# Development of a Wearable Finger Exoskeleton for Rehabilitation
###### Abstract
IOTA [25] is two-degree-of-freedom (DOF) thumb exoskeleton that can actuate carpontacapral (CMC) and metacarpophalangeal (MCP) joints through motion ranges required for daily activities; the actuators for the CMC and MCP joints are located off-board of the orthotic device, inside a control box. Actuation of the joints is achieved by two servos and two spring-return cable transmissions connected between the servos and the orthotic device. Pneumatic Muscle-Torsion Spring (PM-TS) for finger therapy, is a wearable robotic hand for assisted repetition, which uses a pneumatic muscle actuator structure and a torsion spring (TS) and has two DOF for the driven fingers, which makes the movement of fingers more suitable and flexible [26]. Robotic system-to-hand rehabilitation [27], uses an exoskeleton with two DOF for finger rehabilitation of problems of motion caused by cerebrovascular event. ExoGlove [28] is a soft wearable exoskeleton that comprises an embedded glove with pneumatic actuators of variable stiffnesses for hand assistance and rehabilitation applications. The Assistive Rehabilitation Robotic Glove [29] consists of two novel designs for robotic glove rehabilitation using an exoskeleton to provide actuation for flexion, thereby limiting the number of active actuators required. HX [30] is an exoskeleton that has been designed to maximize comfort, wearability, and user safety, exploiting chains with multiple degrees-of-freedom with a modular architecture. ExoHand [31] is an exoskeleton from Festo that can be worn like a glove. The fingers can be actively moved and their strength amplified; the operator's hand movements are registered and transmitted to the robotic hand in real-time. The five-fingered haptic glove design [32] is a mechanism with a light weight and a portable actuator system that fits on the hand. ATX [33] is an exoskeleton created to facilitate research in hand rehabilitation therapy. The actuatedfinger exoskeleton [20] provides independent control of all three joints of the index finger. HEXORR [17] is a device that provides a full range of motion (ROM) for all of the hand's digits. A hand exoskeleton system for index finger rehabilitation [34] uses both active and passive rehabilitative motions. Finally, the novel exoskeleton robotic system for hand rehabilitation [35] is a novel hand exoskeleton rehabilitation device that facilitates tendon therapy exercises. Table 1 presents a comparative review of exoskeletons developed for hand rehabilitation. Not all of the exoskeletons can be applied effectively to daily life, e.g., only a few can be used alone without a large drive device. Some are too complex, bulky, and unwearable, with many active DOF, or are too expensive for home and personal use. By following this approach, inspired by extreme portability and affordability, this work presents a new finger mechanism based on linkage approximation, using only one active degree of freedom per finger to obtain full actuation and it was assembled using a 3D printing machine from a thermoplastic polymer, acrylonitrile butadiene styrene (ABS); the structure of the proposed exoskeleton presented in this paper is based on human hand capabilities, with the ranks of motion and physical length as important criteria. \begin{table}
\begin{tabular}{c c c c c c c} \hline \hline  
This paper is organized as follows: In Section 2, the design of the finger exoskeleton is presented. Section 3 develops the kinematics and dynamics for the proposed exoskeleton with one DOF. Section 4 presents experimental results for the exoskeleton kinematics and dynamics, followed by proper structural analysis. Section 5 presents the discussion on the proposed exoskeleton and, finally, in Section 6, some important conclusions and suggestions for future research are presented.