Fabric muscle with a cooling acceleration structure for upper limb assistance soft exosuits

Abstract

Soft exosuits used for supporting human muscle strength must be lightweight and wearable. Shape memory alloy (SMA) spring-based fabric muscles (SFM) are light and flexible, making them suitable for soft and shape-conformable exosuits. However, SFMs have a slow actuation speed owing to the slow cooling rate of the SMA spring. This paper proposes a forced air-cooling fan-integrated fabric muscle (FCFM) that improves the cooling rate by arranging a thin-diameter SMA spring bundle with a high surface-area-to-volume ratio inside a breathable fabric with integrated fans. The relaxation time of an FCFM weighing 30 g and containing a 2.6 g SMA spring bundle, which contains 200 thin springs, was reduced by over 70.2% via forced-air cooling using the integrated fans. A 4 kg weight, which is 1530 times the mass of the SMA spring bundle, was hung from the FCFM and was repeatedly actuated in ten-second cycles. An upper limb assistive soft exosuit with FCFMs was fabricated and worn on a mannequin holding a dumbbell, and the arm extension time after flexion was improved by 4.5 times. Additionally, the assistive performance of the exosuits for repetitive tasks in specific scenarios was evaluated, and the strong potential of the proposed FCFM for soft exosuits was verified.

Soft Wearable Rehabilitation Robots with Artificial Muscles based on Smart Materials: A Review

“…Reproduced under the terms of the CC BY license. [ 101 ] Copyright 2022, The Authors, published by Springer Nature. d) Carlos III University of Madrid elbow SWRR.…”

“…In most research in this area, the reported value was torque. Human Body [34,51,139,140] Skeletal muscle Human Body [34,46,[50][51][52]141] Skeletal muscle Step signal 1.55 Wearable assembly Korea Institute of Machinery and Materials [101] SMA (spring) Human Body [34,46,50,51,142] Skeletal However, for the hand, some devices have been developed to replicate/generate the force required for grasping and pinch activities. In the case of facial expressions, as with the finger joint, it is not measured on torque but the force that muscles generate in a direction to generate facial expressions.…”

“…At the Korea Institute of Machinery and Materials, Park et al [101,102] presented an SWRR made of fabric muscle with a cooling acceleration structure for elbow extension assistance (Figure 10c). The device is actuated by fabric muscle that consists of SMA spring bundles, conductive fabrics, cover fabrics, and electrical wiring.…”

“…However, some of the deficiencies in smart materials can be remedied through the SWRR design. Human Body [34] Skeletal Muscles 20 N/A 0.1 20 Maximum N/A Korea Institute of Machinery and Materials [101] Universidad Iberoamericana [82] (2018) TCP 10 5.4 1.1 %0.02 L: N/A D: 2.5 mm Bio-robotics and Smart Systems Laboratory [59] (2017) MENRVA Group [81] (2016) TCP 15. 0.9 N/A 0.1 N/A KAIST [97] Ajou University [92] (2020) SMA 5 10.5 594 %1 L: 800 mm D: 0.15 mm Carlos III University of Madrid [52] [89] (2009) SMA %3 10 203 %0.025 L: 2.5 m D: 0.25 mm Artificial Intelligence Laboratory [88] The required torque depends on two different aspects, the generated force and the lever arm.…”

Development of a comfort suit-type soft-wearable robot with flexible artificial muscles for walking assistance

“…Furthermore, research has been lacking on wearable robots that take comfort into consideration from the early stages of the development process. This has led to the development of soft and flexible suit-type wearable robots, wherein anchoring methods are utilized to stabilize the wearable robots on the body 4 , 5 . The anchoring methods can be classified based on the methods and materials used: elastic forces of stretchy fabrics 6 , stitching techniques 7 , webbing straps 8 , and hook and loop fasteners 9 .…”