Rapid Attitude Reorientation for Defunct Spacecraft Deorbit Manoeuvre based on Robust Piece-wise Affine MPC

As spacecraft reach the end of their operational life, they pose a significant threat to active spacecrafts in orbit. This paper presents an approach for rapid deorbit attitude reorientation of defunct spacecraft using Robust Piece-wise Affine Model Predictive Control (RPWA MPC) for attitude control. An innovative method where multiple solid fuel micro thrusters with brief operational duration are employed for rapid attitude reorientation. A theoretical attitude characteristic analysis for defunct spacecraft is conducted, and simulations assess the impact of environmental disturbances. Based on the analysis, this study introduces a unique single-axis attitude control strategy focused on the pitch axis to achieve the desired deorbit attitude. Given the need for the spacecraft to attain this deorbit attitude within a fixed number of control periods, a RPWA MPC controller is designed. Due to high non-linearities arising from environmental disturbance torques, the PWA model breaks down the MPC into multiple computationally feasible discrete models to reduce computational complexity. A disturbance observer is designed to provide real-time estimation of the disturbance torques in the PWA model, enhancing the robustness of the system. Numerical simulations demonstrate that only thirty micro thrusters are needed to achieve the required attitude reorientation, enabling the spacecraft to reach deorbit attitude efficiently before igniting the deorbit thrusters.