Nonsingular Terminal Sliding Mode Guidance Law with Time-Varying Impact Angle Constraints

In the missile guidance problem with the impact angle constraint, the existing impact-angle-control guidance laws cannot work well when the desired impact angle varies with time. For this purpose, a nonsingular terminal sliding mode guidance law is proposed. The main idea is to design two sliding surfaces: the first surface is used to reduce the relative distance of missile-target; and the second surface is designed to meet the requirement of time-varying impact-angle. The first surface is switched to the second one when the relative distance of attacking missile and target is less than a specified value. Additionally, the stability of the guidance system is proved by using Lyapunov function. Numerical simulation results shows that the proposed guidance law can achieve the expected performance.