Nutation is one of unwanted motions from the viewpoint that spins about the principal axes are the simplest and the most unchangeable. Thus far, nutation control and spin inversion maneuvers have been treated from different perspectives for the stabilization of spinning spacecraft. Many nutation control systems have tried to guarantee asymptotic global convergence to the reference axis spin. Meanwhile, whether the final spin direction is parallel or anti-parallel to the reference axis has been overlooked in nutation control problems. Therefore, this study incorporates the spin inversion control problems into global nutation control issues preventing the spacecraft from unwanted inverted turns.
Freely spinning body in three-dimensional space continuously tends to spin according to the law of inertia. Even under external torques or internal energy dissipation, motion of a spinning object changes gradually. Therefore, an actuator exerting continuous torque such as a reaction wheel can be proper equipment for nutation control rather than thrusters.
This research tackles these problems in a unified framework by applying a predictive control for minor axis spinners with a single transverse wheel. Predictive control seeks a control input minimizing a cost function in the form of weighted sum of predicted output error and control effort. A two-step design approach of the proposed application defines the cost function as: 1) angular momentum only on the orthogonal plane to the minor axis, and 2) angular momentum augmenting the error of the desired minor axis. Corresponding weight parameters are designed based upon physical meanings, and a final desired state or an on-line time-varying trajectory is suggested as a reference for successful and effective control.
The first control law is called PNC1 (predictive nutation controller 1), and the second is PNC2. PNC1 has a form of proportional and derivative feedback controls. PNC1 is shown to be essentially globally stable a...