A Low-noise, High-bandwidth Magnetically-levitated Momentum-wheel for 3-axis Attitude Control from a Single Wheel

This paper proposes a new concept for attitude actuation for small satellites that uses active magnetic bearings to support and tilt a spinning rotor to provide 3-axis attitude control of the satellite using a single actuator. A controlled 3D motion in the spinning rotor provides a conventional torque output about the momentum axis and a gyroscopic torque output about any direction in the plane normal to the spinning axis. Therefore, a single tilting momentum-wheel can generate torque along the three principal axes of the satellite, providing mass and power savings, or redundancy. In this paper we present a model of, and results from the engineering model that has been built of the tilting magnetically-levitated momentum-wheel. The control loop that levitates and tilts the rotor is discussed. The 3axis actuation of this wheel is demonstrated with simulations of the wheel fitted to the TopSat small satellite. The bandwidth and torque output of the wheel are compared with a conventional momentum wheel’s. The power consumption, operation and stiffness of the magnetic bearing are discussed. The 2.5 micrometre translational and 0.1 milliradian rotational control of the wheel obtained in experiments with the engineering model are demonstrated.