Extended state observer based output control for spacecraft rendezvous and docking with actuator saturation.

Area of Science:

• Aerospace Engineering
• Control Systems Theory
• Robotics

Background:

• Spacecraft rendezvous and docking are critical for space missions.
• Controlling a chaser spacecraft to dock with an uncontrolled tumbling target presents significant challenges due to unpredictable motion and external disturbances.
• Actuator saturation further complicates control design, potentially leading to instability.

Purpose of the Study:

• To develop a robust output-feedback control strategy for chaser spacecraft docking with tumbling targets.
• To achieve precise relative position tracking and attitude synchronization.
• To address challenges posed by external disturbances and actuator saturation without requiring precise target motion information.

Main Methods:

• Combined extended state observer (ESO) technique with backstepping control methodology.
• Incorporated a Nussbaum-type function to handle actuator saturation nonlinearities.
• Utilized Lyapunov stability analysis to guarantee convergence of errors.

Main Results:

• The proposed control strategy ensures that relative position and attitude errors converge to small regions around the origin.
• Demonstrated robustness against external disturbances.
• Successfully compensated for actuator saturation effects.

Conclusions:

• The developed output-feedback control strategy is effective for spacecraft rendezvous and docking with uncontrolled tumbling targets.
• The method provides guaranteed stability and convergence, even with actuator saturation and unknown target dynamics.
• Numerical simulations validate the proposed approach's performance and robustness.