.JPG) | ABSTRACT An increase in the number of cardiac patients and a decrease in number of heart donors has triggered the development of artificial heart pump to support the proper functioning of the heart. |
There is also an increase in demand for smaller sized pumps with long term application. All these factors have stimulated the use of a magnetically-levitated rotary blood pump as Left Ventricular Assistant Devices. The demand of volume and pressure of blood varies from person to person. Moreover, the prevention of cannular ventricle collapse at suction, dependence of pump performance on its inlet, and outlet conditions has necessitated control of the pump. Also, the available invasive pressure and flow transducers limit the use, due to their low reliability, periodic calibration, and assembling problem.
In this work, three independent and quantitative non-invasive measurement methods for the estimation of pump parameters from intrinsic parameters were developed, substantiated, and compared. The first method used DC motor current and the motor speed as the inputs to the system. In this method, behavior of brushless DC motor was studied using its working model. Pump speed and bearing current were the inputs for the second estimation technique. In this method, pump performance and impeller behavior were continuously monitored in three axes (X,Y,theta). The third method is conceptualized on the output of the Hall Effect sensors, which were used for sensing the position of impeller, and the pump speed. The behavior of the sensor output with the impeller position in four axes (X,Y,Z,) was developed using a real impeller in model housing. The data were analyzed in Microsoft Excel 2007 and MATLAB using least square estimation techniques and Fourier series expansion. An algorithm for each technique was developed. In addition, the propagation of errors and uncertainties at each step of estimation method were accounted and calculated, with the results for each method compared.
