Performance of a Single-Axis Controlled Magnetic Bearing for Axial Blood Pump

This paper presented a prototype axial blood pump with a single-axis controlled magnetic bearing. The magnetic suspension system is realized by using passive magnetic bearings for radial direction balancing, and an electromagnetic actuator to stabilize the axial direction actively. A sensor assembly for axial position sensing is also presented. This sensor can measure axial position with good accuracy. The rotor has an inner impeller structure to accommodate fluid flow, and it is driven by a brushless DC motor. A prototype pump was built and tested both in air and in water. The experimental results demonstrated successful pump operations. The rotor can be stably levitated in the air gap. The motor was operated up to 4500 rpm in air, and 6000 rpm in water. The maximum radial position error was about 0.5 mm when the motor was running at speeds near the critical frequency. Axial position errors were less than 0.1 mm for all the experiments performed.