Attitude control of flexible spacecraft subject to disturbances with unknown frequencies

Abstract

The disturbance rejection and vibration suppression problem (DRVSP) of flexible spacecraft has been investigated recently when the disturbance frequencies are exactly known. In this paper, we further consider the same problem when the disturbance frequencies are unknown. An adaptive state feedback controller is proposed, which employs an internal model to reject the external disturbance with unknown frequencies and an adaptive law to estimate the unknown frequencies. Note that the proposed controller can not only solve the DRVSP of flexible spacecraft without the measurement of the modal variables, but also guarantee that the estimated frequencies converge to their true values. Simulation results illustrate the effectiveness of the proposed controller.