Abstract
An optical rotary encoder and software have been developed to control a microprocessor-based motordriven, totally implantable cardiac assist device. The electro-mechanical actuator incorporated with the encoder was attached to a pusher-plate-type blood pump having 60 ml net stroke volume. In vitro experiments showed that the supply voltage to the motor is changed promptly in response to the change in afterload, and that the maximum efficiency increased to around 11 % from 6 % obtained with the open-loop control. The maximum outflow was 6.4 l/min, and the system could be operated at the pumping rate of 120 bpm against the afterload of 150 mmHg. These results indicate that the system fulfills the designed specifications.
