伪卫星网络定位算法研究

发布时间：2019-05-08 22:02

【摘要】：北斗卫星导航系统(BDS)是我国研制的全天候的区域卫星导航系统。北斗系统和其他类似的GNSS不论是在陆地、海洋还是在天空中都已经是获取定位导航信息的最佳途径,而且发挥着越来越重要的作用。然而,由于BDS/GNSS信号本身的限制和人们对位置信息越来越多样化的需求,其在室内定位、山谷、隧道等信号被遮挡的区域便无法满足定位需求。伪卫星系统,作为一个GNSS的增强系统便可以解决这个问题,不仅可以提供额外的类GNSS信号,还可以在完全没有GNSS信号的区域进行独立组网定位。而且,伪卫星的加入使得利用载波相位测量量进行精密定位成为了可能,使系统定位精度可以达到厘米级。为了跟踪并研究国内外在伪卫星领域先进的研究成果,本文的研究内容主要有以下几个方面。首先,本文通过对国内外伪卫星技术研究现状的总结,并结合对北斗系统的分析,详细阐述了北斗伪卫星系统的工作原理并对设计了其中的信号体制和导航电文。另外还重点分析了北斗伪卫星系统中时间同步、整周模糊度解算、非线性滤波、组网布局等关键技术。其次,分析了伪卫星几何结构对其定位性能的影响,并详细论证了精度因子这一评价其几何结构优劣的指标。从理论上分析了伪卫星对北斗的增强原理,并结合北斗星历数据进行了精度因子的仿真分析。再次,讨论了远近效应、多径效应对伪卫星布局选址的影响,并在考虑这些影响因素的情况下,以精度因子为指标,提出了一种结合惩罚因子的自适应遗传算法在伪卫星布局优化中的应用。结果表明,该方法完全可以完成在多个限制条件下的伪卫星布局优化工作,其中自适应的遗传算法在收敛速度上更具优势。最后,对比分析了定位算法中线性化误差对北斗系统、伪卫星系统的影响。结合对线性化误差来源的分析,分别在北斗系统、北斗伪卫星系统场景下利用扩展卡尔曼滤波、二阶扩展卡尔曼滤波、无迹卡尔曼滤波进行了仿真分析,并对比了三者的定位精度。结果表明,在伪卫星距接收机距离较近且伪卫星布局不好的情况下,系统的非线性程度更大,此时,UKF能够提供更好的定位精度。但是当定位星座距离接收机较远时,EKF、EKF-2、UKF拥有近似的定位精度。
[Abstract]:Beidou Satellite Navigation system (BDS) is an all-weather regional satellite navigation system developed in China. Beidou system and other similar GNSS are already the best way to obtain navigation information on land, sea and sky, and play a more and more important role. However, due to the limitation of the BDS/GNSS signal itself and the increasingly diversified demand for location information, it is not possible to meet the location requirements in the areas where the indoor location, valley, tunnel and other signals are occluded. Pseudo-satellite system, as a GNSS enhancement system, can solve this problem. It can not only provide additional GNSS-like signals, but also provide independent network positioning in areas without GNSS signals. Moreover, the addition of pseudo-satellite makes it possible to use carrier phase measurement for precise positioning, so that the positioning accuracy of the system can reach centimeter level. In order to track and study the advanced research results in the field of pseudosatellite at home and abroad, the main contents of this paper are as follows. Firstly, through summarizing the research status of pseudo-satellite technology at home and abroad, and combining with the analysis of Beidou system, this paper expounds the working principle of Beidou pseudo-satellite system in detail, and designs the signal system and navigation message among them. In addition, the key technologies of Beidou pseudo-satellite system, such as time synchronization, integer ambiguity resolution, nonlinear filtering, network layout and so on, are also analyzed. Secondly, the influence of pseudo-satellite geometric structure on its positioning performance is analyzed, and the precision factor, which is an index to evaluate its geometric structure, is demonstrated in detail. In this paper, the enhancement principle of pseudo-satellite to Beidou is analyzed theoretically, and the precision factor is simulated and analyzed with the data of Beidou ephemeris. Thirdly, the effects of near-far effect and multi-path effect on the location of pseudo-satellite are discussed, and the precision factor is taken as an index when these factors are taken into account. In this paper, an adaptive genetic algorithm combined with penalty factor is proposed to optimize the placement of pseudo-satellites. The results show that the proposed method can be used to optimize the pseudo-satellite layout under multiple constraints, and the adaptive genetic algorithm has more advantages in the convergence rate. Finally, the influence of linearization error on Beidou system and pseudo-satellite system is analyzed. Combined with the analysis of the source of linearization error, the extended Kalman filter, the second-order extended Kalman filter and the unscented Kalman filter are simulated in Beidou system and Beidou pseudo-satellite system respectively. The positioning accuracy of the three methods is compared. The results show that when the pseudo-satellite is close to the receiver and the pseudo-satellite layout is not good, the nonlinear degree of the system is greater, and the UKF can provide better positioning accuracy. However, when the constellation is far away from the receiver, EKF,EKF-2,UKF has an approximate positioning accuracy.
【学位授予单位】：西南交通大学
【学位级别】：硕士
【学位授予年份】：2017
【分类号】：TN967.1

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