声表面波色散延时线激励的高精度时间间隔测量方法

高精度时间间隔测量技术对国民经济与国防建设意义重大,论述了一种新的高精度时间间隔测量方法,可以达到1ps量级甚至更高的测量精度。该方法利用声表面波色散延迟线作为时间内插器,时间内插器起到时间拉伸的作用,从而可以获得多个观测值,由于平均的效果,总的测量误差将被大大降低。理论分析与仿真实验均表明该方法可以达到很高的时间测量精度,是切实可行的。     

Kalman滤波的铷原子钟控制算法

以GPS接收机输出的1pps信号为参考信号,采用Kalman滤波算法对铷原子钟的参数进行估计,计算铷原子钟的频率调整量,对铷原子钟进行调整,使其和UTC时间保持同步。实验结果表明,受驯铷原子钟输出1pps与UTC（NTSC）钟差的标准差优于3.5 ns,钟差峰峰值优于15 ns,100 s采样的Allan方差为1.83×10 -12 ,10000 s采样的Allan方差为6.1×10 -13 。实验证明了基于Kalman滤波的铷原子钟控制算法,使铷钟获得了较好的准确性和长期稳定性,且对其短期稳定性影响最小,是一种可靠稳定的铷钟控制方法。     

高分辨率多径时延测量算法

提出一种基于最小二乘准则的高分辨率多径信号时延测量方法。对参考信号作三阶样条插值获得每条多径信号最小二乘意义的最优估计,用每条多径信号的测量值重构接收信号,通过反复迭代使重构信号是接收信号最小二乘意义的最优估计,实现多径信号的时延测量。仿真结果表明：新算法在低信噪比、窄带信号条件下仍能获得较高的时延测量精度,性能优于MUSIC类时差测量算法。     

基于3D Zernike矩的巡检器与空间站的相对导航算法

针对航天器相对导航问题,以空间站表面为"特殊地形",提出一种基于大型航天器表面巡检的相对导航算法。首先,运用巡检飞行器上的TOF （Time of Flight）相机测量空间站表面局部点云数据,以该点云数据为实时图,以空间站表面先验点云数据为基准图。然后,利用3D Zernike矩与三维地形间的一一对应关系,将三维地形匹配转化为基于3D Zernike矩的特征向量匹配。在此基础上求解实时图与匹配上的基准图间的相对位置、相对姿态,从而确定两航天器间的相对导航参数,并通过实验分析了匹配精度及速度的主要影响因素。最后,将该相对导航参数与惯性系统推算的相对导航参数在扩展卡尔曼滤波器的框架下实现信息融合,估计了巡检飞行器与空间站间的相对位置、相对姿态,实验结果表明,相对位置精度优于0.002 m,相对姿态精度优于0.1°。     

载人飞船回收着陆半实物仿真系统关键技术研究

载人飞船回收着陆半实物仿真系统是通过模拟飞船返回压力环境,将回收程控装置硬件实物接入仿真回路的一个半实物仿真试验平台。文章简要介绍了该半实物仿真系统的结构,重点叙述了该半实物仿真系统中特有的负压高精度快速调节压力模拟、多通路指令信号处理、混合式网络、多阶段动力学仿真框架等关键技术。     

基于特征空间变换的运载火箭Pogo模型降阶方法

针对运载火箭Pogo状态空间模型存在维数高和奇异性的问题,开展了 Pogo模型的降阶方法研究.基于特征空间变换理论,导出了一般形式的Pogo状态空间模型的解耦形式.该形式与推进系统和结构系统的模态频率相对应,从而通过模态截断或保留感兴趣的模态实现有效的模型降阶.同时,还给出了降阶方法的实数运算公式.在两种不同型号推进系...     

基于北斗三号的多区域实时动态授时服务系统

面向新一代移动通信和物联网等领域对高精度、低成本授时的需求,针对典型的实时动态授时服务只能单区域覆盖的问题,提出了一种基于北斗的多区域实时动态精密授时服务系统.该系统由标准时间、时间基准站、高精度时间频率实时传递链路、数据中心和时间用户等部分组成,可实现标准时间实时动态授时服务的全国多区域覆盖.依托中国科学院国家授时中...     

Predicting lean blow-off of bluffbody stabilized flames based on Damköhler number

Lean Blow-Off(LBO) prediction is important to propulsion system design. In this paper,a hybrid method combining numerical simulation and Da(Damk?hler) model is proposed based on bluffbody stabilized flames. In the simulated reacting flow, Practical Reaction Zone(PRZ) is built based on OH radical concentration, and it is considered to be the critical zone that controls LBO.Da number is obtained based on the volume-averaged parameters of PRZ. The flow time scale(s_f)indicates the residence time of the fresh mixture flowing through the PRZ. It is obtained based on the characteristic length and volume-averaged axial velocity of the PRZ. The chemical time scale(s_c) indicates the shortest time needed to trigger the reaction of the mixture. It is obtained by commercial software CHEMKIN through monitoring the transient variation of the reactor temperature. The result shows that the average Da number under different LBO conditions is 1.135(the Da number under each LBO condition ranges from 0.673 to 1.351). This indicates that the flow time scale and chemical time scale are comparable. The combustion is in a critical state where LBO is easy to occur. With the increase of the fuel mass flow rate(the global fuel/air ratio increases from 0.004761 to 0.01095), s_f increases from 0.001268 s to 0.007249 s, and s_c decreases from 0.00124 s to0.00089 s. Accordingly, Da number increases from 1.023 to 8.145, which shows that the combustion becomes more stable. The above results show that the method proposed in the present study can properly predict the LBO limits of combustors, which provides important technical supports for combustor design and optimization.     

Object-based rice mapping using time-series and phenological data

Remote sensing techniques are often used in mapping rice, but high quality time-series remote sensing data are difficult to obtain due to the cloudy weather of rice growing areas and long satellite revisit interval. As such, rice mapping is usually based on mono-temporal Landsat TM/ETM+ data, which have large uncertainties due to the spectral similarity of different vegetation types. Moreover, conventional pixel-based classification method is unable to meet the required accuracy for rice mapping. Therefore, this study proposes a new strategy for mapping rice in cloud-prone areas using fused data of Landsat-8 OLI time-series and phenological parameters, based on the object-based method. We determine the critical growth stages of paddy rice from observed phenological data and MODIS-NDVI time-series data. The spatial and temporal adaptive reflectance fusion model (STARFM) is used to blend the MODIS and Landsat data to obtain a multi-temporal Landsat-like dataset for classification. Finally, an object-oriented algorithm is used to extract rice paddies from the Landsat-like, time-series dataset. The validation experiments show that the proposed method can provide high accuracy rice mapping, with an overall accuracy of 92.38% and a kappa coefficient of 0.85.     

反向喷管堵盖释放时间及同步性测量

研究了固体火箭发动机推力终止试验时，反向喷管堵盖打开时间及同步性测量方法，在测量中配置了抗干扰能力强，时间分辨率为微秒级的数字记录系统和多功能模拟记录系统，解决了时间测量中产生和获取起始脉中肯主终止脉主号的关键技术，消除了引爆机的产生的冲击和气体电离的影响，该测量方法经过多次充气容器冷试和发动机地面静止试验的考核，证实了测出的数据准确可靠，克服了时间测量数据分散度大的缺点。