Structural dynamic responses of a stripped solar sail subjected to solar radiation pressure

The stripped solar sail whose membrane is divided into separate narrow membrane strips is believed to have the best structural efficiency. In this paper, the stripped solar sail structure is regarded as an assembly made by connecting a number of boom-strip components in sequence. Considering the coupling effects between booms and membrane strips, an exact and semi-analytical method to calculate structural dynamic responses of the stripped solar sail subjected to solar radiation pressure is established. The case study of a 100 m stripped solar sail shows that the stripped architecture helps to reduce the static deflections and amplitudes of the steady-state dynamic response. Larger prestress of the membrane strips will decrease stiffness of the sail and increase amplitudes of the steady-state dynamic response. Increasing thickness of the boom will benefit to stability of the sail and reduce the resonant amplitudes. This proposed semi-analytical method provides an efficient analysis tool for structure design and attitude control of the stripped solar sail.     

一种用于GPS时差比对数据处理的卡尔曼滤波器设计

介绍了一种用于GPS时差比对数据处理的自适应卡尔曼滤波器,在Matlab环境下编写了离散时间形式的卡尔曼滤波算法程序,利用该算法对GPS信号与铯原子频标的时差比对数据进行了分析处理,最后介绍了该算法的数字芯片FPGA实现。     

对接动力学仿真试验台再现频率指标验证

为验证对接动力学仿真试验台再现对接动力学过程中频率0~6 Hz相对运动的能力,用弹性棒方案再现频率0~6 Hz的碰撞过程,由建模与设计计算选定弹性棒的悬臂长度、刚度和航天器质量等设计参数,仿真分析了碰撞过程的接触碰撞力、变形量与速度,以及再现频率等的影响。结果表明:设计参数合理,精度考核方案可行。     

单片宽带频谱分析芯片设计

文章介绍了单片宽带实时频谱分析芯片的设计原理和方法,并在FPGA上进行了原型验证。设计中采用了基于多相滤波器组的下变频方案,并对下变频后每一路数据进行重叠加窗处理。为了减小芯片面积,对后端的FFT分析模块进行了优化设计,提出了将两条蝶形运算级合并为一条流水线的新型FFT设计构架。该设计可以不间断地处理数据,从而实现信号的无缝捕获。     

提高GPS接收机四相鉴频频率牵引性能的算法设计

针对四相鉴频器在定频差下增益周期性波动所导致的性能下降,提出一种包络四相鉴频器(EFQFD)捕获算法结构。通过分析四相鉴频器(FQFD)的工作机制及噪声特性,建立频率牵引过程的非线性比例积分模型,并对FQFD和EFQFD的性能从鉴频范围、噪声门限、牵引速度等方面进行理论对比分析,基于GPS信号典型噪声参数的牵引过程计算机仿真结果证明,EFQFD增益约提高23%。     

Using cross correlation to estimate Doppler frequency

Doppler frequency estimation with high accuracy is very important for precise orbit determination and scientific studies in deep space exploration. In this paper, we propose a new method which implements cross correlation of only received signals from one single station to estimate Doppler frequency. The algorithm is relatively simple and it can achieve high accuracy even when signal to noise ratio (SNR) is very low. Moreover, the accuracy can be further improved by implementing frequency compensation, especially when the frequency dynamic range is high. Simulations were performed and results proved the validity of this method. X-band observations on MEX (Mars Express) and Juno were performed by a 13 m telescope of Wuhan University, which was equipped by two back ends, i.e. CDAS (Chinese Data Acquisition System) and RSR (Radio Science Receiver). Raw data recorded by the CDAS were processed by using the proposed method, and the estimated frequencies were in good agreement with the real time frequency estimation values by the RSR. What’s more, the accuracy by using cross correlation was higher than the one of RSR.     

精密时间频率，国防命脉所在——国防时间频率专业的发展

精密时间频率设备及其计量技术是国防科技工业的基础,总结了国防科技工业在晶体元器件、频率综合、原子频标、时间频率计量等时频领域的发展现状,并指出时间频率专业今后的发展方向。     

夹芯的典型参数对夹层板受迫振动影响分析

根据伽辽金法,用Matlab/Simulink软件对推导的经典板假设理论、一阶剪切理论蜂窝夹层板运动方程进行了数值仿真。简单算例的计算结果表明两者基本一致。基于一阶剪切理论讨论了蜂窝夹芯泊松比对蜂窝夹层板低阶频率的影响。发现当泊松比接近1时对频率响应有显著的影响。     

吸气式脉冲爆震发动机壁温试验

为了探索各频率下管壁温度随时间的变化趋势及爆震管外壁面的温度分布规律,对爆震室内径68mm,长2 000mm,以汽油为燃料、空气为氧化剂的吸气式脉冲爆震发动机进行试验,用热成像仪对稳定工作在10Hz,20Hz,40Hz下的管壁温度进行了监测。结果表明:同一频率下随时间的增加壁面温度增加速度减小;热平衡时壁面温度随频率的增加而增长,10Hz,20Hz,40Hz热平衡时外壁面最高温度分别在726℃,1011.5℃,1159.5℃以上;热平衡前管壁温度的增长速度随频率的增加而增加,管壁温度的增长速度跟频率约成正比;爆震室上沿着压缩波叠加至形成爆震的方向,温度在外壁面上递增分布,在爆震形成区温度最高,从爆震形成区到发动机出口处,温度在外壁面上逐渐降低;各频率下最高温度区位置基本不变,距点火位置1 350mm左右;同一轴向位置上的外壁面温度随频率的增加而增加,温度的增长幅度随频率的增加而减小。     

改善铷原子钟物理部分温度系数的研究

铷原子钟的温度系数是决定其长期频率稳定度的关键因素,物理部分的温度系数又是铷原子钟温度系数的重要组成部分.为了改善物理部分的温度系数,在理论分析的基础上开展了试验研究,结果表明:提出的改善物理部分温度系数的措施是有效的.这对于进一步提高星载铷原子钟频率稳定度具有积极作用.