Soft Exosuit Based on Fabric Muscle for Upper Limb Assistance

Upper limb exosuits (ULEs) are wearable robots that can assist arms to lift or support an object. However, heavy wearable equipment often interferes with the free movement of a person's arms, which have a wide range of motions. This article presents the design and manufacturing processes for a ULE that does not restrict the range of motion of the person wearing it and that can be folded to a small, palm-sized volume for portability. The light and flexible ULE employs a fabric woven from shape memory alloy (SMA) springs (FWS) as an actuator. The FWS uses SMA springs coiled with microdiameter SMA wires, and it exhibits the soft and flexible characteristics of a fabric. The proposed lightweight ULE weighs 540 g and supports the muscular strength for the bending motion of an elbow. The experimental results indicated that the proposed ULE reduced the muscle activity of subjects by approximately 50–70% when they held a load of up to 10 kg under the condition that their temperature was controlled to be 50 °C or lower. This result suggests that the proposed ULE can be used to provide strength assistance for delivery or construction workers.