Abstract

This work presents theoretical and experimental means for achieving impeller stability in a magnetically levitated left ventricular assist device (LVAD). These types of medical devices are designed to boost the native heart`s ability to pump blood by means of mechanical energy transfer using a rotating impeller. Magnetic suspension of the impeller eliminates bearing friction and reduces blood damage, but it requires active controls that monitor the impeller`s position and speed in order to generate the forces and torques required to regulate its dynamic behavior. To accomplish this goal, this work includes: 1) a dynamic system model derived using energy and momentum conservation 2) dynamic analysis including stability, controllability and observability, and 3) development of two control algorithms: proportional integral derivative and sliding mode control. Experimental validation included component behavior, model accuracy, and the characterization of controller performance using a physiological simulator. The system model proved to be an adequate representation of the system while levitating in air, but additional research is needed to model hydrodynamic and gyroscopic effects. After the prototype`s subcomponents were tested, calibrated and/or modified to fit the control requirements, both control strategies were successful in controlling the rotor as it spun at 6000 rpm pumping 6L/min of water at 80mmHg. A maximum speed of 6500 rpm was achieved with speed control within 5% over most of the operating range. The control platform and many of the methods presented here are continually being used and improved towards the implantation of the device in a human subject in the future.

Library of Congress Subject Headings

Rotary pumps--Testing; Rotary pumps--Design and construction; Blood--Circulation, Artificial; Heart--Left ventricle; Medical instruments and apparatus--Design and construction

Publication Date

8-1-2009

Document Type

Thesis

Department, Program, or Center

Mechanical Engineering (KGCOE)

Advisor

Day, Steven

Comments

Note: imported from RIT’s Digital Media Library running on DSpace to RIT Scholar Works. Physical copy available through RIT's The Wallace Library at: TJ917 .G66 2009

Campus

RIT – Main Campus

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