Direct Determination of Aircraft Quaternion Parameters Using a Combined Inertial-GPS Instrumentation System

Hosam K. Fathy, J. Garth Thompson, and Peter J. Gorder

Abstract:	The total deliveries of U.S.-made General Aviation airplanes declined from 17,811 planes in 1978 to 928 in 1994[2]. Reversing this downward spiral can only be achieved through the development of inexpensive yet accurate and reliable instrumentation systems for GA aircraft[3]. Discussed herein is a combined GPS-inertial instrumentation system that attains these objectives. The instrumentation system uses GPS instruments for position, velocity, and attitude determination, and, using state filters, combines these GPS readings with accelerometer and rate gyroscope measurements to obtain accurate, smoothly filtered, quasi-continuous aircraft state estimates[3]. The paper specifically focuses on a new GPS attitude determination algorithm that generates quaternion estimates directly, thereby alleviating the Euler singularity problem. The convergence, speed, and accuracy of the algorithm are analyzed. The paper then discusses how the filtered attitude rates generated by the state filters can be used for predicting cycle slip and propagating the values of GPS cycle ambiguities that are vulnerable to slip. The performance of this cycle ambiguity resolution system is discussed, and the paper concludes with a brief discussion of the layout of the overall instrumentation package.
Published in:	Proceedings of the 12th International Technical Meeting of the Satellite Division of The Institute of Navigation (ION GPS 1999) September 14 - 17, 1999 Nashville, TN
Pages:	2009 - 2016
Cite this article:	Fathy, Hosam K., Thompson, J. Garth, Gorder, Peter J., "Direct Determination of Aircraft Quaternion Parameters Using a Combined Inertial-GPS Instrumentation System," Proceedings of the 12th International Technical Meeting of the Satellite Division of The Institute of Navigation (ION GPS 1999), Nashville, TN, September 1999, pp. 2009-2016.
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