全数字IMU方案研究

分析了现有IMU内部模拟电路的不足，提出全数字IMU方案和结构框图，其内容包括高精度模数转换电路、高速数学运算平台、陀螺数字伺服电路、高精度数字温控电路和以数字滤波数据融合为核心的计算方法。论证了陀螺回路数字控制方案、陀螺模糊温度控制方案，确定出陀螺回路A／D采样频率应大于3000Hz，高精度A／D转换器采样频率应大于500Hz，且位数不应低于18bit。最后，展示了已经研制成功的3项试验结果：24bit A／D与陀螺和加速度计联机实测结果、CPU和24bit A／D间接口通讯逻辑接口和基于模糊控制的陀螺温控系统。     

高精度加速度计A/D转换电路的温漂补偿

从理论上分析了温度变化对高分辨率A/D转换芯片输出的影响,通过静态试验建立了加速度计输出与A/D转换电路温漂之间的关系,并依照这种关系对加速度计输出进行了补偿,补偿后加速度计输出精度得到了明显提高。     

采用GRIN透镜的数字式光纤加速度计系统设计

为使测量加速度计的传感器小型化，且不受电磁干扰，根据GRIN透镜在1／4波节处具有入射光线与出射光线成中心对称的特性^[1]，首次提出并研制了采用GRIN透镜制成的微型光纤加速度计。闭环负反馈电路设计技术被应用于该加速度计中，使之成为一个具有调宽脉冲再平衡性能的新颖加速度测量系统。对该系统进行的数字仿真和精度定量分析表明：该光纤加速度计具有测量线性范围宽，精度高的特点，可广泛应用于惯性测控系统中。     

重力梯度仪加速度计控制回路分析与设计

加速度计是旋转加速度计重力梯度仪的核心元件,梯度信号测量要求其加速度计具有高分辨率和低的噪声水平,这就需要对现有石英加速度计进行改进,通过表头抽真空,提高控制回路增益来抑制噪声,提高分辨率.抽真空后表头近似为无阻尼状态,其控制回路中需增加阻尼补偿的环节,避免系统在工作频段附近出现振荡;并且,对控制回路中的校正环节也进行了重新设计,加入积分环节,使系统对位置信号的稳态误差为零,大幅度提高工作频段的系统开环增益,从而有效地提高了系统的动态测量精度.     

陀螺加速度计高速闭环动态测角系统设计

从运载火箭惯性导航系统的核心仪表-陀螺加速度计对测角系统的技术要求出发,设计一种新型的陀螺加速度计高速闭环动态测角系统。它选择变磁阻多级旋转变压器进行角位置测量,并采用两相绕组激磁、一相绕组输出的脉冲调宽型鉴幅的运行方式;在分析其工作原理的基础上,从放大器、控制器、数字函数发生器、输出接口四个方面给出了测角系统的具体设计方法,最后进行了误差测试与跟踪转速测试验证。实测结果表明,采用传感器误差为1.5′的测角系统,分辨率为0.84375′,综合误差约为2.5′,最大跟踪转速为538(°)/s。该系统满足使用要求,设计方案有效可行。     

模态分析在高精度加速度计结构设计中的应用

石英振梁式加速度计是一种频率输出的高精度加速度计。石英谐振器是石英振梁式加速度计的关键部件。由于高动态性能要求，在结构设计阶段，必须对其进行模态分析。用模态分析理论和有限元软件工具，进行结构模态分析和谐响应分析，揭示其结构的静、动态性能。理论分析和计算机仿真结果表明所设计的结构能满足使用要求，同时为改善优化设计时的效率和质量提供依据和方法。     

高精度加速度计分辨率的动态估算方法

高精度定位定向系统和重力测量系统需要高分辨率的加速度计,传统测试方法难以确定高精度加速度计的分辨率。对此,提出了一种使用双轴转台动态估算加速度计分辨率的方法,即匀速旋转调制法。将加速度计安装在双轴转台台面上,待转台调平,台面绕倾斜轴转过一个小角度后锁死,回转轴以一定的角速度旋转调制以对重力加速度分量进行细分,将加速度计的输出采样后进行FFT低通滤波,通过加速度计峰值与谷值处输出变化最大值的分析可以确定加速度计的分辨率。最后,对某型加速度计分辨率进行了实验验证,测试结果表明,当倾斜角度为0.001°,旋转调制角速率为10(°)/s,采样率为32 Hz时,输入的加速度最大变化为9.36×10-8g,加速度计敏感到的加速度变化量为1.05×10-7g。     

一种采用圆片级真空封装的全硅MEMS三明治电容式加速度计

全硅MEMS加速度计具有温度特性好、封装体积小、成本低的优点,从而成为小型化GNC(制导、导航与控制)系统的关键器件。给出了一种具有三层硅结构的MEMS三明治加速度计的设计、加工以及圆片级真空封装方法,其中,中间硅摆片的3D结构通过双面KOH湿法腐蚀制造,腐蚀过程中使用台阶化的SiO_2作为硬掩模。硅盖板的加工主要通过KOH各向异性腐蚀和电感耦合等离子体垂直刻蚀完成。最后,上、下硅盖板通过基于Au-Si共晶反应的全硅键合技术从两侧与硅中间摆片进行键合,并实现圆片级真空封装。三明治加速度计的腔体内封装了压力为200 Pa的高纯氮气。测试结果表明,所述加速度计的闭环输出灵敏度为0.575 V/g,零位误差为0.43 g。加速度计的-3dB带宽为278.14Hz。加速度计1 h的输出稳定性为2.23×10-4 g(1σ)。加速度计在全温范围(-40℃~60℃)内的输出漂移为45.78 mg,最大温度滞环为3.725 mg。     

梳齿式微机械力平衡加速度计

讨论了一种梳齿式微机械加速度计，介绍了表头微机构的特点和系统工作原理。通过对加速度计机械模型的分析，计算得出了加速度计的主要设计性能指标。另外还比较完整的提供了加速度计各项性能试验的数据，试验结果与理论分析能很好地吻合，说明加速度计的性能指标基本达到设计要求，证明这种加速度计的设计是成功的。     

硅微谐振式加速度计数据采集系统设计

硅微谐振式加速度计能将被测加速度直接转换为稳定性和可靠性都很高的频率信号,因此可以获得优良的性能.高分辨率频率信号的获取需较长的测量时间,而在导航和姿态控制等应用中,测量时间一般又限定在较短的10 ms内.针对10 ms内对中心谐振频率为20 kHz、标度因数为100 Hz/g、量程为±50g.分辨率为±1mg的硅微谐振式加速度计输出的差分频率信号进行测量的要求,讨论荻取加速度测量值的数据采集系统的设计方法.介绍采用基于高速锁相环倍频和CPLD计数的频率测量方案和数据采集系统主要包括的整形电路、倍频电路、计数电路、微控制器和串行通信电路的设计方法.测试表明,设计的系统经达到了设计目标.     

Multi-level modeling of woven glass/epoxy composite for multilayer printed circuit board applications

The objective of this paper is to develop a hybrid homogenization method to predict the elastic properties of a common woven glass/epoxy composite substrate for multilayer circuit board applications. Comprehensive high resolution 3D finite element (FE) models of a quarter of the repeated unit cell (RUC) for the woven glass/epoxy composite were developed based on different micromechanical schemes. . Specifically, four different micromechanics schemes were investigated: self-consistent, Mori–Tanaka, three-phase approach and composite cylinder assemblage (CCA). The element based strain concentration matrices were determined and used to obtain the homogenized woven glass/epoxy composite properties via a specially developed MATLAB code. Attention was further devoted to the predictions of the homogenized elastic moduli of the multilayer printed circuit board (PCB). The results from our simulations, based on Mori–Tanaka and CCA, are in good agreement with existing experimental results, indicating that the newly proposed homogenization scheme can be used as a design tool to predict the overall properties of woven composite materials typically used in multilayer PCB applications.     

高速飞行器中空翼结构高温热振动特性试验研究

远程高速飞行器飞行速度快, 滞空时间长, 飞行过程中翼、舵等结构会出现长时间的剧烈振动, 由气动加热产生的高温还会使飞行器材料和结构的弹性性能发生变化, 从而引起翼、舵等结构振动特性的改变.因此获得高温与振动复合环境下的远程高速飞行器翼、舵等结构的振动特性参数对于高速飞行器的安全设计具有非常重要的意义.将高温热环境试验系统与振动试验系统相结合, 在对中空翼面结构进行振动激励的同时使用红外辐射加热方式对翼面结构生成可控的热环境, 并通过自行设计的耐高温引伸装置将中空翼结构的振动信号传递到非高温区进行数据采集与分析的方式, 实现了高达800℃~900℃的力热复合环境下的翼结构固有频率、模态等振动特性参数的试验测试, 其试验结果为远程高速飞行器中空翼结构在高温振动环境下的动特性分析和安全可靠性设计提供了重要依据.     

转台控制系统的DSP实现

从软、硬件两方面介绍了一种基于TMS320F206的数据采集及控制系统在转台控制中的应用。这种以高速SP芯片为核心的控制系统,能实现更先进的控制算法。     

Using digital holographic microscopy for simultaneous measurements of 3D near wall velocity and wall shear stress in a turbulent boundary layer

A digital holographic microscope is used to simultaneously measure the instantaneous 3D flow structure in the inner part of a turbulent boundary layer over a smooth wall, and the spatial distribution of wall shear stresses. The measurements are performed in a fully developed turbulent channel flow within square duct, at a moderately high Reynolds number. The sample volume size is 90 × 145 × 90 wall units, and the spatial resolution of the measurements is 3–8 wall units in streamwise and spanwise directions and one wall unit in the wall-normal direction. The paper describes the data acquisition and analysis procedures, including the particle tracking method and associated method for matching of particle pairs. The uncertainty in velocity is estimated to be better than 1 mm/s, less than 0.05% of the free stream velocity, by comparing the statistics of the normalized velocity divergence to divergence obtained by randomly adding an error of 1 mm/s to the data. Spatial distributions of wall shear stresses are approximated with the least square fit of velocity measurements in the viscous sublayer. Mean flow profiles and statistics of velocity fluctuations agree very well with expectations. Joint probability density distributions of instantaneous spanwise and streamwise wall shear stresses demonstrate the significance of near-wall coherent structures. The near wall 3D flow structures are classified into three groups, the first containing a pair of counter-rotating, quasi streamwise vortices and high streak-like shear stresses; the second group is characterized by multiple streamwise vortices and little variations in wall stress; and the third group has no buffer layer structures.     

A new facility for time-resolved PIV measurements in rotating channels

A new facility to measure the time evolution of 2D velocity fields in a rotating channel is presented, and the accuracy is discussed in detail. Measurements are made by means of a time-resolved PIV system composed of a continuous laser diode, coupled by a fiber optics cable to a laser plane optical module, and a CMOS high-speed camera. Both the PIV system and divergent channel are fixed on a 2.5 m rotating disk. This allows a direct measurement of the relative velocity of flows with Reynolds numbers between 3 × 10³ and 3 × 10⁴ and Rotation numbers between 0.0 and 0.52. These values correspond to the flow conditions in small radial impellers and can be independently adjusted by a change of the relative flow velocity and RPM. It is shown that this new facility allows high signal-to-noise ratios, and that the direct acquisition of the data in a rotating frame drastically reduces the measurement error. The accuracy and high spatial and temporal resolution of the measurements allow a detailed analysis of boundary layer characteristics in stationary and rotating conditions.     

基于FPGA驱动微陀螺旋转的移相电路

传统的微陀螺转子驱动电路采用对模拟信号直接移相实现,为了解决模拟信号直接移相时移相范围有限、调试复杂等不足,设计出了基于FPGA的数字式驱动微陀螺旋转移相电路。通过FPGA产生相位差信号,经D/A转换电路和巴特沃兹滤波电路处理后输出信号。该数字式移相方法产生的信号的相位差（0°～360°）、频率均可调,为涡流旋转微陀螺转子提供了理想的信号源。     

Experimental characterization of nonlinear systems: a real-time evaluation of the analogous Chua’s circuit behavior

This paper presents an experimental characterization of the behavior of an analogous version of the Chua’s circuit. The electronic circuit signals are captured using a data acquisition board (DAQ) and processed using LabVIEW environment. The following aspects of the time series analysis are analyzed: time waveforms, phase portraits, frequency spectra, Poincaré sections, and bifurcation diagram. The circuit behavior is experimentally mapped with the parameter variations, where are identified equilibrium points, periodic and chaotic attractors, and bifurcations. These analysis techniques are performed in real-time and can be applied to characterize, with precision, several nonlinear systems.     

轴对称体通气空泡的水动力试验研究

本试验的目的是研究轴对称体在通气空化下从局部空泡发展到超空泡状态过程中对水动力的影响，探讨怎样才能实现空化减阻的问题。根据试验要求及目的我们设计了一雷体模型及一整套的试验装置，并在重力直流式水洞中对模型进行一系列的试验，包括自然空化试验与通气空化试验。试验过程中采用了三分力天平、数据采集／转换卡及计算机记录水动力数据。整个试验过程解决了两个关键问题：一是怎样获得稳定的通气量，二是如何进行数据采集处理。采用1127／1128型空气速度校准器的过滤器／调压器组件改装做成一个通气装置解决第一个问题；采用12位16通道的PCL-818L型A／D转换卡，用LABVIEW语言编写的实时采样软件来处理数据。根据试验所得到的数据，进行深入的分析，得到了在通气空泡发展到超空泡状态可以大大减小阻力的结论。     

An advanced off-axis holographic particle image velocimetry (HPIV) system

Holographic PIV (HPIV) is the most promising candidate for the next generation full-field velocimetry that can measure high spatial resolution instantaneous three-dimensional (3D) velocity fields. To explore the maximum performance capabilities of HPIV including spatial resolution, off-axis holography based HPIV has become a major direction of development. A fully automated off-axis HPIV system based on an injection-seeded dual-pulsed YAG laser and 3D data processing software has been implemented in the laser flow diagnostics lab (LFD). In our system, 90-degree particle scattering, dual reference beams, in situ reconstruction/data processing, and 3D velocity extraction based on a fast “concise cross correlation” (CCC) algorithm are utilized. The off-axis HPIV system is tested for an acoustically excited air jet and the wake of a surface-mounted tab in a water channel flow, giving instantaneous 3D velocity fields for both flows. Experimental data of instantaneously measured 3D flow structures using this technique show great promise. Received: 12 August 1998/Accepted: 20 October 1999