GPS/INS组合系统空中对准方法研究

针对单天线的GPS与捷联惯性导航组合系统,提出了一种空中对准方案,不同于传统的传递对准方法,仅依靠GPS测量信息进行速度匹配,完成空中初始对准。该方案采用扩展卡尔曼滤波方法解决对准过程中的非线性问题。仿真结果表明该方案的对准精度(1σ)可以达到水平姿态误差0.07,°方位误差0.3°。     

多模自适应目标图像跟踪

本文建立了图像序列中含加性和乘性两种噪声模型影响下的目标偏移值测量模型。并针对目标机动性，采用多模虑波器和两段卡尔曼虑波器对目标状态进行估值，有效抑制了各种噪声影响，又消除了显式的目标机动性检测，且有较高的实时性和较少的存储量等优点。     

基于绝对速度测量计的自主导航探讨

对用激光原理进行绝对速度测量和由它实现自主导航的概念进行了探讨。利用3个陀螺仪和3个激光测速计按直角坐标方式配置,即可组成基于绝对速度测量计的捷联式惯性测量组合。这种方法的优点是简化计算和有利于提高精度。     

冷热两股气流在圆管内掺混的速度场、温度场与辐射通量场的数值方法

用数值方法求解冷热两股轴对称平行射流在圆管内掺混的流场、温度场和辐射通量场。计算采用一种通用性的数值方法,其特点是强烈地以物理本质为基础,而不仅仅是单纯的数学推导。这样做,能方便地分析和解释计算结果,使之更真实地接近于实际。 通过计算,分析了当引射系数改变时,掺混的流场,温度场和辐射通量场的变化规律,其结果与实验数据比较一致。     

月球探测器转移轨道的特性分析

主要分析了月球探测器由近地点出发，在假定末端条件不变的情况下，其转移轨道的特性参数对初始条件和变轨所需的速度脉冲等的影响；考虑的特性参数的变化包括转移轨道倾角的变化，近地点高度的变化和转移时间的不同．     

Application of small-size antennas for estimation of angles of arrival of HF signals scattered by ionospheric irregularities

A modification of the Doppler Interferometry Technique is suggested to enable estimating angles of arrival of comparatively broadband HF signals scattered by random irregularities of the ionospheric plasma with the use of small-size weakly directional antennas. The technique is based on the measurements of cross-spectra phases of the probe radiation recorded at least in three spatially separated points. The developed algorithm has been used to investigate the angular and frequency-time characteristics of HF signals propagating at frequencies above the maximum usable one (MUF) for the direct radio path Moscow-Kharkiv. The received signal spectra show presence of three families of spatial components attributed, respectively, to scattering by plasma irregularities near the middle point of the radio path, ground backscatter signals and scattering of the sounding signals by the intense plasma turbulence associated with auroral activations. It has been shown that the regions responsible for the formation of the third family components are located well inside the auroral oval. The drift velocity and direction of the auroral ionosphere plasma have been determined. The obtained estimates are consistent with the classical conception of the ionospheric plasma convection at high latitudes and do not contradict the results of investigations of the auroral ionosphere dynamics using the SuperDARN network.     

非开普勒轨道下卫星交会变轨决策研究

针对卫星在非开普勒轨道下的运动特征,提出了研究卫星交会变轨决策的方法。首先,在Hill坐标下,采用比例导引方法求解卫星进行变轨机动时所需要的速度增量。然后,再通过Lagrange插值算法解出卫星在任意特征点上变轨机动所需要的速度增量,根据数字仿真得出大量的仿真数据并画出满足变轨决策条件的决策曲面。最后,对决策曲面的涵义做出分析,说明了该方法对于研究非开普勒轨道下卫星变轨决策问题具有一定的意义。     

锥运动条件下新的速度误差补偿项研究

经典的捷联惯导积分算法往往需要在姿态更新过程中对圆锥误差项进行精确补偿。虽然考虑了载体姿态变化的影响,但速度更新算法通常忽略了圆锥效应的作用。就圆锥误差项引起的速度误差进行了研究。指出其与陀螺角增量对速度更新的影响方式相同。在假设的线性斜坡模型条件下,利用两个连续的角增量和比力增量,详细推导了新的速度误差项的二子样更新补偿算法。在一种特殊的机动条件下,即当载体绕横轴作圆锥角振动的同时又沿立轴作同频同相的线振动,推导的二子样优化算法能够使该误差补偿项的平均性能最优。仿真结果证明该优化算法能够对新的速度误差积分项进行有效的补偿。     

测速雷达信标测量数据复原新方法

给出了一种测速雷达信标测量多普勒频率复原的新方法,此方法与目标运动的初始轨道参数无关。与已有方法相比较,新方法解决了已有数据复原方法对初始轨道参数的依赖性,理论上消除了初始轨道参数精度对数据复原精度的影响。通过与已有方法计算结果的比对分析表明,新方法能够满足数据处理精度要求,具有较好的适用性,是实现信标测量数据复原的有效途径。     

Vertical shear at the equatorial F-region ionosphere during post-sunset hours

The characteristics of the equatorial F-region zonal plasma drift during post-sunset period have been investigated using the multi-frequency HF Doppler radar. The pattern of the zonal plasma drift is such that it starts with a westward drift during the pre-sunset hours, followed by an eastward drift shortly after the E-region sunset. The zonal plasma drift is characterized by the presence of a positive vertical shear around the post-sunset period and maximum shear is observed at the time of the peak of the pre-reversal enhancement in the vertical drift. The presence of vertical shear in the zonal drift is associated with the post-sunset velocity vortex existing at the equatorial F-region.