Optimal trajectory tracking for missiles with Doppler Beam Sharpening radars

This paper investigates optimal trajectory tracking for missiles fitted with Doppler Beam Sharpening seekers, which are used to generate a radar image of the terrain. The guidance problem for this type of sensor is complex as constraints must be imposed on the flight path of the missile to ensure the seeker can obtain adequate crossrange resolution for target recognition and aimpoint selection. Terminal position and impact angle constraints are also imposed in the guidance problem. An open-loop skid-to-turn trajectory optimization problem is solved numerically and then used as an optimal trajectory to follow using closed-loop in-flight controls. This closed-loop guidance is based on linear quadratic regulation with a switchover to an impact angle guidance law. In this paper we also investigate the effectiveness of a preview term based on prediction of the future trajectory from the current state. Results with and without the preview term are presented for a test example.