基于光纤陀螺的教学实验寻北仪

光纤陀螺可测量沿其轴向转动角速度,利用此功能通过四位置法可以实现寻北、实验室所在纬度以及地球自转角速度的测量.本文介绍光纤陀螺寻北仪和四位置法的工作原理.另外还介绍了寻北仪的实验装置和基本操作过程,以及对数据的处理方法.     

速率光纤陀螺寻北仪倾斜补偿算法研究

针对速率光纤陀螺寻北仪,提出了一种倾斜补偿算法.通过采用积分滑动和最小二乘拟合滤波技术,对光纤陀螺和加速度计原始测量信号进行数据处理.试验数据表明,采用本算法解决了由倾斜角存在影响其寻北准确度的关键技术问题.同时给出了提高光纤陀螺寻北仪的准确度的可能因素.     

单轴光纤陀螺寻北仪四位置寻北误差分析

基于光纤陀螺寻北仪误差模型和光纤陀螺的误差特性,从理论上对光纤陀螺寻北仪寻北误差进行了分析,提出寻北仪主要包括系统误差和器件误差两个方面的误差源,并分别对不同误差源引起的寻北误差进行推导,得到光纤陀螺寻北仪寻北精度主要受陀螺零偏漂移、安装误差和转台测角精度决定的结论。对光纤陀螺寻北仪各误差源引起的寻北误差进行仿真实验,在考虑系统误差的条件下,0.01°/h精度的光纤陀螺寻北误差最大可达0.045°,实验结果证明了理论分析的正确性。     

光纤陀螺动态寻北转位控制系统设计

针对光纤陀螺动态寻北仪实际应用中存在的转位误差以及高频测量噪声问题,对寻北仪转位机构引入低通滤波和反馈回路,设计出了一种新的转位控制系统,有效地减小了由于光纤陀螺和转位机构的误差带来的系统误差,从而提高了动态寻北仪的寻北精度;实验结果表明,相同条件下该控制系统能有效缩短寻北时间,提高定位精度至4″,具有较好工程实用前景。     

车辆寻北车长镜的设计与实现

 描述了一种车辆寻北车长镜的设计,采用2个光纤陀螺和2个加速度计,解决了惯性测量组件力学编排结构设计与寻北、瞄准线稳定共享陀螺信息的问题,设计系统控制流程和组合算法,在保障车长镜瞄准线稳定精度的同时,增加了车体方位平台非调平状态下任意位置的寻北功能,寻北方法是：车长镜方位固定四位置转动,每个位置点停止、延迟、数据采样、存储,四位置转动完毕后,对存储数据组合、滤波、解算,输出寻北结果。对方案设计、实现途径和解算推导方法作了详细论述,性能测试验证设计实现达到预期效果。     

光纤陀螺寻北仪控制系统的设计和实现

陀螺寻北系统在军事和民用领域具有极广阔的应用。该文介绍了一种使用光纤陀螺实现自寻北系统的实现方法。系统采用DSP和计算机相结合的方法，其中用DSP进行数据采集及系统控制，DSP和计算机以RS232串口方式进行通信，用计算机实现数字滤波、数据解算和实时状态显示，完成寻北。寻北结束给出初始方位角，并用激光光斑指示北向。已完成的系统根据采用陀螺精度不同，达到3～10mrad寻北精度，可以满足相应寻北精度要求的军事和民用目的。     

捷联寻北信号采集系统研究

基于捷联寻北信号采集系统,提出了一种在不同地理纬度下准确获得陀螺数据拟合曲线的方法。首先计算得出了在不同地理纬度下动调陀螺输出的电流大小,根据其变化调整信号采集模块的采样电阻值,设计了基于数字电位器的自调整采样电阻系统;然后数据处理系统根据采集到的陀螺信号自动计算工作地点的地理纬度,自调整采样电阻系统通过地理纬度自动设置采样电阻的阻值,进而获得准确的数据拟合曲线。本方法确保了寻北仪在不同地理纬度时满足寻北精度要求,适应性强,稳定性高。     

光纤陀螺在转台测试中的应用

光纤陀螺是一种速率陀螺,其适合用来对转台作低速测试.根据转台所用编码器的参数,分析了转台不同角速率下光纤陀螺所需的数据刷新率及陀螺零偏稳定性对测量结果的影响.用光纤陀螺测量了转台以1°/s角速率转动时的角速率波动,对陀螺输出数据作了功率谱分析,并与示波器直接测量的结果进行了对比,结果表明光纤陀螺的测量结果是正确的;应用光纤陀螺对转台以(0.05°/s,1°/s)范围内固定角速率转动时的角速率波动进行了测量,通过对测量结果的分析表明:光纤陀螺可以用于转台的测试,它能测量出转台低速转动时的角速率波动;最后给出了光纤陀螺对转台角速率测试的下限.     

基于温度激励的光纤陀螺光纤环瞬态特性检测

光纤陀螺基于萨尼亚克效应测量垂直于光纤环平面的敏感轴方向上的旋转分量。光纤环是光纤陀螺的核心部件,光纤环的缠绕质量直接影响着光纤陀螺的整体性能,对光纤环的缠绕质量全面检测十分必要。针对目前光纤环检测手段的局限性,提出了一种基于温度激励的光纤陀螺光纤环瞬态特性检测方法,全面表征了光纤环的缠绕质量。建立了光纤环柱面坐标三维计算模型,采用有限元方法定量分析光纤环不对称度和局部温度激励位置精度对光纤环瞬态响应的影响,同时开展了光纤环温度激励相应实验,实验结果与光纤环三维物理模型数值计算结果相一致,在理论和实验上验证了光纤环瞬态特性检测方法的可行性。     

基于小波神经网络的光纤陀螺误差补偿方法

为了提高光纤陀螺的测量精度,提出了一种基于小波神经网络的误差补偿方法。首先使用小波分析中的Mallat分解算法提取出陀螺信号中的主趋势项,对其误差余项进行重构。然后将重构信号作为小波神经网络的目标输出,将原始陀螺信号作为训练样本。为了提高小波神经网络的训练速度同时防止其陷入局部极小值,采用增加动量因子和自适应调整学习速率的方法来改进训练方法。训练后建立的神经网络模型对光纤陀螺误差具有良好的估计能力。结果表明,经过小波神经网络方法补偿后,光纤陀螺的输出精度达到了0. 019 4°/s,光纤陀螺的测量性能得到了提高。     

Point defects on graphene on metals

Understanding the coupling of graphene with its local environment is critical to be able to integrate it in tomorrow's electronic devices. Here we show how the presence of a metallic substrate affects the properties of an atomically tailored graphene layer. We have deliberately introduced single carbon vacancies on a graphene monolayer grown on a Pt(111) surface and investigated its impact in the electronic, structural, and magnetic properties of the graphene layer. Our low temperature scanning tunneling microscopy studies, complemented by density functional theory, show the existence of a broad electronic resonance above the Fermi energy associated with the vacancies. Vacancy sites become reactive leading to an increase of the coupling between the graphene layer and the metal substrate at these points; this gives rise to a rapid decay of the localized state and the quenching of the magnetic moment associated with carbon vacancies in freestanding graphene layers.     

基于Matlab分析负荷对多联机IPLV的影响

多联机有其特殊的优点,但是不同部分负荷的组合对IPLV的影响仍需进一步研究。文中建立IPLV与部分负荷的相关公式,运用MATLAB软件分析不同卸载级负荷与IPLV的关系,从而确定不同部分负荷的最优组合。     

Remarks on KdV-type flows on star-shaped curves

We study the relation between the centro-affine geometry of star-shaped planar curves and the projective geometry of parametrized maps into RP¹. We show that projectivization induces a map between differential invariants and a bi-Poisson map between Hamiltonian structures. We also show that a Hamiltonian evolution equation for closed star-shaped planar curves, discovered by Pinkall, has the Schwarzian KdV equation as its projectivization. (For both flows, the curvature evolves by the KdV equation.) Using algebro-geometric methods and the relation of group-based moving frames to AKNS-type representations, we construct examples of closed solutions of Pinkall’s flow associated with periodic finite-gap KdV potentials.     

X-ray diffraction on chlorine adsorbed on graphite

Cl₂ layers adsorbed on Grafoil have been investigated by X-ray diffraction between 78 and 285 K. Mono- and submonolayers crystallize in a parallelogram lauttce, incommensurate with the (001) graphite surfaces, the molecules oriented almost perpendicular to the surface. The structure is closely related to that of the (001) planes of three-dimensional solid chlorine. For coverages above the monolayer completion bulk crystalization sets in.     

Note on duality on polarized symplectic manifolds

In this note we use some of the results of [3] to derive a general duality theorem for the cohomologies of foliated structures on a manifold. The result is applied to the special case of a symplectic manifold M on which the foliation is given by a complex polarization F in the sense of geometric quantization. We obtain, for example, a rigorous proof of the fact that for a smooth function ƒ on M whose Hamiltonian vector field leaves F invariant, the spectrum of the corresponding prequantization operator v(ƒ) coincides with the spectrum of its transpose, under the above duality. This latter result was obtained by Simms in [12] under certain hypotheses. Proofs of the validity of those hypotheses are now available in the literature; cf. [3] and [7].     

Space-charge effects on multipactor on a dielectric

Analyzes the effects of space charge shielding on the steady state of a multipactor discharge on a dielectric. Analytic methods are used to obtain an exact function for the potential in the discharge, assuming a Maxwellian distribution of emitted electrons. An equation for the amount of power deposited on the dielectric by the multipactoring electrons, for a given saturation level, is given. A simple method for obtaining the saturation level, for a given material, is obtained