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Centrifugal pendulum vibration absorbers (CPVAs) are passive devices and a proven technology for reducing torsional vibrations in rotating systems, including helicopter rotors and crankshafts of internal combustion engines. CPVAs consist of pendulums mounted on a rotor, driven by system rotation, and tuned to counteract engine-order fluctuating torques acting on the rotor, thereby smoothing vibrations. In this study, a unifilar CPVA configuration is proposed to address torsional vibrations in electric machines (EMs). A principal challenge in this application is the high-orders of torsional vibration inherent in current EM operation. As order increases, the path radius of curvature that the absorber mass is required to follow (for proper tuning) diminishes, which presents machining challenges. A dynamic model for a unifilar CPVA is developed and then linearized to compute the tuning orders of the system. A quadratic formula is derived whose roots govern the two natural orders of the system and initial results show a desirable large separation between these orders in a prototype design. The developed model will facilitate future simulation studies of the system forced vibration response to characterize the stability and vibration control performance of this design.
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Hyperuniformity and phase enrichment in vortex and rotor assemblies
Abstract Ensembles of particles rotating in a two-dimensional fluid can exhibit chaotic dynamics yet develop signatures of hidden order. Such rotors are found in the natural world spanning vastly disparate length scales — from the rotor proteins in cellular membranes to models of atmospheric dynamics. Here we show that an initially random distribution of either driven rotors in a viscous membrane, or ideal vortices with minute perturbations, spontaneously self assemble into a distinct arrangement. Despite arising from drastically different physics, these systems share a Hamiltonian structure that sets geometrical conservation laws resulting in prominent structural states. We find that the rotationally invariant interactions isotropically suppress long-wavelength fluctuations — a hallmark of a disordered hyperuniform material. With increasing area fraction, the system orders into a hexagonal lattice. In mixtures of two co-rotating populations, the stronger population will gain order from the other and both will become phase enriched. Finally, we show that classical 2D point vortex systems arise as exact limits of the experimentally accessible microscopic membrane rotors, yielding a new system through which to study topological defects.
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- Award ID(s):
- 2004469
- PAR ID:
- 10362701
- Publisher / Repository:
- Nature Publishing Group
- Date Published:
- Journal Name:
- Nature Communications
- Volume:
- 13
- Issue:
- 1
- ISSN:
- 2041-1723
- Format(s):
- Medium: X
- Sponsoring Org:
- National Science Foundation
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