Development of a new generation prosthetic hand with fast responsive SMA based artificial muscle and large load-holding capability

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Shape memory alloy (SMA) wires are now the preferred choice for soft artificial muscles. However, SMA artificial muscles have two problems, including limited load holding ability due to their soft nature and slow response due to their long cooling-off period. In response this research developed a fast response magnetorheological elastomer (MRE) artificial muscle based on SMA and a controllable magnetorheological fluid (MRF) exoskeleton to improve the loading capability. This new artificial muscle retains its soft nature and also accelerates the cooling speed of its SMA wire to increase its response speed. The controllable MRF exoskeleton is flexible enough to allow the soft fingers to bend as required while being stiff enough to hold up heavy loads. From the beginning of this year, I have built a control circuit and program for the new artificial muscle and after that, the new artificial muscle and MR exoskeleton have been assembled to be a finger for further testing. The bending performance of the finger has been conducted. The maximum bending angle and the response speed of the finger have been evaluated. The holding capability of the new prosthetic finger has also been evaluated. Our testing results proved that this new artificial muscle, compared with conventional SMA artificial muscles, can improve the response speed by up to 333% while straightening. The new artificial muscle and the MRF exoskeleton assembled a robotic finger and our tests verified that the loading capability of the new finger has increased by 440% compared to the pure SMA manipulator.