DEVELOPMENT OF A PROTOTYPE MAGNETICALLY SUSPENDED ROTOR VENTRICULAR ASSIST DEVICE

A continuous flow centrifugal blood pump with magnetically suspended i mpeller has been designed, constructed and tested. The system can be f unctionally divided into three subsystem designs: 1) centrifugal pump and flow paths, 2) magnetic bearings, and 3) brushless DC motor. The c entrifugal pump is a Francis vane type design with a designed operatin g point of 6 L/min flow and 100 mmHg pressure rise at 2,300 RPM. Peak hydraulic efficiency is over 50%. The magnetic bearing system is an al l active design with five axes of control. Rotor position sensors were developed as part of the system to provide feedback to a proportional -integral-derivative controller. The motor is a sensorless brushless D C motor. Back electromotive force voltage generated by the motor is us ed to provide commutation for the motor. No slots are employed in the motor design in order to reduce the radial force that the bearings mus t generate. Tests pumping blood in vitro were very encouraging; an ind ex of hemolysis of 0.0086+/-0.0012 was measured. Further design refine ment is needed to reduce power dissipation and size of the device. The concept of using magnetic bearings in a blood pump shows promise in a long-term implantable blood pump.