Sliding Mode Disturbance Observer Based Control for Relative Position and Attitude Coupled Spacecraft with State Constraint

When approaching an out-of-control satellite, the service spacecraft needs to have high attitude and position control accuracy, and meet the view field constraint of the measurement sensor. In addition, the control accuracy of service spacecraft is also affected by various external disturbances such as environmental disturbance and flexible appendages disturbance. To solve the above problems, a composite hierarchical anti-disturbance controller considering state constraint is proposed based on a sliding mode disturbance observer(SMDO), where SMDO is used to estimate and reject the multi-disturbances. Numerical simulations are performed to verify the effectiveness of the proposed SMDO and composite controller.