13 October 2008 Nonlinear/linear combination filter for SINS alignment
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In order to improve the initial alignment accuracy of Strapdown Inertial Navigation System (SINS) in case of large attitude errors, a combination of nonlinear Unscented Kalman Filter (UKF) and the linear Kalman Filter (KF) has been considered. For large initial attitude errors, both in heading and the level plane, application of the KF to the linearized error model of SINS does not yield good initial attitude estimation. To overcome this problem, the UKF has been employed. Initially state feedback has not been applied to maintain the nonlinear nature of the system. It is applied at the end of estimation using UKF. Simulation results for stable base SINS alignment have shown high level of accuracy for heading estimation but not equally so for the level plane. However, after employing state feedback at this point linearized approximation of the error model is justified. The superior performance of KF for linear systems is then exploited. Simulation results show marked improvement as compared to the single use of UKF or the KF.
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Majeed Salman, Majeed Salman, JianCheng Fang, JianCheng Fang, Fan Xu, Fan Xu, "Nonlinear/linear combination filter for SINS alignment", Proc. SPIE 7128, Seventh International Symposium on Instrumentation and Control Technology: Measurement Theory and Systems and Aeronautical Equipment, 71281Y (13 October 2008); doi: 10.1117/12.806754; https://doi.org/10.1117/12.806754

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