Abstract
A control method using the back electromotive force generated in the motor windings of the 3-phase brushless do motor has been developed for an implantable cardiac assist device. The pulse-width modulation with the fixed duty ratio and variable voltage is useful for this control method. Two of the 3 nodes of the motor are driven by the squared wave voltage signals having the same amplitude and opposite phases, and the remaining node is used to detect the phase information of the back electromotive force signal. This method is applied when the the motor speed is high, while the open-loop control method is used for the low speed.
