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GPS filtering to minimize ionosphere divergence error for safe aircraft landing.

机译：GPS过滤可最大程度地减少电离层发散误差，以确保飞机安全着陆。

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摘要

Aircraft use navigation guides to help pilots land especially in low visibility conditions. The commonly used Instrument Landing System is very effectively yet expensive and inflexible. The Global Positioning System (GPS) can be used to design potentially cheaper and more versatile navigation systems. The Local Area Augmented System (LAAS) is one of the proposed systems for navigation. However it is yet to be certified by the Federal Aviation Administration (FAA) owing to its susceptibility to certain rare events which can potentially cause a system failure in LAAS.; LAAS implements the idea of using differential corrections from a nearby reference station to increase the accuracy of the position estimate of the user. One of the biggest threats to LAAS, which undermines the concept of differential corrections, is an ionospheric storm caused by high solar activity. The ionosphere is a spherical shell of ionized gases over earth and affects radiowave communication passing through it. Although ionospheric storms are rare events, under certain worst cases they can be undetectable and might cause a missed landing. Therefore to ensure the safety of the usage of LAAS, this problem is addressed in this research.; Errors due to the ionospheric storm are magnified by the standard real-time smoothing filter in LAAS, the Hatch Filter. The Hatch Filter leverages the two components of GPS signals, namely the code and carrier measurement, and provides excellent attenuation of noise under nominal conditions. However under the influence of the ionospheric storm, the Hatch Filter suffers a delay in its position estimate and hence produces a systematic bias.; This thesis designs two alternative real-time smoothing filters with the motivation of increasing insensitivity towards ionospheric storms without sacrificing the "nominal day" noise attenuation. The first design uses mathematical rigor to optimize a general linear digital filter for the least maximum transient error under the influence of an ionospheric storm. The optimized linear filter is found to reduce the maximum transient error by a maximum of 20% during the offline simulation test conducted on GPS data. The second filter is designed with the motivation of reducing steady state errors caused by the ionospheric storm. This filter is nonlinear and is able to overcome the limitations of linear filters (which suffer degraded transient error while reducing steady state errors). In the offline experiments the nonlinear filter attained zero steady state error in each case and also reduced the maximum transient error as compared to the Hatch Filter.
机译：飞机使用导航指南来帮助飞行员降落，尤其是在能见度较低的情况下。常用的仪表着陆系统非常有效，但价格昂贵且不灵活。全球定位系统（GPS）可用于设计可能更便宜，功能更多的导航系统。局部增强系统（LAAS）是拟议的导航系统之一。然而，由于它易受某些可能导致LAAS系统故障的罕见事件的影响，因此尚未获得美国联邦航空管理局（FAA）的认证。 LAAS实现了使用附近参考站的差分校正来提高用户位置估计精度的想法。破坏差分校正概念的LAAS面临的最大威胁之一是高太阳活动引起的电离层风暴。电离层是地球上离子化气体的球形壳，影响通过它的无线电波通信。尽管电离层风暴是罕见的事件，但在某些最坏的情况下，它们可能无法被检测到并可能导致飞机降落。因此，为了确保使用LAAS的安全性，本研究解决了这个问题。电离层风暴引起的误差被LAAS中的标准实时平滑滤波器（舱口滤波器）放大。剖面线滤波器利用GPS信号的两个分量，即代码和载波测量，在标称条件下可提供出色的噪声衰减。但是，在电离层风暴的影响下，舱口盖滤波器的位置估计会延迟，因此会产生系统偏差。本文设计了两个可选的实时平滑滤波器，其动机是在不牺牲“标称日”噪声衰减的情况下增加对电离层风暴的不敏感性。第一个设计使用数学上的严谨性来优化通用线性数字滤波器，以在电离层风暴的影响下将最大的瞬时误差最小化。在对GPS数据进行的离线模拟测试中，发现优化的线性滤波器可将最大瞬态误差最大降低20％。设计第二个滤波器的目的是减少电离层风暴引起的稳态误差。该滤波器是非线性的，能够克服线性滤波器的局限性（线性滤波器的瞬态误差降低，而稳态误差减小）。在离线实验中，与Hatch滤波器相比，非线性滤波器在每种情况下均达到零稳态误差，并且还减小了最大瞬态误差。

著录项

  • 作者

    Sen, Shiladitya.;

  • 作者单位

    Tufts University.$bMechanical Engineering.;

  • 授予单位 Tufts University.$bMechanical Engineering.;
  • 学科 Engineering Mechanical.
  • 学位 M.S.
  • 年度 2008
  • 页码 84 p.
  • 总页数 84
  • 原文格式 PDF
  • 正文语种 eng
  • 中图分类
  • 关键词

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