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Browsing by Subject "motor"

Now showing 1 - 3 of 3
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    Bearingless AC Homopolar Machine Design and Control for Distributed Flywheel Energy Storage
    (2015-06) Severson, Eric
    The increasing ownership of electric vehicles, in-home solar and wind generation, and wider penetration of renewable energies onto the power grid has created a need for grid-based energy storage to provide energy-neutral services. These services include frequency regulation, which requires short response-times, high power ramping capabilities, and several charge cycles over the course of one day; and diurnal load-/generation-following services to offset the inherent mismatch between renewable generation and the power grid's load profile, which requires low self-discharge so that a reasonable efficiency is obtained over a 24 hour storage interval. To realize the maximum benefits of energy storage, the technology should be modular and have minimum geographic constraints, so that it is easily scalable according to local demands. Furthermore, the technology must be economically viable to participate in the energy markets. There is currently no storage technology that is able to simultaneously meet all of these needs. This dissertation focuses on developing a new energy storage device based on flywheel technology to meet these needs. It is shown that the bearingless ac homopolar machine can be used to overcome key obstacles in flywheel technology, namely: unacceptable self-discharge and overall system cost and complexity. Bearingless machines combine the functionality of a magnetic bearing and a motor/generator into a single electromechanical device. Design of these machines is particularly challenging due to cross-coupling effects and trade-offs between motor and magnetic bearing capabilities. The bearingless ac homopolar machine adds to these design challenges due to its 3D flux paths requiring computationally expensive 3D finite element analysis. At the time this dissertation was started, bearingless ac homopolar machines were a highly immature technology. This dissertation advances the state-of-the-art of these machines through research contributions in the areas of magnetic modeling, winding design, control, and power-electronic drive implementation. While these contributions are oriented towards facilitating more optimal flywheel designs, they will also be useful in applying the bearingless ac homopolar machine in other applications. Example designs are considered through finite element analysis and experimental validation is provided from a proof-of-concept prototype that has been designed and constructed as a part of this dissertation.
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    Combining TMS and EEG for Characterizing Motor Network Interactions and Improving Motor Recovery after Stroke
    (2016-12) Johnson, Nessa
    Imaging of electrophysiological activity within the brain is crucial to understanding function in both healthy and disease conditions. The overall goal of this dissertation is to use both non-invasive neuromodulation and non-invasive neuroimaging to characterize and manipulate underlying neurological network dynamics in both healthy and stroke affected subjects. The two main applications of work are for the evaluation of peripheral motor activity on motor network dynamics in healthy subjects, and as a brain-based treatment for motor recovery after stroke. Combined transcranial magnetic stimulation (TMS) and electroencephalography (EEG) imaging can be used to analyze cortical reactivity and connectivity of underlying brain networks. However, the effect of corticospinal and peripheral muscle activity on TMS-evoked potentials (TEPs), particularly in motor areas, is not well understood. One aim of the present dissertation is to evaluate the relationship between cortico-spinal activity, in the form of peripheral motor-evoked potentials (MEPs), and the TEPs from motor areas, along with the connectivity among activated brain areas. This research demonstrates that TMS-EEG, along with adaptive connectivity estimators, can be used to evaluate the cortical dynamics associated with sensorimotor integration and proprioceptive manipulation. Stroke is a devastating neurological disorder which can result in lasting impairment affecting quality-of-life. Combining contralesional repetitive TMS (rTMS) with EEG-based brain-computer interface (BCI) training can address motor impairment after stroke by down-regulating exaggerated inhibition from the contralesional hemisphere and encouraging ipsilesional activation. Another aim of this dissertation was to evaluate the efficacy of combined rTMS+BCI, compared to sham rTMS+BCI, and BCI alone, on motor recovery after stroke in subjects with lasting motor paresis. As evaluated in a series of stroke patients, such a brain-based neuromodulatory and imaging approach for rehabilitation could potentially lead to greater understanding of the influence of brain network dynamics in recovery and design of optimal treatment strategies for individual patients. Our findings demonstrate the feasibility and efficacy of not only combined rTMS+BCI but also BCI alone, as demonstrated by significant improvements over time in behavioral and electrophysiological measures. In summary, the present dissertation research developed and evaluated the combination of neuromodulation and neuroimaging for the non-invasive mapping of motor network activities in the diseased and normal brain. Evaluations were conducted in healthy controls to evaluate the influence of peripheral muscle activity on resulting neural network activity, as well as in stroke patients to provide a brain-based treatment for motor rehabilitation. The results obtained suggest the importance of non-invasive spatiotemporal neuroimaging, along with non-invasive neuromodulation, for providing insight into neuroscience questions and providing novel treatments for clinical problems in a brain-based manner.
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    Novel Artificial Urinary Sphincter for Stress Urinary Incontinence Treatment
    (2017-09) Mishra, Avishek
    The American Medical System’s AMS 800TM has been the gold standard for over 40 years with over 150,000 patients treated for Urinary Incontinence and is the leading treatment for male stress urinary incontinence (SUI) following prostate surgery. Type III SUI, or intrinsic sphincter deficiency, is the inability of the urethra to maintain closure pressure sufficient to keep the patient clinically dry at rest and during periods of heightened activity (~120 cmH2O; coughs, sneezes, posture changes, and exercises). The current AMS 800TM is not personalized to a patient’s needs and compromises with an in between pressure- as high (61-70 cmH2O) as it can be without exceeding safety threshold levels. As such many men still leak when they are active. The market is hungry for a device that can adapt to the patient’s level of activity, reducing pressure most of the day to protect the urethra and then briefly increasing the pressure when he is more active. We are developing a novel implantable pump (henceforth called “add-on device”) which will be an add-on to the AMS 800TM and it includes a solenoid coil-cum-plunger and a fluid reservoir within the pump body. The add-on device will be small, light-weight and battery powered, and maintain compatibility with the AMS 800TM device. The device idea is in its proof-of-concept stage. This add-on device can be a possible solution to reducing the risks including urethral atrophy (leading to return of incontinence) and erosion (leading to infection of the implant) resulting from the constant pressure.