A Prototype Left Ventricular Assist Artificial Heart Pump: An Integrated Permanent Magnet and Active Magnetic Bearing Suspension System

Abstract

The progress in the development of ventricular assist artificial heart pumps is continuing. This paper describes the magnetic suspension for a unique prototype axial flow pump designed for approximately 6 L/min at 100 mm Hg performance with an operating speed of approximately 7,000 rpm. The integrated magnetic suspension design provides a direct non-contact blood flow path through the pump with no obstructions which might create low flow areas and thrombosis (blood clots). The magnetic suspension is a combination of permanent magnets (PMs) and active magnetic bearings (AMBs). There are two radial AMBs which support the four degrees of freedom at the ends of the axial pump impeller and an axial PM thrust bearing. The axial PM bearing supports the direction of the largest fluid force on the impeller. A major objective of artificial hearts is to have extremely low power consumption. Thus the integrated PM and AMB suspension system has an operating magnetic suspension power of approximately 2 watts. The design, numerical modeling, and testing of the magnetic suspension system to support the fluid loads and the g loads are described in the paper.

Identification of a solid-core active magnetic bearing in current and voltage drive modes

“…The derivation of equations (9) and (10) is explained as follows. Substituting the equations of f j (j ¼ 1, 2, 3, 4) into equation (1) and considering equations (5) and 6, we have…”

“…As a new type of mechatronic product, active magnetic bearings (AMBs) possess several unique advantages over conventional bearings, such as achieving a very high rotating speed with no contact, no wear, no friction and no need of lubrication. In recent years, AMBs play a very important role in many industrial applications, including high-speed spindles, 1,2 gas compressors, 3 flywheel energy storage systems, 4 artificial heart pumps 5 and turbo-molecular pumps. 6 The rotor and stator of an AMB are typically laminated to reduce the eddy-current effects, 3,7,8 as Faraday's law shows that eddy currents are induced when the magnetic field changes in conductors.…”

“…However, since a laminated construction decreases the strength of the structure, a solid-core construction will be a good choice in such application where it contains a thrust bearing [9][10][11] or where the size of the magnetic bearing gets smaller. 5,12 Eddy currents are evident in a solid-core AMB, but they are omitted when setting up the analytical model using the magnetic equivalent circuit (MEC) method, leading to a significant error between the analytical model and the real system. In order to describe a solid-core AMB more precisely, which means that the eddy-current effects should be considered in modelling, several studies have been carried out on the behaviour of eddy currents and their influence on system dynamics.…”

Electromagnetic actuators for controlling flexible cantilever beams

“…Another interest application of magnetic bearings can be found in medical devices such as artificial heart pumps. [11] In this specific case, both active and passive magnetic bearings are used in a combined configuration to support the pump's impeller when subjected to blood flow forces. The bearings should have low power consumption and also the ability to prevent contact between the impeller and the pump's housing when large dynamic loads are applied.…”

“…Another interest application of magnetic bearings can be found in medical devices such as artificial heart pumps . In this specific case, both active and passive magnetic bearings are used in a combined configuration to support the pump's impeller when subjected to blood flow forces.…”