【作者】 牛飞；

【导师】 韩春好；

【作者基本信息】 解放军信息工程大学 ， 大地测量学与测量工程， 2008， 博士

【摘要】 本文紧紧围绕利用星基增强系统(SBAS)和地基增强系统(GBAS)对卫星导航系统(GNSS)进行完好性增强这一主题展开研究,主要内容如下:1、归纳总结了卫星导航系统完好性保障的理论与方法,明确了民用航空对卫星导航系统的性能需求,给出了系统完好性的概念及其监测方法,研究分析了系统完好性保障领域存在并需解决的问题。2、对欧洲GALILEO卫星导航系统进行了系统仿真,分析了GALILEO系统的性能和完好性保障方法。通过分析得出,GALILEO系统星座部署较GPS星座更具优势,GALILEO系统GDOP值的变化规律在低仰角情况下与GPS相当,在高仰角情况下具有明显优势。3、研究了分米级星基增强系统的关键技术,并进行了精度分析。对基于伪距与载波相位组合观测量和精化摄动力模型的卫星轨道与钟差的精密确定进行了分析研究。通过采用全球的GPS数据,预报3小时精度优于15cm,采用国内一类基准站+部分国际站,国际站用网络取滞后1小时的观测数据定轨,预报2小时轨道精度可优于20cm,卫星钟差的解算精度可以达到0.3ns。采用精化格网电离层模型,由上海多功能GPS综合服务网的观测数据建立VTEC单站模型,校正SHSS站观测的PRN25卫星信号的电离层延迟,扣除系统偏差后精度好于0.2m。4、研究分析了WAAS的电文系统,阐述了星基增强系统如何通过其电文系统对差分及完好性信息进行准确的传播。通过分析得出,WAAS电文系统充分考虑了卫星快变、慢变改正数和电离层延迟改正数及其误差范围等参数的表示方法,此外还考虑了改正数误差范围的退化因子,用户可通过电文中的完好性信息在时域上更加准确的估计改正数残留误差,从而更加准确地估计定位域误差保护限值。5、针对星基增强系统完好性参数取值相对保守和加权最小二乘定位解算中权阵计算相对不合理问题,提出了综合考虑精度和完好性的SBAS定位解算优化方案。在适当放宽完好性要求条件下调整完好性参数UDRE和GIVE取值,可以更好地符合真实卫星信号的误差特性,并进一步计算新的权阵。使用新权阵的加权最小二乘解可以在一定程度上提升定位结果的精度;使用新调整的完好性参数UDRE和GIVE计算得出的VPL值更小,对定位误差仍具有包络作用;采用自适应的载波相位平滑伪距时间可使得定位精度达到最优。6、针对星载原子钟相位异常和频率异常情况,提出了一种基于平稳时间序列的星载原子钟异常监测算法。该算法通过对卫星钟差进行双差处理构建平稳时间序列,然后对平稳时间序列中的异常进行监测,其实质是从平稳的随机过程中监测不平稳的状态,从而达到监测卫星钟相位异常和频率异常的目的。7、研究了JPALS的原理、关键技术和核心算法。通过分析研究得出LB-JPALS的DFS算法与SB-JPALS的WLFS算法有些近似,但又不完全相同,主要区别是,WLFS算法是对L1和L2宽巷组合观测值进行实数域的平滑处理,而DFS算法是对L1(或L2)单频观测值的平滑处理。因而,SB-JPALS机载设备必须是双频接收机以满足WLFS处理过程,并且WLFS算法的宽巷组合观测值已在平滑处理前将电离层延迟消除,因而不存在平滑中存在的电离层延迟快速变化在码和相位之间存在偏差的问题。8、对基于非零均值非高斯分布的多路径误差模型进行了膨胀分析。该方法的提出基于用户端计算定位域保护限值的前提条件是伪距域残差服从零均值高斯分布,然而伪距域残差中的主要分量多路径误差并非服从零均值高斯分布。本文从多路径误差分布的分析入手,引入“包络”的概念,推导了三种多路径误差分布模型,并针对每种误差分布模型,分别研究了如何构造零均值高斯分布模型“包络”非高斯分布的多路径误差分布模型,并计算相应的膨胀因子,从理论上体现了完好性保障方法的严密性和有效性。9、研究了地基增强系统的异常监测体系和流程。该体系由一系列的异常监测算法与执行逻辑构成,比星基增强系统的异常监测体系更全面,要求更高。它可以对卫星导航信号、观测量和电文进行比较全面的监测,并能对故障点进行有效地定位、隔离和排除。10、研究了基于B值Sigma的异常监测算法。这种监测算法是针对伪距域出现的异常随机误差而提出的。基于B值Sigma开方监测算法是在时域开窗,并对窗口内采样点Sigma求平方和构造检验量;基于B值Sigma累积和监测算法是对B值标准化之后,求累积和构造检验量,通过将检验量与限值比较判定是否有异常发生。仿真计算结果表明,基于B值Sigma开方监测算法和基于B值Sigma累计和监测算法均能够有效地监测GBAS参考站异常随机误差。11、针对局部电离层风暴对地基增强系统的影响,引入了局部电离层风暴模型并提出了相应的监测算法,并在此基础上改进了伪距差分算法。若电离层风暴发生在局域差分有效服务区内,使电离层延迟误差在空域和时域上去相关化,则会对系统完好性构成较大威胁。对此,本文提供时域异常监测的CCDMA算法和DSCMA算法,提出空域异常监测的DRSMA算法,并改进了伪距差分算法,以在电离层风暴发生时对伪距差分改正数进行补偿。仿真结果表明,改进的伪距差分定位算法能有效减小用户定位结果的系统偏差,提高定位精度。更多还原

【Abstract】 The dissertation mainly focuses on the theory and algorithms about GNSS integrity of Satellite-Based Augment System and Ground-Based Augment System, the main works and contributions are summarized as follows:1. The theory and methods are introduced and discussed on GNSS integrity. The GNSS performance requirements are analyzed, the conception of integrity is defined and the monitoring methods are studied, finally some technical challenges are listed which are the mianly works to study.2. Simulation system of GALILEO is built, through which the performance of GALILEO is analyzed, and the methods of integrity ensurement are studied. According the analysis with the simulation system, the conclusion can be drawn that the constellation of GALILEO is better than that of GPS because the value of GDOP of GALILEO is similar to that of GPS at low elevation and much better than that of GPS at high elevation.3. The base frame and key techniques of Wide Area Precise Point Position at decimeter-level is studied, and a primary accuracy analysis is made. Precise orbit and clock is determined by using combined measurement consisted of pseudorange and carrier phase.Though analyzing, it is shown that the error of pridicted orbit within 3 hours is less than 15 centimeter using the data from the sations allover the world, and the error of pridicted orbit within 2 hours is less than 20 centimeter using the data from the domestic and aboard sations of the first kind.The error of the pridicted clock is less than 0.3ns.The error of the ionosphere delay coreection built by SHSS reference station conducted from system bias using optimized grid ionosphere model is less than 0.2m.4. The SBAS message system is studied, it is expatiated how to define and transport the differential and integrity information exactly and roundly. The SBAS message system not only considers the fast correction, long term correction and ionosphere delay correction and bouds the error of these corrections, but also considers the degenerated factors, using these corrections and dagenetated factors, more exact error bound can be estimated at position domian.5. A new method which optimizing accuracy and stability is studied. If the requirement of integrity is relaxed and the value of UDRE and GIVE is adjusted so as to fit the reality, the position accuracy can be improved using Least-Squares based on the new weight. The VPL will be smaller than before using the adjusted sigma. The accuracy at position domain can be improved by adjusting adaptive carrier smoothing using code-carrier divergence .6. a x~2 monitoring method is studied to detect the atomic clock anomaly of the navigation satellites by making atomic clock bias twice difference and biulding the balanced time serial.Through analyzing, the conclusion can be drawn that double difference method is effective for the phase anomaly but not effective for frequency anomaly,and x~2 method based balancedtime serial is effective for both phase anomaly and frequency anomaly.7. The key principle and algorithoms of Joint Precise Approach System are studied. Through analyzing the conclusion can be drawn that the DFS algorithm of LB-JPALS is similar to the WLFS algorithm of SB-JPALS, and the diffrence between them is that the Wide-Lane mixed measurement of L1 and L2 frequence is smoothed by carrier phase towards WLFS algorithm and the pseudorange of single frequence is smoothed by carrier phase towards DFS algorithm. So the reciever of SB-JPALS must be double frequece reciever so as to satisfy WLFS algorithm, and WLFS algorithm need not care about code carrier divergence as the ionosphere delay has been removed befor smoothing.8. The integrity algorithom of GBAS based on non-gausss distribution is studied. The primary method of calculating VPL is based on the gauss distribution of the sigma of the residual pseudorange error, but multi-path error is the main component of the residual pseudorange error and is not gauss. A new method how to inflate the sigma is studied so as to ensure rigorous theoretically.9. The system and flow how to monitor anomaly of GBAS is designed. The system is consist of some algorithoms used to monitoring anomaly and execute logic, the system is more entirely and difficult than SBAS, with the system and the execute logic, mesurement and message can be monitored and can be isolated if they seems to be anomaly.10. The monitoring algorithm on Sigma anomaly based on B-Value is studied. Through the analysis it is shown that the Sigma Monitoring Algorithm based on B-Value and SUM Algorithm are also effective to anomaly error of the pseudorange correction.11. The effect toward GBAS when ionosphere storm occures is modeled and the monitoring algorithms are studied, and the method of Local Area Difference is improved.GBAS is based on the case that the errers on the pseudoranges observed by user and reference station is similar, so the correction provided by reference station is used to correct the pseudorange measurements observed by users. But when ionosphere anomaly is met, the errers between the the station and user is quit different and the positioning solution is effected.The dissertation provides CCDMA and DSCMA algorithm to detect the ionosphere anomaly, and the differential positioning solution of GBAS is improved. It’s shown that the provided algorithm mitigrates the threat for GBAS.更多还原