靶场T型架光电经纬仪精度检测方法的研究与应用

根据T型架光电经纬仪结构特点,设计了偏心方法,利用动态精度靶标对T型架光电经纬仪进行脱靶量、静态、动态及跟踪随机均方差的检测,通过某型号光电经纬仪的实际检测验证了该偏心方法的正确性。     

Reliability estimation of rotary lip seal in aircraft utility system based on time-varying dependence degradation model and its experimental validation

With several attractive properties, rotary lip seals are widely used in aircraft utility system, and their reliability estimation has drawn more and more attention. This work proposes a reliability estimation approach based on time-varying dependence analysis. The dependence between the two performance indicators of rotary lip seals, namely leakage rate and friction torque, is modeled by time-varying copula function with polynomial to denote the time-varying parameters, and an efficient copula selection approach is utilized to select the optimal copula function. Parameter estimation is carried out based on a Bayesian method and the reliability during the whole lifetime is calculated based on a Monte Carlo method. Degradation test for rotary lip seal is conducted and the proposed model is validated by test data. The optimal copula function and optimal order of polynomial are determined based on test data. Results show that this model is effective in estimating the reliability of rotary lip seals and can achieve a better goodness of fit.     

A global empirical orthogonal function model of plasmaspheric electron content

Based on the method for establishing a global plasmaspheric model using observations from COSMIC and MetOp-A orbit determination GNSS receivers, Chen et al. (2017) obtained a global plasmaspheric total electron content product with a spatial resolution of 2.5° × 5° and a time resolution of 4 h. In this paper, we use those global plasmaspheric electron content product in 2008, 2010, 2011, 2012, 2014 for 1446 days to establish a global plasmaspheric empirical model based on empirical orthogonal function (EOF). The model can well characterize the spatiotemporal variation of plasmaspheric electron content (PEC) and the influence of solar radiation on it. Only the first four orders of EOF sequences can characterize the 98.43% features of the original PEC dataset. The principal component coefficient Pk is decomposed twice during modeling, and the combination of trigonometric function and linear function is used to model Pk to characterize the solar cycle, annual cycle, semi-annual cycle and quarter-cycle variation. We compare the PEC model values with the actual observation data, the results show that the empirical PEC model values are highly correlated with the actual observations. The correlation between the two is above 0.96, and the RMS maximum of the difference between the PEC model values and the observed values are 0.70 TECU, and the average of the difference between the PEC model values and the observed values are −0.18 TECU, respectively. In addition, we validate the reliability of the global plasmaspheric model established by two empirical orthogonal function decomposition method using actual observation data, according to the global distribution of the differences between the PEC model values and the observed values in low solar activity and high solar activity, it can be seen that under low solar activity and high solar activity conditions, the model has good adaptability.     

Experimental and numerical study on pressure oscillation in a combustor with rotary valve

A rotary valve coupled in a combustor assembly can generate periodic pressure oscillations inside the combustor and can be used to study the combustion instability in the combustion chamber of a rocket engine. This paper proposes a cold gas flow experimental system based on a rotary valve and a corresponding rotation model. A 3D numerical model is proposed to obtain the transient flow inside the rotary valve, and the dynamic mesh technique and User-Defined Functions (UDFs) are adopted to implement a swing motion instead of a rotary motion. Several cold gas flow experiments are carried out at rotating speeds of 75 225, and 375 rpm to verify the validity of the numerical model. The effects of rotating speed, stroke length ratio and radius of the RED (Rotor Exhaust Duct) on the pressure oscillations are studied using this numerical model. The results show that the maximum and peak-to-peak values of the pressure oscillations gradually decrease with increasing rotating speed. The ratio of the corresponding peak-to-peak value to the maximum pressure (pressure amplitude ratio) is reduced from 1.81 to 0.6%. The stroke length ratio affects the pressure waveform because it leads to a change in the time spent in the non-exhaust stage. When the stroke length ratio is 0, the waveform closely resembles a sine wave. With the increase in the stroke length ratio, the pressure waveform exhibits a more square or a triangular wave shape. Finally, a high-frequency and high-amplitude pressure oscillation can be obtained by appropriately increasing the radius of the RED.     

基于旋转阀的脉冲爆震火箭发动机实验

针对现有条件下电磁阀高频与大流量不可兼得的矛盾,设计了一种凸轮式旋转阀,以此来控制脉冲爆震火箭发动机氧化剂、燃料和隔离气体的间歇式供给.基于该旋转阀,以汽油和富氧空气为推进剂,进行了不同频率下的实验.实验结果表明,推进剂和隔离气供给压力与点火相位直接影响到能否稳定起爆.随着频率的增加,在1～ 10 Hz范围内,降低隔离氮气压力、调整点火相位可实现发动机的稳定工作;10Hz以上时,仅需要提高油气的供给压力.基于该旋转阀控制技术,脉冲爆震火箭发动机实现了工作频率30 Hz的稳定工作.     

Accuracy and consistency of different global ionospheric maps released by IGS ionosphere associate analysis centers

Due to the differences of ionospheric modeling methods and selected tracking stations, the accuracy and consistency of Global Ionospheric Maps (GIMs) released by Ionosphere Associate Analysis Centers (IAACs) are different. In this study, we evaluate and analyze in detail the accuracy and consistency of GIMs final products provided by six IAACs from three different aspects. Firstly, the comparison of these GIMs shows that the mean bias (MEAN) is related to the modeling methods of various IAACs. The variation trend of the standard deviation (STD) is consistent with the solar activities, and accompanied by certain seasonal and annual periodic variations. The MEAN between IGS and each center is about −1.3 to 1.0 TECU, and the STD is about 1.4–2.5 TECU. Secondly, the validation with GPS TEC shows that the STD of CODE is the smallest at various latitudes, and the STD is about 0.7–4.5 TECU. Thirdly, The validation with the Jason2 VTEC shows that the STD between Jason2 and IAACs is about 4.4–5.2 TECU. In addition, the STD between Jason2 and six GIMs in the areas with more tracking stations is better than that of the regions with fewer tracking stations in different latitude regions. Regardless of whether the tracking stations are more or less, the MEAN and STD in high solar activity are larger than in low solar activity.     

Analysis of laser ranges and angular measurements data fusion for space debris orbit determination

In the framework of space debris, the orbit determination process is a fundamental step, both, for researchers and for satellite operators. The accurate knowledge of the orbit of space debris objects is needed to allow space debris characterization studies and to avoid unnecessary collision avoidance maneuvers.The accuracy of the results of an orbit determination process depends on several factors as the number, the accuracy, the kind of processed measurements, their distribution along the orbit, and the object-observer relative geometry. When the observation coverage of the target orbit is not homogeneous, the accuracy of the orbit determination can be improved processing different kind of observables. Recent studies showed that the satellite laser ranging technique can be successfully applied to space debris.In this paper, we will investigate the benefits of using laser ranges and angular measurements for the orbit determination process. We will analyze the influence of the number of used observations, of the covered arc of orbit, of each observable, and of the observation geometry on the estimated parameters. Finally, using data acquired on short observation arcs, we analyze the achievable accuracies for the orbital regimes with the highest space debris density, and to the consequences of the data fusion on catalog maintenance operations. The results shown are obtained using only real data (both angular and laser measurements) provided by sensors of the Swiss Optical Ground Station and Geodynamics Observatory Zimmerwald owned by the Astronomical Institute of the University of Bern (AIUB) and for some studies also using ranges provided from other stations of the International Laser Ranging Service (ILRS).     

弹道导弹的飞行试验与精度鉴定

通过总结我国第一代弹道导弹的研制经验,分析国外导弹试验和精度鉴定工作的经验,对工作程序、试验弹道选择、飞行试验发数安排与精度鉴定等问题进行了讨论,并提出了对我国第二代弹道导弹精度鉴定工作对策的初步思考。     

水下目标定位ST系统的测量原理

根据ST系统测量设备空间布局的几何关系,推导出了该系统的观测方程,建立了水下目标运动轨迹测量的数学模型,并对模拟的目标运动轨迹进行了定位精度的仿真计算。     

旋转导向系统井身轨迹旋转测量方法研究

通过分析旋转导向过程中对系统及其系统内各个分部件的影响,建立了旋转导向井身轨迹旋转测量方法的数学模型。针对理论分析,建立了Matlab仿真模型,并进行了仿真图形分析。最后,进行了试验验证,给出试验结果。从整个试验过程和试验结果可以证明所研究的测量方法是正确并可行的。