Non-fragile negative imaginary output feedback control for attitude stabilization of flexible spacecraft

The robust non-fragile attitude stabilization controller for flexible spacecraft with model parameters uncertainty is difficult to be synthesized with negative imaginary system which is widely applicable for the vibration control of flexible structures. To address this issue, this paper proposes a negative imaginary output feedback H_∞ synthesis strategy, in which the model parameters uncertainty, controller gain perturbations, unknown inertia and actuator faults are considered simultaneously. This strategy can guarantee that the closed-loop attitude control system has asymptotical stability with H_∞ performance and approximates to negative imaginary. The iterative algorithm under linear matrix inequality constraints gives the conditions for the existence of such controller. In addition, external disturbance and input saturation are also taken into account. Compared with the general non-fragile H_∞ controller, the numerical simulations demonstrate the superiority of the proposed controller in attitude stabilization and vibration suppression of flexible spacecraft.