Applying NIORAIM to the Solution Separation Method for Inertially-Aided Aircraft Autonomous Integrity Monitoring

Patrick Y. Hwang

Abstract:	The use of inertial aiding to improve the availability and continuity performance of an integrity monitor over the standard snapshot RAIM FDE algorithm is represented by an established class of methods called Aircraft Autonomous Integrity Monitoring (AAIM) that also exploits inertial data, in contrast to RAIM which is limited to using only receiver measurement information. Even though the system availability of the AAIM methods is already quite high for non-precision approach (NPA) when using a very high-grade inertial sensor, any further improvement in availability performance will be beneficial for operational environments that require even tighter alert limits than NPA or where lower stability inertial sensors are used. The recent-introduced NIORAIM (Novel Integrity- Optimized RAIM) concept for enhancing RAIM availability performance can also be applied to the solution separation methodologies as well. This paper will describe the incorporation of NIORAIM specifically to an AAIM mechanization called Normalized Solution Separation. In this particular scheme, separate solutions maintained by a bank of integrated GPS/INS Kalman subfilters are statistically compared to detect the validity of a hypothesis, namely, whether a fault exists on one of the satellites and which one. The paper will describe the modifications needed in the design of the Kalman filters to exploit the benefits of NIORAIM. The paper will also evaluate the performance of NIOAAIM, both in terms of near steady state conditions from satellite geometry variation as well as in abrupt transient conditions due to satellite constellation changes. By and large, the benefits of NIORAIM are realized in the steady-state performance of the NIOAAIM system. However, since Horizontal Integrity Limit (HIL) availability outages can be relatively brief in a lot of cases, it is the transient behavior of the system that may prove to be more important to optimize. This paper shows how the transient performance may be modified to get the best availability performance.
Published in:	Proceedings of the 2005 National Technical Meeting of The Institute of Navigation January 24 - 26, 2005 The Catamaran Resort Hotel San Diego, CA
Pages:	992 - 1000
Cite this article:	Hwang, Patrick Y., "Applying NIORAIM to the Solution Separation Method for Inertially-Aided Aircraft Autonomous Integrity Monitoring," Proceedings of the 2005 National Technical Meeting of The Institute of Navigation, San Diego, CA, January 2005, pp. 992-1000.
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