Codes cross-correlation analysis and data/pilot code pairs optimization for Galileo E1 OS and GPS L1C

The Galileo E1 open service (OS) and the global positioning system (GPS) L1C are intending to use the multiplexed binary offset carrier (MBOC) modulation in E1/L1 band, including both pilot and data components. The impact of data and pilot codes cross-correlation on the distortion of the discriminator function (i.e., the S-curve) is investigated, when only the pilot (or data) components of MBOC signals are tracked. It is shown that the modulation schemes and the receiver configuration (e.g., the correlator spacing) strongly affect the S-curve bias. In this paper, two methods are proposed to optimize the data/pilot code pairs of Galileo E1 OS and GPS L1C. The optimization goal is to obtain the minimum average S-curve bias when tracking only the pilot components a the specific correlator spacing. Figures of merit, such as S-curve bias, correlation loss and code tracking variance have been adopted for analyzing and comparing the un-optimized and optimized code pairs. Simulation results show that the optimized data/pilot code pairs could significantly mitigate the intra-channel codes cross-correlation, and then improve the code tracking performance of MBOC signals.     

基于FPGA和DSP的高性能伺服控制器设计

针对高性能伺服控制器对复杂的控制算法以及较小延时的需求,研究了一种基于FPGA和DSP的高性能伺服控制器设计方法。FPGA完成电流环、坐标变换、空间脉宽矢量调制、电流位置读取,DSP则负责速度环、位置环和上位机通信,使系统既能实现复杂的控制算法,又能将延时控制到最小,从而保证控制器的最佳性能。此外,详细介绍了两者之间的通信方式以及三环控制器设计。试验数据结果表明,伺服控制器速度环带宽能达到100 Hz,额定转速下稳速精度在1 r/min以内,定位精度能达到0.02°,证实了该控制器结构的实效性。     

GPS/BDS/INS tightly coupled integration accuracy improvement using an improved adaptive interacting multiple model with classified measurement update

An Extended Kalman Filter (EKF) is commonly used to fuse raw Global Navigation Satellite System (GNSS) measurements and Inertial Navigation System (INS) derived measurements. However, the Conventional EKF (CEKF) suffers the problem for which the uncertainty of the statistical properties to dynamic and measurement models will degrade the performance. In this research, an Adaptive Interacting Multiple Model (AIMM) filter is developed to enhance performance. The soft-switching property of Interacting Multiple Model (IMM) algorithm allows the adaptation between two levels of process noise, namely lower and upper bounds of the process noise. In particular, the Sage adaptive filtering is applied to adapt the measurement covariance on line. In addition, a classified measurement update strategy is utilized, which updates the pseudorange and Doppler observations sequentially. A field experiment was conducted to validate the proposed algorithm, the pseudorange and Doppler observations from Global Positioning System (GPS) and BeiDou Navigation Satellite System (BDS) were post-processed in differential mode. The results indicate that decimeter-level positioning accuracy is achievable with AIMM for GPS/INS and GPS/BDS/INS configurations, and the position accuracy is improved by 35.8%, 34.3% and 33.9% for north, east and height components, respectively, compared to the CEKF counterpart for GPS/BDS/INS. Degraded performance for BDS/INS is obtained due to the lower precision of BDS pseudorange observations.     

基于最优传播路径的EMA/EKF定位算法研究CSCD

针对室内环境下蓝牙系统易受非视距影响,采用蓝牙到达角(AOA)解决室内行人定位存在较大偏差的问题,研究基站几何分布和定位算法对定位精度的影响。关于蓝牙信号在传播过程中易衰减及产生多径等因素影响定位性能,对基站安装位置与信号接收范围关系进行研究,建立基站分布优化模型,使用遗传算法(GA)求解基站布设最优位置。在此基础上,提出了基于改进指数移动平均(EMA)算法结合扩展卡尔曼滤波(EKF)算法进行误差补偿。实验结果表明,该方法的平均定位误差为0.89m,相较于EKF定位精度更高,证明了所提方法的有效性。     

编队飞行卫星在间断式导航、天基干涉仪和分工式工作星的可行性构想

对将编队飞行卫星应用于用户间断性三维无源自主定位导航 ,用干涉仪对敌方目标被动定位和卫星分工式工作的可行性进行初步分析对比研究 ,除指出这些构想的队形要求和优点外 ,同时也给出其缺点和存在的困难     

多传感器组合导航系统研究

设计了一种由INS、GPS和Doppler测速雷达构成的多传感器组合导航系统。采用GPS伪距、伪距率以及Doppler速度与INS组合 ,建立了其卡尔曼滤波方程 ,设计了飞行轨迹 ,给出了惯性元件精度较低时组合系统的仿真输出。仿真结果表明 ,多传感器组合导航系统能有效提高导航精度 ,降低对惯性元件的性能要求 ,是导航系统的发展方向     

卫星定位技术的新发展

围绕卫星信息源、用户接收机性能、兼容接收、差分定位、卫星状态实时诊断等方面，介绍卫星定位技术的新进展。     

一种伪卫星动态抗多径方案

为降低伪卫星(PL)增强全球卫星定位系统(GPS)的多径效应，在分析多径特点的基础上，提出了一种通过PL运动使各点的多径参数发生变化，并经过平滑处理实现抗多径的方案。最后分析了方案中采用码分多址(CDMA)、频率偏值(FDMA)和时分信号结构(TDMA)技术时的一些技术问题和解决设想。     

基于微小卫星的空间目标光学探测定位方法

为实现空间目标的天基光学观测,利用双星定位原理,采用仅测角的观测方式,结合最小二乘法建立了双星几何定位模型。考虑到星点提取作为光学定位算法中的重要一环将直接影响最终的定位精度,因而针对就星图处理部分,分析了星图的灰度特点,采用阈值分割法进行了去噪处理,选取了几种质心法对星点进行提取,利用真实星图对提取结果进行比较,选出了形心法和阈值质心法 2种较为可行的星点提取算法。通过仿真计算和蒙特卡洛误差分析结果可知,不考虑误差时,定位误差小于 10-5 m;考虑主要误差源时,定位误差小于 100 m;且姿态误差对定位方法的精度影响最大,数值上可以达到总误差的 0.9倍以上,速度误差的影响最小,只有总误差的 1/30,可以忽略;定位误差近似呈高斯分布且误差的大小与误差源近似呈线性关系。由此可见,文章所建立的定位算法可以对空间目标实现较为精确的定位。     

双星定位的三参数方法及其精度分析

研究了两颗地球同步轨道卫星 (双星 )定位的几何关系对双星定位精度的影响。设计了双星交汇角、双星俯仰角和双星视角三个参数来刻画双星交汇 ,这三个参数能够反映定位的几何关系。在此基础上得到的双站交汇精度估计算法能适应测站基线长、观测距离远等布站和观测几何关系不好的情形。最后做了仿真验证