Initial cooperative alignment control for non-contact annular electromagnetic stabilized spacecraft.

The non-contact annular electromagnetically stabilized spacecraft (NCAESS) is an effective solution to improve the attitude control performance. However, a critical issue that must be addressed is the initial alignment control problem when the two modules are released into the non-contact state during on-orbit operation. This paper proposes a two-module cooperative alignment control method based on the nonlinear disturbance rejection model predictive control (NDRMPC) algorithm, which guarantees both collision avoidance and rapid stabilization of the NCAESS. Compared with the traditional method that are only applicable to small release angles and angular velocities, the proposed method features two significant improvements. First, it enables the prediction and planning of the future state trajectory of the NCAESS, allowing the payload module to actively participate in collision avoidance, thereby ensuring the relative states of the two modules stays within the safety threshold. This enables the proposed method to effectively handle four release states with large angles and angular velocities. Second, the developed NDRMPC algorithm achieves precise predictive control of the NCAESS, while its optimization problem relies solely on a nominal model, which can be calculated in parallel or offline, thus ensuring the system meets its real-time requirements. To verify the feasibility and effectiveness of the proposed method, numerical simulations are conducted in this paper. The results demonstrate that the method successfully avoids collision between the two modules, while achieving the rapid asymptotic convergence, effectively solving the initial alignment control problem of the NCAESS.