抛物面镜调校双波段光学系统光轴的误差分析

通常采用离轴抛物面镜来对双波段成像光学系统的光轴进行校准以便实现两个成像系统的像素级图像融合,但抛物面镜和点光源安装时所产生的误差会影响两个光轴的校准精度。根据几何关系及光学成像原理,推导了离轴抛物面镜对焦点附近点光源的成像公式,在此基础上分析了抛物面镜和点光源的安装误差对双波段成像光学系统光轴校正造成的影响。根据推导的误差分析公式可将可见光通道和红外通道双波段光轴的平行性误差控制在1个像素以内。     

抛物面镜调校双波段光学系统光轴的误差分析

通常采用离轴抛物面镜来对双波段成像光学系统的光轴进行校准以便实现两个成像系统的像素级图像融合,但抛物面镜和点光源安装时所产生的误差会影响两个光轴的校准精度。根据几何关系及光学成像原理,推导了离轴抛物面镜对焦点附近点光源的成像公式,在此基础上分析了抛物面镜和点光源的安装误差对双波段成像光学系统光轴校正造成的影响。根据推导的误差分析公式可将可见光通道和红外通道双波段光轴的平行性误差控制在1个像素以内。     

基于自由涡的风轮失谐气动特性研究EI北大核心CSCD

采用一种改进的自由涡方法研究了风切变条件下,叶片安装角存在偏差的失谐风轮的气动特性。计算方法由模拟叶片气动力的非线性升力线法和模拟尾迹涡运动的时间精确自由尾迹法构成。以某2.5 MW风力机为例,计算了功率曲线和叶片气动力分布,并与Bladed软件和CFD计算结果进行了比较。研究了切变风条件下,不同叶片安装角偏差量,风轮推力、扭矩、偏航力矩和俯仰力矩的变化。结果表明,所采用的计算方法是准确有效的。风轮叶片安装角偏差,对风轮推力和扭矩影响较小,对风轮偏航和俯仰力矩影响较大。不同叶片安装角偏差量相反,会显著增加风轮偏航和俯仰力矩波动。     

基于自由涡的风轮失谐气动特性研究

采用一种改进的自由涡方法研究了风切变条件下,叶片安装角存在偏差的失谐风轮的气动特性。计算方法由模拟叶片气动力的非线性升力线法和模拟尾迹涡运动的时间精确自由尾迹法构成。以某2.5 MW风力机为例,计算了功率曲线和叶片气动力分布,并与Bladed软件和CFD计算结果进行了比较。研究了切变风条件下,不同叶片安装角偏差量,风轮推力、扭矩、偏航力矩和俯仰力矩的变化。结果表明,所采用的计算方法是准确有效的。风轮叶片安装角偏差,对风轮推力和扭矩影响较小,对风轮偏航和俯仰力矩影响较大。不同叶片安装角偏差量相反,会显著增加风轮偏航和俯仰力矩波动。     

拼接式钢带光栅编码器测角误差分析与修正

针对望远镜对高精度测角技术的要求,分析了机械安装偏心、加工椭圆度误差、轴系晃动等对新型拼接式钢带光栅编码器测角的影响,并制定了相位差为90°的4读数头软件细分测角方案。在机械安装偏心为10μm、加工椭圆度为2μm、轴系晃动为0.6″的实验平台上进行了逆时针和顺时针测角实验,两组实验测角误差RMS值分别为0.393″和0.488″。实验表明：该测角方案能消除机械安装偏心、加工椭圆度误差等对测角数据的影响,实现了亚角秒级测角。     

舰艇作战系统校准间隔优化研究

校准间隔优化是舰艇作战系统动态对准理论的重要组成。针对目前作战系统校准间隔确定缺乏理论支撑、历史对准误差数据使用率较低的情况,本文根据历史对准误差数据的特点,提出了利用EEMD-LSSVM-BP组合预测的校准间隔优化方法。首先利用EEMD将对准误差数据分解成若干不同频率的分量,分解后的各分量通过LSSVM进行预测,LSSVM的相关参数由QDE算法优化获得,各预测分量通过BP神经网络进行非线性重构,得到最终的预测结果,最后根据预测值对校准间隔进行优化调整。仿真实例表明,组合预测方法比单独的预测方法具有更高的精度,可以应用于作战系统校准间隔的优化过程。     

激光多普勒自主测速仪天线安装误差对测速精度的影响

为了减小激光多普勒自主测速仪天线安装误差引起的测速误差,以多普勒频移原理为基础,通过旋转矩阵的复合变换推导出测速误差与安装误差间的函数关系,分析了三个安装误差角对三维测速精度的影响,并对旋转矩阵采用Bursa模型线性化后在整体最小二乘准则下给出安装误差角的最优估计,从而实现测速误差的补偿。仿真结果表明:测速误差随速度的增大而增大,影响纵向、横向测速精度的主要因素是偏航角,影响垂向测速精度的主要因素是纵倾角,补偿后三维测速误差显著减小。     

双频激光干涉仪的混频分析与研究

针对以往文献提出的探测非线性误差方案比较复杂,通常不容易实行的缺点,设计了一套简单有效的系统,用以区分由光源偏振态非理想和偏振分光镜(PBS)漏光引起混频造成的非线性误差。实验结果表明,光先后两次经过PBS后漏光分量将会大大减少,相对于由光源非正交分量引起的混频误差可以忽略不计。为了最大限度地减小安装误差,提出了一种切实有效地调整PBS的方法,确保入射光水平分量的偏振面平行于偏振分光镜的参照面,并以布儒斯特角入射。     

基于多头读数布局的圆光栅自校准方法研究

针对测角系统在线校准问题,提出了一种基于多读数头布局的自校准方法。通过多组传感器的测量数据,利用圆封闭原则和傅里叶级数的性质,建立测量值与误差之间的函数关系,并基于多读数头布局原理,对自校准读数头布局进行优化,以提高校准方法对误差的抑制能力,实现单读数头测角传感器的自校准。设计了单轴转台,搭建了自校准测角系统,并进行了实验验证。实验结果表明:测角系统采用自校准方法后,单读数头测角传感器的测角误差为6.10″,在相同的测量环境下,其校准精度接近借助外部参考标准的传统谐波标定方法。自校准方法可有效抑制测角误差,显著提高测量精度。     

大功率超声功率计的研制及高强度聚焦超声肿瘤治疗头功率检测

研制一种将机械天平、辐射压力法和智能控制结合在一起的大功率超声功率计,该功率计可以安装不同种类的反射靶面或吸收靶面对多种超声换能器进行功率测量;用砝码对该功率计进行校准和误差分析,结果显示该功率计具有稳定性好、精度高、测量范围大的特点。用锥面反射靶和吸收靶对高强度聚焦超声肿瘤治疗头的输出功率进行测量,实验结果表明:一方面该功率计可以满足大功率、高精度测量要求,另一方面被测量的临床治疗用高强度聚焦超声肿瘤治疗头的驱动电压在600-2200 V之间,其功率输出稳定、可靠,在此范围之外功率输出误差变大,超过5％。     

Interferometric technique for measurement of droplet diameter

The paper considers the optical contact-free method of droplet diameter sizing in the flow cross-section utilizing light interference on a droplet. Distribution of light scattered by a particle was analyzed for different configurations of the measurement system using the Mie theory and approximation of geometrical optics. Basic measurement errors and dynamic range were determined. Possibility of measurements with camera mounting at the angle of 90° to the plane of a laser sheet is shown; this simplifies setup calibration and evens characteristics over the image field. The procedure of measurement system calibration and a set of algorithms for data processing are suggested. The suggested approaches were applied for measurement of characteristics of the gas-droplet jet.     

跨声速盒式翼布局双翼气动干扰研究

盒式翼布局相对常规布局可以很大程度地减小诱导阻力,同时平滑的升力分布有利于减小跨声速激波阻力,但双翼间的气动干扰是跨声速盒式翼布局存在的主要问题.为掌握跨声速双翼气动干扰特性,选用超临界翼型RAE2822作为双翼翼型,对M=0.75,正负交错两种情况下双翼几何参数对布局升阻特性的影响进行数值研究.结果表明,增大双翼的纵向距离可以减弱双翼间气动干扰,使升阻比提高至无干扰升阻比.其中,前翼在下、后翼在上的负交错布局在双翼纵向距离为1.5倍上翼弦长时即可接近无干扰升阻比,更有利于提升布局的升阻特性.负交错时双翼的垂直间距对布局升阻比影响不大,无翼差角且减小前翼弦长有利于提高升阻比.      

加工误差引入的薄型KDP晶体附加面形

针对惯性约束聚变（ICF）驱动装置中口径为400 mm400 mm薄型频率转换KDP晶体在45放置状态下产生的附加面形问题,采用有限元分析软件ANSYS,建立了以实测数据为基础的大口径薄型KDP晶体的应变模型和有加工误差的夹具模型,仿真分析了KDP晶体的加工误差和夹具的加工误差对KDP晶体附加面形的影响, 给出了KDP晶体附加面形变化的P-V值和RMS值。在此基础上,通过对KDP晶体的加工误差及夹具支撑表面不同类型和不同大小加工误差的分析和比较,得出:KDP晶体边缘的加工误差和夹具支撑表面的凹型加工误差是引起较大附加面形的原因之一,KDP晶体的加工误差也会导致其面形变化不均匀,而夹具支撑表面的凸型、波浪形加工误差和压条表面的随机加工误差对KDP晶体附加面形的影响相对较小,且支撑表面的随机加工误差引起的附加面形变化介于其他两者之间。     

超光谱大气CO_2监测仪光谱定标误差修正

超光谱大气CO_2探测需对遥感器进行精确表征及定标,其中光谱定标工作最为基础。针对传统实验室定标方法获取的波长定标系数不确定度高等特点,开展基于气体吸收法原理的光谱定标误差修正研究,该方法与仪器使用状态一致,提高了定标系数实用性。首先利用辐射传输进行了理论光谱及误差因素模拟计算,并基于大气环境模拟定标仓开展了大气XO_2吸收光谱测量实验,最后采用LM算法进行光谱误差修正迭代优化。光谱定标误差修正结果表明:光谱偏差均值由修正前的0.03 cm~(-1)下降到修正后0.008 cm~(-1),且系统性与突变性误差得以剔除,大大提高了地面光谱定标精度,为后续温室气体反演奠定了基础。     

飞行器上层大气层空气动力特性探讨

针对近地轨道飞行器所面临的上层大气层(100～300 km)空气动力学问题,对几类典型航天器构型的上层大气层气动力特性进行了分析,给出了典型气动布局在该空域的气动力基本规律,取得了对上层大气层气动力关键影响因素的初步认识.在上层大气层,飞行器的绕流属于自由分子流状态.研究发现,气体分子与不同材质物面的相互作用反映出截然...     

Phase shifting algorithms for non-sinusoidal waveforms with phase shift errors

In phase shifting interferometry, phase errors due to harmonic components of a fringe signal can be minimized by applying synchronous phase shifting algorithms with more than four samples. However, when the phase shift calibration is inaccurate, these algorithms cannot eliminate the effects of a non-sinusoidal waveform. It is shown that by taking a number of samples beyond one period of the fringe pattern, phase errors due to the harmonic components of the fringe signal can be eliminated, even when there exists a constant error in the phase shift interval. A general procedure for constructing phase shifting algorithms that eliminate these errors is derived. A seven-sample phase shifting algorithm is derived as an example, in which the effect of the second harmonic component can be eliminated in the presence of a constant error in the phase shift interval.     

波片对偏振激光干涉仪非线性误差的影响

利用琼斯矩阵理论,研究了基于偏振移相技术的激光干涉仪中1/4波片和1/2波片的非理想因素导致非线性误差的产生机理和变化规律.理论研究表明:在导致波片处于非理想状态的各个因素中,干涉仪中两个1/4波片的差模延迟角误差Δεq所产生的恒定偏置误差和接收装置中1/4波片的延迟角误差εq3所引起的一次谐波非线性误差,是组成干涉仪非线性误差的最主要的两个部分;波片各种误差源非理想因素导致的非线性误差在小误差情况下经线性叠加后由干涉仪最终输出.     

Simultaneous measurement of optical rotation angle and retardance

In this study, an optical scheme based on Stokes-Mueller Formalism and rotating wave-plate Stokes polarimeter is successfully developed to simultaneously measure optical rotation angle and retardance. The average relative errors in the measured rotation angle and retardance of a half-wave plate which are solved by nonlinear equations of detected Stokes parameters are determined to be just 0.74% (1.16% for a perfect half-wave plate with retardance of 180°) and 0.40% respectively. The average relative error in the measured rotation angles of glucose solutions with concentrations ranging from 0 to 1.2 g/dl is determined to be 4.53% (2.98% under calibration with sample cell). From the inspection of simultaneous measurement of rotation angle and retardance in a glucose solution followed by a half-wave plate, the average relative error in the measured rotation angles of glucose solutions is determined to be 4.23% (1.81% under calibration with sample cell). The correlation coefficient between the measured rotation angle and the glucose concentration is found to be 0.99966, while the standard deviation is just 0.00357°, and the average relative error in the measured retardance of a half-wave plate is determined to be just 0.47%. Consequently, the derived algorithm for simultaneously measuring rotation angle and retardance is feasible, and the developed system is evaluated with a precision of 10% approximately in rotation angle and a high precision of 0.0032% in retardance measurement.     

点衍射干涉仪波面参考源误差及公差分析

为了保留光纤点衍射干涉仪容易对准以及衍射光束易于控制的优点,同时又能实现大数值孔径（NA）光学系统的检测,设计了一种新型的波面参考源（WRS）,它保留了光纤点衍射和微孔点衍射的优点,可满足大NA极紫外光刻物镜系统波像差检测的要求。本文在分析各种误差的基础上,搭建了WRS原理光路并对WRS的系统误差标定算法进行详细的研究,得到WRS标定时旋转平台的角度公差为0.5°,跳径时偏离系数为0.5%。这一新型WRS误差分析及标定对于实现高精度的检测具有十分重要的意义,最终为实现WRS系统误差标定提供理论基础。     

An efficient calibration method for SQUID measurement system using three orthogonal Helmholtz coils

For a practical superconducting quantum interference device(SQUID) based measurement system,the Tesla/volt coefficient must be accurately calibrated.In this paper,we propose a highly efficient method of calibrating a SQUID magnetometer system using three orthogonal Helmholtz coils.The Tesla/volt coefficient is regarded as the magnitude of a vector pointing to the normal direction of the pickup coil.By applying magnetic fields through a three-dimensional Helmholtz coil,the Tesla/volt coefficient can be directly calculated from magnetometer responses to the three orthogonally applied magnetic fields.Calibration with alternating current(AC) field is normally used for better signal-to-noise ratio in noisy urban environments and the results are compared with the direct current(DC) calibration to avoid possible effects due to eddy current.In our experiment,a calibration relative error of about 6.89 × 10-4is obtained,and the error is mainly caused by the non-orthogonality of three axes of the Helmholtz coils.The method does not need precise alignment of the magnetometer inside the Helmholtz coil.It can be used for the multichannel magnetometer system calibration effectively and accurately.