Qualitative indicator-based guidance scheme for bank-to-turn missiles against couplings and maneuvering targets

This paper deals with the design of a three-dimensional (3-D) robust guidance scheme for bank-to-turn (BTT) missiles against couplings and target maneuver. Firstly, the missile-target coupled relative dynamics are established. Then, a qualitative indicator (QI) is designed based on Lyapunov stability theory for both coupling and target maneuver terms to indicate whether they strengthen or weaken the system stability. Moreover, a nonlinear disturbance observer (NDOB) with fixed-time convergence is introduced to estimate the unknown target acceleration. A robust guidance scheme is proposed by synthesizing QI, sliding mode control (SMC) and NDOB. The stability of guidance system is proven via Lyapunov stability theory. Finally, numerical simulations are executed to validate the effectiveness of proposed guidance scheme.