Date of Award

Spring 5-7-2021

Level of Access Assigned by Author

Open-Access Thesis

Degree Name

Master of Science (MS)

Department

Mechanical Engineering

Advisor

Babak Hejrati

Second Committee Member

Mohsen Shahinpoor

Third Committee Member

Andrew Goupee

Abstract

A healthy gait is often taken for granted when walking. However, if a stroke, spinal cord injury (SCI), or traumatic event occurs the ability to walk may be lost. In order to relearn how to walk, gait rehabilitation is required. Including arm swing in gait rehabilitation has been shown to help in this process. This thesis presents two tasks to investigate the mechanics of arm swing and ways to provide assistance to induce arm swing in gait rehabilitation.

The firsts task completed was a study on the effects of forearm movement during gait. Twelve healthy subjects walked under three conditions at two self selected speeds. The first condition observed was natural walking, the second condition the subjects wore an artificial forearm with their forearms restricted, and the third condition the subjects’ forearms were restricted without the artificial forearm. It was observed that the the lower extremities’ range of motion and spatiotemporal parameters did not change between conditions. However when the subjects wore the artificial forearm, significant decreases were observed in the shoulders, trunk, interlimb coordination, and shoulder trunk correlations. In addition, increases in muscle activity also occurred in the biceps, trapezius, and posterior deltoids during the second condition. The amount of energy exerted also increased when wearing the artificial forearm, but not significantly. Only restraining the forearms mainly affected shoulder rotation at the subjects’ normal walking speed. These results indicate that the body actively controls forearm movements during walking to mitigate unwanted movements. It does this by reducing shoulder and trunk rotation.

The second task was the design and validation of a distally located upper extremity exoskeleton to assist with arm swing during gait rehabilitation. This exoskeleton utilizes a hybrid double parallel linkage (DPL) that allows the exoskeleton to mimic the work-space of a healthy shoulder. The motor is distally located from the shoulder and located on a ALICE backpack. This provides several ergonomic benefits such as reducing the weight on the wearer’s arm. The torque is transferred from the motor to the arm through a pulley system. The exoskeleton’s ability to generate arm swing was validated on a passive dummy arm. The exoskeleton was tested under two conditions. The first condition was in-plane arm swing, which simulated motion strictly in the sagittal plane. The second condition was out-of-plane arm swing to simulate arm swing when the shoulder is internally rotated. Each condition was tested at frequencies of 0.67, 0.80, 1.10 Hz. It was observed that the exoskeleton can generate highly correlated movements in the passive arm at each of the tested frequencies with low time lags. In addition the exoskeleton was also tested on two subjects. Similarly, arm movements were highly coordinated to motor movements. Based on these results, this exoskeleton design has the potential to aid in gait rehabilitation.

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