For designing the assistive wearable rehabilitation robots, it is challenging to design the robot as energy efficient because the actuators have to be capable of overcoming human loads such as gravity of the body and spastic torque continuously during the assistance. To address these challenges, we propose a novel design of soft artificial muscle that utilizes shape memory alloy (SMA) spring actuators with pre-detwinning process. The SMA spring was fabricated through a process called pre-detwinning, which enhances the linearity of the SMA spring in martensite phase and unpowered restoring force, which is called passive force. The fabricated SMA spring can contract >60%. Finally, the soft wearable robot that can assist not only the gravitational torque exerted on the elbow by passive force, but also the elbow movements with active force was designed with a soft artificial muscle. A soft artificial muscle consists of the bundles of pre-detwinned SMA springs integrated with the stretchable coolant vessel. The stiffness of the muscle was measured as 1125 N/m in martensite phase and 1732 N/m in austenite phase. In addition, the muscle showed great actuation frequency performances, the bandwidth of which was measured as 0.5 Hz. The proposed wearable mechanism can fully compensate the gravitational torque for all the angles in passive mode. In addition, the proposed mechanism can produce high torque up to 3.5 Nm and movements in active mode.

中文翻译：

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基于预解缠形状记忆合金弹簧致动器的软质人造肌，为可穿戴机器人提供高被动辅助扭矩。


在设计辅助可穿戴康复机器人时，将机器人设计为节能机器人具有挑战性，因为执行器必须能够在辅助过程中持续克服人体重力和痉挛扭矩等人体负荷。为了应对这些挑战，我们提出了一种新颖的软人造肌设计，该设计利用形状记忆合金 （SMA） 弹簧致动器进行预分离工艺。SMA 弹簧是通过一种称为预解缠的过程制造的，该过程增强了 SMA 弹簧在马氏体相中的线性度和无动力恢复力，这称为被动力。制造的 SMA 弹簧可以收缩 >60%。最后，设计了一款软体可穿戴机器人，该机器人不仅可以辅助被动力施加在肘部上的重力矩，还可以辅助具有主动力的肘部运动。柔软的人造肌肉由预先解开的 SMA 弹簧束与可拉伸的冷却剂容器集成而成。肌肉的刚度在马氏体相中测量为 1125 N/m，在奥氏体相中为 1732 N/m。此外，肌肉表现出出色的驱动频率性能，其带宽测量为 0.5 Hz。所提出的可穿戴机构可以在被动模式下完全补偿所有角度的重力矩。此外，所提出的机构可以产生高达 3.5 Nm 的高扭矩和主动模式下的运动。