Reaction Wheel Parameter Identification and Control through Receding Horizon-Based Null Motion Excitation

A torque tracking and parameter identification scheme using a receding horizon optimization is developed for an over-actuated spacecraft Reaction Wheel Array (RWA). Additional actuator motion, constrained to the null-space of the array, is provided in order to enhance persistence of excitation. Therefore, the system parameters are learned without inducing large perturbations to the controllable body (e.g., spacecraft bus). Constraining the excitation inputs to the nullspace, or null-motion excitation (NME), provides a way of adding information about the actuator misalignments with perturbations that are local to the trajectory, and scaled by the size of the parameter error. The discussed method provides a solution to the torque tracking problem, while simultaneously providing parameter identification through minimization of an appropriately defined objective function that penalizes the predicted parameter error covariance. The potential of the receding horizon approach to outperform the baseline null motion excitation algorithm proposed in earlier publications is demonstrated through simulations.