Robust variable structure control of flexible spacecraft containing input nonlinearity/dead-zone

This paper proposes a robust control algorithm for stabilization of a three-axis stabilized flexible spacecraft in the presence of parametric uncertainty, external disturbances and control Input nonlinearity/dead-zone. This control algorithm is based on variable structure output feedback control design technique, and explicitly accounts for the control input nonlinearity/dead-zone in the stability analysis. The controllers guarantee the global reaching condition of the sliding mode in the spacecraft dynamics system and ensure that the system trajectories globally converge to the sliding mode. Moreover, in the sliding mode, the investigated dynamics system still bears the insensitivity to the uncertainties and disturbances as the system with linear input. An additional attractive feature of the control method is that the structure of the controller is independent of the elastic mode dynamics of the spacecraft, since in practice the measurement of flexible modes is not easy or feasible. Numerical simulations show that the precise attitude control and vibration suppression can be accomplished using the derived controller for both cases with and without adaptive control.