Nonlinear control of a magnetically levitated single-axis controlled axial blood pump

This paper presents a nonlinear control scheme of a magnetically levitated single-axis controlled axial blood pump. The rotor has a hollow structure for fluid flow, and the impeller is mounted on the rotor inner surface. The magnetic suspension system is realized using two passive magnetic bearings for radial direction balancing and an electromagnetic actuator for axial position balancing. Owing to the nonlinear electromagnetic actuator force, the system is inherently nonlinear. In particular, when the rotor starts up or far away from the operating point, rotor dynamics is severely nonlinear. For these reasons, a nonlinear PID and starting controller is proposed to improve rotor dynamics. The experimental results validated that the control system is more stable with the proposed scheme.