Design and Analysis of a Two-Axis-Magnetic Bearing with Permanent Magnet Bias for Magnetically Suspended Reaction Wheel

A magnetically suspended reaction wheel (MSRW) for high-precise stabilization of spacecraft attitude is described in this paper. The speed range of the MSFW is from -6000 r/min to 6000 r/min, and angular momentum at normal speed is 30 Nms. A two-axis-magnetic bearing with permanent magnet bias is designed for reducing the power and minimizing the size, etc. The magnetic force, current stiffness, and negative position stiffness are derived by the equivalent magnetic circuit. The nonlinearity of this radial magnetic bearing is shown by using the characteristic curves of force-current-position, current stiffness, and position stiffness considering all the positions of the rotor within the clearance space and the control current. The maximum bearing capacity is given in this paper. The analysis and design method in this paper that can predict all the performance of the radial magnetic bearing with permanent magnet bias can be supplied for the design and analysis of the magnetic bearing wheel system. The errors of current stiffness and position stiffness for the two-axis-active magnetic bearing calculated by the linearized model compared with the FEM method are 5.9 % and 4.5 % respectively. The linearized model is validated by the FEM.