Model-Free Adaptive Attitude Control for Partially Constrained Combined Spacecraft With Adversarial Disturbances

This paper investigates the attitude control of a combined spacecraft with partial constraints. These partial constraints may lead to relative motion between the end-effector and the target spacecraft, especially when the target generates output disturbance torques. This significantly impacts the dynamics and control of the combined spacecraft. In this paper, by introducing generalized coordinates to describe the relative motion, a dynamic model is derived based on the Lagrangian method to characterize the motion of the combined spacecraft in both rigid mode and relative motion mode. Additionally, a model-free adaptive controller based on a disturbance observer is developed to stabilize the partially constrained combined spacecraft, with an update law designed to adjust the observer gains for improved estimation performance. Simulation results show that: 1) the established dynamic model effectively describes the dynamic characteristics of the partially constrained combined spacecraft; 2) the proposed control method proves effective, achieving higher steady-state accuracy under time-varying disturbances compared to a previous model-free adaptive control method.