基于扩张状态观测器的永磁同步电机混沌系统自适应滑模控制

针对部分状态不可测的永磁同步电机混沌系统, 结合自适应滑模控制和扩张状态观测器理论, 提出一种基于扩张状态观测器的永磁同步电机自适应混沌控制方法, 取消了系统所有状态完全可测的限制. 通过坐标变换, 将永磁同步电机混沌模型变为更适宜控制器设计的Brunovsky标准形式. 在系统部分状态和非线性不确定项上界均未知的情况下, 基于扩张状态观测器估计系统未知状态及不确定项, 并设计自适应滑模控制器, 保证系统状态快速稳定收敛至零点. 仿真结果表明, 该控制器能够改善滑模控制的抖振问题以及提高系统鲁棒性. 关键词： 永磁同步电机 混沌控制 扩张状态观测器 自适应滑模     

基于神经网络和滑模控制的不确定混沌系统同步

基于滑模控制技术和径向基函数神经网络,设计出一种神经滑模控制器,实现了两个不确定混沌系统的同步.控制器的设计不依赖于系统的数学模型,只与系统的输出状态有关,而且对参数不确定性和外界干扰具有较强的稳健性.最后,利用本方法设计出控制器实现了未知Lorenz系统的自同步、未知Lorenz系统与Chen系统之间的异结构同步,而且响应时间短,同步效果好. 关键词： 混沌同步 滑模控制 神经网络 不确定混沌系统     

飞行模拟转台非线性干扰观测器反步滑模控制器设计

本文针对考虑不确定性的飞行模拟转台伺服系统,提出了一种基于非线性干扰观测器的反步全局滑模补偿控制方法。该方法采用反步控制方法设计转速期望虚拟控制,然后利用非线性干扰观测器观测系统不确定干扰,进而对引入非线性干扰观测器的系统设计自适应全局滑模控制器,实现了飞行模拟转台伺服系统期望转角信号的鲁棒跟踪控制,仿真结果表明,该方法控制效果良好,具有很好的工程应用价值。     

考虑模型不确定性和时延的静止无功补偿器自适应滑膜控制器设计

静止无功补偿器(static var compensator,SVC)不仅可以为电力系统提供无功支撑、稳定电压,其附加控制还可以有效提高系统暂态稳定性,但SVC模型参数的不确定性以及广域测量信号时延等外部干扰给附加控制器的设计带来很大的难度.提出了一种基于自适应滑模变结构理论的SVC鲁棒控制器设计方法,所设计控制器能有效提高系统暂态稳定性,并且其对于模型不确定性以及时延有较好的鲁棒性.首先根据区域惯量中心的运动方程建立了包含SVC的电力系统模型;然后将滑模变结构理论应用于电力系统模型中,求得SVC附加控制律,并通过自适应律优化控制器参数;最后通过四机两区域系统以及IEEE9节点系统对SVC控制器效果进行了仿真验证.结果表明,SVC自适应滑模控制器可以有效提升系统暂态稳定性,并且其性能优于传统的线性控制方法.     

浮球式惯导平台悬浮稳定问题的动力学建模与控制

以浮球式惯导平台的悬浮稳定为研究对象, 全面分析了平台的干扰特性, 建立了液浮支撑模型, 推导了在受扰条件下稳定部件的六自由度运动方程. 针对外部环境、流场阻力、模型参数不确定、未建模动态和测量噪声等干扰问题, 设计了基于高增益扩张观测器的滑模控制器. 数值仿真表明, 液浮稳定结构可以有效隔离外界干扰的影响, 提高平台的抗干扰能力; 所提出的控制方法可以有效抑制系统的抖振, 实现平台的高精度快速稳定控制. 与前期的研究相比, 控制器的动态响应和稳定性能提升了50%. 关键词： 浮球式惯导平台 悬浮稳定 高增益扩张观测器 滑模控制     

Lorenz混沌系统的近似有限时间稳定控制

针对Lorenz混沌系统,研究其有限时间稳定控制问题.考虑系统存在不确定非线性,提出一种可使受控Lorenz系统实现近似有限时间稳定的控制方法.改进并设计一种扩张状态观测器,解决了受控Lorenz系统中不确定非线性未知问题.通过引入奇异扰动性理论,分析了闭环系统的近似有限时间稳定性.仿真实验结果验证了该控制方法及扩张状态观测器的有效性. 关键词： Lorenz混沌系统 近似有限时间稳定 扩张状态观测器 奇异扰动     

基于无记忆状态观测器的多时滞不确定非线性系统的自适应控制

针对一类多时滞不确定非线性系统,研究了基于无记忆状态观测器的自适应控制问题.时滞状态扰动的上界未知,在控制中通过自适应律估计未知参数,并利用估计值设计了不依赖于时滞的无记忆状态观测器和控制器,基于Lyapunov-Krasovskii函数证明了观测误差渐近收敛到零.最后仿真结果说明了该方法的有效性.     

一类混沌系统的同步方法

针对一类混沌系统的特点,任意构造满足一定条件的响应系统,根据滑模控制策略得到实现两者同步的反馈控制器.在可测同步误差基础上,利用扩张状态观测器来估计驱动系统与“构造”的响应系统之间的差异,把上述反馈控制策略转变为物理可实现的控制器并实现两者的同步.以Duffing和Chua’s电路为例的仿真表明效果良好 关键词： 混沌同步 滑模控制 扩张状态观测器     

用滑模控制方法实现具有扇区非线性输入的主从混沌系统同步

分析了一个具有扇区非线性输入且含有参数不确定性以及外部噪声干扰的主从混沌系统的同 步控制问题.设计了一类同步滑模变结构控制器，并从理论上证明了该控制器的有效性.研究 表明该控制器不受受控系统的参数变化和噪声干扰的影响，具有很强的鲁棒性.最后通过对 主从Duffing_Holmes系统的仿真研究，验证了该控制器的有效性. 关键词： 混沌同步 滑模变结构控制 扇区非线性输入 不确定性     

不确定混沌系统的参数识别与同步控制器的backstepping设计

设计了一种参数观测器，对不确定Rossler系统中的未知参数进行了识别，采用backstepping方法实现了异结构不确定Rossler系统和Coullet系统之间的混沌同步.根据稳定性原理，确定了同步控制器的结构和控制增益的取值范围.仿真模拟结果表明，在参数观测器和backstepping控制器的共同作用下， Coullet系统所有的状态变量严格地跟踪了不确定Rossler系统的混沌轨迹，从而证明了该观测器和控制器的有效性.     

Theoretical analysis and simulation of conjugate heights for dual-conjugate AO system in lidar

A multi-conjugate adaptive optics （MCAO） can offer a possibility of widening field of view （FOV） characterized by the isoplanatic angle, and the choose of conjugate height becomes a basic problem for MCAO, which influences the size of iosplanatic angle. Considering the application of lidar, the isoplanatic angle＇s expressions of two deformable mirrors （DMs） MCAO for uplink and downlink are deduced. The effects of conjugate heights for dual-conjugate AO are thoughtfully discussed, and the isoplanatic angles are further analyzed. The results show that the isopanatic angle varies with the conjugate height and reaches the maximum as the conjugate height is at the optimal altitude. Moreover, the optimal conjugate height changes with the propagation distance.     

Quick single-photon detector with many avalanche photo diodes working on the time division

Due to the limit of response speed of the present single-photon detector, the code rate is still too low to come into practical use for the present quantum key distribution (QKD) system.A new idea is put up to design a quick single-photon detector.This quick single-photon detector is composed of a multi-port optic-fiber splitter and many avalanche photo diodes (APDs).Au of the ports with APDs work on the time division and cooperate with a logic discriminating and deciding unit driven by the clock signal.The operation frequency lies on the number N of ports, and can reach N times of the conventional single-photon detector.The single-photon prompt detection can come true for high repetition-rate pulses.The applying of this detector will largely raise the code rate of the QKD, and boost the commercial use.     

Characterization of PolyA and PolyC mismatches by Raman spectroscopy

A.C mismatches are studied by Raman spectral characterization of PolyA, PolyC, and their equimolar complex in solution of 0.14 mol/L Na ,pH7.0.Experimental results show that A·C mismatches occur to be A/B (mainly A) conformers, and unlike Watson-Crick base pairing, this kind of mismatches is stabilized by only one hydrogen bond involving cytosine N4H2 and adenine N7.The formation of A·C complex makes the base stacking interactions much stronger, and conformation of the backbone more ordered, which leads to obvious Raman hypochromic effect with some shifts in corresponding bands.     

Improvement of four-wave mixing-based wavelength conversion efficiency in dispersion shifted fiber by 40-GHz clock pumping

40-GHz clock modulated signal as a pump to improve the efficiency of four-wave mixing (FWM)-based wavelength conversion in a 26.5-km dispersion shifted fiber (DSF) is investigated. The experimental results demonstrate that the conjugated FWM component has higher intensity with the clock pumping than that with the continuous-wave (CW) light pumping. The improvement of FWM-based wavelength conversion efficiency is negligible when the pump power is less than Brillouin threshold. But when the pump power is greater than Brillouin threshold, the improvement becomes significant and increases with the increment of pump power. The improvement can increase up to 9 dB if pump power reaches 17 dBm.     

Multi-pulse operation of a Kerr-lens mode-locked femtosecond laser

Our experimental results show that the presence of a proper amount of negative group velocity dispersion is essential to multi-pulse operation of a Kerr-lens mode-locked femtosecond laser. We demonstrate that the pulse separations and the number of pulses contained within a cavity round trip are strongly dependent on the initial perturbations. The results allow us to get a better understanding on the influences of the convoluted self-phase modulation and intra-cavity dispersions on the stable multi-pulse oscillation in a Kerr-lens mode-locked femtosecond laser.     

Propagation of Helmholtz-Gauss beams in weak turbulent atmosphere

Based on the Rytov approximation of light propagation in weak turbulent atmosphere,the closed-form expressions of field and average irradiance of each one of the four fundamental families of Helmholtz-Gauss (HzG)beams:cosine-Gauss beams,stationary Mathieu-Gauss beams,stationary parabolic-Gauss beams,and Bessel-Gauss beams,which are propagating in weak turbulent atmosphere,are obtained.The results show that the field and average irradiance can be written as the product of four factors:complex amplitude depending on the z-coordinate only,a Ganssian beam.a factor of complex phase perturbation induced by atmospheric turbulence,and a complex scaled version of the transverse shape of the non-diffracting beam.The effect of weak atmospheric turbulence on irradiance distribution of the HzG beam can be ignored.     

An effective method for reducing speckle noise in digital holography

An effective method for reducing the speckle noise in digital holography is proposed in this paper.Different from the methods based on classical filtering technique,it utilizes the multiple holograms which are generated by rotating the illuminating light continuously.The intensity images reconstructed by a series of holograms generated by rotating the illuminating light possess different speckle patterns.Hence by properly averaging the reconstructed intensity fields,the speckle noises can be reduced greatly.Experimental results show that the proposed method is simple and effective to reduce speckle noise in digital holography.     

Influence of purity of HfO2 on reflectance of ultraviolet multilayer

The impurities in two kinds of HfO2 materials and in their corresponding single layer thin films were determined through glow discharge mass spectrum technology and secondary ion mass spectrometry(SIMS) equipment respectively.It was found that ZrO2 was the main impurity in the two kinds of HfO2 either in the original HfO2 materials or in the electron beam deposited films.In addition,the difference of Zr content in the two kinds of HfO2 single laver films was much laxger than that of the other impurities such as Ti and Fe.which showed that it was just ZrO2 that made the difference between the optical performance of the film products including the two kinds of HfO2.With these two kinds of HfO2 and the same kind of SiO2.we deposited HfO2/SiO2 multilayer reflective coatings at the wavelength of 266 nm.Experimental results showed that the reflectances of these two mirrors were about 99.85% and 99.15% respectively,which agreed well with the designed results what were based on the optical constants obtained from the corresponding single layer thin films.     

Speech enhancement by array crosstalk resistant ANC and spectrum subtraction

Microphone array-based speech enhancement has great importance for speech communications and speech recognition. To reduce the aperture of the microphone array and to increase the effect of the speech enhancement will greatly broaden the application areas of the microphone array. An array crosstalk resistant adaptive noise cancellation method is therefore presented. And then an improved spectral subtraction algorithm is further cascaded to obtain better enhancement results. Theoretic analysis and experiments indicate that the proposed scheme needs only a very small microphone array while it simultaneously achieves a higher SNR improvement. Besides, the proposed scheme can be used in many noisy environments and is easy for real-time implementation.