AssistOn-Finger: An under-actuated finger exoskeleton for robot-assisted tendon therapy

Abstract

We present ASSISTON-FINGER, a novel under-actuated active exoskeleton for robot-assisted tendon therapy of human fingers. The primary use for the exoskeleton is to assist flexion/extension motions of a finger within its full range, while decreasing voluntary muscle contractions helping to keep the tendon tension levels to stay within acceptable limits, avoiding gap formation or rupture of the suture. The device can also be employed to administer range of motion (RoM)/strengthening exercises. ASSISTON-FINGER is designed to be passively back-driveable, can cover the whole RoM of patients, and can do so in a natural and coordinated manner. In particular, the device employs human finger as an integral part of its kinematics and when coupled to a human operator, the parallel kinematic structure of exoskeleton supports three independent degrees of freedom, dictated by the kinematics of the human finger. Automatically aligning its joint axes to match finger joint axes, ASSISTON-FINGER can guarantee ergonomy and comfort throughout the therapy. The self-aligning feature also significantly shortens the setup time required to attach the patient to the exoskeleton. We present the kinematic type selection for the exoskeleton to satisfy the design requirements for tendon therapy applications, detail optimal dimensional synthesis of the device considering trade-offs between multiple design criteria and discuss implementation details of the exoskeleton. We also present feasibility studies conducted on healthy volunteers and provide statistical evidence on the efficacy of exoskeleton driven exercises in keeping the average muscle recruitment and the maximum tendon tension levels as low as human guided therapies.

A structured overview of trends and technologies used in dynamic hand orthoses

“…This concept can be generalized under the term functional degrees of freedom (fDOF) [ 108 ], which means that complex movement patterns can be generalized and achieved by less complex actuation strategies. This is a viable approach for dynamic hand orthoses as complex multi-DOF movements are unnecessary for many rehabilitation purposes [ 60 , 109 ] and grasping patterns that are used during ADL can be generalized [ 110 ]. Underactuation, in particular, is a popular method as it reduces weight and complexity [ 65 , 74 , 86 , 93 , 97 , 109 , 111 ] and it facilitates passive adaptation for better object manipulation [ 86 , 94 ].…”

Sensors and Actuation Technologies in Exoskeletons: A Review

“…Therefore, needle EMG remains a method for accurate neurological examinations where high measurement accuracy is strictly required. In some of the analyzed works [ 119 , 120 , 121 , 122 , 123 ], EMG was used to collect data on the activation pattern of a subject wearing an exoskeleton.…”

“…Hybrid sensor network positioning is present in the literature [ 74 ]. For example, in the works by Rudd et al [ 139 ] and by Ertas et al [ 121 ], the authors presented low cost exoskeleton solutions exploiting a simple potentiometer integral with the driven shaft of a gearbox downstream of a simple DC motor. In the paper by Hunt et al [ 140 ], piezo-resistive sensors were inserted in a theoretic project of a shoulder exoskeleton.…”

Design, Development and Evaluation of a New Hand Exoskeleton for Stroke Rehabilitation at Home

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