Stiffness measurement of radial hybrid magnetic bearing in MSFW

To measure the current stiffness and displacement stiffness of a radial hybrid magnetic bearing, a new stiffness measurement method is proposed for a magnetically suspended flywheel (MSFW). Firstly, the suspension force and stiffness characteristics of the radial hybrid magnetic bearing are studied using magnetic circuit method and finite element method. Secondly, a detailed stiffness measurement method for a radial hybrid magnetic bearing is proposed. It has two procedures: one is the determination of the relationship between the rotor displacement and the corresponding current when the gravity of the rotor is in the +X (or +Y) direction and −X (or −Y) direction respectively, and the other is the calculation of the current stiffness and the displacement stiffness of the radial hybrid magnetic bearing in an MSFW according to the relationship between the rotor displacement and the current. Three prototype MSFWs with angular moments of 15 Nms are manufactured, and they mainly consist of two axial hybrid magnetic bearings and one radial hybrid magnetic bearing. The proposed stiffness measurement method of the radial hybrid magnetic bearing is verified by all prototype experiments.