Fixed-Time Disturbance Observer Based Nonsingular Fast Terminal Sliding Mode Guidance with Impact Angle Constraint

In this paper, an impact-angle-constrained nonsingular fast terminal sliding mode control (NFTSMC) based guidance law with fixed-time disturbance observer (FxTDO) is proposed in the presence of uncertain disturbances. Without the requirement of the upper bound of the disturbance and its derivative, a bi-limit weighted fixed-time disturbance observer is used to estimate the unknown lumped disturbance. In order to attenuate the chattering and ensure convergence within finite time, a nonsingular terminal sliding mode guidance method is adopted with the disturbance estimation. Numerical simulation results with some comparisons demonstrate the effectiveness of the proposed method.