高精度光纤陀螺信号的在线建模与滤波

针对高精度光纤陀螺随机误差,在分析其一般时间序列模型的基础上,提出了一种改进型二阶自回归AR(2)模型,可以在线建立光纤陀螺随机误差模型.根据该模型,采用卡尔曼滤波算法,实现了光纤陀螺惯导系统在对准与导航过程中光纤陀螺随机误差的实时滤波.滤波结果和Allan方差分析证明,光纤陀螺信号中角随机游走、零偏不稳定性、速率随机游走、速率斜坡和量化噪声五项噪声源误差系数都小于滤波前的二分之一,有效减小了光纤陀螺随机误差,提高了光纤陀螺精度.     

小波理论应用于光纤陀螺信号处理的实验研究

本文分析了小波变换的特点，并根据光纤陀螺信号零点漂移的非平稳随机性和非正态分布特性，提出了利用小波变换所具有的时频局部化优点对光纤陀螺信号漂移进行消噪处理，实验表明该方法提高了光纤陀螺的准确度，这对于光纤陀螺的实际工程应用起到积极的作用。     

GPS／FOG组合导航系统自适应滤波器设计

结合GPS姿态测量系统导航的特点和光纤陀螺敏感角速度范围宽、启动速度快的特点，提出了一种光纤陀螺辅助GPS导航的方法，采用自适应滤波技术设计了组合导航算法，并进行了大量的试验，试验结果表明，利用光纤陀螺辅助GPS导航方法可行．     

基于BP神经网络的光纤陀螺仪温度建模研究

目前光纤陀螺应用广泛，但是其性能容易受到环境温度影响，从而影响到惯性导航系统的性能．光纤陀螺的温度特性具有非常复杂的非线性特点，而BP神经网络具有良好的逼近复杂非线性函数能力。使用BP神经网络建立光纤陀螺温度特性的黑箱模型，不对零漂和标度因子进行补偿，而直接对陀螺输出进行校正．经实际数据检验，该建模补偿方法比未经补偿和经过传统工程补偿方法的精度提高了两个数量级．与传统的线性模型相比较，本文基于BP神经网络建立的光纤陀螺温度模型具有补偿方法简单，精度高，通用性好等优点．     

基于寻北技术的测斜仪初始对准方法

在捷联惯导技术应用到石油采掘与矿井勘探领域的背景下,探讨如何使用低精度的惯性传感器获得精确的初始姿态信息。本文借鉴陀螺寻北仪的两位置寻北方案,研究了基于寻北技术的初始对准方法,利用该方法可滤除惯性传感器的常值漂移。仿真表明在使用低精度的惯性传感器条件下,利用该方法能获得较高精度的初始姿态信息。     

光纤陀螺技术的军事应用及前景

介绍了光纤陀螺的原理及种类,通过将光纤陀螺与其它陀螺进行比较,总结出了光纤陀螺的优点.最后,综述了光纤陀螺在武器装备上的应用,并对光纤陀螺的应用前景作了预测.     

光纤陀螺温度漂移的多变量模型

针对光纤陀螺温度漂移的补偿问题,本文提出一种线性多变量光纤陀螺温度漂移建模方法.建立的模型由两部分组成:陀螺输出的自回归项和温度梯度的多项式分布滞后项(PDL).自回归项描述光纤陀螺历史输出对当前输出的影响,PDL项描述由温度变化引起的陀螺漂移.根据模型的线性特性,采用最小二乘法确定模型参数.用实测的光纤陀螺温度漂移数据进行了模型的有效性验证.实验结果表明,提出的线性多变量模型能有效补偿光纤陀螺的温度漂移,补偿后光纤陀螺的精度提高50%以上.     

再入式光纤陀螺实用化技术研究

再入式光纤陀螺（Re—FOG）使相互干涉的两路光循环进入光纤环,通过缩短光纤长度克服温度和应力引起的误差。本文研究了再入武光纤陀螺实用化的相关技术;提出了一种采用脉冲相位调制的信号检测方法;设计了专门的数据通讯模块。实验结果表明：所提出的信号检测方法可分离出所需循环次数的信号并解算出陀螺转速;所设计的通讯模块能保证实现陀螺与导航计算机之间的快速、稳定、准确的数据传送。再入式光纤陀螺可成为实用化的新型光纤陀螺。     

布里渊光纤陀螺光纤环形腔研究

提出了一种用于布里渊光纤陀螺的光纤环形腔设计方法。在分析了布里渊光纤陀螺原理的基础上,利用琼斯矩阵光学的理论以及光纤中的受激布里渊散射理论,详细研究了布里渊光纤环形腔的特性。通过对腔内外光强的细致分析,得出布里渊光纤陀螺环形腔对于腔的耦合系数及输入光强的要求。实验结果表明,该方法用于设置布里渊光纤陀螺工作点,能够保证斯托克斯光的最大传输效率,并有效抑制光路中的散粒噪声。     

基于无源耦合技术的高速并行光接收模块的设计与实现

提出了一种实现高速并行光接收模块中光电探测器(PD)列阵与光纤列阵精密无源耦合对准的方法,设计并制作了用于这种光学精密对准的所有组件,并用此耦合对准方法完成了PD阵列与光纤阵列之间的光耦合,制作出了12信道并行光接收模块.耦合完成的PD列阵与光纤列阵的对准误差小于1μm,从光纤列阵耦合进入PD列阵的光功率耦合效率大于8...     

Multiple alignment through protein secondary-structure information

It is well known that protein secondary-structure information can help the process of performing multiple alignment, in particular when the amount of similarity among the involved sequences moves toward the "twilight zone" (less than 30% of pairwise similarity). In this paper, a multiple alignment algorithm is presented, explicitly designed for exploiting any available secondary-structure information. A layered architecture with two interacting levels has been defined for dealing with both primary- and secondary-structure information of target sequences. Secondary structure (either available or predicted by resorting to a technique based on multiple experts) is used to calculate an initial alignment at the secondary level, to be arranged by locally scoped operators devised to refine the alignment at the primary level. Aimed at evaluating the impact of secondary information on the quality of alignments, in particular alignments with a low degree of similarity, the technique has been implemented and assessed on relevant test cases.     

Fast Compass Alignment for Strapdown Inertial Navigation System

Initial alignment is the precondition for strapdown inertial navigation system (SINS) to navigate. Its two important indexes are accuracy and rapidity, the accuracy of the initial alignment is directly related to the working accuracy of SINS, but in selfalignment, the two indexes are often contradictory. In view of the limitations of conventional data processing algorithms, a novel method of compass alignment based on stored data and repeated navigation calculation for SINS is proposed. By means of data storage, the same data is used in different stages of the initial alignment, which is beneficial to shorten the initial alignment time and improve the alignment accuracy. In order to verify the correctness of the compass algorithm based on stored data and repeated navigation calculation, the simulation experiment was done. In summary, when the computer performance is sufficiently high, the compass alignment method based on the stored data and the forward and reverse navigation calculation can effectively improve the alignment speed and improve the alignment accuracy.     

基于局部切空间排列与MSVM的齿轮箱故障诊断

针对齿轮箱故障特征重叠难以有效分离问题,提出基于局部切空间排列与多核支持向量机的齿轮箱故障诊断模型。在由振动信号时域统计指标及内禀模态分量能量构造的多元特征空间中,据局部切空间排列算法对多元特征进行非线性降维处理,得到初始低维流形结构,获取最优敏感特征向量;将该特征向量输入至多核支持向量机进行学习训练与故障辨识。局部切空间排列能克服传统降维方法的不足,多核支持向量机可实现复杂故障高精度、自动化智能诊断。通过齿轮箱故障模拟实验验证该方法的有效性。     

冷压印光刻中斜纹光栅对准信号计算模型

采用傅里叶光学的方法,分析了冷压印光刻中新型斜纹光栅对准标记的透光特性。分析表明,对准信号与光栅副相对位移之间是正弦变化关系,且对准位置附近是一个陡直的线性区。该区对准信号的灵敏度很高,适合于多层套刻对准,根据信号和位移的线性关系,给出初步的对准信号计算模型。由于抗蚀剂的存在,使晶片表面反射率随位移而变化,提出用反射率因子进行修正的方案。反射率因子中包含有位移信息,将其与初步对准信号模型相乘,得到修正的计算模型。由新模型,研究了抗蚀剂平均厚度不同对对准信号的影响,说明要获得高灵敏度的信号,抗蚀剂厚度应取满足压印条件的最小值。     

Fusion splicing of polarization preserving fibers

A novel technique is developed to detect any principal axis misalignment of polarization preserving fiber. The technique is based on measurement of reflect-returned power for the fiber oputput endface that is depolarized by the birefringence of the fiber. It is confirmed theoretically and experimentally that principal axis alignments of 0 and 45 degrees can be successfully made only by minimizing and maximizing the monitoring level, respectively. On the basis of the alignment method, a fusion splicing technique is proposed for polarization preserving fibers. It is confirmed theoretically and experimentally that all principal axes alignment, core axis alignment, and splices loss estimations can be simply and sequentially attained with the present technique. Using the technique, +/-0.5 degree angular alignment resolution and +/-0.05-dB splice loss estimation accuracy are satisfactorily achieved.     

离子束旋转刻蚀工艺误差对均匀照明的影响

介绍一种离子束旋转刻蚀工艺,该工艺可用于制作真正意义上连续位相分布的衍射光学元件。对工艺系统中离子束不均匀度和基片与掩模板中心对准误差对器件性能的影响作了模拟计算,并根据对误差的模拟分析提出了工艺改进方案。     

融合几何特征的ICP改进算法在数字化测量评价中的应用

针对ICP算法对初值依赖程度高、在配准过程中可能陷入局部最优解的问题,提出了一种融合几何特征的ICP改进算法。利用零件具有丰富几何参数的特点,首先对实测点云进行基于曲率的体素采样,尽可能保留几何特征,再将点云的曲率差值和法向量夹角差值引入算法的目标误差函数中进行迭代计算,当目标误差函数达到设定阈值时迭代结束,得到最终配准结果。利用复杂曲面标准件进行了点云配准实验验证,结果表明：相较ICP算法,融合几何特征的ICP改进算法的收敛速度更快、误差更低;相较快速全局配准加ICP配准算法,融合几何特征的ICP改进算法在保证配准准确性的同时,减弱了对初值的需求,简化了点云配准过程。融合几何特征的ICP改进算法为促进零件的准确数字化测量评价提供了有力支撑,具有技术借鉴价值。     

Role of ion flux on alignment of carbon nanofibers synthesized by DC plasma on transparent insulating substrates

A key factor to the implementation of devices with vertically aligned carbon nanofibers (VACNFs) is fundamental understanding of how to control fluctuations in the growth direction of the fibers. Here we demonstrate synthesis of VACNF on transparent and insulating substrates by continuous direct current (DC) plasma for realization of cellular interface suitable for transmission optical microscopy. To maintain continuous glow discharge above the substrate, a metal grid electrode layer (Cr) was deposited over silica with windows of exposed silica ranging in size from 200 μm to 1 mm. This electrode geometry allows for synthesis of VACNFs even within an insulating window. This observation and the observed trends in the alignment of nanofibers in the vicinity of grid electrodes have indicated that the alignment does not correspond to the direction of the electric field at the substrate level, contrary to previously proposed alignment mechanism. Computational modeling of the plasma with this grid cathode geometry has shown that nanofiber alignment trends follow calculated ion flux direction rather than electrical field. The new proposed alignment mechanism is that ion sputtering of the carbon film on a catalyst particle defines the growth direction of the nanofibers. With this development, fiber growth direction can be better manipulated through changes in ionic flux direction, opening the possibility for growth of nanofibers on substrates with unique geometries.     

Simple technique for the generation of plane surface normal to optic axis direction of uniaxial crystal

What we believe to be a new experimental technique for the generation of a plane crystal surface perpendicular to the optic axis direction of a transparent birefringent uniaxial crystal is presented. A simple setup has been described for the initial optic axis alignment of a raw uniaxial crystal blank. Error correction methods have been illustrated. A technique for producing high optical quality surfaces by block polishing plane parallel crystal surfaces normal to the direction of the optic axis, in one setting, is discussed. The block with angular graduations facilitates the correction of angular error. A new conoscopy setup has been coupled to a Fizeau interferometer for high accuracy testing of the optic axis alignment with respect to the surface normal of the relevant polished surface of the uniaxial crystal. The results obtained for a quartz crystal blank are presented.     

High transmittance in-plane switching liquid crystal mode using double-exposed UV alignment method

In general, the super in-plane switching (S-IPS) liquid crystal (LC) mode is widely used for LCD applications because of its wide-viewing properties. However, it can also diminish the aperture ratio in active areas due to the zigzag pattern. In this paper, we proposed an IPS LC mode that has wide-viewing properties even if the stripe-patterned electrodes, which can provide a high transmittance property, are applied using the double-exposed UV alignment method to the upper/lower domain of the active area. The initial alignment direction of the upper/lower domain was optimized with simple experiments and we achieved both the superior dark level in the initial mode and wide-viewing properties in the applied voltage mode. As a result, we obtained an increased aperture ratio of about 10% and a higher optical transmittance of 15% compared to the conventional S-IPS LC cell because of the high aperture ratio without any optical loss of the initial dark state and viewing angle property.