Robust Partial-state Feedback Attitude Control for Tracking Tumbling Target

This paper investigates the partial-state feedback attitude control problem of tracking an uncontrolled tumbling target in the presence of external disturbances and control input saturation. Firstly, a nonlinear relative attitude motion model is presented, and a dead-zone operator based model is investigated to describe the input saturation phenomenon. Subsequently, a novel model-assisted extended state observer is established to estimate the unmeasured states and the lumped uncertainties. Then, by combining the extended state observer technique with sliding mode methodology, an output-feedback anti-saturation control strategy that removes the need for full-state measurements between the two spacecrafts is proposed. Within the Lyapunov framework, the proposed control strategy is able to guarantee that the relative attitude errors can converge to small regions containing the origin. Finally, numerical simulations are performed to demonstrate the effectiveness of the presented control strategy.