Abstract: An artificial heart assembly, designed for implantation into a subject, which may be a total artificial heart or a ventricular assist device. The heart assembly has a blood inlet conduit, a blood outlet conduit, a pumping mechanism for pumping blood from the blood inlet conduit to the blood outlet conduit, and means for reversibly driving the pumping mechanism in a opposite directions over a stroke having a length defined by a pair of endpoints. The driving means has a motor which is braked by a braking means which has means for determining the actual speed of the pumping mechanism, means for comparing the actual speed of the pumping mechanism with a braking speed, and means for selectively applying the brake to the motor based upon the relative magnitudes of the actual speed and the braking speed.