Design Modeling and Testing—A Compact Variable Stiffness Actuator for Knee Joint Dimensions

Stroke rehabilitation exoskeletons require joint mechanisms capable of replicating physiological stiffness modulation to adapt to accommodate varying gait phases. This paper presents a novel compact variable stiffness mechanism (VSM) for knee exoskel-etons, based on a simplified three-bar linkage topology. The proposed design achieves a tunable quasi-stiffness range of 0.15–2.0 NM/deg. Static characterization under a 2kg load demonstrated up to 23.0N of collision force attenuation in softening regimes (λ< 2.3)through passive viscoelastic dissipation, whereas hardening behavior (λ≥2.3) pre-served precise torque-angle characteristics scalable to physiological loading. Parametric analysis showed an 89% correlation between theoretical and scaled experimental stiff-ness profiles for values from 0.5 to 2.5. The proposed architecture enables decoupled optimization of impact safety and positional precision, offering a clinically adaptable solution for hemiparetic gait assistance.