Design and experimental study of Shape Memory Alloy (SMA) spring as actuators in wrist exoskeleton
This paper presents the design, modeling, and experimental assessment of a wrist exoskeleton actuated by Shape Memory Alloy (SMA) springs to support flexion-extension and radial-ulnar deviation of the wrist. A dynamic model based on the Euler-Lagrange formulation was developed and simulated to est...
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| Main Authors: | , |
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| Format: | Article |
| Language: | en en |
| Published: |
Universiti Kebangsaan Malaysia
2026
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| Subjects: | |
| Online Access: | http://irep.iium.edu.my/127475/7/127475_Design%20and%20experimental%20study.pdf http://irep.iium.edu.my/127475/13/127475_Design%20and%20experimental%20study_Scopus.pdf http://irep.iium.edu.my/127475/ https://www.ukm.my/jkukm/volume-3801-2026/ |
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| Summary: | This paper presents the design, modeling, and experimental assessment of a wrist exoskeleton actuated by
Shape Memory Alloy (SMA) springs to support flexion-extension and radial-ulnar deviation of the wrist. A
dynamic model based on the Euler-Lagrange formulation was developed and simulated to estimate the joint torque
requirements, which ranged from 0.26–0.32 Nm for standard wrist movements. A prototype is fabricated and tested
incorporating four SMA spring actuators fixed on an arm splint, with targeted actuation for generating different
wrist motion. Experimental findings revealed that the prototype delivered torque values surpassing simulation
requirements for flexion (0.332 Nm) and extension (0.328 Nm) motions, whereas lower torque was observed for
radial and ulnar deviations, likely due to actuator placement and frictional losses. The actuation cycle frequency for
flexion-extension was measured to be 0.018 Hz, primarily constrained by the thermal characteristics of the SMA
springs. Another important observation is enhanced speed during SMA reversal motion (from extension to flexion)
resulted from antagonistic actuation of the SMA. To further improve the torque and speed generation, an optimal
SMA actuator with reduced thermal mass (thinner diameter, bundle configuration) and active cooling can be designed.
Overall, the SMA-driven wrist exoskeleton exhibits promising potential as a lightweight, wearable system for effective
wrist joint assistance. |
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