Study on magnetic bearings system in axial-flow blood pump

The system power and heat can be reduced in axial-flow Maglev blood pump whose rotor is suspended by two radial permanent magnetic bearings and one axial active magnetic bearing. But the strong force couple between the radial bearing and axial bearing makes it more difficult in rotor´s axial motion control. By theory and simulation analysis, the axial characteristic of radial permanent magnetic bearing was studied, and the axial motion control model of the rotor was built. Using Hall sensors, rotor´s axial displacement measurement system is designed. Experiment results indicate that this measurement has good linearity and sensitivity. Based on these studies, the incomplete differential PID controller was designed. Under this controller, the blood pump rotor has been stably suspended in five degree of freedom in any space-angle, and the stable suspension can be recovered in 0.1s when the rotor was disturbed by an impulsion. This work can promote the progress of maglev blood pump at home.