局域增强系统级联双频平滑技术研究(英文)

针对电离层误差时间梯度和空间梯度对局域增强系统的不利影响,提出使用级联双频平滤波方法解决此问题。级联双频平滤波先使用一个双频平滑滤波器精确估计电离层误差,利用得到的估计值修正码伪距观测量中的电离层误差,再使用一个双频平滑滤波器削弱噪声。这样,电离层误差被完全从平滑过程中移出,由L2码观测量引入的附加的噪声也被压制。基于中国民航新航行系统实验室的局域增强系统测试平台所采集的数据对级联双频平滤波的有效性和基于级联双频平滤波的局域增强系统的精度进行了分析。结果表明级联双频平滤波技术可以同时消除电离层误差时间梯度和空间梯度导致的平滑滤波残差和差分校正残差,并具有较低的滤波噪声。     

基于参考站误差估计的GNSS区域增强技术

研究了应用于民航航路、铁路、内河水运等领域的分布式卫星导航区域增强系统的定位方法,分析了参考站误差、单参考站电离层和对流层误差,提出了一种基于参考站误差估计的多站差分GNSS区域增强技术。仿真结果表明,该方法可减小参考站误差对多站差分的影响,解决现有技术中单差分系统用户与地面站的距离增加定位误差增大的问题,并增加了定位精度,同时提高了系统的可靠性和覆盖效率。     

双频双星座地基增强系统精度和完好性算法

针对单频单星座地基增强系统（GBAS）无法满足飞机III类精密进近与着陆导航性能需求的问题，提出了将北斗导航卫星系统（BDS）与全球定位系统（GPS）进行融合，构建一种新型的基于GPS/BDS的双频双星座GBAS。首先，分析了GBAS的工作原理，并对Hatch滤波器的误差进行了分析，给出了一种适用于双频GBAS的无码载偏离载波相位平滑伪距算法；然后，对机载完好性算法进行了研究，给出了H0和H1假设下的机载保护级计算方法；最后，进行了系统验证实验，实验结果表明，单星座GBAS不能满足飞机III类精密进近与着陆导航的性能需求，GPS和BDS融合后可见卫星个数得到提升，优化了卫星几何分布，进而使得系统的可用性由80.6081%提升到大于99.9999%。     

GNSS最优载波相位平滑伪距研究

平滑常数是影响载波相位平滑伪距精度的关键参数,实际数据处理时主要依据经验设定平滑常数。这种主观设定过程缺乏理论依据,无法达到最优平滑效果。针对此问题,以适用于实时GNSS载波相位平滑伪距的经典Hatch递推滤波算法为基础,在连续时间域上分析了载波相位平滑伪距误差的主要构成,给出了总误差估算公式,分析了平滑常数对平滑精度的影响传导机制。进一步,采用令平滑总误差最小为目标的极值法推导给出了最优载波相位平滑常数的计算公式,给出了最优载波相位平滑伪距的完整处理步骤。最优平滑常数算法在数学意义上最优,大幅压缩了伪距测量误差,又不会引入过大的电离层发散误差。通过两个实际算例,证明了算法有效性。     

Position-Domain Hatch Filter for Kinematic Differential GPS/GNSS

Motivated by the accuracy benefit of the Hatch gain compared with the Kalman-type gain and the advantage of position-domain (PD) filtering compared with range-domain (RD) filtering under frequent changes in visible satellite set, this paper proposes a PD Hatch filter for kinematic differential satellite-based positioning. It is shown that the Hatch gain generates white residual sequence in both the RD and the PD. An experiment result demonstrates that the proposed PD Hatch filter is advantageous in real-time kinematic positioning.     

Impact of receiver inter-frequency bias residual uncertainty on dual-frequency GBAS integrity

Dual-Frequency Ground-Based Augmentation Systems(GBAS) can be affected by receiver Inter-Frequency Bias(IFB) when Ionosphere-Free(Ifree) smoothing is applied. In the framework of the proposed GBAS Approach Service Type F(GAST-F), the IFB in the Ifree smoothed pseudorange can be corrected. However, IFB residual uncertainty still exists, which may threaten the integrity of the system. This paper presents an improved algorithm for the airborne protection level considering the residual uncertainty o...     

SINS/BDS紧组合系统中自适应 两阶段扩展卡尔曼滤波

在实际应用中，以伪距/伪距率为观测量的SINS/BDS紧组合导航系统，存在量测噪声的统计特性与实际不相符的情况，传统扩展卡尔曼滤波（EKF）方法无法有效解决这一问题，从而引起滤波误差增大。提出了一种SINS/BDS紧组合导航系统的GDOP估算及在线估计量测噪声的自适应两阶段EKF（ATEKF）方法，该方法使用经过紧组合修正后的SINS输出的位置，并结合星历数据中提供的卫星位置求解GDOP。在此基础上，利用GDOP值以及新息，实现了紧组合导航系统的量测噪声方差阵（Rk）的在线实时估计，从而达到自适应滤波的效果，改善导航精度。     

Formulation of a time-varying maximum allowable error for ground-based augmentation systems

Ground-based augmentation systems (GBAS), such as the federal aviation administration's local area augmentation system (LAAS), protect GPS users against signal anomalies by monitoring for rare satellite faults. This paper introduces a new, time-varying MERR (maximum-allowable error in range) formulation that enables proof of integrity for ground-based fault monitoring. The time-varying MERR supersedes earlier MERR methods which relied on a static integrity test. The utility of these earlier methods was limited in that they neglected GBAS time-to-alert (TTA) requirements and restricted the choice of the monitor filter, requiring its impulse response to match that of the user ranging-error filter. By contrast, the time-varying MERR explicitly incorporates TTA and places no restrictions on monitor filter design. These attributes are critical for correctly evaluating system integrity and for crediting the integrity benefits of GBAS systems with aggressive filter designs and process timing.     

拐点平滑滤波技术研究

提出了滤波算法的一种新的有效点判断原则,即拐点平滑法;介绍了该技术的数学模型及滤波原理;通过仿真计算,探讨了应用该判据时滤波半径、拟合阶次等滤波参数对位置参数滤波结果的影响情况,并进行了实测数据解算。该判据在中心平滑算法的最佳应用条件下,综合考虑了截断误差,提高了飞行器位置参数的滤波精度,尤其适用于加速度剧烈变化的飞行轨迹。     

顾及空间分布和NLOS的UWB室内可信定位方法

针对现行室内可信定位存在的三维定位精度低与结果可信度难以定量评估的难点,提出了一种可信超宽带(UWB)室内定位模型。该方法采用无迹卡尔曼滤波和IGG-III抗差理论模型,解决了UWB定位中的非线性化和非视距误差问题;同时,为提高该方法定位结果的可信度,进一步构建了一种兼顾UWB基站空间分布和非视距误差的可信精度评估模型。与现有模型相比,提出的方案可有效实现基于UWB的室内高精度可信定位。仿真和实测数据结果表明：1)与传统最小二乘结果相比,该方法可提高30%～40%的UWB定位精度;2)引入IGG-III抗差模型可提高11%的定位精度;3)非线性化误差对UWB定位精度的影响不尽相同,约为22%～50%;4)提出的可信度评估模型可实时准确评估UWB定位精度。     

GNSS广域差分改正数估计方法研究

随着我国北斗三号基本系统的正式运行,基于地面监测站的广域差分增强系统成为进一步提升卫星导航定位精度的手段之一。在码噪声多径误差修正(CNMC)的基础上,使用等效钟差方法实现GNSS卫星轨道与钟差误差的解耦,并依据卫星轨道运动的动力学特性,引入希尔差分方程描述卫星轨道误差变化,实现对轨道误差的实时卡尔曼滤波估计。基于GPS实测数据,对改正前后的用户等效测距误差(UERE)和定位精度进行了对比研究。实验结果表明,采用该方法,UERE标准差由改正前的0.456 m减小至0.227 m,降幅达到50.22%;整体水平定位误差(95%置信区间)由0.981 m减小至0.782 m,垂直定位误差(95%置信区间)由1.991 m减小至1.131 m,分别提升了20.29%和43.19%,差分改正效果明显。     

电离层对单频卫星导航系统伪距差分定位的影响

用计算机仿真方法 ,给出了单频卫星导航系统伪距差分后 ,定位误差受电离层影响的一些结果。伪距差分定位能够校正电离层时延误差 ,但校正精度随用户与基准站到同一颗卫星倾斜因子的不同而不同。为此 ,提出了一种改进的伪距差分方法。仿真结果表明 ,改进后有明显效果     

天线整流罩对GNSS观测值与定位精度影响研究

当前大部分城市为保护卫星连续运行参考站(CORS)系统基准站天线安装了整流罩,但天线整流罩对观测值以及基准站坐标影响的研究仍显不足。为解决基于广州CORS(GZCORS)的网络RTK高程测量存在较大偏差的问题,基于2016—2021年观测站数据,以及拆除基准站天线罩前后的观测数据质量与定位效果相关分析,对天线整流罩对GNSS观测值与高程定位精度的影响进行了深入探究,并分别进行了静态仿动态和城市车载动态定位测试验证。研究结果显示,天线整流罩在一定程度上会增加原始观测值的多路径效应影响,降低约10%的数据可用率,并对基准站高程定位结果产生1～14 cm的系统性偏差,进而影响用户RTK高程定位效果。定位结果显示,拆除基准站天线罩后,基于GZCORS的RTK水平定位均方根误差(RMS)为1 cm左右,高程定位精度RMS为2 cm左右;城市场景下车辆动态定位精度RMS为15～20 cm,满足车道级定位性能。     

Intelligent SINS/RDSS Integrated Algorithms for Land Vehicle Navigation

This is a discussion of the design of strap-down inertial navigation systems (SINS) and radio determination satellite service (RDSS) integrated navigation algorithms. The research aims at testing the effectiveness of artificial intelligence (AI)-aided Kalman filtering (KF) approaches for land vehicle applications. A back-propagation neural network (BPNN)-aided K*F algorithm and a fuzzy inference-based KF algorithm are presented in order to overcome the time delay of RDSS positioning provided by a double-star positioning system in China. Traditional KF causes biased solutions, and indeed, leads to filter instability easily since the time delay of RDSS positioning, in an active mode, is hard to be modeled and sometimes suffers from RDSS outages. Therefore, a fuzzy inference is used to correct the variance matrix of KE measurement noises adaptively; and a trained BPNN corrects the outputs of the Kalman filter. The algorithms proposed herein have been verified on real SINSIRDSS data. collected in land vehicle tests and are compared with other approaches. The results demonstrate that fuzzy inference-based KF algorithms improve the positioning accuracy to over 40 % better than KF algorithms, and BPNN-aided KF algorithms have the same precision as GPS which is the reference station In dynamic experiments without RDSS outages. The test results with RDSS outages indicate that the fuzzy inference-based KF is feasible but with positioning errors of hundreds of meters, so the BPNN-aided KF is designed to efficiently compensate for RDSS outages and improve system performance.     

北斗单点定位的误差补偿方法

北斗是我国自主研制的卫星导航定位系统,当前北斗的单点定位精度优于10m。为提高该系统的定位精度,必须对由其误差源引起的定位误差进行修正。基于对北斗卫星导航系统的组成、定位算法及定位误差的认识,对导航系统定位中星历误差、电离层误差和对流层误差进行了深入分析,提出了减小星历误差的曲面模型、减小电离层误差的双频组合消电离层模型和减小对流层误差的高精度区域融合模型的单点定位误差补偿方法,并应用Matlab软件对修正模型方法进行仿真计算。对比修正前后的定位结果,修正后的定位误差更小,证明了所提出的修正模型是可行的。     

载波相位平滑伪距在GPS/SINS紧组合导航系统中的应用

针对GPS/SINS紧组合导航系统中伪距噪声大从而引起组合导航系统精度低的问题,提出了将载波相位平滑伪距方法引入到组合导航系统中,利用具有较高精度的载波相位对低精度伪距进行平滑滤波,在建立观测方程的同时,为了减小Kalman滤波器计算量,选用最佳4颗卫星的伪距与伪距率作为观测值,并提出了一种四面体选星法,该方法不需要进行矩阵求逆运算,减小了运算量。利用光纤陀螺捷联惯导系统与GPS接收机搭建了实验验证系统,通过车载实验对所提出的方法进行了验证,实验结果表明,经过载波相位平滑后的伪距噪声得到了降低,从而能够进一步提高GPS/SINS组合导航系统的定位精度,其位置误差均方根值相比无载波相位平滑减小近40%。     

自适应增量 Kalman 滤波方法

提出自适应增量Kalman滤波(AIKF)的概念和定义,建立自适应增量Kalman滤波模型及其分析方法,给出主要的计算步骤.传统自适应Kalman滤波(AKF)方法能够对事先未知的系统噪声和量测噪声的统计量进行有效的估计.但是,传统自适应Kalman滤波方法也无法对由于环境因素(如深空探测)的影响、测量设备的不稳定性等原因产生的未知时变测量系统误差进行补偿和校正,从而产生较大的滤波误差,甚至导致发散.提出的自适应增量Kalman滤波方法不但能够对系统噪声和量测噪声的统计量进行估计,而且还能成功消除这种测量系统误差,有效地提高滤波精度.该方法计算简单,便于工程应用.      

一种简易的双星定位系统定位解算方法

双星导航定位系统采用双星定位体制,其定位基本原理为三球交会测量原理,其中2颗量测量与用户到2颗卫星的距离有关,与用户高程有关的第3个量测量是决定系统定位精度的关键因素.为此,为了简化定位算法,文章根据地球椭球几何及大地纬度的相关知识,推导了与用户高程有关的第3个量测量的精确模型,进而建立了用户的定位算法.该算法具有简单...     

考虑测量噪声的朗道自适应惯量辨识方法

传统朗道自适应惯量辨识方法只有一个自适应系数可以调节,难以同时兼顾辨识速度和辨识精度,导致速度自适应控制系统在测量噪声较大的情况下容易不稳定。为解决这一问题,提出了一种考虑测量噪声的朗道自适应惯量辨识方法。该方法采用相同的低通滤波器对速度和电磁转矩同时进行滤波,保证了辨识模型与无滤波时的相同。在此基础上综合调节自适应系数和滤波器时间常数,在保证辨识速度的前提下减小辨识系统的噪声,提高辨识精度,从而提高了速度自适应控制系统的稳定性。仿真和试验验证了所提方法的正确性和有效性。     

Analysis of airborne GPS multipath effects using high-fidelity EM models

Airborne GPS systems are being upgraded to provide sufficient positioning accuracy to support automatic landing operations in low visibility conditions. This is made possible by differential GPS (DGPS), in which the errors common to the airborne receiver and ground station are removed by knowledge of the latter's precise location. However, errors specific to the airborne system remain, of which the dominant components are receiver noise and multipath. To support the assessment of the integrity of the signal in space, these residual errors are incorporated in a statistically based error model, designated as the "standard model." The standard model is defined as the standard deviation of a Gaussian distribution that overbounds the residual pseudo-range (PR) error. It relates the standard deviation of the overbounding distribution to the elevation angle of the satellite relative to the local level coordinate system. The international community is currently developing improved standards to enable DGPS systems to support landings in the worst visibility conditions (i.e., CAT III). As a part of this development, the standard model for multipath is being re-evaluated and an improved model is sought. In order to better characterize the residual multipath errors, tools for accurate calculation of the airframe scattering effects are needed. Development of such tools is the subject of this paper. A new method for accurately computing pseudo-range error, based on the use of high-fidelity EM models, is described. This approach provides new insight into the mechanisms causing multipath error.