A Big-data Inspired Precision Improvement Algorithm for Autonomous Navigation Based on Period Variable Stars

Periodic variable navigation can realize the integration of positioning, attitude determination, timing and other functions. As a novel autonomous navigation method, autonomous management and autonomous operation of spacecraft are the main direction of great significance to reduce the burden of ground measurement and control, to improve the viability of spacecraft, While, the precision of the navigation is very critical for the use of periodic variable navigation for the long range spacecraft. So, we propose a big-data inspired precision improvement algorithm in this paper. Period variable star phase time measurement is used as observation information, and accomplished by the orbital dynamics equation of spacecraft motion. According to the gathering of the sampling data and the sensor data, a self-learning system is trained with the parameters from the nonlinear filtering methods. Based on the Unscented Kalman Filtering, an autonomous navigation algorithm of period variable star is established to realize the navigation and positioning of spacecraft. Under the measurement conditions of a single sampling interval of 0.01s and the measurement precision of period variable star phase observation time of 10^??5s, It can be find that the navigation position determination precision can reach 400m, the speed determination precision can reach 0.3m/s, and the measurement precision can reach 10^??5s with our proposed algorithm.

     

高精度瞄准镜零位走动量检测研究

为了解决高精度瞄准镜性能检测难点——检测各种环境试验条件下的零位走动量,设计了基于CCD图像检测技术的测试系统,该系统通过对高精度瞄准镜连接座上定位点试验前后位置测量,获得定位点位置差量,依据位置差量调整枪镜固定基座,使瞄准镜的连接座上的定位点复原至试验前位置,进而测量、计算出零位走动。通过对平行光管、CCD光学系统焦距的计算和系统精度分析,并经实际工程应用可知,测量精度不大于2.16",测量范围不小于4320",达到检测指标要求。结果表明,该测试系统检测方法正确可靠、检测精度高,为高精度瞄具零位走动的检测提供了方法。     

机载稳瞄系统稳定精度与视距关系的研究

直升机在飞行过程中由于发动机和旋翼的强烈振动给机载稳瞄系统带来强烈扰动,严重影响光电系统的作用距离。在稳瞄系统伺服控制的补偿下,残余的扰动量可以用稳定精度来表示,稳定精度所表示的残余扰动量对视距的影响仍然不可忽视。稳定精度和作用距离是机载稳瞄系统的关键技术指标,找到稳定精度与作用距离之间的关系是机载稳瞄系统设计的关键。本文基于红外系统作用距离计算的原理,建立红外成像系统动态调制传递函数和动态最小可分辨温差的数学模型,并设计一套实验装置和实验方法,通过实验模拟直升机载稳瞄系统的扰动状态,测试红外成像系统的动态最小可分辨温差,根据最小可分辨温差曲线计算不同扰动量下红外成像系统的作用距离,最后分析出机载稳瞄系统稳定精度与作用距离之间的关系,为机载稳瞄系统稳定精度的设计奠定了坚实的理论基础。     

采用天线组阵辅助的连线干涉测量载波相位解模糊

针对航天器初始轨道精度无法满足连线干涉测量（CEI）载波相位解模糊需求的问题,提出了一种采用短基线天线阵辅助的解模糊方法。从理论上分析了载波相位模糊产生的原因以及不同方向角、不同基线长度条件下解模糊对轨道预报精度的最低要求,对具有代表性的1 km短基线天线阵在主站测距加两基线方向角（Rlm）体制下的定位精度进行了仿真,结果表明,方向角越大,该方法的无模糊基线长度扩展能力越强。最后给出了达到最优测角精度的基线长度设置和解模糊流程。     

The AMPTE UKS Three-Dimensional Ion Experiment

This instrument measures the three-dimensional (3-D) distribution function of positive ions at the UKS. Novel electrostatic analyzers using 2600 turning angle cover all viewing angles as the spacecraft rotates. The instrument has sufficient resolution to measure the solar wind as well as giving full 3-D coverage within a spin period. The operation of the experiment and organization of the data are synchronized to the spacecraft spin. A sample of the real-time data showing magnetospheric boundary crossings is presented.     

基于Opencv的运动目标的检测和跟踪

检测运动物体需要无运动物体的背景图像,所以,首先应用多帧像素平均值法提取了运动视频序列的背景图,从背景图像中分离目标像素,获取目标的质心坐标,并应用质心跟踪法以灰色图像序列为基础,对运动的目标进行实时检测和跟踪。质心跟踪法的目标位置通过质点的中心来确定,该算法计算简单,计算量小,其稳定性与精度主要取决于序列图像的分割及其阀值的确定情况。文中给出了用Opencv实现算法的具体过程和关键代码,并且设计了跟踪运动车辆的控制界面,方便了实时监控。实验结果表明,该方法可以实现视频序列中运动目标的识别,具有实时性、并能给出较好的识别效果。     

MEMS惯性测量单元航姿更新中的测量误差估算方法

利用MEMS惯性测量单元测量载体的航姿,需要借助精密转台且较难精确估算测量误差,导致成本高误差大.针对该问题,该文利用卡尔曼滤波器在线估算载体的姿态和陀螺仪的偏置,提出一种优化航姿精度的测量误差估算方法.通过推导测量误差的数学模型,分析航姿精度随测量误差变化的关系,得到最优航姿时的测量误差值.采用一种MEMS惯性测量单...     

Statistical study of the influence of building architectural properties on scattered fields in urban environment

Statistical studies on the reflection coefficient of concrete–glass building facades are conducted using a fast and an accurate method based on the Green’s functions. The variation of different architectural parameters, such as concrete permitting and distribution, size and type of windows, are studied. The influence of selected parameters on the total reflection coefficient of the building is quantified for different incidence and observation angles as well as in different diffraction zones.     

Satellite-to-Satellite Range-Rate Measurement

The measurement of range rate between two low-orbiting spacecraft with a precision of better than 1 ?m/s provides a means for sensing global gravity variability. An analysis is given to show the conditions under which this precision can be realized, with emphasis on the requirements of NASA's Geopotential Research Mission. Experimental results obtained with a millimeter-wave demonstration system are presented along with a proposed design for a spaceborne instrument.     

Modeling of nonreciprocal six-pole transformer based on helicon resonator

A model of a six-pole nonreciprocal transformer representing a helicon resonator with three inductance coils placed at 120° angles is discussed. Calculations of transformer’s inductive parameters and scattering matrix components are presented. It is shown that such a transformer appears to be a nonreciprocal Y-circulator.     

基于分布式网络的航天器真空热试验控制系统

传统的航天器真空热试验控制系统采用集中控制模式,系统精确度和可靠性较低,无法满足新型航天器的研制需求.为此设计了一套基于分布式网络、具备高可靠性和高控制精确度的控制系统.该控制系统所有终端均遵循以太网传输控制协议/因特网互联协议,以实现分布式的网络通信,并采用航天产品可靠性设计原则;同时在系统设计中采用增量式数字比例积分微分(PID)控制算法,运用模糊数学的基本理论和方法,设计了一种模糊自适应PID控制算法.控制系统中运用了数字信号处理技术,以保证控制能力的实现.经相关测试表明,该控制系统控制精确度高,动态特性良好,抗干扰能力强,可满足新型航天器研制需求.     

The AMPTE CCE Magnetic Field Experiment

The AMPTE CCE spacecraft carries a high-resolution Magnetic Field Experiment for the operational purpose of determining spacecraft attitude and to fulfill the scientific objectives of providing magnetic-field measurements necessary for the determination of particle pitch angles, identification of geospace boundaries, measurement of geomagnetic activity, and the study of magnetospheric current systems and plasma processes. This experiment includes a fluxgate-magnetometer system with the sensors mounted on a 2.3-m boom to reduce spacecraft-related measurement errors. Te experiment has 7 automatically switchable ranges from ±16 to ±65 536 nT (full scale) and resolutions commensurate with a 13-bit A/D converter in each range (±0.002-±8 nT). Approximately 8.6 vector-samples/s are acquired, with information on fluctuating fields in the 5-50-Hz range provided by a system of filters and peak detectors. This instrument was operated from the time of the launch of the CCE spacecraft and is presently working in all modes as designed. The details of this experiment and early data are presented in this paper.     

基于改进广义回归神经网络和主成分分析的宽带DOA估计

为了获取较高的宽带信号的DOA(direction-of-arrival)估计精度,提出了基于改进的广义回归神经网络(IGRNN,improved generalized regression neural network)和主成分分析(PCA,principalcomponent analysis)的宽带DOA估计算法。选用PCA方法对训练样本进行降维,以降低神经网络的复杂度;利用粒子群算法优化GRNN的参数;根据选取不同的聚焦角度确定粗估计、精估计的训练模型,通过粗估计得出目标的大致方位后,利用精估计模型得出最终的估计结果,避免了聚焦角度对估计精度的影响。仿真结果表明,本文提出的算法具有较好的估计精度和较高的工作效率。     

航天器-测站迭代测量技术研究

针对星地测控网测量控制与数据传输相结合的特点,提出航天器-测站迭代的测量技术以提高航天器测量精度。基于对星地测控网模型的研究和相关测量误差的分析,详细说明星站迭代测量原理和全网迭代测量流程,采用计算仿真实验检验迭代测量效果。实验结果表明,采用迭代测量技术,将直接测量结果精度提高约55%。     

高空平台不稳定对平台间光通信性能的影响及抑制

考虑晃动对平台间光通信的影响,结合Γ大气扰动模型,推导出平台间光通信的误码率表达式,进一步分析平台晃动条件下平台间光通信捕获、跟踪和瞄准(APT)系统的设计要求。结果表明,发送端偏转和接收端的垂直运动对平台间光通信性能影响较大,而接收端偏转和发送端的水平运动对平台间光通信性能影响较小;满足平台间光通信误码率小于10-6的APT系统瞄准精度应低于50μrad。     

高精度微光学器件激光直写光刻系统研究

设计一套高精度激光直写光刻系统,它采用带17位增量式编码器的松下MINAS A系列交流伺服马达,同时还采用基于高精密滚珠丝杆和超精密线性滑轨导向的x-y运动平台,可以实现约30 nm的运动控制灵敏度。针对该系统开发一套基于ISA总线的三维运动控制卡。实验表明该激光直写光刻系统完全能够满足光刻精度的要求,并且具有控制简单、行程轨迹精确等特点,适用于许多微光学器件加工领域。     

基于粒子群算法复合型磁靶结构参数优化调整

通电线圈与永磁体复合型磁靶需要确定的结构参数类别较多,如果不采用有效的优化算法加以优化调整,很难通过经验设定来达到理想的磁场模拟精度。为了解决这一问题,提出了一种基于粒子群算法的复合型磁靶结构参数优化调整方法,该方法将电流参数、永磁体大小、区段间距、区段的长度同时进行优化,并通过一仿真算例验证了方法的有效性。     

基于时间-距离像的弹道目标进动特征提取新方法

进动是弹道目标最常见的微动形式,进动特征的差异为雷达识别真实弹头和诱饵提供了一种新的途径。针对弹道目标的进动特性,推导了弹道目标上任意一散射点的进动径向距离变化数学模型。通过分析散射点一维距离像随时间变化的规律,提出了一种基于时间-距离像的弹道目标进动特征提取新方法。该方法首先从弹道目标时间-距离像信号中准确提取出所有强散射点径向距离变化的线性和信号,进而通过分析这一信号的频谱特性,估计出了弹道目标的自旋、锥旋频率及进动角。计算机仿真结果表明:该方法具有很高的估计精度和良好的抗噪性。      

基于标校经纬仪的测量船坞内标校新方法

光轴漂移和惯性导航设备惯性元件更新维护,是船载无线电测量设备测量精度逐渐下降的主要原因。为此,提出了一种标校新方法,以标校经纬仪测量数据为基准,在甲板系中标定无线电测量设备零位和轴系误差,同时通过坐标系取齐达到消除惯导姿态测量误差的目的。分析表明,该方法完全满足无线电测量设备标校精度要求,具有简便、经济、高效等优点,是保持和提高测量船测量精度的有效途径。     

Hydrophilic and Antimicrobial Zeolite Coatings for Gravity‐Independent Water Separation

Condensing heat exchangers onboard manned spacecraft require hydrophilic fin surfaces to facilitate wetting and wicking of condensate to achieve gravity‐independent water separation in the zero‐ or micro‐gravity environment of space. In order to prevent the proliferation of microbes, the coating must also be biocidal. Here we show for the first time that zeolite A and ZSM‐5 coatings deposited via in‐situ crystallization on stainless steel and aluminum alloys have excellent hydrophilicity, biocidal properties, and adhesion. Water contact angles below 5° were obtained on most substrates tested. When silver‐ion exchange is carried out on the zeolite A coating, it becomes highly antibacterial. This biocidal capability of zeolite A is regenerative by repeated ion exchange. All coatings exhibit the highest rating of 5B as determined by adhesion test ASTM D‐3359‐02 (American Society for Testing and Materials). These properties, in addition to zeolite coating's low‐temperature crystallization process and demonstrated corrosion resistance, make zeolite coatings advantageous over the current sol–gel coatings and well suited for use in condensing heat exchangers onboard manned spacecraft.