Three-Dimensional Approach Angle Guidance Under Varying Velocity and Field-of-View Limit Without Using Line-of-Sight Rate

In this article, a practical three-dimensional (3-D) guidance is designed to achieve trajectory constrained flight, i.e., arriving at the destination with desired approach angles under limited field-of-view (FOV) and varying velocity. For this goal, the nonlinear engagement model is first transformed to a set of new differential equations in terms of the line-of-sight (LOS) angles. Then, the approach angle constraints are handled by constructing two reference range profiles as cubic polynomials of LOS angles. By solving the unknown coefficients involved in the polynomials, a semianalytical 3-D guidance solution is derived from the second-order range dynamics. To meet the FOV limit and avoid the initial guidance saturation, the achievable approach angle set is determined for capturability analysis by introducing the look angle dynamics with respect to the range profiles. The technique does not involve the model linearization, guidance switching logic, constant velocity assumption, and LOS rate information. Notably, only the LOS angle measurement is required during the guidance process once the initial conditions are provided, which makes it preferable for vehicles equipped with passive angles-only sensors. Extensive numerical simulations and Monte Carlo test are conducted to validate effectiveness and robustness of the proposed technique.