Development of sensorless control system for pediatric pulmonary circulatory assist device using shape memory alloy fibers

In order to promote the pulmonary circulation after Fontan operation, we developed a pediatric pulmonary circulatory assist device using shape memory alloy fibers. In this study, we developed the sensor-less control system for the pulmonary circulatory assist device and examined its fundamental functions. The SMA fiber showed a linear relationship between the internal resistance and longitudinal contraction. We measured the change in current of the fiber during the operation. Electric current increased from 1.4 to 1.8 A during operation, and the maximum current supply was measured at the end of the contraction. Therefore, we could be estimated the device contraction by the measurement of current which was calculated by voltage sampling of fiber units. Prevention of the overheating of the fiber unit was one of the problem throughout the operation of the device, and we could achieve the elimination of excess current supply by detecting the fiber voltage as well as the estimation of electric power supply without ineffective contraction. Consequently, the method in this study might be applied as a highly reliable totally implantable system.