Soft Exoskeleton With Fully Actuated Thumb Movements for Grasping Assistance

It has been clinically proven that exoskeletons are effective self-training rehabilitation or daily living assistance devices for patients with hand dysfunctions. However, exoskeleton-assisted hand exercises with high degrees-of-freedom are considered as challenging tasks because the digit space, especially the thumb, cannot accommodate enough actuators. In this article, we report a tendon-driven soft hand exoskeleton with a hybrid configuration for thumb actuation. The soft hand exoskeleton system uses the least number of actuators to realize full degrees-of-freedom actuation for all digits. It is tested on a stroke patient with hemiplegia and a healthy subject. The experimental results show that the hand exoskeleton could assist the stroke patient to accomplish various training tasks, such as thumb encircling, grasping, pinching, releasing, and writing. It was found that digit trajectories and joint angle changes of the stroke patient were close to those of the healthy subject. Especially, the range of motion of the stroke patient shows significant improvement with the hand exoskeleton assistance compared to that without the hand exoskeleton assistance. The research in this article paves the way to develop fully actuated soft hand exoskeleton that can be eventually integrated with an electroencephalogram or electromyography for self-training rehabilitation or daily living assistance.

I. Introduction

Strokes have become the leading cause of disability, causing the loss of hand function of many patients, with more than 13.7 million new stroke patients worldwide each year. Approximately 40% of stroke victims are from China [1], [2], whilst in the United States, approximately 0.8 million people suffer from strokes each year [3]. Studies have revealed that rehabilitation training in the first three months after stroke is critical, and most patients can recover 48%–91% of their motor functions during this period [4]. After discharged from the hospital, 85% of patients can walk without assistance; however, motion of the upper limbs and hands usually cannot be fully recovered for most patients. Therefore, continuous rehabilitation training through repetitive movements is needed in order to further recover hand functions. Rehabilitation training usually heavily relies on occupational therapists, who may not be conveniently available. To alleviate the demand for intensive care from occupational therapists, a variety of rehabilitation hand exoskeleton devices have been developed [5]–[8].