基于实数编码自适应遗传算法的整周模糊度快速解算

针对整周模糊度解算中实时性不强的问题,提出了一种基于实数编码的自适应遗传算法。首先利用卡尔曼滤波求解整周模糊度的浮点解,然后采用排序和多次(逆)双乔里斯基分解对浮点解及其协方差阵进行降相关处理,降低整周模糊度各分量之间的相关性,最后利用已知基线确定模糊度搜索空间,基于实数编码,将自适应遗传算法应用在整周模糊度的搜索解算过程中,求得整周模糊度的最优解。仿真结果表明,本文算法与Lambda算法相比,耗时更少;与简单遗传算法相比,具有更强的收敛能力,是一种高效的整周模糊度快速解算方法。     

单差PPP相位偏差估计方法及有效性分析

针对常规浮点解精密单点定位收敛时间长的问题,分析了PPP模型中模糊度不具备整数性质的原因,采用方向数据统计的计算方法,以单差模糊度为研究对象,对相位偏差进行了建模估计。算例从精密单点定位单差模糊度固定、定位精度以及收敛速度等方面对相位偏差改正的有效性进行了分析,结果表明,经相位偏差改正后的PPP模糊度固定成功率、收敛速度有了明显提高,定位精度较浮点解提高了一个量级。     

星间自主相对测距中载波相位整周模糊解算方法研究

载波相位整周模糊度解算是利用载波相位进行星间无线电相对距离测量的关键。介绍编队小卫星的工作特点,针对星间相对距离实时、高精度测量的要求,详细阐述利用双频伪码和载波相位观测值解算载波整周模糊度的方法,推导伪码、载波相位测量误差与模糊度解算误差的关系,讨论降低误差的方法。计算机仿真结果表明,该方法可以在单个测量历元获得载波相位整周模糊解算,解算精度与伪码测距精度成正比关系。     

一种快速求解整周模糊度的方法

针对FARA方法搜索整周模糊度组合数比较大,LAMBDA方法需要浮点解精度比较高的缺点,提出一种求解GPS载波相位测量整周模糊度的分步法。用LAMBDA方法搜索出来的整周模糊度作为FARA方法的初始解,进而用FARA方法解算出它的最终解。实验结果表明,该方法能缩短搜索整周模糊度的时间,快速准确地确定整周模糊度。     

一种改进蚁群算法的DGPS整周模糊度求解

为了更精确地解算DGPS整周模糊度,把仿生学中的蚁群算法应用到模糊度固定解搜索环节,并在传统蚁群算法的基础上引入自反馈因子,改善了传统算法在整周模糊度解算中收敛速度慢、易于陷入局部极小的缺点.实例结果表明,在和LAMBDA算法的1000个历元对比实验中,改进蚁群算法的搜索成功率要优于LAMBDA算法,且接近百分之百,利...     

星间链路测量中的载波相位测距算法研究

运用双频伪码/载波相位组合方式求解整周模糊度的方法实现星间链路中的载波相位测距。在双频伪码/载波相位组合原理的基础上,对不同组合方式下的测量误差进行分析,并研究了增大载波频率时的载波相位测距手段。仿真结果表明,算法能得到较准确的整周模糊度值和精度较高的测距值,实现了载波相位高精度测距。     

一种GPS快速定位技术研究

用LAMBDA方法确定GPS载波相位测量的整周模糊度,需要较高精度的浮点解。但用短时间GPS观测值构建的法方程容易出现病态,以致法方程的解很不稳定。本文使用谱修正迭代法,消除法方程病态,进而用LAMBDA方法确定整周模糊度。我们的实验结果表明,对于1min左右的单频GPS载波相位测量,利用本文方法即可正确地解算出它的整周模糊度,从而实现厘米级定位。     

北斗系统整周模糊度及周跳的确定算法

在进行卫星导航定位时,利用载波相位比利用码相位进行定位拥有更好的定位精度和安全性,并可以提升用户的满意度,然而得到测相伪距的前提是明确载波相位的整周模糊度和周跳数。首先根据三频模糊度分解模型将整周模糊度解算出来;然后利用三频码伪距/载波相位组合法进行周跳数的求解;最后仿真验证了整周模糊度解算方法的正确性,并分析比较多频接收机型号的不同对卫星信号周跳值的影响。     

载波相位测量中整周模糊度的解算与仿真

对整周模糊度解算全过程进行描述并提出GPS信号受到干扰条件下确定整周模糊度的一种方法。该方法将惯导伪距作为待定点目标位置的近似值 ,代入双差相位测量方程里 ,推导出误差项 ,通过最小二乘算法得到实数解的整周模糊度 ,再分别通过快速模糊度搜索法和综合模糊度搜索法进行整周模糊度搜索 ,通过仿真检验该方法的正确性同时对比两种算法性能。     

一种适用于动态姿态测量的换星方法

利用GPS双差载波相位能够进行高精度的相对定位,进而确定载体姿态.该双差模型要求解算过程中接收机对初始历元的可见星进行持续跟踪,因而在卫星"落下"和"升起"时,往往需要重新初始化,使得实际应用中定姿效率受到影响.本文基于单差裁波相位观测方程提出一种实用的换星算法,该算法通过动态调整待求的整周模糊度向量,能够有效地处理卫星的"落下"和"升起",以及参考星的变换,保证整个姿态测量过程中算法的连续性,最大程度地利用了所有时刻可见星的观测信息,进一步提高了姿态解算的精度,缩短了初始化时间,提高了解算效率,对于动态姿态测量系统的实际应用具有重要意义.实际测试表明,新的换星算法是有效的.     

一种解算整周模糊度几何算法实现GPS快速测姿

在多天线GPS姿态确定系统中,整周模糊度的确定一直是姿态解算的一个难题。针对载波相位双差模型,本文提出一种新的几何解算双差整周模糊度的方法。该方法首先利用C/A码数据完成姿态初步解算;然后根据初步解算的姿态参数、各天线间基线分量参数和卫星到接收机在当地水平坐标系中的向量,再利用本文提出解算双差整周模糊度几何算法求取整周模糊度双差值;将整周模糊度双差值代入载波相位双差模型反解精确的各天线坐标分量,由取得的各天线坐标分量解算得到精确的姿态参数。同时,应用本文所提出的方法,对采集的GPS多天线静态数据和动态数据进行了姿态测量解算,验证了所提方法的有效性。     

蚁群算法在DGPS动态整周模糊度解算中的应用

在基线长度已知的情况下,利用零空间约束动态求解GPS双差整周模糊度,进行解的去相关后,应用蚁群算法在整周模糊度空间内寻优。根据实测算例解算结果,蚁群算法在很少的解样本数内获得了很好的搜索结果,与遗传算法结果相比较,证明了蚁群算法在相同搜索率的情况下,具有更高的搜索可靠性。     

Geometry-free linear combinations for Galileo

Global navigation satellites of the European Galileo system transmit code signals on four carriers in the L1, E5a, E5b and E6 band.New geometry-free linear combinations are presented that eliminate the geometry terms (user to satellite ranges and orbital errors), the clock errors of the user and satellites and the tropospheric delay. The remaining parameters of these carrier phase combinations include integer ambiguities, ionospheric delays, carrier phase multipath and phase noise. The weighting coefficients are designed such that the integer nature of ambiguities is maintained. The use of four frequency combinations is highly recommended due to a noise reduction of up to 14.4 dB and an ionospheric reduction of up to 25.6 dB compared to two frequency geometry-free combinations.Moreover, a modified Least-squares Ambiguity Decorrelation Adjustment (LAMBDA) algorithm is suggested, which differs in two points from the traditional approach: the baseline is replaced by the ionospheric delay and the correlation is caused by linear combinations instead of double differences. For correct ambiguity resolution, the ionospheric delay can be determined with millimeter accuracy. This is quite beneficial as the ionosphere represents the largest source of error for absolute positioning.     

基于岭估计理论实现GPS快速定位研究

针对在短时间内 GPS观测方程的法方程容易形成病态的实际 ,探讨用岭估计理论消除其病态性的方法 ,然后用 LAMBDA方法确定其整周模糊度。实验证明 ,对于单频 GPS接收机 ,在 1 min左右 ,利用该技术即可正确确定整周模糊度 ,从而实现厘米级定位     

伽利略卫星定位系统三载波姿态确定技术研究

利用伽利略卫星定位系统来确定载体的姿态是伽利略系统的重要应用领域。目前利用GPS确定姿态的算法比较复杂，初始化时间较长，本文详细地介绍了伽利略定位系统三载波模糊度解算技术（TCAR）的要点，分析了TCAR技术求解模糊度的概率分布特点，提出了基于小模糊度搜索空间的单差模糊度搜索策略，克服了传统TCAR技术模糊度确定错误率较高的缺点。以低轨卫星姿态确定为应用对象，利用STK软件工具与Matlab进行了联合仿真，仿真结果表明，该方案完全可行，效果理想，适合单历元姿态确定。     

Novel closed-loop approaches for precise relative navigation of widely separated GPS receivers in LEO

This paper deals with the relative navigation of a formation of two spacecrafts separated by hundreds of kilometers based on processing dual-frequency differential carrier-phase GPS measurements. Specific requirements of the considered application are high relative positioning accuracy and real-time on board implementation. These can be conflicting requirements. Indeed, if on one hand high accuracy can be achieved by exploiting the integer nature of double-difference carrier-phase ambiguities, on the other hand the presence of large ephemeris errors and differential ionospheric delays makes the integer ambiguities determination challenging. Closed-loop schemes, which update the relative position estimates of a dynamic filter with feedback from integer ambiguities fixing algorithms, are customarily employed in these cases. This paper further elaborates such approaches, proposing novel closed loop techniques aimed at overcoming some of the limitations of traditional algorithms. They extend techniques developed for spaceborne long baseline relative positioning by making use of an on-the-fly ambiguity resolution technique especially developed for the applications of interest. Such techniques blend together ionospheric delay compensation techniques, nonlinear models of relative spacecraft dynamics, and partial integer validation techniques. The approaches are validated using flight data from the Gravity Recovery and Climate Experiment (GRACE) mission. Performance is compared to that of the traditional closed-loop scheme analyzing the capability of each scheme to maximize the percentage of correctly fixed integer ambiguities as well as the relative positioning accuracy. Results show that the proposed approach substantially improves performance of the traditional approaches. More specifically, centimeter-level root-mean square relative positioning is feasible for spacecraft separations of more than 260 km, and an integer ambiguity fixing performance as high as 98% is achieved in a 1-day long dataset. Results also show that approaches exploiting ionospheric delay models are more robust and precise of approaches relying on ionospheric-delay removal techniques.     

A vectorial bootstrapping approach for integrated GNSS-based relative positioning and attitude determination of spacecraft

Traditionally in multi-spacecraft missions (e.g. formation flying, rendezvous) the GNSS-based relative positioning and attitude determination problem are treated as independent. In this contribution we will investigate the possibility to use multi-antenna data from each spacecraft, not only for attitude determination, but also to improve the relative positioning between spacecraft. Both for ambiguity resolution and accuracy of the baseline solution, we will show the theoretical improvement achievable as a function of the number of antennas on each platform. We concentrate on ambiguity resolution as the key to precise relative positioning and attitude determination and will show the theoretical limit of this kind of approach. We will use mission parameters of the European Proba-3 satellites in a software-based algorithm verification and a hardware-in-the-loop simulation. The software simulations indicated that this approach can improve single epoch ambiguity resolution up to 50% for relative positioning applying the typical antenna configurations for attitude determination. The hardware-in-the-loop simulations show that for the same antenna configurations, the accuracy of the relative positioning solution can improve up to 40%.