Estimation of sonobuoy position relative to an aircraft using extended kalman filters.

Abstract

In airborne anti-submarine warfare there is a need to more accurately determine the positions of sonobuoys on the surface of the vater. This report develops two algorithms which employ extended Kalman filters to determine estimated position. The bearing from the aircraft to the sonobuoy is the primary measurement. Range information is not available. The first algorithm is a six-state filter which was reduced from the 13-state system developed by the Orincon Corporation Its states include relative jjosition, relative velocity, and inertial misalignments. The second algorithm includes two cascaded Kalman filters. The primary two-state filter estimates sonobuoy position. A secondary filter estimates drift from information obtained from the primary filter. Both algorithms successfully estimated sonobuoy position for simulated aircraft data. The effect of a ircraf t-to-sono bucy range, the frequency of measurement, and changes in altitude are also analyzed.