基于RFM的机载余度计算机软件快速测试平台

现代飞机普遍采用电传飞行控制系统,飞行控制计算机是该系统的核心。为了提升飞控计算机的可靠性,普遍采用余度技术构建余度飞控计算机,该计算机由多个通道构成,每个通道有一个CPU,互相构成备份。但是,这给飞控计算机的软件调试和测试带来的巨大的困难,因为各个通道的机载软件之间相互同步、通信和交叉监控,必须并行调试和测试,这就造成了机载软件调试和测试的滞后,必须等待真实的飞控计算机开发出来之后才能开展工作。本文提出了一种基于RFM(反射内存)的余度计算机快速原型测试平台设计方法。该平台使用商用货架产品构成余度计算机的多个冗余通道,使用RFM模拟多通道间的通信、同步过程,通过对底层驱动封装实现硬件故障模拟和余度功能模拟,方便实现软件调试和从性能、功能测试,大大提高了开发效率,减少了研制周期。     

飞行控制系统故障诊断与重构技术研究

对于高空长航时无人机高性能要求,提出一种多等级余度飞行控制系统。结合飞行控制系统各组成部分的结构特点,给出了传感器信号的余度信号管理技术,机载计算机通道故障诊断与仲裁技术;伺服子系统故障隔离和控制分配重构技术。试验结果表明该飞行控制系统故障诊断与重构方案设计合理可行,不仅较好地完成了飞行控制系统的余度管理任务,而且有效提高了故障检测率抑制了虚警,保证了系统的可靠性与容错能力。     

三余度飞控系统余度管理算法设计与研究

为了提高无人机飞行控制系统的可靠性,针对样例飞行控制计算机分布式架构的特点设计了余度管理策略。针对多CPU同步困难及同步后的积累性时漂误差问题,通过任务同步算法和简化版的TPSN同步算法相结合实现了各CPU之间的时间同步,有效地降低了时漂带来的影响,同步精度可达到0.1毫秒以内。采用基于“距离”的封装表决算法完成三余度决策输出功能,降低了开发的难度,减少了传统方式的代码冗余。采用系统重构策略对故障CPU进行管理,通过系统降级与故障恢复提高系统可靠度。最后对关键环节进行了功能测试,测试结果表明各环节可达到功能和指标要求,验证了所提出的余度管理策略的合理性和有效性。     

三余度飞行控制计算机FlexRay节点通信设计

飞行控制计算机是飞行控制系统的核心组成部分,为进一步提高中小型无人机的安全可靠性,采用了软、硬件结合的三余度管理技术。首先采用模块化的设计思想,设计了系统三余度飞行控制计算机的硬件架构,包括串口、开关量、模拟量、CAN和FlexRay总线以及外扩SRAM等硬件资源;然后设计余度管理策略,该部分提出了软件表决和硬件仲裁两级余度管理思想;此外,为克服传统CAN总线负载量和通信速率等方面的不足,引入了FlexRay总线通信技术,并详细分析了总线通信数据流,设计了基于FlexRay的总线通信机制;最后进行半物理仿真实验,验证FlexRay总线通信功能,验证结果表明设计方案合理可行。设计的三余度飞行控制计算机硬件集成性高且易扩展升级,FlexRay总线通信功能也满足设计需求,具有很高的应用价值。     

混合三余度无人机飞控计算机硬件结构设计及可靠性分析

飞控计算机是整个无人机飞控系统的核心部件,其可靠性直接影响着无人机的飞行安全;为了提高飞控计算机的稳定性和可靠性,结合工程实践,提出了一种混合三余度无人机飞控计算机硬件结构设计方案,概括描述了各组成部分的工作原理,并采用马尔科夫模型对该方案进行了可靠性分析;数据结果表明,混合三余度无人机飞控计算机较单机可靠性有了明显提高,满足无人机飞控计算机的可靠性要求,可作为高可靠性长航时无人机飞控计算机设计的参考方案。     

不同机载测试网络环境对IEEE 1588时钟同步系统性能的影响分析

为深入研究不同机载测试网络环境对IEEE 1588时钟同步系统性能的影响,提出了使用正态分布曲线描绘时钟同步误差的方法。通过分析IEEE1588时钟同步系统的工作原理,决定采用硬件方式测量时钟同步误差分布,并利用统计学的分析方法,分析不同的机载测试网络环境对IEEE 1588时钟同步系统性能的影响。分析结果表明网络拓扑结构、网络节点负载和外部环境温度都对IEEE 1588时钟同步系统的性能有一定影响,其中网络拓扑结构的变化对IEEE1588时钟同步精度的影响比较大。这一研究成果对网络化机载测试系统的设计与使用具有一定的借鉴意义。     

机载位移传感器故障检测与信号重构

为了避免机载系统故障诊断与重构中单纯增加余度数目所带来的问题,针对电传飞控系统中应用较多的位移传感器,提出了一种基于特征的检测电路、检测方法以及信号重构方案。方案基于位移传感器工作时两次级线圈回路电压和值恒定的特征,实现了对初级、次级回路的一次断线检测,在检测到次级线圈一次断线时,又利用正常工作特征并根据另一次级线圈所获得的信息对断线信号进行重构。分析和测试表明,所提出的位移传感器故障检测以及重构算法仅需增加极少的硬件电路,且检测及重构方法实时性高,在不增加传感器余度数目的条件下,能大大提高系统的可靠性。     

高可靠分布式容错计算机架构的研究

分布式系统因其具有分散安装、可靠性高、扩展性好、维修成本低、健壮、安全等诸多优点,国内外相继开展分布式计算机高可靠性技术的研究。本文提出了高可靠分布式容错计算机的构架设计思路,并对TTE总线的选用进行了分析论证,重点描述了成员一致性保证和余度同步等关键技术。     

基于虚拟仪器的测控系统平台

一个大的复杂的测试系统往往系统的测量、输入、输出、结果分析分布在不同的地理位置，仅用一台计算机并不能胜任测试任务，需要由分布在不同地理位置的若干计算机共同完成整个测试任务。计算机网络技术、总线技术与数据库技术的发展，乃至Internett网的发展拓展了虚拟仪器测试系统的应用范围。利用网络技术将分散在不同地理位置不同功能的测试设备联系在一起，使昂贵的硬件设备、软件在网络内得以共享，减少了设备重复投资。一台计算机采集的数据可以立即传输到另一台处理分析机上进行处理分析，实现实时采集、实时监测。重要的数据实行多机备份，提高了系统的可靠性。对于有些危险的、环境恶劣的不适合人员操作的数据采集工作可实行远程采集，将采集的数据放在服务器中供用户使用。     

飞机交流电源特性参数测量研究

飞机机载电源系统供电品质直接关系到飞机用电设备可靠工作和飞行安全,为此,2006年国际标准组织推出了新的机载电源标准ISO1540-2006;本文根据该标准要求,提出了一种机载电源的稳态和瞬态特性的测试的实用方法;建立了测量的数学模型;采用虚拟仪器技术,设计硬件测试平台,包括功率因数可调的大功率数字化程控负载和计算机数据采集系统;基于LabVIEW开发了测试软件;为满足暂态特性的测量要求和精度要求,采用了NI高速高精度数据采集卡,实现了较高的测量精度,综合测量误差小于0.5%,并在暂态测量中,考虑了负载接触器吸合时间;该测试系统可以用来检验恒频机载交流电源的特性是否符合国际标准要求,以保证飞行安全。     

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.