Design of a SMA-based soft composite structure for wearable rehabilitation gloves

Abstract

The combination of smart soft composite structure based shape memory alloy (SMA) and exoskeleton technology has the advantages of light weight, energy saving, and great human-exoskeleton interaction. However, there are no relevant studies on the application of SMA-based soft composite structure (SSCS) in hand exoskeletons. The main difficulty is that directional mechanical properties of SSCS need to comply with fingers movement, and SSCS can deliver enough output torque and displacement to the relevant joints. This paper aims to study the application of SSCS for wearable rehabilitation gloves and explore its bionic driving mechanism. This paper proposes a soft wearable glove (Glove-SSCS) for hand rehabilitation actuated by the SSCS, based on finger force analysis under different drive modes. The Glove-SSCS can support five-finger flexion and extension, weighs only 120 g, and adopts modular design. Each drive module adopts a soft composite structure. And the structure integrates actuation, sensing and execution, including an active layer (SMA spring), a passive layer (manganese steel sheet), a sensing layer (bending sensor) and connection layers. To obtain a high-performance SMA actuators, the performance of SMA materials was tested in terms of temperature and voltage, temperature at the shortest length, pre-tensile length and load. And the human-exoskeleton coupling model of Glove-SSCS is established and analyzed from force and motion. The results show that the Glove-SSCS can realize bidirectional movements of fingers flexion and extension, with ranges of motion are 90–110° and 30–40°, and their cycles are 13–19 s and 11–13 s. During the use of Glove-SSCS, the temperature of gloves is from 25 to 67°C, and the surface temperature of hands is from 32 to 36°C. The temperature of Glove-SSCS can be kept at the lowest temperature of SMA operation without much impact on the human body.

Adaptive control for shape memory alloy actuated systems with applications to human–robot interaction

“…However, the study does not delve into the robustness considerations of the robot system. Xie et al (2023) embedded SMA into a conformal material and proposed a hand rehabilitation wearable glove actuated by an SMA-based Soft Composite Structure (SSCS). This structure is characterized by simple actuation and a large force-to-weight ratio.…”

Soft Pumps: Catalysts for Advancing Fluid‐Driven Soft Robots

“…The pump for soft robots should also be lightweight to avoid placing too much burden on users, and the materials used should be comfortable, breathable, and compatible with human skin to avoid allergies or irritation. For instance, a rehabilitation glove typically weighs about 50–120g, [ 19–22 ] and the pump driving such gloves should have a comparable weight. Additionally, the ideal pumps for soft robots should be untethered and battery powered to achieve portability.…”