Abstract：To adapt to the requirement of high performance precision strike, an impact angle constraint guidance law is proposed by employing a novel adaptive sliding mode observer in this paper. Firstly, the guidance system model with strict feedback is built with the target maneuvering acceleration as unknown bounded uncertainty. Secondly, an adaptive sliding mode disturbance observer based on super twisting sliding mode is derived to accurately estimate the differential bounded disturbance, with its finite time convergence property proved using quadratic Lyapunov functions. Thirdly, the impact angle constraint guidance law is designed based on the fast nonsingular terminal sliding mode and adaptive sliding mode disturbance observer, and the finite time convergence of the guidance system is proved based on the finite time stability theory and the homogeneous theory, and the convergence regions of the sliding variable and the system states are also given. Simulation results indicate that the proposed guidance law can not only guarantee high guidance accuracy, but also satisfy the impact angle constraint.
