2002 Volume 40 Issue 4 Pages 201-213
The electromechanical or electrohydraulic mechanisms conventionally used for driving pulsating ventricular-assist devices (VADs) must use a movement converter. It is this movement converter that is the main item preventing the miniaturization of VADs and improvement the level of reliability. This paper suggests a linear oscillatory actuator (LOA) for VADs that provides reciprocating motion without requiring a converter mechanism. It consists of a stator with a single-winding excitation coil and a mover with two permanent magnets. The mover moves back and forth when forward and reverse electric currents are supplied to the excitation coil. We first propose a newly designed inner stator/outer mover LOA. The structure of the inner stator has led to a reduction in total coil resistance because the winding diameter of the coil is shorter than the outer stator. A large force is required to drive a VAD in the systolic phase; however, a small force is sufficient for the diastolic phase. For this reason, we propose using a non-symmetrical LOA that generates high thrust on one side alone. A magnetic field analysis was applied to examine the proposed configurations and design the prototype LOA. The dimensions of the prototype LOA are 60mm in diameter and 24mm inn thickness, and it has a mass of 465g and a volume of 68mL. In the large-thrust phase, at an input power of 20W, the starting static thrust was approximately 87N and maximum static thrust was approximately 195N. In the small-thrust phase, for the same input of 20W, the starting static thrust was approximately 43N and maximum static thrust was approximately 70N. The static thrust of the large-thrust phase was approximately three times larger than the small-thrust phase with the same electrical power input.