Application of wavelet package filtering in the de-noising of fiber optic gyroscopes

To reduce the drift error existing in the output signal of fiber optic gyroscopes （FOG）, a mathematical model of the FOG output signal is set up; the error characteristics of the FOG output signal are analyzed, and semi-soft threshold filtering is chosen based on the comparison of hard threshold and soft threshold filtering. The semi-soft threshold wavelet package filtering method is applied in the filtering of the FOG output signal. Experiments of the stationary and dynamic FOG output signals filtered with the wavelet package analysis are carried out in a lab environment, respectively. Experiments done with the real-time measured FOG signal show that the method of semi-soft threshold wavelet package filtering reduces the mean square error from 5 （°）/h to 1 （°）/h, so it is effective in eliminating the white noises and the fractal noises existing in the FOG. The novel method proposed here is proved valid in reducing the FOG drift error, satisfying the technical demands of high precision and realtime processing.

An Open-Loop Test of a Resonator Fiber Optic Gyro

The resonator fiber optic gyro （R-FOG） ,which utilizes a resonance frequency change due to the Sagnac effect,is a promising candidate for the next generation inertial rotation sensor. In this study, an open-loop R-FOG is set up using phase modulation spectroscopy. First,the demodulation curve is obtained using a lock-in amplifier. From the demodulation signal,a gyro dynamic range of ± 4.2rad/s is obtained. Then,using different phase modulation frequencies,the open-loop gyro output signal is measured when the gyro is rotated clockwise or counterclockwise. The bias drift as a function of time is also measured. The fluctuation of the output over 5s is about 0.02rad/s. The drift can be reduced by taking countermeasures against system noise.

Research on fiber optic gyro signal de-noising based on wavelet packet soft-threshold

Gyro＇s drift is not only the main drift error which influences gyro＇s precision but also the primary factor that affects gyro＇s reliability. Reducing zero drift and random drift is a key problem to the output of a gyro signal. A three-layer de-nosing threshold algorithm is proposed based on the wavelet decomposition to dispose the signal which is collected from a running fiber optic gyro （FOG）. The coefficients are obtained from the three-layer wavelet packet decomposition. By setting the high frequency part which is greater than wavelet packet threshold as zero, then reconstructing the nodes which have been filtered out noise and interruption, the soft threshold function is constructed by the coefficients of the third nodes. Compared wavelet packet de-noise with forced de-noising method, the proposed method is more effective. Simulation results show that the random drift compensation is enhanced by 13.1%, and reduces zero drift by 0.052 6°/h.

Residual intensity modulation in resonator fiber optic gyros with sinusoidal wave phase modulation

We present how residual intensity modulation(RIM) affects the performance of a resonator fiber optic gyro(R-FOG) through a sinusoidal wave phase modulation technique. The expression for the R-FOG system's demodulation curve under RIM is obtained. Through numerical simulation with different RIM coefficients and modulation frequencies, we find that a zero deviation is induced by the RIM effect on the demodulation curve, and this zero deviation varies with the RIM coefficient and modulation frequency. The expression for the system error due to this zero deviation is derived. Simulation results show that the RIM-induced error varies with the RIM coefficient and modulation frequency. There also exists optimum values for the RIM coefficient and modulation frequency to totally eliminate the RIM-induced error, and the error increases as the RIM coefficient or modulation frequency deviates from its optimum value; however, in practical situations, these two parameters would not be exactly fixed but fluctuate from their respective optimum values, and a large system error is induced even if there exists a very small deviation of these two critical parameters from their optimum values. Simulation results indicate that the RIM-induced error should be considered when designing and evaluating an R-FOG system.

NUMERICAL MODEL OF THERMAL TRANSIENT EFFECT IN FIBER OPTIC GYRO

The sensitivity of the interferometric fiber optic gyro in the presence of time varying thermal gradients plays a key role in its performance. It is well known that this sensitivity is due to the difference of index changes between the points symmetrical with respect to the middle of the coil. In order to reduce this sensitivity, different winding patterns, such as quadrupolar winding, were introduced to keep the thermal environment of the symmetrical points. In this paper, a numerical model of the transient temperature distribution in the gyro was established. The temperature gradient of the coil was solved in conjugation with the nature convection heat transfer in the aperture between the coil and the case. Effects of the winding pattern and the design of its case were investigated to optimize the design of the interferometric fiber optic gyro.

Dynamic Free-Spectral-Range Measurement for Fiber Resonator Based on Digital-Heterodyne Optical Phase-Locked Loop

We propose a novel scheme, based on digital-heterodyne optical phase-locked loop with whole-fiber circuit, to dynamically measure the free-spectral-range of a fiber resonator. The optical phase-locked loop is established with a differential frequency-modulation module consists of a pair of acousto-optic modulators. The resonance-tracking loop is derived with the Pound-Drever-Hall technique for locking the heterodyne frequency of the OPLL on the frequency difference between adjacent resonance modes. A stable locking accuracy of about 7 × 10?9 and a dynamic locking accuracy of about 5 × 10?8 are achieved with the FSR of 8.155 MHz, indicating a bias stability of the resonator fiber optic gyro of about 0.1?/h with 10 Hz bandwidth. In addition, the thermal drift coefficient of the FSR is measured as 0.1 Hz/?C. This shows remarkable potential for realizing advanced optical measurement systems, such as the resonant fiber optic gyro, and so on.

ELM-AdaBoost模型在光纤陀螺温度误差补偿中的应用

针对光纤陀螺零偏与温度之间复杂的非线性关系,引入极限学习机(extreme learning machines,ELM)模型补偿光纤陀螺的零偏温度误差;针对单个ELM在预测准确性和稳定性不足及其对奇异样本敏感的问题,引入自适应增强算法(adaptive boosting,AdaBoost)建立ELM-AdaBoost预测模型改善光纤陀螺性能,分析光纤陀螺的温度误差机理及模型参数对预测精度的影响,给出ELM算法隐含层神经元个数及AdaBoost算法迭代次数的确定方法。仿真结果表明:基于ELM-AdaBoost预测模型的补偿效果优于多元线性回归模型和单个ELM神经网络模型,并具有良好的泛化性能和温度适用性,补偿后陀螺零偏均方根误差降低93%以上,显著改善了光纤陀螺零偏稳定性能。

高精度惯性导航系统的技术预见

面对水下装备无人化/智能化的发展趋势,系统分析国内外知名惯性导航系统生产公司的产品,梳理水下装备的核心设备—惯性导航系统的发展趋势。基于工具检索国内外知名惯性导航系统公司的公开文献、专利以及产品手册等开源信息,提炼关键信息以及参数进行对比分析。目前,光纤陀螺惯性导航系统在国内已成为实现水下装备高精度定位的核心产品,基于谐振陀螺的惯性导航系统尚处于研发阶段。国际市场上,基于激光陀螺的惯性导航产品正逐渐被基于谐振陀螺和光纤陀螺的惯性产品替代。从法国赛峰和Exail这两家顶尖公司的产品指标看,谐振陀螺高精度惯性产品相比光纤陀螺高精度惯性产品而言,无论在体积还是在质量上都有较大优势,后续可能完全替代光纤陀螺系统成为市场主流。

基于光纤陀螺的工程结构形变检测精度分析

针对光纤陀螺形变检测系统在应用中遇到的形变精度难以评估和运行速度难以选择问题,对形变检测精度和光纤陀螺性能之间的关系进行了分析。从光纤陀螺的工程结构形变检测机理出发,基于光纤陀螺误差模型,分析了光纤陀螺零偏重复性误差和稳定性误差与形变检测误差的对应关系,在此基础上还仿真分析了检测系统的运行速度与检测精度的关系。仿真结果表明,当运行速度较快时,稳定性误差是影响检测精度的主要因素,当运行速度较低时,重复性误差是影响检测精度的主要因素,若采用中精度光纤陀螺,运行速度2 m/s时,可实现均方根为8.514μm的形变测量精度。研究成果可为光纤陀螺工程结构形变检测技术的工程应用提供理论指导。

采用激光光源线宽展宽的光纤陀螺标度因数性能提升技术

光纤陀螺中使用激光光源代替传统宽谱光源有利于提升性能和降低成本,但激光光源作为一种窄线宽的高相干光源,将其用于光纤陀螺又会引入瑞利散射、克尔效应和偏振交叉耦合等干扰,因此有必要对激光光源进行线宽展宽。首先对基于高斯白噪声外部相位调制的激光光源线宽展宽方法进行理论分析,建立光谱展宽卷积模型。其次采用延迟自相关测量方法验证了高斯白噪声外部相位调制对激光光源线宽的展宽效果。最后基于仿真分析结论,搭建了激光器线宽展宽光源装置,将激光光源的光谱展宽成线宽20 GHz的光谱,应用于光纤陀螺并验证了标度因数性能,为激光光源在光纤陀螺中的应用提供了理论基础,具有一定的工程应用价值。

基于暂态过程优化的谐振式光纤陀螺背向散射噪声抑制方法研究

针对谐振式光纤陀螺受背向散射噪声影响严重的问题,在优化三角波调制解调参数的基础上,提出了一种基于暂态过程优化的噪声抑制方法。该方法通过部分采样和均值滤波,在不改变陀螺光、电硬件配置的前提下,优化了三角波调制时存在的暂态过程现象,提高背向散射噪声的抑制比,改善解调曲线工作区的线性度。搭建样机并进行实验后,结果表明,基于暂态过程优化的噪声抑制方法能将暂态过程的占空比由64.3%降低至12.1%,解调后背向散射噪声的抑制比达到46.8%,且解调曲线工作区线性度达99.6%。可见,基于暂态过程优化的方法能有效提高谐振式光纤陀螺背向散射噪声的抑制能力,并改善解调曲线工作区的线性度。

光纤陀螺Shupe效应温度补偿模型研究

针对光纤陀螺温度补偿问题,以光纤陀螺Shupe效应原理为基础,仿真了变温温度场下光纤环温变情况。根据仿真模型的结果,试验多温度传感器采集光纤环不同位置温度数据,建立了多温度传感器补偿模型,分析了不同补偿模型之间的差异。并使用构造温度数据的方法,建立了构造温度补偿模型,验证了此模型在提升补偿精度与补偿适应性上的特点,为实际工程应用中提供了可行的补偿方法。

基于Cortex-M3的组合罗经显控软件的设计与实现

为解决传统光纤陀螺罗经系统价格昂贵的问题,利用低成本的光纤陀螺罗经和双天线卫星定位定向系统组成组合罗经的主罗经单元成为重要措施。组合罗经显控单元的主控芯片采用基于Cortex-M3的LPC1768,为了减少大量代码的编写、缩短软件开发周期,屏幕选用迪文串口屏,通过串口接收主罗经发来的报文,将船舶航向以罗盘图片的方式在屏幕上实时显示出来。同时,为了方便不同的用户使用,设计了3种显示模式:罗经模式、航向模式以及导航模式。经实船测试,该显控软件的设计可行且能够满足航行要求。

一种光纤速率陀螺组件系统误差的两级补偿方法

针对某型光纤速率陀螺组件系统误差复杂、补偿难的问题,提出了一种两级误差补偿方法,实现了系统全温综合误差的补偿。首先,通过理论分析得到了系统误差类型,包括:三轴陀螺不正交、刻度系数、模拟电路误差及刻度系数温度、模拟电路温度误差,并结合试验,分析验证了其误差特性。根据误差特性制定了两级补偿方法,并通过一级补偿了三轴陀螺不正交、刻度系数、模拟电路误差,在此基础上,通过二级补偿了刻度系数温度、模拟电路温度误差。试验表明,该补偿方法能将系统输出精度提高一个数量级,具有一定的工程应用价值。

陀螺用超细径保偏光纤机械强度评估方法

针对陀螺应用场景下超细径保偏光纤机械强度评估需求,提出一种基于可拉伸骨架的超细径保偏光纤强度评估方法,超细径保偏光纤绕制于可拉伸骨架之上形成光纤环圈可模拟出成环应力过程,采用该光纤环圈构建光纤陀螺,环圈骨架内的压电堆栈可驱动骨架带动超细径保偏光纤周期性拉伸,对超细径保偏光纤起到应力激励施加效果可激发光纤疲劳以实现光纤强度快速评估与筛选,同时在超细径保偏光纤内形成相位调制功能以实现陀螺偏置调制,陀螺信号长期输出变化情况可表征超细径保偏光纤力学特性优劣。该方法能够体现出超细径保偏光纤成环应力施加的复杂性和陀螺应用光纤长期张紧、弯曲等条件下应力长期演变性,有助于陀螺用超细径保偏光纤强度评估与筛选。

光学陀螺背向散射问题综述(特邀)

光学陀螺作为光电惯性导航系统的核心器件,在众多领域发挥着举足轻重的作用。随着科学技术的不断进步,传统的激光陀螺、轻质化的光纤陀螺以及集成化的微光陀螺齐头并进、蓬勃发展,但无论是哪一种陀螺样式,在性能优化的过程之中都不可避免地需要考虑背向散射的问题。背向散射是光学陀螺中的一种噪声源,其会带来陀螺的输出偏置或闭锁效应,从而影响其性能。为了更好地理解光学陀螺中的背向散射机制,首先从半经典理论下的自洽方程组出发讨论背向散射的基本原理,而后依照光学陀螺的发展脉络,分析各种光学陀螺的背向散射分析方法、测量手段以及抑制方法,最后对目前光学陀螺中有关背向散射亟待解决的问题进行总结并展望。

高精度光纤陀螺用宽谱ASE光源的设计及验证

ASE光源是卫星用高精度光纤陀螺光路的核心部件,光源性能会影响陀螺的噪声、零偏和标度因数稳定性等性能指标。具有高功率、宽光谱的ASE光源能够提升陀螺产品的精度和稳定性。采用双程前向结构完成了宽谱ASE光源的工程化应用设计,最终实现了输出功率≥5 mW、谱宽≥10 nm的典型高斯型宽谱ASE光源在高精度光纤陀螺宇航产品中的批量应用。此外,针对未来高精度光纤陀螺性能进一步提升的需求,采用平坦滤波和高斯滤波相结合的技术完成了谱宽≥20 nm ASE光源的设计及研制。

定向井避光纤射孔技术及其应用

套管外永置式光纤动态监测已成为智慧油田发展的重要方向,不损伤光纤的安全射孔技术作为其关键配套技术显得十分重要。围绕避光纤射孔需求,将磁性定向测井方法与陀螺定向射孔技术相结合,提出了一种适应于定向井的新型避光纤射孔技术,在对光缆固定器重力高边方位角进行探测解析的基础上,设计安全射流方位,将支撑定位装置和安装了定位导向捕捞装置的零相位单翼射孔枪组合,实现精准避光纤射孔。在长庆油田的应用结果表明,定向井避光纤射孔技术可在井斜大于5°的定向井中实现安全避光纤射孔作业,应用效果良好,值得进一步推广。

光纤陀螺的随机误差性能评价方法研究

N秒平均法与Allan方差法是2种常用的光纤陀螺随机误差性能评价方法,其得到的指标是衡量光纤陀螺性能的重要依据。结合2种性能评价方法的特点,对二者进行了分析与对比,并推导了2种方法所得性能指标的关系表达式:首先从随机信号处理的角度对N秒平均法进行了分析,得到了其幅频响应函数;继而对Allan方差法所辨识的量化噪声、角度随机游走、零偏不稳定性、角速率随机游走、速率斜坡5种随机误差模型进行了分析,并推导了5种随机噪声的N秒平均性能指标。根据俄罗斯产某型号光纤陀螺的随机误差模型进行了仿真,结果表明仿真信号的性能指标与理论推导结论具有较好的一致性。在一定程度上揭示了2种光纤陀螺性能评价方法的内在联系,对2种评价方法的实际应用具有一定指导意义。

基于漂移布朗运动的光纤陀螺加速贮存寿命评估

众多"长期贮存,一次使用"的军事应用需求决定了光纤陀螺的贮存寿命指标的重要性,为此针对在贮存期内具有长寿命、高可靠性特点的光纤陀螺,实施加速贮存退化试验,并采用基于漂移布朗运动的方法,对光纤陀螺的贮存寿命与可靠性进行评估。依据光纤陀螺的贮存故障模式影响及危害性分析结果,确定了加速模型,并结合线性漂移布朗运动的特点,建立了光纤陀螺可靠性评估模型。利用加速贮存退化试验的试验数据对光纤陀螺贮存寿命进行评估,得到了评估结果,从而验证了方法的适用性。