Adaptive Integral Sliding Mode Guidance Law with Impact Angle Constraint Considering Autopilot Lag

For the interception problem of maneuvering targets, considering impact angle constraint and first-order autopilot lag, an adaptive integral sliding mode guidance law is designed. A new nonsingular finite-time integral sliding mode surface is constructed, which consists of LOS angle, LOS angular rate and LOS angular acceleration, and ensures that the states of the guidance system converge to zero on the sliding mode surface in a finite time. Moreover, an adaptive law is designed to estimate the upper bound of the target's unknown acceleration. The Lyapunov stability theory proves that the guidance system can converge to zero strictly in a finite time with the proposed guidance law. Finally, the simulation results verify the effectiveness of the designed guidance law.