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

形状记忆合金（SMA）钢丝现在是柔软人造肌肉的首选。然而，SMA人造肌肉存在两个问题，一是由于其柔软的特性而限制了其承载能力，二是由于其冷却时间长而反应缓慢。为此，本研究开发了基于SMA的快速响应磁流变弹性体（MRE）人工肌肉和可控磁流变液（MRF）外骨骼，以提高其承载能力。这种新型人造肌肉在保持其柔软性的同时，也加快了其SMA丝的冷却速度，提高了其反应速度。可控磁流变体外骨骼足够灵活，可以让柔软的手指根据需要弯曲，同时又足够坚硬，可以承受重物。从今年年初开始，我已经为新的人造肌肉构建了控制电路和程序，之后，新的人造肌肉和MR外骨骼已经组装成一个手指，以便进一步测试。对手指的弯曲性能进行了研究。评估了手指的最大弯曲角度和反应速度。新假指的握持能力也进行了评估。我们的测试结果证明，与传统的SMA人造肌肉相比，这种新型人造肌肉在矫直时的响应速度提高了333%。新的人造肌肉和MRF外骨骼组装成一个机器人手指，我们的测试证实，与纯SMA机械臂相比，新手指的负载能力提高了440%。

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.