Intercetp angle constrained guidance law using adaptive extended state observer

In this paper, a novel nonsingular terminal sliding mode guidance algorithm is proposed for an interceptor missile against maneuvering targets with falling angle constraints. Firstly the relationship between line-of-sight (LOS) angle and the attack angle requirement is established. Then an adaptive varying-gain extended state observer (AESO) is introduced to estimate the target acceleration, which significantly suppresses the peaking phenomenon exist in conventional extended state observer, especially at the initial time. The stability of the entire system is demonstrated based on the Lyapunov theory. Simulation results show that the proposed guidance law combining AESO outperforms the conventional algorithm with accurate intercept angle and smooth control inputs.