Attitude Tracking and Vibration Suppression During Flexible Spacecraft Maneuver under Input Nonlinearities and Measurement Errors

This paper addresses attitude tracking and vibration suppression problems during the flexible spacecraft maneuvers under the influence of system parametric uncertainties, external disturbances, and actuator nonlinear saturation without utilizing intelligent materials or smart vibration suppression actuators. Specifically, we develop a dual observer-based backstepping (DOB-BST) controller that employs a recursive control design to devise observers to estimate and attenuate the effect of perturbations in spacecraft attitude kinematics and dynamics. Moreover, the proposed DOB-BST controller uses an input compensator to mitigate the adverse impacts of saturation nonlinearity in a closed-loop system. The proposed control structure offers finite time convergence of closed-loop system states to a small neighborhood of zero. In addition, we give system state convergence regions and derive explicit tuning conditions to downsize the convergence region using Lyapunov stability analysis. Finally, the simulation experiment results confirm the performance of the proposed control algorithm despite the multiple system constraints.