The problem of estimating the feedback necessary for the implementation of the proportional navigation guidance law on a guided projectile with a strapdown seeker is addressed through the development of a line of sight rate extended Kalman filter (EKF). The seeker is assumed to be computer vision based, which requires the filter to accommodate significant time delays due to the processing requirements of computer vision algorithms, although specific computer vision algorithms are not discussed here. The effect of errors in the attitude solution on line of sight rate observer performance are analyzed and accounted for in the Kalman filter design. Simulations of a highly maneuverable projectile engaging a moving, but non-maneuvering target are presented to evaluate the filter. It is found that since attitude is not strongly observable on projectiles in free fall, better line of sight rate results might be possible when the attitude solution used to calculate line of sight rate comes directly from angular rate sensor integration instead of an attitude Kalman filter.
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