Development of hybrid magnetic bearings system for axial-flow blood pump

Abstract

Studies have shown that failure of the cardiovascular system is one of the most common health disorders causing premature deaths in our society. Heart transplantation is the last option for those patients who suffer from heart diseases. Artificial heart pumps are good candidates for implantable ventricular assist systems that can solve the problem of deficiency in the number of available organ donors. One of the key technologies of our rotary heart pump is the design of a rotor that is magnetically suspended by two hybrid magnetic bearings (HMBs) and driven by a Lorentz-type motor. The HMBs will help to eliminate mechanical contact, which leads to material wear, red blood cell damage, heat generation, platelet aggregation, thrombus growth, and even pump failure. Therefore, artificial heart pumps supported by magnetic bearings have been widely employed [1-9]. Yamane et al. [5] and Yuhki et al. [6] developed a centrifugal blood pump with pivot bearings to suspend an impeller. Akamatsu et al. [7] and Nojiri et al. [8] reported a blood pump whose impeller was levitated by an axial magnetic bearing; however, their magnetically coupled motor-shaft to drive the impeller was supported by ball bearings. There are mainly two types of blood pumps, namely, centrifugal and axial-flow types. Due to their better anatomical fit, axial-flow blood pumps are preferred [4]. In this chapter, a fully magnetically levitated axial-flow blood pump is developed using two 5-degree-of-freedom (DOF) controlled HMBs. Proportional-integral-derivative controllers (PID controllers) are used to control the proposed HMBs. The proposed Lorentz-type motor drives the rotor in sensorless mode using STMicroelectronics's ST7FMC microcontroller. In this system, the rotor can rotate with speeds of up to 14,000 revolutions per minute (rpm) in stable suspension. This chapter describes the development of the HMBs system of the axial-flow blood pump, including its design, principles, control, and performance. © 2008 Springer Science+Business Media, LLC.