A 3-Degrees-Of-Freedom Lightweight Flexible Twisted String Actuators (TSAs)-Based Exoskeleton for Wrist Rehabilitation
Mihai Dragusanu, Nicolas Guinet, Bhivraj Suthar, Tommaso Lisini Baldi, Domenico Prattichizzo, Monica Malvezzi
AI summary
Problem
Traditional wrist rehabilitation requires intensive therapist supervision, while existing cable-driven exoskeletons often suffer from high inertia, bulk, and complex transmission mechanisms that limit wearability and comfort.
Approach
The authors developed a 3-DOF tendon-driven exoskeleton powered by twisted string actuators that eliminates gears and pulleys, reducing weight and encumbrance while enabling precise, adaptable wrist motion tracking and assistance.
Key results
- Achieved low tracking errors (RMSE ≤ 1°) during guided rehabilitation exercises
- Delivered required range of motion: 115° flexion/extension, 70° radial/ulnar deviation, 150° pronation/supination
- Provided sufficient therapeutic torque (0.35 Nm for flexion/extension and deviation, 0.06 Nm for pronation/supination)
- Demonstrated a lightweight, modular prototype with integrated safety, tracking, and control systems
Why it matters
Provides clinicians and rehabilitation engineers with a portable, precise, and comfortable wearable platform to enhance patient recovery and reduce reliance on constant therapist supervision.
Abstract
This letter introduces a lightweight, three-degrees-of- freedom exoskeleton for wrist rehabilitation powered by Twisted String Actuators (TSAs), specifically designed to support flex- ion/extension, radial/ulnar deviation, and pronation/supination movements. Leveraging the high power-to-weight ratio of TSA actuation system, the exoskeleton ensures effective, comfortable, and personalized rehabilitation exercises. The device comprises five TSAs arranged in a tendon-driven configuration, enabling precise control and adaptability to various user anatomies. The experi- mental evaluations was conducted on a prototype demonstrating the device’s ability to accurately replicate wrist movements guided by a physiotherapist, achieving low tracking errors (RMSE ≤ 1◦). The exoskeleton effectively achieves the desired wrist range of motion—115◦for flexion/extension, 70◦for radial/ulnar devia- tion, and 150◦for pronation/supination—with torque capabilities suitable for rehabilitation purposes (0.35 Nm for flexion/extension and radial/ulnar deviation, and 0.06 Nm for pronation/supination).