We proposed a new method to detect the central position of the motor in the implantable pulsatile Left Ventricular Assist Device (LVAD) with pancake-shaped blood sac and pusher plate on a cylindrical cam. The central position of the motor is needed to estimate the pump output in our system. If this method is enough accurate, position sensors do not have to be used. The motor current waveform was used to find the central position. The motor current of the LVAD usually was found to increase in the systolic period, and decrease in the diastolic period. Therefore, there exists a rapid decrease of the motor current when the LVAD change its phase from the systolic period to the diastolic period. To find central position, we measured the hall sensor value where the motor current decreases rapidly. The experimental conditions are; Preload(Left Arterial Pressure) was sequentially raised by 5, 10, 15, 20, 25 mmHg, and afterload(Aortic Pressure) 60, 80, 100, 120 mmHg and the Pump rate 60, 70, 80 bpm. On those preload and afterload conditions, the hall sensor value were 72nd ≈75th pulse out of 140 pulses at the pump rate of 60 bpm, 73rd ± 76th pulse at the pump rate of 70 bpm, 74th ± 78th pulse at the pump rate of 80 bpm. That means that the deviation of detection error can be considered 3±4 pulses - it is less than 3% compared to the total pulses of one cycle. Due to this error, the estimated pump output can have 0.2L/min error. It is considered enough acceptable. In vivo experiments for further verification of the estimation method are to be followed.