Adaptive sliding mode control for attitude tracking of flexible spacecraft with bounded inputs

This paper deals with the trajectory tracking for a flexible spacecraft subjected to bounded control input under parameter uncertainties and external disturbances. A simplified adaptive sliding mode control system is designed for the attitude tracking control and vibration suppression of flexible spacecraft, with the degree of sharpness of the control permitted to vary with time according to a set of user-defined parameters. The associated stability proof is constructive and accomplished by the development of a Lyapunov function candidate. It is shown that global stability of the overall system is guaranteed with explicitly accounting for the bounded control input and even in the presence of bounded disturbances and parametric uncertainty. Although control smoothness is preserved at all times, it is important to note that the results of this paper that are derived with respect to bounded control input place no additional restrictions on the body inertias and make no other small-angle assumptions. The closed-loop performance of the new control solution derived here is evaluated extensively through numerical simulations, in which the flexible dynamics is treated as additional disturbance acting on the rigid structure.