Impact vector guidance with monotonically decreasing look angle

This paper addresses the impact vector control guidance (IVCG) problem for missiles equipped with strap-down seekers to impact a stationary target under a field-of-view (FOV) constraint. An auxiliary variable that couples the look angle and the error angle is prescribed as a function of range. Under the stated admissibility conditions, this construction maintains a strictly decreasing total three-dimensional (3D) look angle, while terminal asymptotic analysis predicts convergence of both angles. An achievable impact-direction set is constructed to identify terminal directions compatible with this monotonicity requirement. The main benefit of the proposed 3D approach is that it directly constrains the total 3D look angle, enabling monotonic decrease under a less restrictive condition than decoupled two-dimensional (2D) methods, as evidenced by the larger sampled feasible set obtained for the considered geometry. Terminal asymptotic analysis further predicts the decay of the lateral acceleration command, and the behavior of the guidance law under the considered stationary-target engagement conditions is evaluated through numerical simulations.