UC Santa Cruz

Utilization of reaction wheel array attitude control systems aboard Cubesats is challenging because they tend to consume a significant fraction of the energy budget. In this thesis, battery energy losses incurred by large angle maneuvers in the absence of a regenerative braking system are optimized using a Legendre pseudospectral direct optimal control method. Numerical challenges arising from non-smoothness of the power model are overcome. The value of optimizing battery losses rather than the integral of the sum of squares of control torque is evaluated as a function of system and maneuver parameters. Improvements are found to be significant when the moments of inertia of the reaction wheels are small. Both approaches are shown to outperform the industry standard eigenaxis maneuver. A method for rapidly computing near optimal solutions in orbit based on interpolation from a bank of precomputed solutions is proposed. Optimal trajectories are executed on a real reaction wheel.