Extended Kalman Filter-Based Deeply Integrated GNSS/Low-Cost INS for Reliable Navigation Under GNSS Weak Interrupted Signal Conditions

N.I. Ziedan

Abstract:	This paper presents a deeply integrated GNSS/INS system that utilizes the functionalities of a GNSS receiver and a low cost inertial navigation system (INS) to enable continuous navigation in any environment. The system has the ability to work with weak signals and to provide accurate positioning information during GNSS signal blockage. The GNSS signal acquisition and tracking modules are integrated with an INS. The INS output provides the acquisition module with velocity and acceleration aiding information to remove the receiver dynamics from the received signal prior to acquiring a signal. The errors in the low-cost INS output increase with time, and thus the INS output cannot be used directly to aid the tracking, which works continuously over long period of time. Instead, the INS and the tracking module are integrated together such that the INS provides the tracking module with receiver dynamics aiding information, and the tracking module provides the INS with aiding information to enable the estimation of the INS errors. The code and carrier tracking are performed by Extended Kalman filters (EKF). The EKF for carrier tracking is designed to track the carrier parameters and the INS errors. The measurements of the EKF carrier tracking are taken from two sources. The first source is the received signal integrated with a complex local replica signal, which is compensated by the current EKF estimates of the carrier parameters. The second source is the received signal integrated with another complex local replica signal, which is compensated by aiding carrier parameters calculated from the INS estimates of the position and velocity. The two sets of measurements are used within one EKF to update the carrier parameters and estimate errors in the INS-based calculation of the aiding carrier parameters. The aforementioned EKF is used within the tracking module of each tracked satellite. The error estimates from all the tracking modules are used within another type of EKF to estimate the errors in position, velocity, attitude, accelerometer bias, gyro drift, and the receiver clock bias and drift. The output of the second type of EKF is used to correct the INS output and re-adjust the carrier parameters estimates for each tracked satellite.
Published in:	Proceedings of the 19th International Technical Meeting of the Satellite Division of The Institute of Navigation (ION GNSS 2006) September 26 - 29, 2006 Fort Worth Convention Center Fort Worth, TX
Pages:	2889 - 2900
Cite this article:	Ziedan, N.I., "Extended Kalman Filter-Based Deeply Integrated GNSS/Low-Cost INS for Reliable Navigation Under GNSS Weak Interrupted Signal Conditions," Proceedings of the 19th International Technical Meeting of the Satellite Division of The Institute of Navigation (ION GNSS 2006), Fort Worth, TX, September 2006, pp. 2889-2900.
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