Time synchronization of new-generation BDS satellites using inter-satellite link measurements

Autonomous satellite navigation is based on the ability of a Global Navigation Satellite System (GNSS), such as Beidou, to estimate orbits and clock parameters onboard satellites using Inter-Satellite Link (ISL) measurements instead of tracking data from a ground monitoring network. This paper focuses on the time synchronization of new-generation Beidou Navigation Satellite System (BDS) satellites equipped with an ISL payload. Two modes of Ka-band ISL measurements, Time Division Multiple Access (TDMA) mode and the continuous link mode, were used onboard these BDS satellites. Using a mathematical formulation for each measurement mode along with a derivation of the satellite clock offsets, geometric ranges from the dual one-way measurements were introduced. Then, pseudoranges and clock offsets were evaluated for the new-generation BDS satellites. The evaluation shows that the ranging accuracies of TDMA ISL and the continuous link are approximately 4?cm and 1?cm (root mean square, RMS), respectively. Both lead to ISL clock offset residuals of less than 0.3?ns (RMS). For further validation, time synchronization between these satellites to a ground control station keeping the systematic time in BDT was conducted using L-band Two-way Satellite Time Frequency Transfer (TWSTFT). System errors in the ISL measurements were calibrated by comparing the derived clock offsets with the TWSTFT. The standard deviations of the estimated ISL system errors are less than 0.3?ns, and the calibrated ISL clock parameters are consistent with that of the L-band TWSTFT. For the regional BDS network, the addition of ISL measurements for medium orbit (MEO) BDS satellites increased the clock tracking coverage by more than 40% for each orbital revolution. As a result, the clock predicting error for the satellite M1S was improved from 3.59 to 0.86?ns (RMS), and the predicting error of the satellite M2S was improved from 1.94 to 0.57?ns (RMS), which is a significant improvement by a factor of 3–4.     

基于CBR和RBR的航天测控设备故障诊断专家系统

采用CBR和RBR混合推理设计了航天测控设备故障诊断专家系统，建立了系统的层次诊断结构模型。介绍了产生式和基于案例的知识表示方法，并详述了系统所采用的基于规则和基于案例的诊断推理机制。最后，基于CLIPS和Visual C 混合编程的方法进行了系统实现，详细介绍了两种语言的嵌入设计。     

整体冲破式复合材料薄膜盖的设计与试验研究

以复合材料层合板为基本材料设计了一种结构新颖的整体冲破式复合材料薄膜盖,薄膜盖在导弹引擎产生的气流冲击下整体飞出,提高了导弹的发射效率。通过对薄弱区形式的设计分析以及基本材料的力学性能试验,确定了薄弱区结构形式;通过薄膜盖整体、局部应力分析结合相应的强度理论,确定了带薄弱区薄膜盖的设计方案;然后制作了一批实物并进行了薄膜盖冲破实验,结果表明结构设计合理,理论预测方法准确。该文所建立的方法和研究结果为这类箱盖的设计应用提供了依据。     

A fully automated framework for helicopter rotor blades design and analysis including aerodynamics,structure, and manufacturing

This study describes an integrated framework in which basic aerospace engineering aspects (performance, aerodynamics, and structure) and practical aspects (configuration visualiza-tion and manufacturing) are coupled and considered in one fully automated design optimization of rotor blades. A number of codes are developed to robustly perform estimation of helicopter config-uration from sizing, performance analysis, trim analysis, to rotor blades configuration representa-tion. These codes are then integrated with a two-dimensional airfoil analysis tool to fully design rotor blades configuration including rotor planform and airfoil shape for optimal aerodynamics in both hover and forward flights. A modular structure design methodology is developed for real-istic composite rotor blades with a sophisticated cross-sectional geometry. A D-spar cross-sectional structure is chosen as a baseline. The framework is able to analyze all realistic inner configurations including thicknesses of D-spar, skin, web, number and ply angles of layers of each composite part, and materials. A number of codes and commercial software (ANSYS, Gridgen, VABS, PreVABS, etc.) are implemented to automate the structural analysis from aerodynamic data processing to sec-tional properties and stress analysis. An integrated model for manufacturing cost estimation of composite rotor blades developed at the Aerodynamic Analysis and Design Laboratory (AADL), Aerospace Information Engineering Department, Konkuk University is integrated into the framework to provide a rapid and dynamic feedback to configuration design. The integration of three modules has constructed a framework where the size of a helicopter, aerodynamic performance analysis, structure analysis, and manufacturing cost estimation could be quickly investigated. All aspects of a rotor blade including planform, airfoil shape, and inner structure are considered in a multidisciplinary design optimization without an exception of critical configuration.     

基于PDXP协议的数据监视软件的设计实现

基于UDP（用户数据报协议）组播数据传输方式,通过对接收到数据包中相关PDXP（包数据交换协议）字段的实时解析和挖掘分析,采用BackgroundWorker（后台工作者线程）模型简化多线程交互方式,以分级缓存为基础优化数据存储结构,通过直接调用GDI（图形设备接口）＋绘图接口设计开发高效的UI（用户接口）显示控件,并且利用Linq（语言级集成查询）数据访问技术,以可视化的形式对PDXP数据包的丢包和乱序等问题进行实时判读和基于源码的分析,提供了一种对中心之间交互的数据进行实时连续性监视分析的简捷、直观和有效的途径。     

CCSDS建议在深空通信导航中的应用研究

结合深空通信导航技术的发展趋势,通过分析CCSDS(空间数据系统咨询委员会)的研究领域、应用CCS-DS建议的空间任务,梳理出与深空通信导航相关的CCSDS建议。详细论述了深空任务中射频与调制、带宽频率调制、再生伪码测距以及相对差分单向测距等技术体制的CCSDS建议内容。并重点分析了CCSDS建议对我国深空测控网建设的影响,提出了我国深空测控设备符合CCSDS标准的技术要求。     

跟飞编队卫星相对导航自适应EKF算法研究

针对跟踪星对目标星跟飞编队的相对导航问题,提出了基于自适应扩展卡尔曼滤波（EKF）的相对导航算法。以线性离散化的椭圆参考轨道相对动力学模型为导航状态方程．设计了虚拟测量量及相应的测量矩阵,避免了求解雅可比矩阵的复杂计算。为了适应构型尺寸变化引起的模型误差变化,提出了模型误差在线估计算法。仿真显示,算法具有较快的收敛速度和较高的估计精度。该研究成果可作为卫星编队应用的有益参考。     

基于Kalman滤波的SINS／GPS组合导航系统的误差分析

本文对SINS／GPS系统误差模型进行了推导,在失准角小角度情况下惯性系统误差模型的基础上提出了一种基于Kalman滤波的SINS／GPs组合导航系统的二维误差分析方法。采用工程上较易实现的松耦合的组合方式,建立了位置、速度组合导航模型,并对速度组合、位置组合、速度位置组合方式进行了仿真对比分析。     

基于天文角度观测的机载惯性/天文组合滤波算法研究

针对采用天文/惯性位置组合时对导航选星有特殊要求,提出了基于天文角度观测信息的机载惯性/天文组合滤波方案及算法.对基于天文角度观测的INS/CNS组合导航系统的原理进行了充分阐述,分析并建立了基于单星或多星观测条件下的组合导航系统线性化量测方程,并针对角度观测时高度通道不可观的特点,增加了气压高度输出为系统的观测量,并在此基础上设计了组合滤波器算法.最后进行了组合导航系统仿真,并通过协方差分析的方法对比分析了单星和双星观测条件下的滤波性能.仿真结果表明,即使是在单星观测条件下,组合导航系统也能获得较好的定位精度;若观测星数增多,则可以大大提高系统性能,表明该组合导航系统设计方案是成功可行的.     

基于导航星域和K矢量的快速星图识别算法

星图识别算法是星敏感器的关键技术,快速性和可靠性一直是对其评价的重要指标。提出了基于K矢量查找表和导航星域联合进行超快速星图识别的方法。首先根据星敏感器视场和所能敏感的星等建立全天球导航星表;再依据K矢量的原则对全天的导航星按照星对角距进行分类,建立星对角距所对应导航星的K矢量和K矢量查找表。利用星敏感器视场中的4颗星构成6组星对角距,将其中的5组星对角距所对应K矢量查找表域的星对组进行导航星表域（简称导航星域）的变换,根据另外一组星对角距所对应的K矢量查找表域的值对前面5组导航星域的值同时进行索引比较,直接找到了满足条件的4颗导航星,即完成全天的星图识别。最后,通过计算机仿真,实验室模拟和真实星空实验三个层次验证了此方法的可靠性和快速性。