Magnetorheological Transmission for Total Artificial Heart

Abstract

　We proposed a new transmission to control the flow difference between left and right pumps in total artificial hearts. The transmission consists of input and output shafts, magnetorheological fluid, and electromagnets with adjustable current and position. A motor rotates the input shaft of the transmission. The transmission transfers the torque to the output shaft that rotates with decelerated rotational speed according to the flow resistance of the magnetorheological fluid. First, we measured the output rotational speed when load torque is 5 mNm, and the input rotational speed was 2000 rpm. The rotational speed difference between input and output shafts changed from 450 rpm to 6 rpm when we increased the electromagnet current from 0.4 to 0.55 A. The difference changed from 2 rpm to 219 rpm when we moved the electromagnet position from 2 to 9 mm. Also, we analyzed that magnetic flux density distribution change according to the current or electromagnet position by 3D computational magnetic field analysis. These results show that magnetic flux density distribution affects the output rotational speed. The yield stress is identified based on the measured and analyzed results. In this paper, we show that the developed transmission is enough small and has sufficient transmission performance.