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A significant challenge in the design of fully superconducting (SC) machines is managing ac losses in the SC armature. Recent developments in MgB2 superconducting conductors promise low ac loss conductors suitable for fully SC machines. This paper presents an optimized design targeting low losses and low weight for a 10-MW fully SC generator suitable for offshore wind turbine applications. An outer rotor air-core machine topology is investigated to optimize the design with low weight and low losses. An active shielding concept is used to minimize the pole count without adding excessive weight. This enables a reduction in the electrical frequency for a practical design by a factor of 4 to 5 over current designs, driving ac losses and active components weight lower by an order of magnitude. In this study, armature current is varied to control electrical and magnetic loading in order to minimize losses. A pole count study is conducted to identify the design space suitable for MW scale machines. A comparison is made between active shield, passive shield and a hybrid topology to address the benefits of an active shield for weight reduction. Results suggest that low-pole-count designs with MgB2 conductors will enable machines with less than 1 kW of ac losses.
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Toward Sub-Gram Helicopters: Designing a Miniaturized Flybar for Passive Stability
Sub-gram flying robots have transformative potential in applications from search and rescue to precision agriculture to environmental monitoring. However, a key gap in achieving autonomous flight for these applications is the low lift to weight ratio of flapping wing and quadrotor designs around 1 g or less. To close this gap, we propose a helictoper-style design that minimizes size and weight by leveraging the high lift, reliability, and low-voltage of sub-gram motors. We take an important step to enable this goal by designing a light-weight, micfrofabricated flybar mechanism to passively stabilize such a robot. Our 48 mg flybar is folded from a flat carbon fiber laminate into a 3D mechanism that couples tilting of the flybar to a change in the angle of attack of the rotors. Our design uses flexure joints instead of ball-in-socket joints common in larger flybars. To expedite the design exploration and optimization of a microfabricated flat-folded flybar, we develop a novel user-in-the-loop bi-level optimization workflow that combines Bayesian optimization design tools and expert feedback. We develop four template designs and use this method to achieve a peak damping ratio of 0.528, an 18.9x improvement from our initial design. Compared to a flybar-less rotor with a near 0 damping ratio, our flybar-rotor mechanism maintains a stable roll and pitch with relative deviations < 1°. Our results show that, if combined with a counter-torque mechanism such as a tail rotor, our miniaturized flybar could mechanically provide attitude stability for a sub-gram helicopter.
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- Award ID(s):
- 2054850
- PAR ID:
- 10504544
- Publisher / Repository:
- IEEE
- Date Published:
- Journal Name:
- 2023 IEEE/RSJ International Conference on Intelligent Robots and Systems (IROS)
- ISBN:
- 978-1-6654-9190-7
- Page Range / eLocation ID:
- 2701 to 2708
- Format(s):
- Medium: X
- Location:
- Detroit, MI, USA
- Sponsoring Org:
- National Science Foundation
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- Free Publicly Accessible Full Text
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Accepted Manuscript1.0
- Conference Paper:
- https://doi.org/10.1109/IROS55552.2023.10342256
