Compliant Finger Exoskeleton with Telescoping Super-elastic Transmissions
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Compliant Finger Exoskeleton with Telescoping Super-elastic Transmissions Changsheng Li1 · Yusheng Yan1,2 · Hongliang Ren1,3 Received: 30 March 2019 / Accepted: 6 March 2020 © Springer Nature B.V. 2020
Abstract This paper presents the concept, design, and experimental characterization of a compliant finger exoskeleton with telescoping super-elastic transmissions. Nickel-Titanium (Ni-Ti) rods with the super-elastic feature are adopted as transmission components for the concentric telescoping mechanism to be flexible and safe. The mechanism of this finger exoskeleton is characterized in detail, including the finger connector, the elastic-rod transmission system (ERTS), and the actuator. The performance of compliance is demonstrated by finite element analysis. Then, the finger motion mapping relationship is captured by the experiments for a two-finger prototype. Experiment results show that certain compliance (e.g., 16◦ /2N for the flexion/extension motion of the index finger) can be achieved by the Ni-Ti rods, and reflects in the assisted motion. Keywords Finger exoskeleton · Hand exoskeleton · Super-elastic transmission · Rehabilitation · Ni-Ti rod
1 Introduction The hand/finger exoskeleton can be used for grasp assistance, haptic rendering, rehabilitation, or the augmentation of hand functions. Considering rehabilitation, hand exoskeleton as a device for robot-assisted therapy [3, 4] can improve the motor performance of patients with motor dysfunctions of hands such as spasticity, muscle synergies, lack of tactile sense and joint control [18, 19, 24]. This treatment has been proved to be more effective than conventional therapy [21] and widely studied due to the features of flexibility and ease of use [7]. In the aspect of enhancing the hand
Hongliang Ren
[email protected] Changsheng Li [email protected] Yusheng Yan [email protected] 1
Department of Biomedical Engineering, National University of Singapore, Singapore, Singapore
2
College of Mechanical and Electrical Engineering, Harbin Engineering University, Harbin, 150001, China
3
NUS (Suzhou) Research Institute (NUSRI), Suzhou, 215123, China
function, a hand-finger exoskeleton can automate the movement of the finger or amplify the hand-finger gripping [13]. The physical burden of repetitive actions can be reduced by wearing a hand-finger exoskeleton. In terms of force transmission modes, the hand exoskeletons can be mainly classified to linkage and cable-driven mechanisms [10, 15, 25]. Linkage mechanisms have the advantages of reasonable force transmission characteristics and comfortable to control. However, the wearable part is often bulky because the joints of the robot align with the joints of the finger. For example, HandSOME adopts a fourbar linkage mechanism in which finger joints are stretched to compensate flexor hypertonia for coordinating natural grasping motion [6]. Rutgers Master II is an exoskeleton mounted on the palm side of the hand and capable of providing feedback force against flexion via linkage mechanism [5]. In contrast, a cab
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