Nonlinear Impact Angle Guidance Law Canceling Autopilot Lag for Time-Varying Thrust

Impact angle guidance laws are widely used for miss distance and angle constraints of unmanned aerial vehicles(UAVs). Most research work assumes that UAV speed is constant. However, UAVs equipped with boosters generate time-varying thrust, which results in time-varying vehicle speed. Moreover, autopilot lag, which is an inner loop of a guidance loop, degrades guidance performance because of a delay factor. This paper presents a nonlinear impact angle guidance law that address the delay factor of autopilot and time-varying vehicle speed. The proposed guidance law controls miss distance, impact angle, and cancels autopilot lag. Furthermore, we prove that line-of-sight error of the proposed guidance law is converged in finite time by analyzing Lyapunov Stablity. The proposed algorithm is validated by numerical simulations.