北斗接收机伪距与伪距率的计算及其误差补偿

接收机伪距与伪距率的计算和误差补偿是进行北斗系统应用开发的关键之一。本文利用北斗卫星播发的星历等导航电文数据,计算得到北斗卫星位置与速度等信息,对接收机伪距误差补偿,并计算得到伪距率。利用卫星的位置、速度,得到伪距和伪距率的误差值,验证了伪距和伪距率的有效性。     

北斗二号伪距偏差特性分析及其对定位的影响

伪距偏差是指因卫星下行导航信号非理想状态,导致不同技术状态的终端在接收同一卫星导航信号时产生不同的测距偏差,而现有伪距改正手段尚未考虑该偏差,甚至在双频定位时还会被进一步放大.基于Curtin GNSS研究中心设置的零基线接收机,使用接收机零基线差分解算多组观测终端下北斗二号卫星的伪距偏差,分析其特性,并采用标准单点定位测试伪距偏差改正后的定位精度变化.结果表明:北斗二号各卫星在不同频点的伪距偏差最大可达20cm,B2信号伪距偏差普遍小于B1信号;考虑伪距偏差改正后,标准单点定位在U方向最大提升7.9％,三维方向最大提升5.1％.     

提高导航精度的载波相位平滑伪距方法研究

本文推导了基于载波相位平滑伪距技术的SINS/BD组合导航公式并进行误差分析.结合北斗卫星伪距的无模糊度和载波相位的高精度的特点,在组合导航系统中采用北斗载波相位平滑伪距的方法提高导航的精度,最终对处理效果进行实验验证.验证了此方法提高组合导航精度的有效性.     

基于惯性辅助的北斗接收机完好性监测方法研究

针对传统卫星导航接收机在卫星数小于5颗及卫星星座构型不佳的情况下无法实现卫星故障识别与隔离的问题,结合卫星导航接收机在弹上的实际应用情况,利用惯导的辅助数据设计了一种基于多级Kalman滤波的北斗接收机完好性监测方案,给出了卫星导航接收机的RAIM滤波器结构与故障检测和隔离方法,并对其可用性进行了推导。该方案经过仿真分析及实验测试,结果表明在4颗可见星的条件下,可有效检测并隔离单星阶跃、慢速漂移、慢速随机等北斗卫星伪距和伪距率故障,从而使北斗接收机能够提供连续、精确的导航定位功能。     

惯性卫星紧组合导航系统仿真分析

针对SINS/Satellites进行松组合的不足,直接利用卫星信号接收机原始测量信息(伪距、伪距率),实现紧组合,来提高组合导航系统的精度和抗干扰性。文中详细推导了紧组合导航系统的伪距、伪距率误差模型,以伪距、伪距率差作为输入进行反馈,不仅当可见星数目小于4颗的时候,可以进行反馈,保证了一定的导航精度,而且可以用INS提供导航信息辅助接收机快速捕获卫星信号,这就提高了组合导航系统的容错能力。设计了SINS卫星紧组合导航系统的Kalman滤波器,并进行仿真验证,结果表明,SINS卫星紧组合较松组合有明显优势。     

惯性卫星紧组合导航系统仿真分析

针对SINS/Satellites进行松组合的不足,直接利用卫星信号接收机原始测量信息(伪距、伪距率),实现紧组合,来提高组合导航系统的精度和抗干扰性。文中详细推导了紧组合导航系统的伪距、伪距率误差模型,以伪距、伪距率差作为输入进行反馈,不仅当可见星数目小于4颗的时候,可以进行反馈,保证了一定的导航精度,而且可以用INS提供导航信息辅助接收机快速捕获卫星信号,这就提高了组合导航系统的容错能力。设计了SINS卫星紧组合导航系统的Kalman滤波器,并进行仿真验证,结果表明,SINS卫星紧组合较松组合有明显优势。     

北斗三频海基JPALS无故障导航算法

基于卫星导航系统的海基精密进近与着陆系统(JPALS)是未来舰载机自主着舰引导技术的发展方向。针对当前海基JPALS导航算法的研究都是基于双频观测量,存在无几何滤波时间长、要求的伪距观测量精度较苛刻的问题,提出一种在北斗(BDS)海基JPALS中使用三频观测量的无故障导航算法。通过对在中国东海钓鱼岛海域7天时间使用该导航算法用于精密进近引导的性能进行仿真分析,结果表明:该北斗海基JPALS无故障导航算法使用B1/B2宽巷和B1/B3中巷组合的无几何模糊度预滤波架构只需要8min无几何滤波时间就能实现海基JPALS要求的性能,而且其对伪距观测量的精度要求甚至可以放宽到50cm,使北斗海基JPALS的可用性性能大大提高。此外,载波相位观测量精度不能超过0.7cm时,该北斗三频海基JPALS算法能在3nmile外就实现模糊度固定,使高精度载波相位提早用于海基JPALS精密进近引导。     

北斗卫星导航系统中频信号的产生方法

北斗卫星中频信号在精确导航与授时、合成孔径成像等方面起着关键作用。通过对北斗卫星导航信号的特征进行分析,建立了北斗卫星中频信号的数学模型,并对该模型进行了仿真实现,进而研究了中频信号中路径延迟、噪声和多径干扰对原始北斗信号的影响。研究得到的信号数据可以为导航接收机和信号处理模块提供不同采样率的信号源码,通过这样的方法可以减少大量现场试验,缩短研发时间、降低成本。     

惯性辅助的北斗导航故障自适应方法研究

北斗导航系统完好性是指北斗导航系统不能用于导航服务或导航精度超出给定范围时,具备及时发现故障并通知用户的能力.针对北斗导航完好性检测问题,为改善北斗导航定位系统的精度、连续性、完好性和可用性,研究了基于惯性辅助的北斗导航故障检测方法,设计了北斗导航系统的量测修正与故障检测实现方案,构建了基于新息正交性的自适应滤波北斗/SINS紧组合导航架构,根据滑动窗口内新息动态变化特性修正系统量测噪声方差,在北斗导航信号受到较大干扰、发生异常的情况下,对品质较差的卫星测量信号进行识别,并对检测超出一定阈值的突变卫星信号实现故障隔离,从而提高系统适应能力,增强北斗/SINS紧组合导航系统容错性.构建了北斗/SINS组合导航系统仿真验证模型,结果表明,基于惯性辅助的北斗导航方法能够有效检测出卫星信号故障,提高了系统的适应性和定位精度.     

北斗高动态双频相对定位技术

"北斗"卫星导航定位系统可以进行高精度单点定位和相对定位。本文针对该系统提出了一种相对定位选星策略,分析了几种双频组合方法及适用范围,给出了一种利用B1和B3频率进行双频载波相位差分的方法,并针对具体应用进行了仿真器环境试验验证,为"北斗"卫星导航定位系统建成后高精度相对定位应用提供参考。     

Precise orbit determination for TH02-02 satellites based on BDS3 and GPS observations

The Tianhui-2 02 (TH02-02) satellite formation, as a supplement to the microwave mapping satellite system Tianhui-2 01 (TH02-01), is the first Interferometric Synthetic Aperture Radar (InSAR) satellite formation-flying system that supports the tracking of BeiDou global navigation Satellite system (BDS3) new B1C and B2a signals. Meanwhile, the twin TH02-02 satellites also support the tracking of Global Positioning System (GPS) L1&L2 and BDS B1I&B3I signals. As the spaceborne receiver employs two independent boards to track the Global Navigation Satellite System (GNSS) satellites, we design an orbit determination strategy by estimating independent receiver clock offsets epoch by epoch for each GNSS to realize the multi-GNSS data fusion from different boards. The performance of the spaceborne receiver is evaluated and the contribution of BDS3 to the kinematic and reduced-dynamic Precise Orbit Determination (POD) of TH02-02 satellites is investigated. The tracking data onboard shows that the average number of available BDS3 and GPS satellites are 8.7 and 9.1, respectively. The carrier-to-noise ratio and carrier phase noise of BDS3 B1C and B2a signals are comparable to those of GPS. However, strong azimuth-related systematic biases are recognized in the pseudorange multipath errors of B1C and B3I. The pseudorange noise of BDS3 signals is better than that of GPS after eliminating the multipath errors from specific signals. Taking the GPS-based reduced-dynamic orbit with single-receiver ambiguity fixing technique as a reference, the results of BDS3-only and BDS3 + GPS combined POD are assessed. The Root Mean Square (RMS) of orbit comparison of BDS3-based kinematic and reduced-dynamic POD with reference orbit are better than 7 cm and 3 cm in three-Dimensional direction (3D). The POD performance based on B1C&B2a data is comparable to that based on B1I&B3I. The precision of BDS3 + GPS combined kinematic orbit can reach up to 3 cm (3D RMS), which has a more than 25% improvement relative to the GPS-only solution. In addition, the consistency between the BDS3 + GPS combined reduced-dynamic orbit and the GPS-based ambiguity-fixed orbit is better than 1.5 cm (3D RMS).     

北斗实时精密轨道和钟差产品解算策略及精度评定

随着北斗卫星导航系统全球星座部署即将完成，其应用领域不断扩大，实时精密服务性能受到了极大关注。基于动力学精密定轨方法，设计了北斗卫星实时轨道、钟差算法流程和解算策略。利用不同频点信号，分别计算了BDS-2和BDS-3卫星的实时精密轨道和钟差，建立了完整的轨道和钟差精度评定方法，重点对解算的实时产品的精度进行了评定。结果表明：BDS-2和BDS-3实时精密轨道和钟差产品精度均可满足大部分实时用户的需求。对于B1IB3I频点，BDS-3 MEO卫星的实时轨道精度约为26cm，径向精度约为6cm，实时钟差精度约为0.45ns，且相较于BDS-2，性能更加稳定；对于B1CB2a频点，BDS-3 MEO卫星的实时轨道精度优于20cm，精度和稳定性较高。     

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%。     

基于I、Q信号的北斗接收机跟踪环路设计

传统的北斗接收机一般采用标量跟踪环,每个通道的卫星相互独立,在此 基础上,又发展起来了基于矢量跟踪的接收机,使每个通道的卫星跟踪不再相互独立。 提出的基于I、Q 信号观测的接收机跟踪环路,保留矢量跟踪的特点,并且采用EKF 作 为跟踪环路预处理滤波器,代替传统跟踪环路的鉴别器,可以在高动态的环境下对卫星 信号进行跟踪,提高环路的稳定性,从而可以有效地提高BDS/INS 深组合导航滤波器观 测量的估计精度。主要对高动态信号跟踪进行仿真,并与传统的标量跟踪方法和矢量跟 踪方法的跟踪能力进行比较。实验表明, 改进的矢量跟踪环能够在高动态的环境下运 行,比起传统环路有更小的跟踪误差。     

北斗空间信号误差统计特征及描述方法研究

通过对比北斗卫星导航系统(BeiDou Navigation Satellite System,BDS)广播星历与事后精密星历,提取了轨道和卫星时钟误差。基于北斗轨道误差及北斗卫星时钟误差统计特征分析,构建区别于全球定位系统(Global Positioning System,GPS)的BDS空间信号用户测距误差(Signal-In-Space User Range Error,SISRE)描述方法,对BDS广播星历中用户测距精度(User Range Accuracy,URA)进行了验证。6个月的北斗数据测试结果表明,北斗GEO、IGSO和MEO卫星的URA分别为3.0m、1.9m和1.6m。     

Integrating BDS and GPS for precise relative orbit determination of LEO formation flying

Low-Earth-Orbit(LEO) formation-flying satellites have been widely applied in many kinds of space geodesy. Precise Relative Orbit Determination(PROD) is an essential prerequisite for the LEO formation-flying satellites to complete their mission in space. The contribution of the BeiDou Navigation Satellite System(BDS) to the accuracy and reliability of PROD of LEO formation-flying satellites based on a Global Positioning System(GPS) is studied using a simulation method. Firstly, when BDS is added to GPS, the mean number of visible satellites increases from9.71 to 21.58. Secondly, the results show that the 3-Dimensional(3 D) accuracy of PROD, based on BDS-only, GPS-only and BDS + GPS, is 0.74 mm, 0.66 mm and 0.52 mm, respectively. When BDS co-works with GPS, the accuracy increases by 29.73%. Geostationary-Earth-Orbit(GEO) satellites and Inclined Geosynchronous-Orbit(IGSO) satellites are only distributed over the Asia-Pacific region; however, they could provide a global improvement to PROD. The difference in PROD results between the Asia-Pacific region and the non-Asia-Pacific region is not apparent. Furthermore, the value of the Ambiguity Dilution Of Precision(ADOP), based on BDS + GPS, decreases by 7.50% and 8.26%, respectively, compared with BDS-only and GPS-only. Finally, if the relative position between satellites is only a few kilometres, the effect of ephemeris errors on PROD could be ignored. However, for a several-hundred-kilometre separation of the LEO satellites, the SingleDifference(SD) ephemeris errors of GEO satellites would be on the order of centimetres. The experimental results show that when IGSO satellites and Medium-Earth-Orbit(MEO) satellites co-work with GEO satellites, the accuracy decreases by 17.02%.     

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Kalman滤波和奇偶矢量法的优化RAIM算法

针对传统RAIM算法很难检测微小伪距偏差的问题,可以通过对多个历元的统计检验量进行归一化处理,增大统计检验量的非中心化参数,提高对微小故障的检测率.Kalman新息检测法可以对卫星的故障进行独立检测,具有运算量小、在少星情况时仍能进行故障检测和识别的优点,但是对微小伪距偏差不敏感.针对两种方法的优点提出了基于Kalman滤波和奇偶矢量法的综合RAIM算法.仿真结果表明,该方法不仅可以提高对微小伪距偏差的检测率,同时减少了对可见卫星数的要求,验证了该算法应用于接收机自主完好性检测的可行性和正确性.