Browsing by Author "Simon, Athulya A."

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    Modeling the Metabolic Reductions of a Passive Back-Support Exoskeleton
    Alemi, Mohammad Mehdi; Simon, Athulya A.; Geissinger, Jack H.; Asbeck, Alan T. (2022-01-13)
    Despite several attempts to quantify the metabolic savings resulting from the use of passive back-support exoskeletons (BSEs), no study has modeled the metabolic change while wearing an exoskeleton during lifting. The objectives of this study were to: 1) quantify the metabolic reductions due to the VT-Lowe's exoskeleton during lifting; and 2) provide a comprehensive model to estimate the metabolic reductions from using a passive BSE. In this study, 15 healthy adults (13M, 2F) of ages 20 to 34 years (mean=25.33, SD=4.43) performed repeated freestyle lifting and lowering of an empty box and a box with 20% of their bodyweight. Oxygen consumption and metabolic expenditure data were collected. A model for metabolic expenditure was developed and fitted with the experimental data of two prior studies and the without-exoskeleton experimental results. The metabolic cost model was then modified to reflect the effect of the exoskeleton. The experimental results revealed that VT-Lowe's exoskeleton significantly lowered the oxygen consumption by ~9% for an empty box and 8% for a 20% bodyweight box, which corresponds to a net metabolic cost reduction of ~12% and ~9%, respectively. The mean metabolic difference (i.e., without-exo minus with-exo) and the 95% confidence interval were 0.36 and (0.2-0.52) [Watts/kg] for 0% bodyweight, and 0.43 and (0.18-0.69) [Watts/kg] for 20% bodyweight. Our modeling predictions for with-exoskeleton conditions were precise, with absolute freestyle prediction errors of <2.1%. The model developed in this study can be modified based on different study designs, and can assist researchers in enhancing designs of future lifting exoskeletons.
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    A Novel Method and Exoskeletons for Whole-Arm Gravity Compensation
    Hull, Joshua; Turner, Ranger; Simon, Athulya A.; Asbeck, Alan T. (IEEE, 2020-08-17)
    We present a new method for providing gravity compensation to a human or robot arm. This method allows the arm to be supported in any orientation, and also allows for the support of a load held in the hand. We accomplish this with a pantograph, whereby one portion of the linkage duplicates the arm's geometry, and another portion of the linkage contains a scaled copy of the arm. Forces applied to the scaled copy are transferred back to the original arm.We implement these concepts with two exoskeletons: the Panto- Arm Exo, a low-prole exoskeleton that supports the arm's weight, and the Panto-Tool Exo that supports a mass held in the hand. We present two linkages used for pantographs, and analyze how different linkage dimensions and their positioning relative to the body affect the forces providing gravity compensation. We also measured the effect of the Panto-Arm exoskeleton on fourteen subjects' arm muscles during static holding tasks and a task in which subjects drew horizontal and vertical lines on a whiteboard. Even though the Panto-Arm Exo linkage geometry and forces were not optimized, it reduced the Mid Deltoid by 33-43% and the Biceps Brachii by up to 52% in several arm postures.