Publication Date

2023

Document Type

Dissertation/Thesis

First Advisor

Xia, Ting

Second Advisor

Jaejin Hwang

Degree Name

M.S. (Master of Science)

Legacy Department

Department of Industrial and Systems Engineering

Abstract

Work-related musculoskeletal disorders (MSDs) represent a prevalent concern affecting a wide range of industries. Occupational exoskeletons have garnered attention as a potential solution to alleviate the risk of MSDs by reducing mechanical loads on susceptible body regions. A critical knowledge gap exists regarding the complex interactions between exoskeleton use and the human body, particularly in work environments prone to slips, trips and falls. This thesis work was part of a funded research aiming to determine the effects of exoskeleton use on balance control. The primary purpose of this thesis work was to determine a reliable maker placement protocol that will be used in the funded research. Two motion data-based approaches were chosen to track full-body kinematics. In the direct center of joint approach (RawJC), paired markers were placed on the opposite sides of major body joints with the midpoints serving as joint centers. The centers of mass (CoM) was then derived from the proximal and distal joint centers of segments and further the whole-body CoM. In the skeletal model-based approach, a skeletal model paired with the conventional full-body, 39-marker placement protocol was used to predict the joint centers, the segmental CoM, and the whole-body CoM. During testing, the participants were asked to perform 3 tasks during quiet standing and during walking. The tasks were 1) holding a weight carrying posture with empty hands, 2) carrying weight (7.0 kg) in the hands, and 3) carrying weight in the hands while wearing a mock exoskeleton (10.3 kg). The two approaches were tested in a single setup by placing all necessary markers on the body. The whole-body CoM was calculated in 4 ways: 1) RawJC – using direct measures of joint centers, the Dempster segmentation method, and the segmental masses from Webb Associates, 2) ModelJC – using the model-produced joint centers, the Dempster segmentation method, and the segmental masses from Webb Associates, 3) ModelCoM – using the model-produced segmental CoM and the segmental masses from Webb Associates, and 3) ModelWBCoM – using the model-produced whole-body CoM. During quiet standing, all four motion data-based methods were compared to the center of pressure (FPCoP) obtained using a force plate placed under the participant’s feet. The results showed that the FPCoP was posterior to the RawJC-derived CoM, which was in turn posterior to the 3 model-derived CoM. In the side-to-side direction, the FPCoP located at the middle while the 4 motion data-based CoM were slightly to the left side. The anterior-posterior sway distance, the side-to-side sway distance and the sway speed analyses showed no difference between the 4 motion data-based methods. The task effect analyses showed that wearing the mock exoskeleton caused the CoM to shift a higher position. Also, carrying weight in hands and carrying weight while wearing an exoskeleton caused CoM to shift posteriorly. Both observations on the task effect indicate potentially compromised balance ability. During walking, the analyses of the CoM computing method effect showed that the RawJC and ModelWBCoM methods were similar while the ModelJC and ModelCoM were similar. Together, the data collected in this thesis work suggest that both the RawJC and ModelWBCoM were suitable to study the risk of falls during slips and falls, with a slight preference to the RawJC method due to its simplicity.

Extent

62 pages

Language

en

Publisher

Northern Illinois University

Rights Statement

In Copyright

Rights Statement 2

NIU theses are protected by copyright. They may be viewed from Huskie Commons for any purpose, but reproduction or distribution in any format is prohibited without the written permission of the authors.

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Text

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