Trajectory correcting and tracking based impact angle constrained circular guidance

An impact angle constrained terminal guidance based on circular trajectory correcting and tracking was proposed. The circular trajectory command was generated by circular geometry relationship and corrected by limiting the angle between the desired velocity vector and line of sight. By doing this, the problems of increased flight distance, decreased terminal velocity and large guidance commands induced by large circular arc trajectory were avoided. In order to match the terminal constraints with high precision, a trajectory tracking law was proposed. The circular trajectory command was first transformed into flight path angle and heading angle commands. Then the trajectory tracker based on proportion-derivation was designed to track these commands. Simulation results demonstrated that the corrected circular trajectory is superior to the original circular trajectory in curvature, required load and terminal speed, and the precision on both impact position and angles of the proposed guidance law is high.