The design of LOS reconstruction filter for strap-down imaging seeker

In this paper, the methods of line-of-sight (LOS) and LOS rate reconstruction in strap-down imaging seeker system are investigated. A LOS reconstruction filter for strap-down seeker is proposed. An exact LOS dynamic model of strap-down seeker is constructed by applying fully the output information of rate gyro and measurement information of the seeker. Compared with conventional LOS dynamic models, the relative distance and its rate between the missile and its target, which are unobservable to imaging seekers, together with the unknown maneuver models of the target are unnecessary. As a result, the model is convenient to use. Based on the proposed model, the reconstruction filter is designed to obtain more precise LOS angle, where the theory of unscented transformation (UT) and unscented Kalman filter (UKF) is applied to treat the nonlinearity in the proposed model. The results of computer simulations justify the validity of the LOS reconstruction filter, which can be used to improve the accuracy of LOS rate estimation.