Radial position active control of double stator axial gap self-bearing motor for pediatric VAD

In the last decade, ventricular assist devices (VADs) such as continuous flow rotary blood pumps have been successfully applied to advanced heart disease patients for bridge to transplantation and destination therapy. The success with VAD technology has recently increased significant clinical need for pediatric VADs. However, VADs which are applicable to infants and small children are still in a development stage because of severe design requirements such as long life expectancy, minimal blood damage and miniature device size. Magnetic levitation is an essential technology to enhance durability and blood compatibility of rotary VADs due to elimination of mechanical contact and wear. Miniaturized magnetic systems have strong potential to develop the pediatric VAD. In this study, a novel axial gap double stator self-bearing motor which can control five-degrees of freedom (5-DOF) of rotor postures have been developed for pediatric VAD. The motor has a top stator, a bottom stator and a levitated rotor driven as a synchronous permanent magnet motor. The rotor is axially suspended between the stators which have an identical structure. A double stator mechanism enhances a higher torque production and regulates radial position through active control. This paper proposes a concept of radial position active control and the magnetic suspension ability of developed self-bearing motor. The rotor is successfully levitated and rotated up to 6400 rpm without any physical contact with 5-DOF active control in the air. The radial oscillation amplitudes are actively suppressed with the proposed radial position control concept. The developed 5-DOF controlled self-bearing motor which is suitably miniature as an actuator for pediatric VAD indicates sufficient capability of the magnetic levitation and non-contact rotation