Non-singular terminal second-order sliding mode control of spacecraft on disturbance observer

In order to eliminate the influence of disturbance torque and structural uncertainty on the maneuvering control performance of rigid satellite attitude tracking, a non-singular terminal second-order sliding mode control method based on a novel disturbance observer is proposed in this paper. Firstly, a disturbance observer combined with a tracking differentiator is designed to estimate the uncertain items in the satellite system. The estimated value is used for feedforward compensation, and the estimation error is guaranteed to converge within a limited time. On this basis, a non-singular terminal sliding mode surface is designed to ensure that the attitude error can converge in finite time when the system reaches the sliding mode, and the controller is designed by using the second-order sliding mode reaching law to ensure that the system reaches the sliding mode in a finite time. At the same time, the existing disturbance can be further suppressed when the error of the disturbance observer is not fully converged, and the finite-time stability of the closed-loop attitude tracking system can be achieved, and its stability is strictly proved by the Lyapunov method. Simulation results show that the error of the disturbance estimation value can be converged in limited time, which proves that the control method has good robustness to the existing uncertain disturbances, and the chattering phenomenon is obviously weakened because the disturbance is compensated. © 2023 South China University of Technology. All rights reserved.