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Browsing by Author "Brown, Emily"

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    Assessment of One-Way Releasable Brake Mechanisms for Lower Limb Wearable Robotic Systems
    (2023-03) Brown, Emily
    Lower limb wearable exoskeletons can be used for weight bearing exercise by those with a spinal cord injury to mitigate adverse effects from prolonged sitting. Some exoskeletons have joints that can lock and unlock under computer control. Three categories of releasable brake technologies were analyzed to determine the best locking joint for the University of Minnesota’s Functional Electrical Stimulation Energy Storing Exoskeleton: wrap spring brakes, magnetic particle brakes, and ratchet brakes. Two types of wrap spring brakes were included: off-the-shelf and custom. Fifty Newton-meters was used for the target holding torque for the analysis. Other key requirements were size, weight, power consumption when locked, and switching time. The holding torque to weight ratio of the ratchet brake was an order of magnitude higher than the other technologies. The power required to hold a magnetic particle brake in a locked state increased with holding torque. The other brake technologies consume zero power in the locked state. The magnetic particle brake was determined to be the best brake because of the high holding torque to weight ratio when coupled with a transmission, and the shape and weight optimization options. The magnetic particle brake’s lack of movement after stopping and quick switching times between states are advantages that differentiate the magnetic particle brake from the ratchet and wrap spring brake. Adding additional mechanisms to limit the size of a power source needed and minimize weight of the system should be explored further.
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    What do Courageous Leaders Need to be Effective?
    (Hubert H. Humphrey Institute of Public Affairs, 2010-05-18) Brown, Emily; Fleetham, Sara; Shurilla, Allison; Simonson, Dawn