Anti-disturbance PD controller design for flexible spacecraft attitude stabilization

Both vibrations and model uncertainties will pose great challenges for accurate attitude control of flexible spacecrafts. In this paper, an anti-disturbance proportional-derivative (PD) controller is designed to stabilize the attitude while rejecting the effects of flexible vibrations, environmental disturbances, and unmodeled dynamics, which are assumed as an extended state. This controller comprises two parts, i.e. an extended state observer and a PD controller with feedforward. First, flexible vibrations, environmental disturbances, and unmodeled dynamics are regarded as an extended state which can be estimated by the extended state observer. Then, the estimated extended state can be compensated by feedforward and the attitude can be stabilized by the PD controller. Numerical simulation results are presented to demonstrate the effectiveness of the control scheme.