回转件弯扭测量系统及其不确定度分析

为了准确诊测轴系振动特性,基于激光多普勒的频移原理,提出一种能同时测量旋转轴系弯曲振动、扭转振动和轴系旋转速度的方法。设计了能分离弯扭振动的多普勒外差干涉光路,结合光学差拍及参考光技术,构建了测量系统数学模型。对影响激光多普勒弯扭振动测量的主要因素进行了分析,讨论了各参量对测量结果的影响,并给出了相应的测量不确定度。在置信水平为95%时,瞬时转速的不确定为0.079 r/min,弯曲振动速度分量的不确定为0.001 4 mm/s,其精度能满足旋转状态下轴系振动的综合测量要求。     

基于不确定油液光谱数据的综合传动装置剩余寿命预测

原子发射光谱分析得到的磨损微粒元素浓度是综合传动装置性能劣化评估和剩余寿命预测的重要监测指标。由于系统随机劣化过程和光谱测量误差的影响,油液光谱数据中不可避免包含系统劣化随机性和光谱测量不确定性。然而,现有基于油液光谱数据的剩余寿命预测研究中,没有考虑劣化过程的随机性和测量的不确定性对剩余寿命预测的影响。因此,针对综合传动装置劣化随机性和油液光谱数据测量不确定性对寿命预测的影响,提出一种考虑系统随机劣化和数据不确定测量的综合传动装置劣化过程建模方法。基于随机过程首中时间的概念,定义了综合传动装置的剩余寿命;基于Wiener随机过程,建立了考虑系统随机劣化和不确定测量数据的综合传动装置劣化模型,利用极大似然估计方法,估计了劣化过程模型的参数;利用卡尔曼滤波技术,实现了综合传动装置劣化状态的实时估计与更新,进一步得到了考虑系统劣化随机性和光谱数据测量不确定性的剩余寿命分布。研究结果表明,提出的劣化建模方法能够准确估计装置的运行状态,避免了采用条件维护时间对装置进行维护与保养的局限性;综合传动装置的维护时间预测值比条件维护时间延长了193 Mh（113.5%）;考虑光谱数据测量不确定性的剩余寿命预测方法优于不考虑测量不确定性的方法。     

基于自准直效应的Fabry-Perot干涉仪的设计

报道了基于圆柱型光子晶体自准直效应的低功耗Fabry-Perot干涉仪。该干涉仪是在二维光子晶体中引入两排线缺陷构成的。引入的线缺陷具有高反射率和低透射率。在自准直频率范围0.187c/a~0.201c/a,线缺陷的透射率介于20.77%~40.65%。利用时域有限差分方法对FPI的透射谱进行研究,结果表明对两排缺陷的间距d即使进行微小的扩大也会引起透射峰向低频移动,透射谱的自由光谱范围和透射峰的频率随着d的增大而变小,透射谱的半高宽会随着线缺陷的反射率的提高而逐渐变小。     

Internal tissue displacement measurement based on ultrasonic wave Doppler signal digital detection and its application to fetal movement monitoring

We have developed a fetal movement monitoring system based on small displacement measurement of internal tissues. When ultrasonic pulses are transmitted to the fetus, the reflected ultrasonic waves which have a Doppler frequency shift due to the fetal movements are detected by using an ultrasonic pulsed Doppler technique. In this paper, we propose a displacement measurement method for internal tissues which is based on the Doppler signal digital detection technique. In the method, the received ultrasonic RF signals are sampled with a sampling frequency of four times higher than the centre frequency of the ultrasonic waves; the Doppler frequency shift signals are derived using digital signal processing. From the detected signals, the internal displacements are estimated using the arc-tangent method. The basic algorithm of the detection method has already been used in the area of blood flow sensing, however, we apply the algorithm to the displacement measurement of internal tissues. The comparison between the proposed method and the conventional method is presented. The fetal movement quantitative monitoring system based on the method which has been constructed is shown.     

模拟大气风场及其数据处理技术的研究

热层大气风速的测量可以采用干涉法来进行,由于光源（气辉辐射谱线）的强度很弱,故干涉法对测量系统要求很高。利用半导体激光器（LD）的调制特性和法布里-帕罗干涉仪(FPI)的高光谱分辨能力设计了一种用简单设备进行大气风场模拟与测量的方法。改变LD的驱动电流使其输出激光频率改变,从而模拟气辉辐射的多普勒频移,通过分析FPI获得的干涉图可检测出该频移,进而得到等效风速。模拟风速的相对误差不超过6.5%,最小模拟风速为20.01m/s,且测量结果与LD的线性调制特性很相符。使用该方法可以有效地对多普勒风速测量原理、数据处理方法、系统性能以及测量误差进行分析和评估。     

Accuracy Analysis of the Fabry–Perot Etalon Based Doppler Wind Lidar

A direct detection Doppler wind lidar with the dual Fabry–Perot technique has been built in Hefei, China, and the system is described in this paper. A dual, air-spaced Fabry–Perot etalon is designed as the frequency discriminator and the transmission characteristics are measured with a stabilized cw laser and a pulse laser. The experimental data are found to be in agreement with the designed parameters. The Doppler shift is measured by taking the ratio of the transmitted intensities from the dual etalon. Analysis of the accuracy of Doppler measurement is made by considering the factors of the number of iterations in converting the measured ratio to the Doppler shift, the laser intensity fluctuation and the signal-to-noise ratio. In the sufficient signal-to-noise ratio the velocity accuracy of the Doppler lidar system is estimated to be better than 0.5 m/s.     

A precision analysis and determination of the technical requirements of an atom interferometer for gravity measurement

The influence of the wave-front curvature of Raman pulses on the measurement precision of gravitational acceleration in atom interferometry is analysed by the method of a transmission matrix. It is shown that the measurement precision of gravitational acceleration is largely dependent on the spot size of the Raman pulse, the temporal interval between Raman pulses and the optical path difference of the two counter-propagating Raman pulses. Moreover, the influence of Doppler frequency shift on the precision is discussed. In order to get a certain measurement precision, the requirement for the accuracy of frequency scanning of the Raman pulse to compensate for the Doppler frequency shift is obtained.      

瑞利多普勒测风激光雷达的频率标定方法

频率标定是瑞利测风激光雷达的关键技术。瑞利测风激光雷达中,通过改变压电陶瓷管的电压实现连续调谐F-P标准具腔长,使出射激光频率处于双边缘透过率曲线的交点处。在连续调谐时,由于压电陶瓷管的磁滞效应引起腔长调谐非线性,从而导致系统误差。分析了该误差的原因及特性,提出了静态软件补偿和动态调频跟踪相结合的频率标定方法。若激光出射频率相对F-P标准具漂移小于100 MHz时,在数据反演时补偿该频率偏差;若相对频率漂移大于100 MHz时,将F-P标准具先退回预设腔长以下,通过逐步增加电压的方式,重新实现频率锁定,保证锁定过程处在磁滞回线的电压上升段,避免了磁滞效应引起的误差。多普勒激光雷达与无线电探空仪的两组对比实验中,在15~30km高度,风速最大偏差6.22m/s,平均偏差1.12m/s。     

基于相位调制器与Fabry-Perot干涉仪的激光多普勒频移测量方法

提出了一种激光多普勒频移测量方法, 此方法利用正弦相位调制使信号光在原频率成分基础上产生正负一阶边带, 再由Fabry-Perot干涉仪对调制光振幅和相位进行调整, 使其产生固定频率的拍频信号, 利用此拍频信号的振幅随频率变化而变化的性质来进行多普勒频移测量. 通过理论分析证明该方法具有很高的测量精度, 加工装调难度不大, 兼顾了普通相干与非相干探测方法的优势. 另外通过实验证明该方法的正确性与可行性, 并通过与普通非相干方式比较发现该方法在测量精度上可以提高 约1个数量级. 关键词： 多普勒频移 相位调制 Fabry-Perot干涉仪 拍频     

点式单波束多普勒测流系统的设计方法

为了加快多普勒流速计算速度和提高系统稳定性,提出基于FPGA技术的多普勒测速的设计方法,其中包括信号发射电路和信号接收电路。首先通过M码进行二相相移键控信号的调制,减少了回波误差、增加信号发射能量,有效地降低了水中超声波的能量耗散对信号提取的影响。然后对回波信号进行二相解调,并利用复自相关算法进行分析处理。最后,通过测速实验对所提方法进行验证。实验结果表明,所提方法不仅具有较低的实验误差而且具有较高的可靠性。     

不需要校准激光的法-帕仪中高层大气温度反演方法和观测数据初步分析

本文提出了一种根据FPI观测不需要校准激光而进行温度反演的方法, 给出了进行温度反演的解的解析形式. 依据武汉大学FPI大气温度测量系统获得的630 nm和557.7 nm观测数据, 利用上述方法进行温度反演, 结果表明本文方法不需要校准激光, 能用于不同波长的FPI温度反演.     

多普勒频移修正在测定直升机飞行噪声固有频率中的应用

对于噪声信号采集系统采集的某型直升机的飞行噪声信号,提出了结合机载GPS数据,进行多普勒频移修正,然后叠加多个多普勒频移修正结果,以得到直升机旋翼、尾桨和减速器噪声固有频率的新方法,可以大大减小单次多普勒频移修正的误差。这种方法为确定飞行器飞行噪声固有频率提供了有效的途径。     

基于菲佐干涉仪与多通道光电倍增管阵列的多普勒频移检测技术

提出了基于菲佐干涉仪和多通道光电倍增管(PMT)阵列探测器组合的多普勒频移检测的方案,适用于风速测量的直接探测多普勒激光雷达。首先介绍了工作原理,再根据菲佐干涉仪光谱特征对频移检测用干涉仪进行了优化设计,优化设计的菲佐干涉仪腔长150mm、平板反射率0．755。对提出的菲佐干涉仪和多通道光电倍增管阵列探测器组合的方案进行了数值模拟,以分子散射作为背景噪声,计算了该方法的风速测量误差。模拟结果表明,设计的基于菲佐干涉仪的直接探测多普勒测风激光雷达,在30 s的积分时间内、探测高度5 km以下,风速测量误差可以达到0．56 m/s。     

Accuracy analysis and stabilization design of the Fabry–Perot frequency discriminator in double-edge wind lidars

The measurement error of a double-edge wind lidar caused by a disturbed Fabry–Perot interferometer (FPI) is analyzed. Several error sources such as air pressure variations, temperature changes, and mechanical vibrations are considered in the measurement-error model. The simulation results show that a double-edge wind lidar is so sensitive to environmental variations that the measurement error reaches ±60 m/s if the FPI is not stabilized. In order to compensate the external disturbance acting on the FPI, a nonlinear proportional–integral–derivative (PID) control scheme is designed based on the transmission measurement of the calibration channel. An arc tangent function is used to improve the feedback gain of the usual PID control design. The results show that with the new controller the measurement accuracy of the wind lidar can be improved 4–5 times in comparison with the usual control design, and the range of the measurement error is only ±3 m/s.     

基于匹配光纤光栅法布里-珀罗干涉仪的应变解调方法

提出并实验验证了一种基于匹配光纤光栅法布里-珀罗干涉仪的应变传感器解调方法,该方法综合了光纤法布里-珀罗干涉技术和匹配光纤光栅滤波法的优点.通过半导体制冷片和压电陶瓷组成的闭环负反馈控制系统,精确调节匹配光栅法布里-珀罗干涉仪的温度和应变,有效解决了光栅法布里-珀罗干涉仪的失配问题,从而保证系统静态工作点处于最佳匹配位置,同时能够避免探头因环境温度波动导致的测量误差.实验结果表明,该系统能够响应50～800Hz的输入信号,应变最小分辨力至少为0.4nε/Hz1/2,解调灵敏度高,且不受环境温度波动的影响,因而在动态应变或振动测量中具有较高的实用性.     

Magnetic field measurement based on a stimulated two-photon Raman transition

The magnetic field in the microwave interaction zone of the fountain atomic clock was measured by stimulated Raman transitions.By measuring the two-photon transition frequency between the Zeeman levels of the two ground states,we achieved a magnetic field measurement accuracy of the order of 0.28 nT.This method is immune to the Doppler shift and the AC Stark shift.The second order Zeeman shift of the fountain clock is 170.7×10-15,with the uncertainty of 7.2×10-16.     

Wind profiling from high troposphere to low stratosphere using a scanning Rayleigh Doppler lidar

A scanning mobile Rayleigh Doppler lidar based on the molecular double-edge technique is developed for wind measurement from high troposphere to low stratosphere in 5–35 km. To get higher optical efficiency and make the system more stable, a non-polarized beam splitter cube optically contacted to the FPI is used. This layout also provides a convenient method for null Doppler calibration. The laser frequency drift is measured by a wavelength meter and laser frequency locking is performed and an accuracy of ±?0.5 m/s are obtained in 10 h. Horizontal wind velocity and direction retrieval is described for a detecting method of scanning in four directions. To validate the performance of the lidar, comparison experiments were carried out in in Jiuquan (39.741°N, 98.495°E), Gansu province, northwest of China, from 16th October to 12th November 2015, which showed good agreement with radiosonde.     

Doppler angle and flow velocity mapping by combined Doppler shift and Doppler bandwidth measurements in optical Doppler tomography

Accurate estimation of flow velocity requires measurement of Doppler angle, which is not available in general clinical applications. We describe a novel method of direct Doppler angle and flow velocity mapping that uses a conventional single-beam optical Doppler tomography system. The Doppler angle is estimated by combination of Doppler shift and Doppler bandwidth measurements, and flow velocity is calculated from the Doppler shift and the estimated Doppler angle. In vivo study of lip microvascularization demonstrates that this method is capable of providing both flow speed and flow direction information.     

位相共轭镜耦合到染料激光器中的频移现象

本文建议了一个测量位相共轭镜耦合到染料激光器后,当波长自扫描时,BaTiO_3晶体内的运动光栅的多普勒频移的方法,实验结果表明,多普勒频移Δf<0.2Hz.进一步的分析显示,多普勒频移不能解释朝长波方向扫描的波长自扫描现象.     

瑞利散射多普勒测风激光雷达的校准

 在进行实际风速测量之前,对于新研制的测风激光雷达系统进行校准,可以验证并提高风速测量的准确性。根据瑞利散射多普勒激光雷达的测量原理,提出了利用瑞利散射谱和米散射谱之间的关系,采用运动硬目标实现对瑞利散射多普勒测风激光雷达进行校准的方法。设计了对瑞利散射多普勒测风激光雷达进行校准的实验系统,并给出了详细的校准步骤。