Abstract
Introducing magnetic suspension to the momentum wheel of an artificial satellite is expected to enhance the reliability and the maneuvability of the satellite. However, as the stiffness of the magnetic bearing is rather small, the attitude motion of the satellite may be coupled with the wheel precession to become unstable. Although the attitude motion may be able to be stabilized at the cost of reducing the stability of the wheel precession when the tilting angles of the wheel are controlled actively, it has been difficult to get sufficient stability margin both in the attitude motion of the satellite and in the precessional motion of the wheel without attitude sensors. This paper proposes the new strategy to offer large damping factor both to the satellite motion and to the wheel precession without attitude sensors. That is achieved by introducing an observer which estimates the attitude-rate of the satellite. It is provided that the observer-based compensation is equivalent to the low-pass-filtering whose cut-off frequencies are as low as those of the attitude motion of the satellite. Some numerical examples displayed that the system has good performances.
