Development of a powered variable-stiffness exoskeleton device for elbow rehabilitation

Robot-assisted movement training by means of exoskeleton devices has been proven to be an effective method for post-stroke patients to recover their motor function. However, in order to be used in home-based rehabilitation, the kinematic structure of a wearable exoskeleton device should provide portability and make allowances for the natural joint range of motion for the user. Additionally, the actuated stiffness of the target joint is desired to be adjustable in accordance with the specific impairment level of the patient's upper limb. In this paper, we present a novel portable exoskeleton device which could provide support for rehabilitation patients with variable actuated stiffness in the elbow joint. It has five passive degrees of freedom to guarantee the user's natural joint range of motion and intra-subject variability, as well as an integrated variable stiffness actuator (VSA) which can adjust the joint stiffness independently by moving the pivot position. An elbow power-assist trial with different actuated joint stiffnesses was tested on a healthy subject to evaluate the functionality of the proposed device. By regulating the joint stiffness, the proposed device could provide variable power assistance for the wearer's elbow movements.