Velocity‐free adaptive nonsingular fast terminal sliding mode finite‐time attitude tracking control for spacecraft

Aiming at the attitude tracking control problem of rigid spacecraft under the condition of unmeasurable angular velocity information, a velocity‐free adaptive nonsingular fast terminal sliding mode finite‐time tracking control method is proposed. The finite‐time extended‐state observer is used to estimate the attitude tracking speed errors and the integrated disturbances. Combined with the above control method, a fast nonsingular terminal sliding mode controller with attitude measurement is designed and the adaptive technology is introduced to compensate for the influence of observation errors on the controller. The finite‐time convergence of the observer and the control method was demonstrated based on Lyapunov theory, and the effectiveness of the proposed method is verified by numerical simulations.