Abstract:A fuzzy neural network disturbance observer (FNNDO) based nonsingular terminal sliding mode (NTSM) finite-time control strategy is proposed for a combined spacecraft attitude control system in the presence of counteraction torque output for non-cooperative targets. Firstly, the attitude mathematical model of combined spacecraft is established with the service spacecraft as the reference, and then a FNNDO with adaptive capability is designed for the generalized disturbance torque including inertial uncertainty, counteraction torque, etc., which can achieve effective tracking of the generalized disturbance. Based on the FNNDO, the NTSM controller is designed to demonstrate the finite-time stability of the closed-loop system using Lyapunov theory. Finally, the simulation results show the effectiveness of the control strategy and the superiority of the observer in the observation performance.