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Rehabilitation Engineering and Applied Research Lab (REAR Lab)

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Publication Search Results

Now showing 1 - 8 of 8
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    Dataset for "Investigating shock and vibration exposure of a manual wheelchair during multi-drum testing"
    (Georgia Institute of Technology, 2023-09-21) Misch, Jacob ; Sprigle, Stephen
    Wheelchair users are highly susceptible to injury and immobility in the event of a wheelchair breakdown. Durability, or fatigue life, of manual wheelchair frames is currently evaluated using a standardized multi-drum test, which provides frequent impacts to the casters and rear wheels of the wheelchair. Not much is known about the underlying mechanics of the test, making it difficult to properly assess how appropriate this test is as a predictor of wheelchair frame longevity during real-world usage. This study aimed to investigate the applicability of the multi-drum test as an accelerated durability test by comparing breakdown statistics, vibrations, and shocks between the test and real-world usage. Triaxial accelerometers were used to measure the shocks and vibrations transmitted through an ultralightweight manual wheelchair frame during a portion of the multi-drum test. Occupant mass was varied (80 kg, 125 kg) to reflect standard user weight and maximum weight capacity of the chair. Root-mean-square acceleration and vibration dose values were greatest along the vertical axis, and overall similar for both occupant masses. Comparisons with existing literature suggest that the shocks and vibrations experienced within the multi-drum test far exceed values seen in real-world wheelchair usage. Similarly, frame-based fatigue failures are more common during the multi-drum test. These results suggest that the current test protocol is not well-suited to be an accelerated durability test for manual wheelchairs.
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    Dataset for "Comparison of Propulsion Costs and Vibrations Across Carbon Fiber and Aluminum Rigid Manual Wheelchairs"
    (Georgia Institute of Technology, 2023-09-20) Misch, Jacob ; Allen, Taylor ; Suarez, Alicia ; Sprigle, Stephen
    Propulsion efficiency and vibration exposure are two primary concerns when configuring a manual wheelchair. Recent manufacturing techniques have focused on using lightweight materials like carbon fiber to reduce energy expenditure during propulsion and improve vibration attenuation compared to aluminum or steel frames. This study utilized a robotic wheelchair propulsion device to measure the propulsion cost, vibration exposure at the seat, and vibration transmissibility through the frame during travel over smooth (tile) and textured (brick) surfaces for four rigid ultra-lightweight manual wheelchairs made of carbon fiber (N=1) and aluminum (N=3). Component selection (wheels, tires, casters, cushion) and the robotic occupant parameters (weight, fore-aft weight distribution, propulsion characteristics) were standardized across all four frames. Results show no meaningful differences between the carbon fiber and aluminum frames in any of the three variables (i.e., 95% CI does not fully exceed ±5% for propulsion cost or ±6% for vibration and transmissibility). These findings imply that other frame design features are more impactful to vibrations and propulsion efficiency than the material selection. Minimizing wheelchair vibration exposure and maximizing propulsion efficiency are more easily achieved through considerate selection of components, especially cushions and tires, respectively.
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    Dataset for "Effect of wheels, casters and forks on vibration attenuation and propulsion cost of manual wheelchairs"
    (Georgia Institute of Technology, 2022-08-10) Misch, Jacob ; Liu, Yuanning ; Sprigle, Stephen
    Manual wheelchair users are exposed to whole-body vibrations as a direct result of using their wheelchair. Wheels, tires, and caster forks have been developed to reduce or attenuate the vibration that transmits through the frame and reaches the user. Five of these components with energy-absorbing characteristics were compared to standard pneumatic drive wheels and casters. This study used a robotic wheelchair propulsion system to repeatedly drive an ultra-lightweight wheelchair over four common indoor and outdoor surfaces: linoleum tile, decorative brick, poured concrete sidewalk, and expanded aluminum grates. Data from the propulsion system and a seat-mounted accelerometer were used to evaluate the energetic efficiency and vibration exposure of each configuration. Equivalence test results identified meaningful differences in both propulsion cost and seat vibration. LoopWheels and SoftWheels both increased propulsion costs by 12-16% over the default configuration without reducing vibration at the seat. Frog Legs suspension caster forks increased vibration exposure by 16-97% across all four surfaces. Softroll casters reduced vibration by 11% over metal grates. Wide pneumatic 'mountain' tires showed no difference from the default configuration. All vibration measurements were within acceptable ranges compared to health guidance standards. Out of the component options, softroll casters show the most promising results for ease of efficiency and effectiveness at reducing vibrations through the wheelchair frame and seat cushion. These results suggest some components with built-in suspension systems are ineffective at reducing vibration exposure beyond standard components, and often introduce mechanical inefficiencies that the user would have to overcome with every propulsion stroke.
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    Dataset for "Propulsion cost changes of ultra-lightweight manual wheelchairs after one year of simulated use"
    (Georgia Institute of Technology, 2022) Misch, Jacob ; Sprigle, Stephen
    Manual wheelchairs are available with folding or rigid frames to meet the preferences and needs of individual users. Folding styles are commonly regarded as more portable and storable, whereas rigid frames are commonly regarded as more efficient for frequent daily use. To date, there are no studies directly comparing the performances of the frame types. Furthermore, while differences have been reported in the longevity of the frame types, no efforts have been made to relate this durability back to real-world performance of the frames. This study investigated the propulsion efficiencies of 4 folding and 2 rigid ultra-lightweight frames equipped with identical drive tires and casters. A robotic wheelchair tester was used to measure the propulsion costs of each chair over 2 surfaces: concrete and carpet. A motorized carousel was used to drive the chairs 511 km around a circular track to simulate one year of use for each wheelchair. After simulated use, 5 of the 6 wheelchairs showed no decrease in propulsion effort, indicating that the frames were able to withstand the stresses of simulated use without detrimental impact on performance. In the unused 'new' condition, rigid chairs were found to have superior (>5%) performance over folding frames on concrete and carpet, and in the 'worn' condition rigid chairs had superior performance over folding chairs on concrete, but were comparable on the carpeted surface.
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    Mechanical 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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    Video Demonstrations of Over-Ground AMPS Trials with Intermittent Torque-Controlled Propulsion
    (Georgia Institute of Technology, 2020-10-12) Misch, Jacob P. ; Sprigle, Stephen
    This repository contains videos of the Anatomical Model Propulsion System (AMPS) performing straight and curvilinear maneuvers to characterize the performance of various manual wheelchair configurations. The AMPS was configured with a torque-based motor controller. Different trajectories were deployed for different chairs. The straight maneuver features three 'acceleration phase' pushes followed by four 'steady-state phase' pushes, then the system is allowed to gradually coast to a rest. The slalom maneuver starts with one bilateral push to align the casters straight forward, followed by four alternating unilateral pushes to generate the serpentine-like turning motion. K0004 (high-strength lightweight) chairs were tested over tile and carpet, and were given higher torques than the K0005 (ultra-lightweight) chairs to achieve similar motion. Plots of each of the torque profiles are attached in .png format.
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    Modeling manual wheelchair propulsion cost during straight and curvilinear trajectories dataset
    (Georgia Institute of Technology, 2020-05-11) Misch, Jacob ; Huang, Morris ; Sprigle, Stephen
    Minimizing the effort to propel a manual wheelchair is important to all users in order to optimize the efficiency of maneuvering throughout the day. Assessing the propulsion cost of wheelchairs as a mechanical system is a key aspect of understanding the influences of wheelchair design and configuration. The objective of this study was to model the relationships between inertial and energy-loss parameters to the mechanical propulsion cost across different wheelchair configurations during straight and curvilinear trajectories. Inertial parameters of an occupied wheelchair and energy loss parameters of drive wheels and casters were entered into regression models representing three different maneuvers. A wheelchair-propelling robot was used to measure propulsion cost. General linear models showed strong relationships (R2 > 0.84) between the system-level costs of propulsion and the selected predictor variables representing sources of energy loss and inertial influences. System energy loss parameters were significant predictors in all three maneuvers. Yaw inertia was also a significant predictor during zero-radius turns. The results indicate that simple energy loss measurements can predict system-level performance, and inertial influences are mostly overshadowed by the increased resistive losses caused by added mass, though weight distribution can mitigate some of this added cost. Videos of the test methods used to collect this dataset (wheelchair-propelling robot performing the three maneuvers, coast-down cart test for rolling resistance, and the scrub torque test rig) can be found here:
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    Video Demonstrations of Component- and Systems-Level Test Methods for Wheelchair Propulsion Characterization
    (Georgia Institute of Technology, 2018-11) Huang, Morris ; Misch, Jacob ; Sprigle, Stephen
    The five videos included in this repository demonstrate the fundamental test methods used to characterize performance of various wheelchair components. The Anatomical Model Propulsion System (AMPS) was designed to emulate the weight distribution and force application of a human wheelchair user. Three canonical maneuvers were identified to quantify the effects of rolling resistance, drive wheel scrub, and caster swivel. The ‘AMPS straight.mp4’ file shows the straight maneuver. ‘AMPS left FW turn.mp4’ demonstrates a fixed-wheel turn, where one wheel is locked and scrubbing against the floor as the chair drives the other wheel. The ‘AMPS CCW.mp4’ shows an alternating zero-radius maneuver designed to cause caster swivel by driving the wheels in opposing directions. Also included in this directory are videos representing the standalone coast-down and scrub torque component tests. ‘Caster Wheel Coast-down Test Video.m4v’ shows the coast-down cart loaded with weights and instrumented with accelerometers to log the deceleration of the cart. This test measures the force of rolling resistance acting on the cart. The final video, ‘scrub test demo.mp4’, shows the test rig used to measure scrub torque. A ZwickRoell materials testing machine pulls the steel cable attached to a pulley system, which rotates the load arm and effectively scrubs the tile or carpet swatch against the fixed wheel. These videos were taken in 2017 to use as demonstrations for future researchers and collaborators. More information can be found in Morris Huang’s dissertation located at