Performance Evaluation of a Powered Variable-stiffness Exoskeleton Device for Bilateral Training

Bilateral rehabilitation training has been proposed to help patients of hemiplegia who have partial impairment of the upper limb to regain the ability of daily living (ADL). In this paper, a bilateral training method by means of a novel power-assist exoskeleton device is presented to help post-stroke patients to improve rehabilitation effects. In order to provide appropriate power assistance during home-based rehabilitation, a variable stiffness actuator (VSA) was applied to regulate the output stiffness of the exoskeleton device. This paper presents the performance evaluation of the integrated VSA. The results related to the performance demonstrated that high stiffness could rapidly force the elbow joint to the initial equilibrium position to ensure precise trajectory movement, while low stiffness could allow relatively large deviations from the desired trajectory thus inherently guaranteeing the patient’s safety. In addition, a preliminary elbow rehabilitation trial is performed to evaluate the proposed bilateral rehabilitation strategy. The results show that the proposed bilateral training method can allow the exoskeleton device to smoothly drive the user’s right arm to follow the movements of his left arm.