High-speed magnetically levitated reaction wheels for small satellites

Mechanical wear and stiction can be eliminated by using magnetic bearings instead of ball bearings in spacecraft reaction wheels. Accordingly, the lifetime of attitude control systems can be increased and a smooth torque can be achieved also at speed zero crossings. Moreover, the microvibration emission of the reaction wheels can be minimized and actively controlled. A further advantage of magnetically levitated reaction wheels is the ability to rotate at speeds higher than the state of the art. High-speed reaction wheels can be made smaller in size; however, they require higher power levels for the same reaction torque. Therefore, this paper analyzes the circulation of energy within different reaction wheels of an attitude control system in order to limit the external power requirement. Moreover, integrated position sensors are used for limiting the axial length of the rotors, thereby further increasing the speed limits that may be resulting from rotor dynamics. A functional demonstrator is built and equipped with two different reaction wheel rotors for initial tests. The electrical machine design and the operation of the magnetically levitated reaction wheel systems are verified experimentally.