Accurate estimation of lever arm in SINS/GPS integration by smoothing methods

The direct accurate measurement of lever arm in an integration of Strapdown Inertial Navigation System/Global Positioning System (SINS/GPS) is difficult for airborne applications. In this paper, the lever arm was estimated by KF in taking-off stage, sensing-task stage, landing-over stage, respectively. The estimation precision of lever arm in taking-off stage can be up to 2 cm, which is better than that in other flying stages. According to known observability analysis conclusions, the optimal angular maneuver occurred in taking-off stage, which is most suitable for lever arm estimation. To exceed the estimation precision based on KF, two smoothing methods including Rauch-Tung-Striebel smoother (RTSS) and two-filter smoother (TFS) were developed for precise lever arm estimation. Both RTSS and TFS were applied to the taking-off stage and a millimeter's estimation precision of lever arm was acquired, which improves the estimation precision by an order of magnitude.