W-DFAS rehabilitation Glove: Design and experimental Validation

Shape Memory Alloy (SMA) actuators are attractive for wearable hand rehabilitation due to their high power-to-weight ratio, silent operation, and muscle-like contraction behavior; however, their limited stroke and slow thermal recovery restrict multi-finger actuation in compact gloves. Differential mechanisms that enable one actuator to drive multiple fingers are common in motor-driven hands but remain rare in SMA-based wearable gloves due to force sharing, thermal, and spatial constraints. This study presents a Wearable Dual-Finger Actuation System (W-DFAS) integrating DFAM_6X stroke amplification, a double U-shaped parallel SMA layout, and a hybrid recovery approach combining elastic elements, a passive spring, and PWM-controlled forced-air cooling. Under PWM control at 2.2 A for 1 s, the glove achieved maximum flexion with coordinated MCP–PIP–DIP bending across all four fingers, and total bending angles exceeded 200° for the index/middle and 190° for the ring/little. DFAM transmission analysis showed a fixed experimental gain of 3.19X, reducing required actuator stroke by 68.7% and enabling full-range postures with short SMA strokes (e.g., 12.0 mm at 100% PWM), while reducing required SMA length from ∼ 958 mm (no DFAM) to 300 mm (with DFAM). Forced convection reduced extension recovery to ∼ 7 s, enabling ∼ 7 cycles/min for repetitive rehabilitation tasks. Grasping trials across cylindrical, spherical, box-shaped, and irregular objects demonstrated stable manipulation of ∼ 20–400 g items, supporting ADL-oriented rehabilitation.