A superelastic variable stiffness knee actuator for a knee-ankle-foot orthosis

Bibliographic Details
Main Author:	Tian, Feng
Language:	English
Published:	University of Toledo / OhioLINK 2015
Subjects:	Mechanical Engineering Biomedical Engineering Biomechanics
Online Access:	http://rave.ohiolink.edu/etdc/view?acc_num=toledo1449578210

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spelling	ndltd-OhioLink-oai-etd.ohiolink.edu-toledo14495782102021-08-03T06:34:23Z A superelastic variable stiffness knee actuator for a knee-ankle-foot orthosis Tian, Feng Mechanical Engineering Biomedical Engineering Biomechanics Quadriceps weakness is primarily caused by neurological and muscular diseases. Individuals with such deficiency have limited ability to initiate knee extension or to control knee flexion. Knee-ankle-foot orthoses (KAFOs) are commonly prescribed to assist in abnormal ambulation caused by weak quadriceps. The purpose of this research is to develop a knee actuating system for knee-ankle-foot orthoses, which mimics normal knee joint behavior. The novel device is called the UT dynamic KAFO. This device is based on the superelastic property of Nitinol, an alloy of Nickel and Titanium. As the first step, a literature review for the biomechanics of human walking was performed. This was necessary to study kinematic and kinetic characteristics of a normal knee joint over the entire walking cycle. In this context, the knee kinematic and kinetic characteristics caused by weak quadriceps are discussed and compared to that of the normal knee joint. This understanding is essential in determining the requirements for the novel knee actuating system.The existing KAFOs were comprehensively studied. Three types of KAFOs have been reported in the literature: passive, stance control (SCKAFOs), and dynamic. Various knee-ankle-foot orthoses are discussed, including their designs, functionality, applications, and limitations. Passive KAFOs are the most used conventional type that provides strong support for the knee joint. Stance control KAFOs lock the knee during the stance phase and allow free knee rotations during the swing phase. Dynamic KAFOs control the knee joint throughout the entire walking gait cycle. In addition to the characteristics of existing KAFOs, the fundamental properties and applications of Nitinol, both shape memory and superelastic alloys, were studied.The conceptual design of the dynamic knee actuator with superelastic Nitinol was proposed and numerical simulations were conducted to verify the concept and to determine proper geometries for the actuator. Based on this, the dynamic knee module was modeled and analyzed and the optimal structures were obtained. The resulting knee module has three working modes: free, locked, and dynamic. A control system was developed to operate among the three modes. A prototype was first fabricated using additive manufacturing and then improved to the final device. The final prototype was added to a conventional KAFO.The resulting UT dynamic KAFO was evaluated in motion analysis tests on a healthy subject. The subject had no history of lower extremity pathology. Joint kinematics, kinetics, and electromyography data of both lower limbs was collected and calculated to compare the walking patterns in normal walking and walking with the UT dynamic KAFO. When compared with a locked knee KAFO, the results indicate that the dynamic KAFO is able to improve gait. Thus, we have concluded that the UT dynamic KAFO is able to assist gait in a manner that approximates a normal gait pattern. 2015 English text University of Toledo / OhioLINK http://rave.ohiolink.edu/etdc/view?acc_num=toledo1449578210 http://rave.ohiolink.edu/etdc/view?acc_num=toledo1449578210 unrestricted This thesis or dissertation is protected by copyright: all rights reserved. It may not be copied or redistributed beyond the terms of applicable copyright laws.
collection	NDLTD
language	English
sources	NDLTD
topic	Mechanical Engineering Biomedical Engineering Biomechanics
spellingShingle	Mechanical Engineering Biomedical Engineering Biomechanics Tian, Feng A superelastic variable stiffness knee actuator for a knee-ankle-foot orthosis
author	Tian, Feng
author_facet	Tian, Feng
author_sort	Tian, Feng
title	A superelastic variable stiffness knee actuator for a knee-ankle-foot orthosis
title_short	A superelastic variable stiffness knee actuator for a knee-ankle-foot orthosis
title_full	A superelastic variable stiffness knee actuator for a knee-ankle-foot orthosis
title_fullStr	A superelastic variable stiffness knee actuator for a knee-ankle-foot orthosis
title_full_unstemmed	A superelastic variable stiffness knee actuator for a knee-ankle-foot orthosis
title_sort	superelastic variable stiffness knee actuator for a knee-ankle-foot orthosis
publisher	University of Toledo / OhioLINK
publishDate	2015
url	http://rave.ohiolink.edu/etdc/view?acc_num=toledo1449578210
work_keys_str_mv	AT tianfeng asuperelasticvariablestiffnesskneeactuatorforakneeanklefootorthosis AT tianfeng superelasticvariablestiffnesskneeactuatorforakneeanklefootorthosis
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A superelastic variable stiffness knee actuator for a knee-ankle-foot orthosis

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