高速三维数字图像法测量手机跌落全场应变

为了测量手机跌落时的变形与应变,基于数字图像相关法及双目立体视觉原理,提出一种用于手机跌落试验中变形与应变测量的方法,并研制了相应的高速三维全场应变光学测量系统。针对手机跌落碰撞过程中,角度变化导致散斑匹配失败率高,变形应变场缺损严重的问题,利用高速相机高速采集图像,并改进图像匹配方法,采用顺序逐帧基准匹配,保证了测量精度,提高了应变场完整度。研制了光学测量系统,设计了试验方案,进行了数字图像测量方法与动态应变仪测量结果的对比,对改进的散斑匹配方案进行了验证。试验结果表明,本文的方法使变形应变场的完整度提高了21%,其位移动态测量精度为0.42%,应变测量精度为0.5%。本文的方法和系统可以满足手机跌落碰撞全场变形与应变测量的要求,与传统测量方式相比有明显优势,是研究手机跌落碰撞变形规律的有效途径。     

采样噪声对北斗全球信号测距误差的影响分析

随着北斗卫星导航系统的全球化,基于软件定义无线电的北斗接收机在北斗导航定位中的应用越来越广泛。但是北斗接收机在实时动态差分等高精度测量应用场景下,其基带采样ADC受到采样时钟抖动影响,再叠加固有的量化噪声和热噪声,对北斗信号的扩频测距精度产生不可忽略的影响。本文首先针对北斗公开的B1I、B1C、B2I、B2a和B3I 5种全球信号,描述了ADC采样中时钟抖动、量化噪声和热噪声等采样噪声的数学模型,提出了影响测距的信噪比综合公式,再通过载噪比进而得出测距误差的一般表达式,并给出了高精度测量要求下不同参数选择的工程化定量分析方法,然后针对不同参数对北斗信号测距误差的影响进行了仿真分析,仿真结果表明,在0. 6 cm的测距误差目标下,要求时钟抖动不大于45 ps,接收机中心频率不大于80 MHz,带宽不小于25 MHz,量化位数不少于7位,载噪比不小于30 d B。最后,针对北斗B2I信号进行了实测实验,在时钟抖动为35 ps,接收机中心频率61. 38 MHz,带宽32 MHz,量化位数12位,载噪比67 d B时,解算的测距误差为0. 41 cm,验证了本文方法的有效性。     

空间低温辐射计中的精密电压测量系统

为了基于测温电阻实现空间低温辐射计的腔温测量,研究了系统的电子学测量精度和测量稳定度。结合实际电子学需求,进行方案设计和器件选型,提出了一种新型的基于超低噪基准源LTZ1000ACH,四线制柱状锗电阻GR1400-AA和24位模数转换器LTC2400的对偶相消式精密电压测量系统。对于整个链路信噪比进行了逐级理论计算和分析,并通过电路仿真软件TINA-TI对系统幅频特性和温度响应特性进行了仿真分析,最后在77K液氮环境下对该系统进行了测温精度和长期稳定性测试。实验结果表明:锗电阻实际采样电压值在100μV内波动,长期测量稳定度达到1×10-5;在77K液氮环境下,系统测温精度达到4mK,长期稳定性达到1×10-5。得到的结果基本满足空间低温辐射计电子学部分的设计指标要求。     

A digital signal conversion system for astronomy radio interferometers with small antennas

Results of designing a digital signal conversion system for radio interferometers with small-diameter (up to 12 m) antennas are presented. The system contains four digital signal conversion channels with 500-MHz bandwidths. The output data stream rate in the VDIF format is 2048 Mbit/s per channel, and the cumulative output data flow is 8192 Mbit/s. The observation data flows arrive at the signal recording buffer unit and can be transmitted from there via a 10G Ethernet interface to a correlator in near-real time.     

飞机数字化测量网络布站设计

考虑大尺寸、高精度要求的飞机或特殊机型飞行器需要采用多仪器组合测量网络来完成数字化测量任务,本文对测量网络进行了最优布站设计.介绍了传统的飞机调平理论,提出了飞机数字化调平变换算法,并建立了其不确定度模型.通过不确定度分析和误差依赖性仿真得出飞机各基准点不确定度和水平点位置对测量不确定度的影响.结合由激光雷达、iGPS组成的飞机数字化测量网络的测量特性,提出了飞机数字化测量网络的最优布站设计方案.对某机型飞机水平测量实验验证表明,经布站优化设计后的测量结果精度为0.402mm,提高了约20％.结果显示提出的布站设计方案有效、可行,其分析方法为寻找高准确度、高效率的飞机数字化测量的布站设计提供了参考依据.     

由形态学边缘模式匹配实现数字稳像

针对在一些实际应用场合摄像机设备的震动造成的视频序列失稳,提出了一种基于形态学边缘模式匹配的数字稳像方法.该方法首先利用形态学方法提取视频图像边缘,然后利用当前帧子块与参考帧子块的边缘进行特征匹配,以确定当前帧子块相对于参考帧的局部运动矢量.对得到的局部运动矢量进行分析判决,以确定该局部运动矢量是否为真正的抖动偏移量,消除视频帧本身因存在局部运动目标、低对比度、纹理区域等因素对全局运动矢量估计的影响;最后,通过判别确认的局部运动矢量确定全局运动矢量并进行运动补偿,实现数字稳像.仿真实验表明,由于该方法的块局部运动矢量采用1 bit边缘进行最大相关值估计,因而复杂度低,而采用异常情况判决准则消除了其对真正运动矢量估计的影响,稳像精度高,可应用于因摄像头平移震动等因素造成的视频序列失稳.     

Displacement measurement using digital speckle multi-frequency harmonic wave correlation method

In the displacement measurement using digital speckle correlation method, significant measuring error due to the multi-peak nature of the correlation coefficient function is a critical issue as sometimes the secondary peak can be wrongly determined as the maximum instead of the highest peak. In the multi-frequency harmonic wave correlation method (MHCM) as proposed in this work, for speckle patterns before and after the displacement, correlation calculations were performed on corresponding sets of data matrices assembled by amplitudes/intensities obtained from harmonic waves with different frequencies. The calculated maximum correlation coefficients were compared with each other to locate the maximum in order to measure the displacement. Both ultrasonic speckle MHCM and laser speckle MHCM were applied to the displacement measurement respectively. Measured results indicated that MHCM effectively helps to ensure the correct determination of the maximum correlation coefficient, to avoid random errors caused by other factors and improves the measurement accuracy in the meanwhile.     

A simple point cloud data reduction method based on Akima spline interpolation for digital copying manufacture

Point cloud data acquisition is the first key step in digital copying manufacture. In order to reduce extremely dense acquired data while maintaining data accuracy, this paper presents a simple and practical on-line point cloud data reduction method for digital copying manufacture, which is based on Akima spline interpolation. The basic idea of this method is similar to sketch painting: Outline the broad contour of the curve first and then revise local details until the interpolated curve satisfies the required accuracy. In this method, Akima spline interpolation is adopted to connect acquired points for CNC machining in digital copying process. It obtains a smaller data reduction ratio and a smoother machined surface than conventional methods. Experimental results indicate that the proposed Akima reduction method is able to eliminate redundant data effectively under different required accuracy. The reduction performance of this method is superior to equal ATCD reduction method obviously under the same required accuracy. The proposed method can be used in the real-time data acquisition process of digital copying manufacture to replace traditional methods.     

基于数字孪生的航天器装配质量监控与预测技术

鉴于航天器装配过程中不确定因素多,无法准确有效地预测和评估航天器的实际性能,装配过程中因进行大量复杂的性能试验来验证产品性能指标的符合性而极大影响了装配效率,提出一种基于数字孪生的航天器装配质量在线监控与预测方法。分析了航天器装配执行层面总体流程的特点,在此基础上给出面向航天器装配质量的数字孪生建模方法,以及面向数字孪生构建的产品监控与数据管理方法,最后提出一种基于灰度关联的装配过程质量综合预测方法,可用于航天器装配质量预测。以空间站某泵组件产品为实例,验证了所提方法的正确性。     

粗光栅信号全数字化处理法实现高倍数细分

针对在粗光栅软件细分中的信号误差影响细分数的问题,提出了按细分的主要误差来源分类进行数字滤波和补偿的全数字化处理法,以达到粗光栅高精度测量的要求。首先对光栅测量信号进行有针对性的数字滤波,使其波形接近于理想状态。然后根据误差来源进行数字补偿,通过对软件数字细分原理的分析,推导出了原始信号不正交、幅值不等、谐波失真等误差影响细分结果的表达式,并提出了与此相对应的数字补偿方法。最后用软件细分法对测量信号进行高倍数数字细分。滤波前后波形信号的仿真比较结果验证了基于严格线性相位的FIR数字带通滤波器可以有效地屏蔽光栅信号频谱中的高低频干扰和噪声。研究结果表明,在粗光栅满足一定质量的前提下,利用全数字化处理法能够满足500细分的精度要求。     

Optical disc jitter generator and its calibration system

Jitter is one of the most important parameters for optical disc evaluation. This paper presents a design of a simulated optical disc jitter generator based on a sinusoidal frequency-modulated (FM) signal. An innovative method is proposed to calibrate the jitter generator based on the Bessel-zero method. Finally, measurement uncertainty of the calibration system is described. The results of theoretical analysis and experiments indicate that the expanded uncertainty of measurement is 0.13% in CD mode, and 0.18% in DVD mode, k = 2.     

一种提高LVDS可靠性通信方法的研究

为保证远程测试系统中基于低振幅差分信号技术(low voltage differential signaling,LVDS)串行数据传输的可靠性与准确性,提出了一种(7,4)线性分组码.该方法以牺牲一定有效带宽为代价,通过对线上传输的有效数据增加监督码元极大地降低了数据传输的误码率,提高了数据传输的可靠性.采用驱动器CLC001和自适应均衡器CLC012补偿信号在长线传输中的衰减,提高了信号的完整性,保证了数据传输的可靠性.经仿真验证,在总长为100 m的屏蔽双绞线上,该系统以240 Mbit/s的码率实现了串行数据的零误码率传输.     

有源单臂电桥在激光调阻中的测量原理及实现

论述了在激光调阻中有源单臂电桥的测量原理,提出了高速刻蚀电阻的实现方法,利用两个高精密16位D/A转换器与检流计输出的电压进行比较,实现了数字化高速电阻测量.对影响测量精度的因素进行了分析,该方法对电阻高速测量及其控制方面有一定的参考价值.     

EIT高精度数字解调方法误差分析

EIT测量中,阻抗信息解调方法的精度直接关系到信息提取和EIT成像的质量。数字解调方法与模拟解调方法相比具有抗噪声能力强和设计灵活等优点。高精度数字解调方法是提取EIT复阻抗全信息的重要手段。本文深入研究了采样同步时延和相位抖动对高精度数字解调方法的误差影响,并且采用FPGA验证了EIT解调时的相位误差,实验结果表明合理选择激励频率和采样时钟能提高数字相位解调的精度,这与理论分析完全一致。     

数字式测高仪定位误差的测量及补偿

定位误差是测高仪的主要误差源之一,为了提高测高仪的测量精度,研究了数字式测高仪定位误差的测量及补偿方法.以某公司生产的数字式测高仪为研究对象,以德国SIOS公司微型双平面镜十涉仪SP-D为高精度的标准量,实现了数字式测高仪定位误差的测量.采用二次多项式拟合的方法对测量数据进行曲线拟合,拟合前后的测量数据差值作为校正定位...     

飞机结构件运动数据的动态视觉测量系统

基于近景摄影测量理论和立体视觉技术,提出并实现了一种针对机身结构件在飞行状态下的轨迹、姿态、位移、变形等多种运动数据的动态视觉测量方法.研究了基于工业近景摄影测量的多相机快速自标定方法;飞行状态下相机动态定位及抖动消除技术;刚性结构件的运动轨迹及姿态的快速求取和通过多相机(≥3)协作实现非编码标志点阵列的精确匹配等多项关键技术.在模拟飞行环境下的实验结果表明,相机标定的重投影误差小于0.03 pixel,系统的运动轨迹姿态测量精度可达0.01 mm/1 m,关键点位移变形测量精度可达0.05 mm/1 m,基本满足飞机测试行业的精度和可靠性测量标准.     

Applications of digital signal processing methods in TOF calculation of ultrasonic gas flowmeter

Ultrasonic gas flowmeters (UGFM) are extensively used in petroleum, chemical, natural gas and other fields because of their distinctive measurement advantages. As the core technology of the UGFM, digital signal processing technology determines its measurement accuracy and stability. This paper systematically reviews the signal processing methods for measuring the TOF (time of flight) based on the principle of time difference method. According to the stability of the feature information extracted by different digital signal processing methods, the advantages and disadvantages of each method are analyzed. Aiming at the problems of serious energy attenuation, weak echo signal amplitude, and low signal-to-noise ratio (SNR) when ultrasonic signal propagate in the gas, different signal processing methods are evaluated and compared from the aspects of calculation accuracy, response speed, anti-interference ability and sensitivity to parameter changes. Finally, some improvement ideas and directions for further research are proposed according to the analysis results.     

A novelty digital algorithm for online measurement of dielectric loss factor of electronic transformers

There are many inherent performance limitations using traditional algorithms for online measurement of dielectric loss factor including synchronous sampling, no interharmonics and power system frequency must be invariable. In a non-stationary signal environment where power frequency fluctuation and interharmonic components exist, there is no guarantee of measurement accuracy by using traditional methods. The paper proposed a high-accuracy digital algorithm for online measurement of dielectric loss factor of electronic transformers. Theoretical basis of the new algorithm is based on a new data processing procedure including data truncation and data addition which compensates phase distortion as a result of the spectrum of addition data contains offsets. The algorithm can accurately extract the fundamental signal and calculate dielectric loss factor. Measured results from simulations and practical engineering projects show that the new algorithm has good application feasibility without being affected by the limitations rendered above.     

小型编码器动态精度检测的安装误差控制

研究了小型编码器动态检测过程中由编码器与基准编码器轴系中心线不完全重合产生的偏角导入的安装误差,以便提高编码器检测装置的准确性和可靠性。分析了安装误差对被检编码器检测精度的影响,推导出了存在安装偏角时引入的安装误差公式及其控制范围公式。为了使编码器的动态检测能准确地反映编码器的实际精度,给出了最大偏角值α_(max)及高度差D_(max)的允许范围。使用现有21位检测装置对15位被检编码器进行了检测实验,分别对安装良好、小偏角和大偏角情况下的测量结果和安装误差曲线进行了比较和分析。结果表明:检测15位编码器时,将安装偏角值控制在0.36°以下可满足动态精度检测要求。本文提出的误差公式及控制方法可以运用在不同类型、不同精度的编码器检测过程中,对提高小型光电编码器动态检测的精度和可靠性很有意义。     

M-LFM: a multi-level fusion modeling method for shape−performance integrated digital twin of complex structure

As a virtual representation of a specific physical asset, the digital twin has great potential for realizing the life cycle maintenance management of a dynamic system. Nevertheless, the dynamic stress concentration is generated since the state of the dynamic system changes over time. This generation of dynamic stress concentration has hindered the exploitation of the digital twin to reflect the dynamic behaviors of systems in practical engineering applications. In this context, this paper is interested in achieving real-time performance prediction of dynamic systems by developing a new digital twin framework that includes simulation data, measuring data, multi-level fusion modeling (M-LFM), visualization techniques, and fatigue analysis. To leverage its capacity, the M-LFM method combines the advantages of different surrogate models and integrates simulation and measured data, which can improve the prediction accuracy of dynamic stress concentration. A telescopic boom crane is used as an example to verify the proposed framework for stress prediction and fatigue analysis of the complex dynamic system. The results show that the M-LFM method has better performance in the computational efficiency and calculation accuracy of the stress prediction compared with the polynomial response surface method and the kriging method. In other words, the proposed framework can leverage the advantages of digital twins in a dynamic system: damage monitoring, safety assessment, and other aspects and then promote the development of digital twins in industrial fields.