Abstract
In this study, the control system for a seal-less pivot-bearing supported centrifugal pump bypassing the left ventricular apex to descending aorta was designed based on motor current waveform analysis, and the performance of this system was evaluated in a mock circulatory loop. The control system consisted of an IBM-compatible personal computer and a digital signal processor. The control algorithm consisted of two phases; an initial phase for a rough setting of the pump RPM to provide required pump flow for a given heart rate, and a second phase for fine-tuning the RPM to minimize the suction and regurgitation, that may be present at the pre-set RPM level. Using this control system, we first obtained the native heart rate, then calculated the nominal cardiac output for that heart rate based on the predetermined native heart pump characteristics. This was followed by the estimation of the centrifugal pump RPM, to roughly provide the pump output based on the characteristic curves of the centrifugal pump. Then the suction and regurgitation detection algorithm, based on the motor current waveform analysis, was employed to examine the presence of suction and regurgitation. The threshold level of WDI (waveform deformation index: ratio of the fundamental to the higher order harmonics) set below 0.2, indicated the suction and regurgitation-free operation of the centrifugal pump. The control system responded adequately for sudden changes in the pump afterload and native heart rate. Further study is necessary to evaluate the performance of the system in animal experiments.
