Graduation Year

2011

Document Type

Thesis

Degree

M.S.M.E.

Degree Granting Department

Mechanical Engineering

Major Professor

Kyle B. Reed

Keywords

Archimedean Spiral, Foot Haptics, Gait Adaptation, Gear Mechanics, Human Gait Rehabilitation

Abstract

Persons suffering central nervous system damage, such as a stroke, coma patients, or individuals that have suffered damage to the spinal cord, brainstem, cerebellum, and motor cortex, sometimes develop an asymmetric walking pattern where one leg does not fully swing backward. This uneven gait hinders these individuals in properly and efficiently moving through everyday life.

Previous research in humans and various animals has introduced a split belt treadmill to analyze possible rehabilitation, which can recreate a correct gait pattern by altering the speed of each track. Gait adaptation was achieved by having the split belt treadmill move each leg at a different velocity relative to the ground and thus forcing a symmetric gait. Test subjects‟ gait would adapt to the speeds and a normal gait pattern could be conditioned while on the split belt treadmill. However, after short trials, individuals were unable to neurologically store these feed-forward walking patterns once walking over ground. Also, test subjects would have difficulty adapting their learned walking gait over different walking environments.

The gait enhancing mobile shoe (GEMS) makes it possible to adjust an asymmetric walking gait so that both legs move at a relatively symmetric speed over ground. It alters the wearers walking gait by forcing each foot backwards during the stance phase, operating solely by mechanical motion, transferring the wearer‟s downward force into a horizontal backwards motion. Recreating the split belt treadmill effect over ground by using the GEMS will potentially enable me to test the long term effects of a corrected gait, which is impossible using a split belt treadmill.

A previous prototype of the GEMS [1] successfully generated a split belt treadmill walking pattern, but had various drawbacks, such as variable motion from step to step. My new design of this rehabilitation shoe promises to alter the user‟s gait as a split belt treadmill does, and to be mechanically stable operating without any external power sources.

I designed and constructed a new motion controlled gait enhancing mobile shoe that improves the previous version‟s drawbacks. While mimicking the asymmetric gait motion experienced on a split-belt treadmill, this version of the GEMS has motion that is continuous, smooth, and regulated with on-board electronics. An interesting aspect of this new design is the Archimedean spiral wheel shape that redirects the wearer‟s downward force into a horizontal backward motion. The design is passive and does not utilize any motors and actuators. Its motion is only regulated by a small magnetic pthesis brake. Initial tests show the shoe operates as desired, but further experimentation is needed to evaluate the long-term after-effects.

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