Observer-Based Nonsingular Terminal Sliding Mode Guidance Law with Fixed-Time Convergence

In order to solve the problems of singularity, slow convergence rate and external disturbance, a non-singular fixed-time sliding mode guidance law with attack Angle constraint is proposed. Firstly, a non-singular terminal sliding mode surface is constructed, which ensures that the line-of-sight (LOS) Angle and LOS Angle rate can converge to the expected value within a given fixed time. Secondly, the upper bound of target interference is estimated by constructing a fixed-time observer, where the unknown upper-bound of the external disturbance caused by the target acceleration is estimated online. The stability of the guidance law is analyzed and proved by using Lyapunov stability theory. Finally, the effectiveness and robustness of the guidance law are verified by numerical simulation.