Interference suppression 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 size of systems, triaxial active control magnetic bearings (triaxial AMBs) have been proposed. They consist of some radial and thrust MBs. 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 characteristics when it suspends a rotor in the radial and the thrust direction simultaneously. In order to solve this problem, we propose a position control system with nonlinear compensator that the compensation characteristics are changed by current and rotor displacement. The interference characteristics are investigated using a finite element method. Moreover, the dynamic performance is evaluated, and it is clarified that the proposed control system can suppress the interference.