Modeling and Control of a Magnetic Bearing System for the Magnetically Suspended Centrifugal Blood Pump

Abstract

We have developed a centrifugal blood pump with a magnetically suspended impeller to reduce the hemolysis level for long-term use. The main advance we have made was simplifying the traditional 5 axes controlled magnetic bearing system, since the total device should ultimately be small enough to implant into a human body. A simplified magnetic bearing system with only 3 actively controlled axes was designed to levitate the impeller. The state equations of the magnetic bearing plant were established using Lagrange's methods, and using the results, a linear quadratic optimal controller was designed to regulate the position of the impeller. Flow rate and differential pressure of 5L/min and 300mmHg, respectively at a motor speed of 2750 rpm was achieved from a mock circulation setup. These results show satisfactory performance as a cardiopulmonary bypass device. The lowering of pumping efficiency as the clearance between the impeller and pump housing increased was negligible. Thus for power efficiency, the smallest gap not leading to a hemolysis level rise can be determined as a feasible operation clearance.