Evaluation of Position Controllability of Triaxial Active Control Magnetic Bearing Using Nonlinear Compensator

Abstract

　Magnetic bearings (MBs) levitate and suspend rotors. MBs have some advantages such as low friction, no wear, and no risk of fluid pollution because they can suspend rotors without mechanical contacts and lubricants. To avoid increasing the size of systems, triaxial active control magnetic bearings (triaxial AMBs) have been proposed. We proposed the triaxial AMB without permanent magnets which has an asymmetric structure. It is specially designed for high-temperature turbomachines. However, the triaxial AMB has interference characteris-tics when it suspends a rotor in the radial and thrust direction simultaneously. In order to solve this problem, the position control system with a non-linear compensator is proposed. The compensation characteristics are changed by current and rotor displacement. It is proved that the compensator can suppress the interference. However, it is not clarified how the position controllability changes when the compensation characteristics change. We investigate the position controllability when the compensator has different characteristics.