机械臂D-H参数和减速比几何标定及误差补偿

针对机械臂D-H参数和关节电机减速比不精确导致机械臂绝对定位精度降低的问题,提出了在利用几何分析标定机械臂D-H参数的基础上,通过分析关节实际旋转角度和相应电机编码器码值的线性关系,标定关节电机减速比的方法。针对关节角误差微分补偿法计算量大的缺点,通过推导机械臂末端位姿矩阵误差和关节角误差之间的微分关系建立误差模型,求解关节补偿角,避免了雅各比矩阵的求取,提高了计算效率。最后采用三维激光跟踪仪搭建测量系统,完成了一种6自由度机械臂的标定及补偿实验。实验结果表明,通过参数标定及误差补偿,机械臂的绝对定位误差均值从标定前的2.83 mm和1.14°降低到0.54 mm和0.24°,验证了方法的有效性。     

基于MEMS传感器的姿态测量系统设计

为解决单目三维扫描装置摄像机标定完成后姿态不能改变的问题,针对单目三维扫描装置使用过程中的运动方式与特点,设计了一款基于 MEMS 传感器的姿态测量系统。采用四元数对姿态进行解算,通过三轴姿态确定(TRAID)算法构建量测模型,以无迹卡尔曼滤波(UKF)算法进行数据融合,能有效抑制姿态解算过程中陀螺仪的漂移问题。实验结果表明,利用该系统进行姿态测量时静态误差低于±0.2°,动态误差低于±1°,系统实时性好、适用于动态三维扫描系统。     

空间目标天基光学监视平台的参数仿真分析

利用天基光学系统对空间目标进行监视是重要而有效的手段之一。以在轨运行的低轨卫星为研究对象,对天基光学平台的观察方向、升交点赤经和真近点角等参数进行了优化设置。通过分析可知,观察方向指向左和指向右时可以监视更多的目标,升交点赤经选取在0°、270°和315°对空间目标的监视效果较好,而卫星被截获的概率与真近点角的变化关系并不密切,因此真近点角可以任意选取。根据参数优化结果,以卫星仿真工具包STK(Satellite Tool Kit)为平台,对空间目标天基光学监视平台的轨道参数进行了仿真。     

气固两相平面叶栅气动特性的试验研究

一、前言 Tabakoff等人对气固两相平面叶栅叶片表面上气相压力进行了测量,但是没有对栅后气流参数进行测量。 本文在特殊的气固两相流风洞中,测量了单相纯气流和气固两相流分别以冲角i=-10°、0°、10°流过平面叶栅时,叶片表面上气流压力和栅后气流参数,其目的在于分析冲角对气固两相平面叶栅气动特性的影响。     

基于PSD的风洞模型姿态角光学测量技术研究

开发了一种基于光电探测技术的风洞模型姿态角光学测量技术,实现了对姿态角的精确、实时、非接触测量。对激光探测头、模拟试验平台进行了优化设计,编写了功能齐全的实验软件,模拟了风洞试验运行实况,深入开展了一维和二维角度测量实验和分辨率测试实验。实验结果表明,该技术可对模型变化角度进行实时精确测量,测量范围达到了-10°～10°,测量精密度为0.0023°,测量准确度为0.0026°,分辨率可达到0.001°。该光学测量技术在风洞模型的角度测量和振动测量实验中切实可行,为测量风洞试验模型的姿态及振动提供了一种简洁有效的测量方法。     

三维物体360°面形自动测量方法

提出一种三维物体360°面形自动测量方法.简要介绍了方法原理,系统结构,信息获取与处理方案,并给出对圆锥-圆台金属模块和人头石膏模型360°面形测量结果.     

机载光电平台目标交会定位

根据直线交会测量原理,构建了机载光电平台目标定位数学模型。首先建立5个坐标系,确定了坐标系之间的变换关系,在地心直角坐标系下,根据光电平台观测目标的方位和俯仰角度参数,结合飞机的位置和姿态测量参数,通过坐标变换确定从光电平台到目标之间的观测直线方程。选择一组目标观测直线建立目标交会测量目标函数,根据最小二乘原理,建立关于直线交会点坐标的线性方程组。解出直线交会点的三维坐标并根据从地心直角坐标系到大地地理坐标系的变换关系,计算目标的大地经纬度和高程坐标,通过样本数据进行交会定位精度实验。实验结果表明,本文方法定位结果和实际测量数据接近,经度误差为0.65",纬度误差为0.82",高程误差为5 m,验证了本文方法的准确性。本文方法有效可行,对机载光电平台目标定位具有实用价值。     

激光动态角度测量系统研究

本文介绍了-种可以动态测量角度的激光测试系统。其测角分辨率为0.0025°;测角范围为±45°;测角速度为100°/s.     

基于移相法的光学玻璃应力等倾角全场数字化测量

提出了一种用四步移相法实现光学玻璃应力等倾角全场数字化测量的方法。用数码相机拍摄椭圆偏振光场转过不同角度时的四幅出射光强图像,根据移相法的原理计算出在0°～90°范围内的等倾角β。通过对具有典型应力分布的光学玻璃进行实验验证表明,计算结果与实际情况相符。     

基于I/Q解调原理的数字PAD研制

 I/Q解调器可以同时测量微波信号的相位和幅度。为了消除传统I/Q解调器的不平衡误差,根据I/Q解调原理,应用数字滤波器及Hilbert变换等数字信号处理方法实现了对微波信号的正交解调,可以精确测量任意包络形状微波信号的相位和幅度。测试表明,数字相位和幅度探测器的精度可达±0.5°,重复性误差小于0.2°,温度系数约为-0.1°/℃,相位测量的动态范围为-18~5 dBm,幅度测量的动态范围为-20~0 dBm,其各项指标都达到了BEPCⅡ直线加速器相控系统的要求。     

Guided-Wave Two-Dimensional Acousto-Optic Scanner Using Proton-Exchanged Lithium Niobate Waveguide

Two-dimensional scanning of a 0.6328 mum guided-light beam has been realized using noncolinear acousto-optic (AO) coplanar Bragg diffraction together with colinear AO guided-mode to substrate radiation-mode conversion in a Z-cut Xpropagation LiNbO3 proton-exchanged (PE) waveguide. The two surface acoustic (SAW) waves utilized are at the center frequencies of 500 and 200 MHz, propagating in the Y and X axes, respectively. Two-dimensional scanning of approximately 720 resolvable light beam spots, namely, 18 40 (horizontal vertical) scanning, has been demonstrated using a light beam of 1.0 mm aperture. The total number of resolvable beam spots can be greatly increased from 720 by simply utilizing SAW transducers of larger bandwidth and a light beam of greater aperture. It should also be possible to significantly increase the diffraction efficiency from 3 % by optimizing the parameters of the PE waveguide and the SAWs.     

Effect ofγ-radiation on the spectral luminescence characteristics of impure cadmium tungstate crystals

Results of a study of the effect of γ-radiation on the spectral luminescence properties of cadmium tungstate crystals doped with silver, bismuth, and molybdenum cations are presented. Spectral characteristics of the nondnnnoped crystals are briefly described. Absorption and photo and X-ray luminescence spectra of the crystals taken before and after exposure to γ-radiation (5.5·10⁴ Gy) are compared. It is found that the spectral characteristics of the crystals doped with silver, bismuth, and molybdenum cations do not change markedly after the exposure. The relation between the type of impurity-induced defects, individual characteristics of the impurity cations, and the character of the effect of γ-radiation on the spectral luminescence properties of impure crystals is analyzed (preliminarily). Translated from Zhurnal Prikladnoi Spektroskopii, Vol. 64, No. 1, pp. 55–60, January–February, 1997.     

Measurement of nonlinear coefficient of optical fiber based on small chirped soliton transmission

We measure the waveform and phase curves of short optical pulses before and after transmission over different lengths of fibers by use of the pulse analyzer with the frequency-resolved optical gating (FROG),and numerically simulate pulse evolution under the experimental conditions.The nonlinear coefficient of the fiber is given by comparing the experimental results with the numerical ones.Difference between the experiment and numerical simulation is analyzed.     

Resonance scattering of canonical elastic shells in absorbing fluid medium

Resonance scattering of elastic spherical shell and cylindrical shell while the surrounding fluid medium has absorption is studied. The normal mode solution derived using exact elastic theory and the separation of variables is still applicable. However, the scattering form function has to be modified for the absorbing medium, otherwise the unreasonable result would be obtained. The backscattering form function in the absorbing medium is redefined, and the form function of elastic spherical and cylindrical shell with vacuum or solid matter filled is calculated in various absorption conditions. The results show that the absorption of surrounding fluid leads to notable attenuation of the coincidence resonances in the mid-frequency, but it has a little influence on the low-frequency resonance scattering induced by the filler inside the shell.     

Single-beam self-referenced phase-sensitive surface plasmon resonance sensor with high detection resolution

A versatile and low-cost single-beam self-referenced phase-sensitive surface plasmon resonance(SPR)sensing system with ultra-high resolution performance is presented.The system exhibits a root-mean-square phase fluctuation of ±0.0028.over a period of 45 min.i.e.a resolution of±5.2×10-9 refractive index units.The enhanced performance has been achieved through the incorporation of three design elements:a true single-beam configuration enabling complete self-referencing so that only the phase change associated with SPR gets detected,a differential measurement scheme to eliminate spurious signals not related to the sensor response,and the elimination of retardation drifts by incorporating temperature stabilization in the liquid crystal phase modulato .Our design should bring the detection sensitivity of non-labeling SPR biosensing closer to that achievable by conventional fluorescence-based techniques.     

Influences of SiO2 protective layers and annealing on the laser-induced damage threshold of Ta2O5 films

Ta2O5 films are prepared on BK7 substrates with conventional electron beam evaporation deposition.The effects of SiO2 protective layers and annealing on the laser-induced damage threshold (LIDT) of the films are investigated.The results show that SiO2 protective layers exert little influence on the electric field intensity(EFI)distribution,microstructure and microdefect density but increase the absorption slightly.Annealing iS effective on decreasing the microdefect density and the absorption of the films.Both SiO2 protective layers and annealing are beneficial to the damage resistance of the films and the latter is more effective to improve the LIDT.Moreover,the maximal LIDT of Ta2O5 films is achieved by the combination of SiO2 protective layers and annealing.     

A stereo matching algorithm using multi-peak candidate matches and geometric constraints

Gray cross correlation matching technique is adopted to extract candidate matches with gray cross correla- tion coefficients less than some certain range of maximal correlation coefficient called multi-peak candidate matches. Multi-peak candidates are extracted corresponding to three closest feature points at first. The corresponding multi-peak candidate matches are used to construct the model polygon. Correspondence is determined based on the local geometric relations between the three feature points and the multi-peak candidates. The disparity test and the global consistency checkout are applied to eliminate the remaining ambiguous matches that are not removed by the local geometric relational test. Experimental results show that the proposed algorithm is feasible and accurate.     

Fiber Modal Index Measurements Based on Fiber Gratings

A novel method based on fiber gratings for measuring the effective indices of fiber modes is proposed. The effective index difference between the core mode and a cladding mode was obtained by analyzing the interference fringe of a pair of cascaded long-period fiber gratings. In order to extract the core mode index from the measured index difference, an index matching oil immersion method is proposed. By analyzing the interaction between the cladding mode and the oil applied on the cladding surface, the mode order and the effective index of the involved cladding mode might be calculated. Experimental results about the interference fringe shifts induced by the oil index and the oil-applied length are also presented.     

Optical Pulse Compression Schemes That Use Nonlinear Bragg Gratings

Nonlinear optical pulse compression of picosecond pulses typically requires long lengths of optical fiber and multiple components. Periodic structures, such as fiber Bragg gratings, are highly dispersive at wavelengths outside of the photonic bandgap. This implies that such gratings can be used as very short all-fiber compressors. In this paper a number of such compression schemes are reviewed involving uniform and nonuniform fiber Bragg gratings, relying on both soliton and nonsoliton compression principles. Experimental results supporting the corresponding underlying theory are also presented. Finally, an extension of one of the compression schemes is shown, which allows the generation of adjustable high-repetition rate soliton trains.