Impact of radial force nonlinearities on decentralized control of magnetic bearings

This paper describes impact of nonlinearities of the radial force on decentralized control of active magnetic bearings (AMBs). Two cases with different design are analyzed; one with a considerable impact of magnetic nonlinearities, and other with almost linear magnetic properties. The current and position-dependent radial forces are determined by finite element computation over the entire operating range. The obtained radial force characteristics are incorporated into the proposed dynamic AMB model. The presented results show that nonlinearities of radial force deteriorate dynamic behavior of the closed-loop system; moreover, operating range of the AMB is considerably reduced.