BLDC-control of forces in passive magnetic bearings in blood pump

Artificial heart needs blood pump which satisfies not only mechanical and electrical properties, but also very important biomedical properties, particularly frictionless, with compact design and efficiency. The only one solution to meet the requirements. It is blood pump integrated with BLDC motor with rotor suspended using passive magnetic bearings. Passive magnetic bearings are solution with all required features, they are frictionless, compact and lossless. The one disadvantage is instability of passive bearing system. A new solution for stabilization of magnetic bearings is proposed in this paper. It consists in application of proper control of BLDC drive to obtain forces that together with the forces generated by permanent magnets make overall system stable. Because the only one direction (one degree of freedom) in passive bearings is unstable, it can be stabilized using magnetic forces that come from the motor. An idea of passive bearings stabilized by BLDC drive is presented in the paper. There are also selected results of FEM modelling, magnetic field and force distribution.