On the Observability of an Integrated GPS/INS During Maneuvers

I. Rhee, M. F. Abdel-Hafez and J. L. Speyer

Abstract:	An observability analysis of a GPS/INS system dur- ing maneuvers is presented based upon a pertur- bation model with respect to the Earth-Centered- Earth-Fixed coordinate system. Analysis is per- formed on two types of maneurvers, linear acceler- ation and steady turn. These maneuvers could be used for in-flight INS alignment using GPS. During the constant linear acceleration without rotation rela- tive to the earth, the linear system model is shown to be time-invariant. The observability analysis for the time-invariant linear system model shows that linear acceleration does not change the number of observ- able modes but rather the structure of the observ- able space. For a non-constant linear acceleration or a steady turn, the perturbation linear system be- comes time-varying. For this time-varying system, three types of observability are considered, complete, differential and instantaneous observability. Instan- taneous observability is the strongest properties and means that the state of the system at any time may be determined instantaneously from observation of the output and its derivatives. Instantaneous observabil- ity is important for fast in-flight INS alignment. It is shown that the number of instataneously observable modes is increased by at least 2 during a maneuver. Hence, some linear combinations of the attitude an- gles become instantaneously observable.
Published in:	Proceedings of the 15th International Technical Meeting of the Satellite Division of The Institute of Navigation (ION GPS 2002) September 24 - 27, 2002 Oregon Convention Center Portland, OR
Pages:	1489 - 1499
Cite this article:	Rhee, I., Abdel-Hafez, M. F., Speyer, J. L., "On the Observability of an Integrated GPS/INS During Maneuvers," Proceedings of the 15th International Technical Meeting of the Satellite Division of The Institute of Navigation (ION GPS 2002), Portland, OR, September 2002, pp. 1489-1499.
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