基于PSD的并联微定位平台位姿检测方法

位置姿态（以下简称位姿）检测是研究六自由度定位平台的技术难点之一,为了快速准确测量六自由度并联微定位平台的位姿,验证平台的定位精度,基于多片二维PSD光电位置传感器设计了六自由度光学位姿检测系统。依据几何光学理论,建立了六自由度位姿解算的数学模型。通过仿真计算,该算法可以快速准确解算六自由度定位平台位姿。进一步分析了该模型在考虑存在测量误差时的理论计算误差,结果表明,基于二维PSD位置传感器的六自由度光学位姿检测系统在解算六自由度定位平台位姿的同时,具备较高的测量精度。     

高动态“北斗”双频载波相位差分工程化方法

针对北斗卫星导航系统提出了一种相对定位选星策略,分析了几种双频组合的方法及适用范围,给出了一种利用BI和B3频率进行双频载波相位差分的方法,讨论了算法在工程应用中的一些问题。最后利用北斗信号源输出验证了高动态轨道双频载波相位差分方法。     

基于增强型单频GPS的高精度星间相对定位样条方法

为了实现高精度的分布式SAR星间相对定位,提出了一种基于增强型单频GPS的相对定位样条方法,即在单频GPS测量信息的基础上,增加星间距离观测信息,并结合相对位置参数的连续特性,建立了相对定位的样条模型,最后利用最小二乘法进行参数估计.仿真结果表明,新方法不仅能大大提高相对定位精度,而且还能有效地减少固定整周模糊度所需的历元.最后的理论分析证明了仿真的正确性.      

空间目标纯测角相对定位方法

探讨了利用多个传感器上同步收集的角度观测信息,使用带有差分-自校准方法的推广卡尔曼滤波器来进行空间目标相对定位的可行性。仿真结果表明该方法实时性强,收敛速度快,误差估计精确,具有很好的应用前景。     

基于载波相位三差的航天器GPS/INS组合定姿算法

研究了一种利用GPS载波相位三差观测信息的多天线GPS/INS组合定姿算法,其中包含一个基于惯性测量信息的GPS载波相位周跳检测算法。最后,通过仿真分析验证了该组合算法可以有效提高定姿精度,同时具有较好的稳定性。     

民航GPS地基区域完好性监视系统设计与实现

结合中国地域和空中交通流量分布的特点,提出了中国民航全球卫星定位系统GPS(Global Positioning System)地基区域完好性监视系统GRIMS(Ground-based Regional Integrity Monitoring System)的概念.一个包含7个监测站的地面监测网监测视界内的GPS卫星,判断其可用状况,并将判断结果和重要的监测数据发送到主控站.主控站计算中国范围内的接收机自主完好性监测RAIM(Receiver Autonomous Integrity Monitoring)空洞,同时推算全国民航飞机的实时位置,并向所有位于RAIM空洞中的飞机及时发送完好性告警信息.从卫星出现故障到飞机收到告警信息之间的告警延迟小于7s.该系统已经应用于中国民航,在保证飞行安全的同时提高了飞行效率.      

一种组合导航系统快速滤波方法及半物理仿真

在利用卡尔曼滤波器对数据进行处理时,协方差矩阵的预报运算过程需要的计算量最大,每一步迭代的计算量与n3(n为状态矢量维数)成正比,约占整个卡尔曼滤波过程70%的CPU时间.协方差阵预报计算过程中,数据输入输出所需要的传递工作量也最大.由于微小型飞行器导航系统采用小体积、低功耗、低成本的微处理器作为导航计算机,为了保证导航实时性的要求,提出了一种降维滤波器加矩阵外积法的快速滤波方法来减少MIMU(Micro Inertial Measurement Unit)/GPS(Global Positioning System)/MMC(Micro Magnetic Compass)组合导航滤波算法的计算量,以提高算法的实时性.半物理仿真试验结果表明:此种算法不仅可以提供较为满意的导航精度,而且大大减小了计算量,提高了系统的实时性.      

嫦娥三号巡视器的惯导与视觉组合定姿定位

针对“嫦娥三号”的“玉兔号”巡视器在月面未知环境中避障与安全行进的要求,分析和阐述了“玉兔号”巡视器在地面遥操作中心的控制下利用惯导和视觉组合进行月面导航与精确定位的实现方法,并结合现有的导航定位研究对“玉兔号”巡视器导航与定位的工程创新性进行了总结,阐明了惯导定位和视觉定位技术在“玉兔号”巡视器月面探测过程中的工程应用特点.最后,通过“玉兔号”巡视器着月点的精确定位实验,验证惯导和视觉相结合的定位方法的有效性,定位精度近似达到总行驶里程的1％,这对“玉兔号”巡视器开展月面探索和准确抵达科学目标位置具有重要作用.     

Inhibitory effect of simulated microgravity on differentiating preosteoblasts

The bone loss induced by microgravity is partly due to the decrease of mature osteoblasts. In the present study, we employed the random positioning machine (RPM) to simulate microgravity and investigated the acute effects of simulated microgravity on the differentiation of 2T3 preosteoblasts. Following 7 days’ culture under normal (1 g) condition, cells were exposed to simulated microgravity for 24 h. The results showed that 24 h treatment of simulated microgravity significantly decreased alkaline phosphatase (ALP) activity without changing the cell morphology. In addition, the mRNA expressions of osteogenic genes, including runt-related gene 2 (Runx2), osterix, osteocalcin (OC), type I collagen (Col I) and bone morphogenetic protein (BMP), were dramatically downregulated. Moreover, western blot analysis of total extracellular signal-regulated kinase (Erk) and phosphorylated Erk (p-Erk) indicated that p-Erk level, which represents the Erk activation status, was increased. Taken together, our results suggested that acute exposure to simulated microgravity inhibited osteoblast differentiation through modulating the expression of osteogenic genes and the Erk activity. These findings provide new insight for bone loss due to microgravity and unloading.     

GLONASS-based precise point positioning and performance analysis

Current precise point positioning (PPP) techniques are mainly based on GPS which has been extensively investigated. With the increase of available GLONASS satellites during its revitalization, GLONASS observations were increasingly integrated into GPS-based PPP. Now that GLONASS has reached its full constellation, there will be a wide interest in PPP systems based on only GLONASS since it provides a PPP implementation independent of GPS. An investigation of GLONASS-based PPP will also help the development of GPS and GLONASS combined PPP techniques for improved precision and reliability. This paper presents an observation model for GLONASS-based PPP in which the GLONASS hardware delay biases are addressed. In view of frequently changed frequency channel number (FCN) for GLONASS satellites, an algorithm has been developed to compute the FCN for GLONASS satellites using code and phase observations, which avoids the need to provide the GLONASS frequency channel information during data processing. The observation residuals from GLONASS-based PPP are analyzed and compared to those from GPS-based PPP. The performance of GLONASS-based PPP is assessed using data from 15 globally distributed stations.