Document Type

Dissertation

Date of Award

5-31-2017

Degree Name

Doctor of Philosophy in Biomedical Engineering - (Ph.D.)

Department

Biomedical Engineering

First Advisor

Richard A. Foulds

Second Advisor

Sergei Adamovich

Third Advisor

Gerard G. Fluet

Fourth Advisor

John R. Bach

Fifth Advisor

Jay J. Han

Abstract

Duchenne muscular dystrophy (DMD), a neuromuscular disease with a prevalence of 1 in 3,500-5,000 male births, results in progressive muscle weakness causing loss of independence and imposing the demands of costly and intrusive assistive support and personal care for daily living tasks. Upper extremity function begins to decline while ambulation is still possible and gradually progresses with time, playing a prominent role in loss of independence. Importantly, upper extremity functional limitations exist despite residual muscle strength that is insufficient to lift the arms against gravity. Presently, there exist a number of commercially available assistive devices aimed at augmenting upper extremity functional deficit; however, these devices have been largely unsuccessful in delivering the independence they seek to provide. Passive orthoses, the most common of these commercially available assistive devices, are limited to those in the earlier stages of functional loss because of the imperfect gravity compensation, requirement of sufficient muscle strength to overcome the inertia of the device, and inability to accommodate loss of strength over time. The objective of this project is to overcome the limitations of currently available upper extremity assistive devices for individuals with DMD by using admittance control. Admittance control is an inherently safe and intuitive robotic control paradigm that maps the user’s applied force to the motion of a robot. It is hypothesized that a motorized arm support utilizing the admittance control paradigm will provide individuals with DMD an intuitive and effective means of increasing upper extremity AROM and independence through the use of their residual muscle strength.

The results of this project demonstrate that individuals with DMD who have limited or nonexistent upper extremity function retain residual muscle strength sufficient to generate voluntary movement when the arms are supported against gravity. Furthermore, the results show that admittance control allows for the use of this residual strength to increase the AROM of individuals with DMD to a greater degree than a commercially available passive arm support and provide increased independence in the performance of user-defined priority tasks compared to unsupported movements. The results also show that over one year there is no significant decrease in the AROM provided by the admittance control robot, indicating the viability of an admittance control motorized arm support to provide sustainable improvements in upper extremity function in the presence of progressive muscle loss. Finally, two prototypes are presented that demonstrate a novel approach to upper extremity exoskeleton design. The phase 1 prototype establishes the successful implementation of admittance control as the control paradigm for fully motorizing all degrees of freedom (DOF) of a commercially available passive arm support. The phase 2 prototype demonstrates a modular approach intended to accommodate changes in upper extremity function over time through the successful implementation of one motorized DOF of a commercially available passive arm support while keeping the other DOFs passive. The work presented herein is a comprehensive investigation to establish the benefits of admittance control to increase upper extremity AROM and improve independence for individuals with DMD with the intention of allowing these individuals to maintain optimal quality of life.

Share

COinS