This paper deals with the transfer alignment problem of strap-down inertial navigation systems (SDINS), using electro-magnetic (EM) log velocity information and gyrocompass attitude information of the ship. Major error sources for velocity and attitude matching are lever-arm effect, measurement time-delay, and ship-body flexure (flexibility). To reduce these alignment errors, an error compensation method based on delay state augmentation and DCM (direction cosine matrix) partial matching is devised. A linearized error model for a velocity and attitude matching transfer alignment system is devised by first linearizing the nonlinear measurement equation with respect to its time delay, and augmenting the delay state into conventional linear state equations. DCM partial matching is then properly combined with velocity matching to reduce the effects of a ship's Y-axis flexure. The simulation results show that this method decreases azimuth alignment errors considerably.
This paper examines the transfer alignment problem of the StrapDown Inertial Navigation System (SDINS), which is subject to the ship's roll and pitch. Major error sources for velocity and attitude matching are lever arm effect, measurement time delay and ship-body flexure. To reduce these alignment errors, an error compensation method based on state augmentation and robust state estimation is devised. A linearized error model for the velocity and attitude matching transfer alignment system is derived first by linearizing the nonlinear measurement equation with respect to its time delay and dominant Y-axis flexure, and by augmenting the delay state and flexure state into conventional linear state equations. Then an H 1 filter is introduced to account for modeling uncertainties of time delay and the ship-body flexure. The simulation results show that this method considerably decreases azimuth alignment errors considerably.
Absfnzct-This paper deals with the transfer alignment problem of SDINS(StrapDown Inertial Navigation System) subjected to roll and pitch motions of the ship. Spcifically, to reduce alignment errors induced by measurement time -delay and ship body flexure, an error compensation method is deviced based on delay state augmentation and DCM@irection Cosine Matrix) partial matching. A linearized error model for the ve locity and attitude matching transfer alignment system is first derived by linearizing the nonlinear measurement equation with respect to its time delay and augmenting the delay state into the conventional Linear state euqations. And then DCM partial matching is properly combined to reduce effects of a ship's Y axis flexure. The simulation results show that the present method is effective enough resulting in considerably less azimuth alignment errors. I& TennsY-lman Filter, Measurement Time -Delay, Ship Body Flexure, SDINS, Transfer Alignment.
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