A Series Variable-Stiffness Joint for Robot-Assisted Resistance Training

As the safe and comfortable human-robot interac- tion draw more attention, variable stiffness joints are adopted in the rehabilitation robots for the compliant experiences. For patients with joint injury, resistance training has demonstrated its efficacy in concurrently enhancing muscle strength in the rehabilitation process. Here, we introduce a compact passive joint with variable stiffness and damping generation capability for robot-assisted resistance training. The abilities of serial variable stiffness and passive angle tracking were demonstrated by a prototype. The variable stiffness mechanism was mainly formed by 3D-printing, which only weighs 0.1kg with a wide range of stiffness (0.004-11.176Nm/rad). Moreover, the torque- angular displacement characteristics show excellent linearity at high joint stiffness. Finally, the feasibility of being integrated into the wearable rehabilitation robot has been evaluated.