Variable damping of pneumatic soft robots with shape memory alloys

Variable impedance of upper limbs is critical for multifaceted daily activities, adapting to varying physical environments, and facilitating social interactions. Existing soft wearable robots predominantly focus on stiffness modulation, with minimal attention to damping adjustment. In this study, we introduce a novel soft pneumatic actuator integrated with shape memory alloys (SMAs) to achieve significant damping modulation with minimal stiffness variation. By controlling the SMA temperature, the damping of the actuator can be modulated, as demonstrated by experimental evaluations. Under ideal conditions, results showed a maximum damping increase of 140.9% and a maximum decrease of 91.7%, with a maximum stiffness change of only 8%. Phantom arm demonstrations showed up to 76.2% increase in damping ratio, significantly reducing joint oscillation settling times.