Development and assessment of a hand assist device: GRIPIT

Abstract

Background: Although various hand assist devices have been commercialized for people with paralysis, they are somewhat limited in terms of tool fixation and device attachment method. Hand exoskeleton robots allow users to grasp a wider range of tools but are heavy, complicated, and bulky owing to the presence of numerous actuators and controllers. The GRIPIT hand assist device overcomes the limitations of both conventional devices and exoskeleton robots by providing improved tool fixation and device attachment in a lightweight and compact device. GRIPIT has been designed to assist tripod grasp for people with spinal cord injury because this grasp posture is frequently used in school and offices for such activities as writing and grasping small objects. Methods: The main development objective of GRIPIT is to assist users to grasp tools with their own hand using a lightweight, compact assistive device that is manually operated via a single wire. GRIPIT consists of only a glove, a wire, and a small structure that maintains tendon tension to permit a stable grasp. The tendon routing points are designed to apply force to the thumb, index finger, and middle finger to form a tripod grasp. A tension-maintenance structure sustains the grasp posture with appropriate tension. Following device development, four people with spinal cord injury were recruited to verify the writing performance of GRIPIT compared to the performance of a conventional penholder and handwriting. Writing was chosen as the assessment task because it requires a tripod grasp, which is one of the main performance objectives of GRIPIT. Results: New assessment, which includes six different writing tasks, was devised to measure writing ability from various viewpoints including both qualitative and quantitative methods, while most conventional assessments include only qualitative methods or simple time measuring assessments. Appearance, portability, difficulty of wearing, difficulty of grasping the subject, writing sensation, fatigability, and legibility were measured to assess qualitative performance while writing various words and sentences. Results showed that GRIPIT is relatively complicated to wear and use compared to a conventional assist device but has advantages for writing sensation, fatigability, and legibility because it affords sufficient grasp force during writing. Two quantitative performance factors were assessed, accuracy of writing and solidity of writing. To assess accuracy of writing, we asked subjects to draw various figures under given conditions. To assess solidity of writing, pen tip force and the angle variation of the pen were measured. Quantitative evaluation results showed that GRIPIT helps users to write accurately without pen shakes even high force is applied on the pen.

Design Criteria of Soft Exogloves for Hand Rehabilitation-Assistance Tasks

“…For example, the Kapandji score is used to evaluate thumb performance on pinching and grasping tasks [ 108 ]. SEG assessment also considers the motricity index test (MIT) [ 105 ], the Fugl-Meyer assessment (FMA) [ 46 ], the nine-hole peg test (NHPT) [ 38 ], the Jebsen-Taylor hand test (JTT) [ 44 ], the box and block test (BBT) [ 11 ], the Purdue pegboard test (PPT) [ 45 ], or some writing tasks [ 109 ].…”

Moving toward Soft Robotics: A Decade Review of the Design of Hand Exoskeletons

“…This new trend is especially interesting for biomedical and rehabilitation engineering applications as well, with the hand exoskeleton as one of the examples. A major shift from the use of hard to soft materials can be observed in some of the latest designs of hand exoskeletons, such as the Wyss Institute glove [6,7,8], the Magnetic Resonance Compatible (MRC) glove [9,10,11,12], the National University of Singapore (NUS) glove [13,14,15,16,17] and the Seoul National University (SNU) glove [18,19,20,21,22,23]. The hand exoskeleton is an integral part of rehabilitation robotics that provides rehabilitation exercises and assistance in activities of daily living (ADL), such as gripping and grasping [24].…”

A Finger Grip Force Sensor with an Open-Pad Structure for Glove-Type Assistive Devices

“…To assist reduced grip strength or prevent WMSDs, many assistive hand exoskeletons have been developed [8][9][10][11][12][13][14][15][16] that detect the intention of the wearer's intention via fingerpad contact forces [17][18][19][20], finger motion [20][21][22][23][24], surface electromyography (sEMG) [25][26][27], or multimodal sensing [28]. Although the measurement of fingerpad contact force enables the acquisition of individual finger forces with simple sensors, the tactile sensation of the wearer is inevitably diminished because of the presence of the force sensor between the fingerpad and object being manipulated.…”

“…There are no fixed mechanical joints in the developed device because the glove does not have a rigid frame and precise alignment of the joint axes between the hand of the wearer and the device is not required. For these reasons, glove-type hand exoskeletons have been used in several studies [14][15][16][17][18]. The major improvements relative to previous studies are as follows: The number of measurable DoFs was increased to four, flexion of the index and middle fingers and flexion and adduction of the thumb.…”