遗传算法在跨超声速风洞总压控制中的应用

总压作为风洞控制中的重要流场参数,其调节性能是风洞控制系统能否满足试验要求的重要指标,为提高跨超声速风洞的总压控制水平,需对总压控制策略进行设计。针对某跨超声速风洞对总压控制系统提出的快速性和精确性要求,提出串级控制、智能PID控制和总压分段控制等方法,并利用MATLAB系统辨识工具箱对流场调节阶段的总压系统模型进行了辨识。提出将遗传算法应用于风洞流场调节阶段的PID控制器参数整定中,重点对基于遗传算法的PID控制原理和参数整定步骤进行介绍,并针对遗传算法的遗传算子进行了设计。系统仿真和风洞实际运行情况表明：该方法较常规PID参数整定与优化方法,具有更好的控制性能指标,满足总压控制系统精确性、快速性、鲁棒性等要求,为后续风洞建设和设备改造提供了新方法。     

模糊PID控制在ATP伺服系统中的应用

针对空间光通信ATP伺服系统采用一种模糊PID参数自整定的控制方法,结合模糊控制与常规PID控制的优点,讨论了模糊PID参数自整定控制器的设计方法。利用MATLAB中的模糊控制工具箱进行了系统的辅助设计与仿真实验,并与传统PID控制系统进行比较。仿真结果表明,该控制方法明显优于传统PID控制,并能使ATP系统的视轴稳定性得到提高。     

小型固定翼无人机纵向姿态控制律的研究

针对无人机在实际飞行过程中受到外部环境影响大,控制精度不够高的问题;研究了一种模糊参数自整定PID控制方法来完成对无人机的纵向姿态的控制;该方法在传统的PID控制的基础上,利用无人机实际飞行中的数据,建立起模糊控制规则来实现PID参数自整定,最后在通过建立的纵向姿态模型上进行仿真控制,得出仿真曲线;仿真实验结果表明,所设计的模糊PID控制器,相比于传统的PID控制器具有更好的控制性能,并且具有很好的抗干扰能力,能够满足无人机控制系统的要求。     

DTN中基于贝叶斯的节点相遇概率预测方法

电站锅炉的烟气脱硝过程同其他电站热工过程一样存在一定迟延性和惯性。本文根据目前烟气脱硝系统运行情况,总结分析了氮氧化物(NOX)排放控制过程的特点、影响因素以及控制系统。为解决锅炉运行过程中系统呈现出的大迟延和大惯性问题对整个烟气脱硝控制品质产生的影响,以及实现系统的稳定性和快速性,在原有的串级回路系统中,加入了Smith预估补偿控制器提前预估系统的动态特性并对其进行补偿。根据烟气脱硝系统对象的传递函数,设计了Smith预估补偿控制系统,采用Matlab中的Simulink对控制系统的对象和改进前后的控制系统响应曲线进行仿真分析,可以看出改进后系统动态品质变好,系统的快速性和稳定性也明显提高。     

Smith预估补偿控制在燃煤电厂烟气脱硝控制系统的应用

电站锅炉的烟气脱硝过程同其他电站热工过程一样存在一定迟延性和惯性;根据目前烟气脱硝系统运行情况,总结分析了氮氧化物(NOX)排放控制过程的特点、影响因素以及控制系统;为解决锅炉运行过程中系统呈现出的大迟延和大惯性问题对整个烟气脱硝控制品质产生的影响,以及实现系统的稳定性和快速性,在原有的串级回路系统中,加入了Smith预估补偿控制器提前预估系统的动态特性并对其进行补偿;根据烟气脱硝系统对象的传递函数,设计了Smith预估补偿控制系统,采用Matlab中的Simulink对控制系统的对象和改进前后的控制系统响应曲线进行仿真分析,可以看出改进后系统动态品质变好,系统的快速性和稳定性也明显提高。     

PID参数自整定方法在热风炉燃烧控制中的应用

热风炉是高炉生产系统中重要的组成部分,其燃烧控制是一个相当重要的部分。但是国内大部分的中小型热风炉参数的设置几乎都采用常规PID,这样受人为因素影响严重,不能达到节约能源和优化控制的目的。因此,运用合适的PID参数自整定方法来代替常规PID整定,对煤气和空气流量进行控制,进而改善热风炉的送风效果显得尤为重要。本文设计了热风炉的燃烧控制方案,然后具体对几种不同的PID自整定方法进行研究,并以工业控制系统中常用的带有时间延迟的一阶模型为例,运用MATLAB对具体的PID自整定方法进行研究与仿真。同时,对仿真结果进行比较,得到了各种自整定方法的控制效果和适用范围。以便将PID自整定方法运用到热风炉的燃烧控制中,进而改善其燃烧效果。     

锅炉主蒸汽温度控制系统二次优化控制研究

锅炉主蒸汽温度关系到电厂的安全性和经济性,而主蒸汽温度控制具有大滞后、大惯性、扰动因素多的特点,常用的串级控制很难保证控制精度和稳定性。针对这类被控对象,进行了常规控制系统的分析,提出运用二次优化原理进行控制系统设计,并在控制系统中引入预估模型实现二次优化控制,最后增加非线性均方根放大器环节对优化控制系统再优化。以电厂锅炉主蒸汽温度控制系统为例,对二次优化控制进行了仿真研究,并与传统PID控制进行比较。结果表明,该方法显著提高了控制系统的动态特性、稳态精度及鲁棒性,实现了无超调量、无稳态误差的控制精度。     

基于DSP的专家PID控制在无刷直流电机的应用

针对无刷直流电机传统控制的不足,在DSP控制框架内设计了电机的专家整定PID控制系统;系统将DSP技术和专家控制技术相结合,DSP在完成信息分析处理和协调各部件等工作的同时,计算出无刷直流电机转子转速,转速值与上位机设定值比较后,将差值送入专家整定PID控制器,利用专家整定PID控制器快速、灵活、准确的参数整定优势,输出合适的PWM占空比控制转速,实现电机的闭环控制;仿真结果显示,该控制方法与普通PID控制相比,具有响应快、误差小、抗负载扰动能力强等优点,验证该方案的有效性,具有一定的应用借鉴意义。     

褐煤锅炉蒸汽温度模糊控制仿真研究

本文利用GSE软件建立了600 MW超临界褐煤锅炉蒸汽温度模糊PID控制系统的仿真模型,进行了模糊PID控制效果的仿真研究,并与常规PID控制进行了对比。研究结果发现,在抽炉烟份额从100%降至50%的扰动下,模糊控制方案的主汽温的最小值比常规控制高0.21℃,最大值低0.15℃,动态时间缩短了477 s;再热汽温的最小值比常规控制高0.32℃,最大值低0.49℃,动态时间缩短了387 s。模糊控制下的汽温调节的快速性和稳定性均优于常规控制,证明了该模糊控制方案能够改善控制系统的控制质量。仿真实验的结果对电厂汽温控制系统的优化具有一定的参考意义。     

基于STM32的低功耗智能定位阀控制器设计

针对工业控制中传统阀门定位器稳定性差、定位精度低、抗干扰能力差、智能化程度低等缺点,以及我国自主研发生产高精度阀门定位器上的不足。设计了以ARM Cortex-M3 内核处理器作为核心控制器的低功耗智能定位阀控制系统。设计中采用优化的PID控制算法,并采用齐格勒-尼克尔斯法则,自整定PID参数。通过二线制HART 协议实现与外界设备通讯。实践证明自整定PID参数能够更好的适应各种控制现场,控制系统能够稳定、快速的运行实现了阀门位置的精确定位和本安低功耗设计的要求。     

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.