度快,明显降低了系统在调速过程中的磁链和转矩脉动,表明模糊自抗扰控制具有良好的控制性能,验证了该方法的有效性。     

Guided-Wave Two-Dimensional Acousto-Optic Scanner Using Proton-Exchanged Lithium Niobate Waveguide

Two-dimensional scanning of a 0.6328 mum guided-light beam has been realized using noncolinear acousto-optic (AO) coplanar Bragg diffraction together with colinear AO guided-mode to substrate radiation-mode conversion in a Z-cut Xpropagation LiNbO3 proton-exchanged (PE) waveguide. The two surface acoustic (SAW) waves utilized are at the center frequencies of 500 and 200 MHz, propagating in the Y and X axes, respectively. Two-dimensional scanning of approximately 720 resolvable light beam spots, namely, 18 40 (horizontal vertical) scanning, has been demonstrated using a light beam of 1.0 mm aperture. The total number of resolvable beam spots can be greatly increased from 720 by simply utilizing SAW transducers of larger bandwidth and a light beam of greater aperture. It should also be possible to significantly increase the diffraction efficiency from 3 % by optimizing the parameters of the PE waveguide and the SAWs.     

Hybrid Wavelength and Code Division Multiple Access in Optical Networks

A review of schemes for multiple access in fiber optic networks shows that a hybrid of wavelength and code division multiple access (WCDMA) combines the best features of both. In particular, the hybrid scheme retains the large information carrying capacity of wavelength division multiple access (WDMA) and flexibility of code division multiple access (CDMA). In this paper WDMA, optical CDMA (OCDMA), and WCDMA networks are discussed. In OCDMA networks, concept of incoherent and coherent coding including inverse decoding and matched filter is introduced. The delay performance of both WDMA and WCDMA networks, under the simple suboptimum access protocols based on cyclic search, is computed. It has been shown quantitatively that tuning delay significantly affects the delay performance of both WDMA and WCDMA networks. Futhermore, delay performance of WCDMA networks is always better than the WDMA networks for the same tuning delay, load, and number of users.     

Effect ofγ-radiation on the spectral luminescence characteristics of impure cadmium tungstate crystals

Results of a study of the effect of γ-radiation on the spectral luminescence properties of cadmium tungstate crystals doped with silver, bismuth, and molybdenum cations are presented. Spectral characteristics of the nondnnnoped crystals are briefly described. Absorption and photo and X-ray luminescence spectra of the crystals taken before and after exposure to γ-radiation (5.5·10⁴ Gy) are compared. It is found that the spectral characteristics of the crystals doped with silver, bismuth, and molybdenum cations do not change markedly after the exposure. The relation between the type of impurity-induced defects, individual characteristics of the impurity cations, and the character of the effect of γ-radiation on the spectral luminescence properties of impure crystals is analyzed (preliminarily). Translated from Zhurnal Prikladnoi Spektroskopii, Vol. 64, No. 1, pp. 55–60, January–February, 1997.     

Femtosecond Transform-Limited Pulse Generation by Compensating for the Linear Chirp of SPM Spectra in Dispersion Shifted Fibers

A simple technique of pulse compression, based on the linear chirp compensation of self-phase modulation (SPM) spectra in dispersion shifted fibers, is demonstrated. The optimization procedure is carried out, for a short span of a single-mode fiber, using a parabolic law, which describes the behavior of the squared output pulse width versus the pump peak power in the case of Gaussian pulses. The experimental results give a minimum pulse duration of 233 fs, which is in good agreement with the model. Shorter and coherent pulses, down to 90 fs, have been obtained by inserting an interference filter at the optical output.     

Sorting of bending magnets for the SSRF booster

The Shanghai Synchrotron Radiation Facility(SSRF)booster ring,a full energy injector for the storage ring,is deigned to accelerate the electron beam energy from 150MeV to 3.5GeV that demands high extraction efficiency at the extraction energy with low beam loss rate when electrons are ramping.Closed orbit distortion(COD)caused by bending magnet field uniformity errors which affects the machine performance harmfully could be effectively reduced by bending magnet location sorting.Considering the affections of random errors in measurement,both ideal sorting and realistic sorting are studied based on measured bending magnet field uniformity errors and one reasonable combination of bending magnets which can reduce the horizontal COD by a factor of 5is given as the final installation sequence of the booster bending magnets in this paper.     

Measurement of nonlinear coefficient of optical fiber based on small chirped soliton transmission

We measure the waveform and phase curves of short optical pulses before and after transmission over different lengths of fibers by use of the pulse analyzer with the frequency-resolved optical gating (FROG),and numerically simulate pulse evolution under the experimental conditions.The nonlinear coefficient of the fiber is given by comparing the experimental results with the numerical ones.Difference between the experiment and numerical simulation is analyzed.     

Resonance scattering of canonical elastic shells in absorbing fluid medium

Resonance scattering of elastic spherical shell and cylindrical shell while the surrounding fluid medium has absorption is studied. The normal mode solution derived using exact elastic theory and the separation of variables is still applicable. However, the scattering form function has to be modified for the absorbing medium, otherwise the unreasonable result would be obtained. The backscattering form function in the absorbing medium is redefined, and the form function of elastic spherical and cylindrical shell with vacuum or solid matter filled is calculated in various absorption conditions. The results show that the absorption of surrounding fluid leads to notable attenuation of the coincidence resonances in the mid-frequency, but it has a little influence on the low-frequency resonance scattering induced by the filler inside the shell.     

Single-beam self-referenced phase-sensitive surface plasmon resonance sensor with high detection resolution

A versatile and low-cost single-beam self-referenced phase-sensitive surface plasmon resonance(SPR)sensing system with ultra-high resolution performance is presented.The system exhibits a root-mean-square phase fluctuation of ±0.0028.over a period of 45 min.i.e.a resolution of±5.2×10-9 refractive index units.The enhanced performance has been achieved through the incorporation of three design elements:a true single-beam configuration enabling complete self-referencing so that only the phase change associated with SPR gets detected,a differential measurement scheme to eliminate spurious signals not related to the sensor response,and the elimination of retardation drifts by incorporating temperature stabilization in the liquid crystal phase modulato .Our design should bring the detection sensitivity of non-labeling SPR biosensing closer to that achievable by conventional fluorescence-based techniques.     

Influences of SiO2 protective layers and annealing on the laser-induced damage threshold of Ta2O5 films

Ta2O5 films are prepared on BK7 substrates with conventional electron beam evaporation deposition.The effects of SiO2 protective layers and annealing on the laser-induced damage threshold (LIDT) of the films are investigated.The results show that SiO2 protective layers exert little influence on the electric field intensity(EFI)distribution,microstructure and microdefect density but increase the absorption slightly.Annealing iS effective on decreasing the microdefect density and the absorption of the films.Both SiO2 protective layers and annealing are beneficial to the damage resistance of the films and the latter is more effective to improve the LIDT.Moreover,the maximal LIDT of Ta2O5 films is achieved by the combination of SiO2 protective layers and annealing.