Abstract
An extracorporeal magnetic levitation blood pump consisting of an axial magnetic bearing, a levitation impeller and an axial flux motor has been developed for the purpose of recovering autologous cardiac function of patients with acute heart failure. Rotational speed of a levitation impeller is changed in synchronization with heart beat to increase the blood flow in the coronary artery of a natural heart and reduce the load on the natural heart. The exponential change in the rotating speed of the levitation impeller during pulsating operation causes a detection error of rotating angle, which prevents maintaining constant phase difference between rotor flux and control flux. Increase/decrease in axial attractive force produced by the motor due to the variation of phase difference deteriorates suspension stability of the maglev motor. In this study, the device using the magnet coupling mechanism that can suppress axial vibration of the impeller during pulsating operation was designed. The required performance of the DC motor was evaluated from the performance of conventional maglev motor, and the target performance was set to 3000 rpm maximum rotational speed, 70 mNm torque, 55 N axial load resistance. In the future, an extracorporeal magnetic levitation blood pump with magnet coupling mechanism will be manufactured and the performance will be compared with the conventional device.
