Organizational Unit:
Rehabilitation Engineering and Applied Research Lab (REAR Lab)
Rehabilitation Engineering and Applied Research Lab (REAR Lab)
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ItemMechanical performance characterization of manual wheelchairs using robotic wheelchair operator with intermittent torque-based propulsion(Georgia Institute of Technology, 2020-12-06) Misch, Jacob P.The current manual wheelchair design process lacks consistent and objective connection to performance-based metrics. The goal of this research was to empirically assess over-ground manual wheelchair performances and identify important design trade-offs through the use of a robotic apparatus with a novel cyclic propulsion control method. This research had four specific aims: 1) to design, implement, and validate torque-based propulsion to emulate the intermittent human propulsion cycle with an existing robotic wheelchair tester, 2) to investigate the influence of incremental mass additions to the wheelchair frame on over-ground propulsion characteristics, 3) to demonstrably improve the performance of a representative high-strength lightweight wheelchair by leveraging existing component-level test results, and 4) to characterize the mechanical performances of representative folding and rigid ultra-lightweight wheelchair frames. The outcomes of this research include an objective, repeatable, and validated test method to assess over-ground performances of manual wheelchairs in realistic contexts of use, as well as insight on the mechanics of the system that were previously under-studied or confounded by variabilities within human subject testing. Controlled propulsion tests are used to identify differences between wheelchair configurations. The outcome variable of propulsion cost represents the energetic requirements of propelling each chair a given distance and has direct relevance to manufacturers, clinicians, and wheelchair users alike. Ultimately, these outcomes will inform clinicians and manufacturers about how configuration choices influence propulsive efforts, which can be used in turn to improve their classification techniques and existing design processes. This knowledge will additionally empower wheelchair users to make informed choices during the wheelchair selection process based on objective mechanical performance metrics.
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ItemDevelopment of component and system level test methods to characterize manual wheelchair propulsion cost(Georgia Institute of Technology, 2017-11-10) Huang, MorrisThe current approach to manual wheelchair design lacks a sound and objective connection to metrics for wheelchair performance. The objective of this research was three-fold: 1) to characterize the inertial and resistive properties of different wheelchair components and configurations, 2) to characterize the systems-level wheelchair propulsion cost, and 3) to model wheelchair propulsion cost as a function of measured component and configuration properties. Scientific tools developed include 1) a series of instruments and methodologies to evaluate the rotational inertia, rolling resistance, and scrub torque of wheelchair casters and drive wheels on various surface types, and 2) a wheelchair-propelling robot capable of measuring propulsion cost across a collection of maneuvers representative of everyday wheelchair mobility. This suite of tools were used to demonstrate the variance manifested in the resistive properties of 8 casters and 4 drive wheels, and the impact/tradeoffs of these components (as well as mass and weight distribution) on system-level wheelchair propulsion cost. Coupling these findings with a theoretical framework describing wheelchair dynamics resulted in two empirical models linking system propulsion cost to component resistive properties. The outcomes of this research empower clinicians and users to make more informed wheelchair selections, as well as offer manufacturers a basis by which to optimize their wheelchair designs.
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ItemThe acute effects of physical activity on the stiffness of the plantar skin of people with and without diabetes(Georgia Institute of Technology, 2013-11-18) Wendland, Deborah MichaelDiabetes affects 25.8 million Americans. Complications related to this growing disease impact public health. One secondary complication of diabetes is changes in skin that can contribute to an increased risk for ulceration. Skin of people with diabetes has not been characterized over time nor has the skin’s acute response to exercise been assessed. The objective of this project was to establish the changes in skin properties over time, within different ambient environments, and after acute exercise. This objective sought to address the central hypothesis that skin will demonstrate decreased stiffness and increased elasticity as a result of acute physical activity. Skin stiffness, compliance, and thickness measurements of the plantar foot were compared across time and environment. Skin stiffness and compliance were also compared before and after treadmill walking. First, three devices were validated. Accuracy of the StepWatch was validated for people using assistive devices. The tissue interrogation device (TID), a novel device that measures tangential skin stiffness, and the myotonometer, which measures skin compliance, were validated using elastomer phantoms. Both were found suitable to measure plantar skin properties. Second, skin properties of 16 persons with and without diabetes were measured over time and environmental condition. Skin was variable across subjects over time, but was stable within subjects over a month, supporting the use of a repeated measures approach to interventional study on the plantar skin in people with diabetes. Previous findings for general skin characteristics were supported including the tendency for persons with diabetes to have a thinner epidermis and a thicker dermis than persons without diabetes. Tangential skin stiffness was determined to be less stiff in people with diabetes when measured in a medial-lateral direction. People with diabetes had lower tissue compliance than those without. Skin properties varied across environmental condition, supporting the consideration of testing environment when evaluating skin. Finally, changes in skin properties were evaluated in 32 persons with diabetes before and after treadmill (TM) walking. Using the TID, skin stiffness (tangential) at the great toe of people with diabetes (663.705±4.796 N/m) and without (647.753±5.328 N/m) were different (p=0.040). Stiffness immediately following TM walking did not differ from pre-walking stiffness, but subsequent trials had increased stiffness. Similar, but not significant responses were noted at the first metatarsal head. Compliance using normal loading increased after walking with statistical differences lasting 30-60 minutes.
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ItemThe impact of input during the design of an assistive technology product(Georgia Institute of Technology, 2010-01-11) Choi, Young MiThe design of Assistive Technology (AT) products that are highly functional as well satisfactory is presents many challenges. Various types of input are used in design of AT products to help overcome them. A study was conducted to gather data on the impact that different types of input (from simulation tools, a professional therapist, and end users) during the design of an AT product has on the effectiveness, efficiency and satisfaction of the final design. The results show that input from stakeholders (end users or a therapist) can be very effective. However, effectiveness of the input is influenced by many factors and its impact on the design can be highly variable. Input from simulation tools was also found to be equally effective. Implications of these findings for the process of designing AT products are discussed.
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ItemBiomechanical responses to seated full body tilt and their relationship to clinical application(Georgia Institute of Technology, 2009-08-19) Sonenblum, Sharon EveThe overall goal of this research is to improve the use of seated tilt to increase function, health and quality of life for people using power wheelchairs. Specifically, the objective of this dissertation is to evaluate the biomechanical responses to seated full body tilt and their relationships to the actual use of tilt-in-space wheelchairs. In the first phase of this study, researchers remotely monitored how 45 fulltime power wheelchair users used their tilt-in-space systems. Participants spent an average of 12.1 hours in their wheelchair each day. They spent more than 2 hours seated at positions greater than 15° and performed tilts of 5° or greater every 27 minutes, but rarely performed tilts past 30°. Two distinct types of tilt behavior were identified: uni-modal (staying at a single position more than 80% of the time) and multi-modal (staying at a single position less than 80% of the time). Participants in the multi-modal group tilted significantly more frequently (4 times per hour) than the uni-modal group, and did not have a single typical position. Participants without sensation were more likely to exhibit uni-modal behavior. In the second phase of this study, researchers used interface pressure measurements and laser Doppler flowmetry to study changes in localized loading and superficial blood flow at the ischial tuberosities across different amounts of tilt. Eleven participants with spinal cord injuries were studied in a laboratory setting. Results showed that biomechanical responses to tilt were highly variable. Pressure reduction at the ischial tuberosity was not present at 15°, but did occur with tilts to 30° and greater, and could be explained by the tilt position and upright pressure. Unlike pressure, blood flow increased with all tilts from an upright position, but did not increase when tilting from 15° to 30°. Only 4 of 11 participants had a considerable increase (≥10%) in blood flow at 30° tilt, whereas 9 participants did during maximum tilt (i.e., 45°-60°). Based on the results of this study, tilting for pressure reliefs as far as the seating system permits is recommended to maximize the potential for significant blood flow increases and pressure relief.