Internal-mode based sliding mode variable structure attitude control of flexible spacecraft

The disturbances of flexible spacecraft, such as the uncertainty of rotary inertia and the external disturbances, can be classified as norm bounded variable, harmonic variable, gradient bounded variable, etc. These disturbances severely impact the attitude stabilization of flexible spacecraft. Aiming at the attitude control of flexible spacecraft, a nonlinear controller combining sliding mode variable structure control and internal model principle is designed, which can suppress both the constant interference and the periodic interference. The close-loop system is proved to be stable based on the Lyapunov method and the numerical simulation results verified the effective of the control approach. Moreover, the results show the rapid convergence and high accuracy of steady state error, and the controller can reduce disturbances efficiently.