Field balancing for a magnetically suspended rigid rotor based on magnetic forces equivalence principle

A field balancing method was proposed to solve rotor unbalance vibration problems in a magnetically suspended flywheel (MSFW). Based on the equivalence principle between magnetic control force and unbalance centrifugal force, the rotor unbalance was calculated and corrected by measuring the magnetic forces. A zero-displacement controller was designed to make a rotor rotate around its geometric axis. Then the controlling force of the magnetic bearing was obtained by measuring the control current since the former was a linear function of the latter. This method eliminated the errors introduced by the oversimplification of dynamic model in conventional methods and it was especially applicable for a high-gyroscopic-effect-pancake magnetically suspended rigid rotor. The experiment results demonstrated that the method is effective to improve the balancing accuracy for a magnetically suspended rigid rotor system.