Modeling and attitude control of spacecraft with an unbalanced rotating device

This letter addresses the problem of controlling the attitude of spacecraft endowed with a rotating device, motivated by recent space applications which will make use of large rotating payloads. Due to the presence of uncertain and potentially large inertial asymmetries in the rotating device, an internal force and a torque can appear at interface between the spacecraft and the rotor, causing performance degradation and even affecting the system stability. To counteract such unbalance effects, active balancing systems, using movable masses mounted on the rotating device, are being considered in the literature. During the balancing phase, it is important for the attitude control system to maintain a stable configuration. After deriving a suitable control-oriented model of the multi-body spacecraft, we propose using a coordinate-free attitude controller that ensures safe balancing operations and desirable pointing performance.