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TECHNICAL PAPERS

Development of a New Passive-Active Magnetic Damper for Vibration Suppression

[+] Author and Article Information
Henry A. Sodano1

Mechanical Engineering Department,  Michigan Technological University, 1400 Townsend Dr., Houghton, MI 49931hsodano@mtu.edu

Daniel J. Inman

Center for Intelligent Material Systems and Structures,  Virginia Polytechnic Institute and State University, Blacksburg, VA 24061-0261dinman@vt.edu

W. Keith Belvin

Structural Dynamics Branch,  NASA Langley Research Center, Hampton, VA 23681-0001w.k.belvin@larc.gov

1

To whom correspondence should be addressed.

J. Vib. Acoust 128(3), 318-327 (Nov 03, 2005) (10 pages) doi:10.1115/1.2172258 History: Received December 22, 2004; Revised November 03, 2005

Magnetic fields can be used to apply damping to a vibrating structure. Dampers of this type function through the eddy currents that are generated in a conductive material experiencing a time-changing magnetic field. The density of these currents is directly related to the velocity of the change in magnetic field. However, following the generation of these currents, the internal resistance of the conductor causes them to dissipate into heat. Because a portion of the moving conductor’s kinetic energy is used to generate the eddy currents, which are then dissipated, a damping effect occurs. This damping force can be described as a viscous force due to the dependence on the velocity of the conductor. In a previous study, a permanent magnet was fixed in a location such that the poling axis was perpendicular to the beam’s motion and the radial magnetic flux was used to passively suppress the beam’s vibration. Using this passive damping concept and the idea that the damping force is directly related to the velocity of the conductor, a new passive-active damping mechanism will be created. This new damper will function by allowing the position of the magnet to change relative to the beam and thus allow the net velocity between the two to be maximized and thus the damping force significantly increased. Using this concept, a model of both the passive and active portion of the system will be developed, allowing the beams response to be simulated. To verify the accuracy of this model, experiments will be performed that demonstrate both the accuracy of the model and the effectiveness of this passive-active control system for use in suppressing the transverse vibration of a structure.

Copyright © 2006 by American Society of Mechanical Engineers
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References

Figures

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Figure 5

Schematic showing the variables associated with the conducting plate

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Figure 6

Damping force as a function of the distance form beam to magnet

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Figure 7

Block diagram of closed loop system

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Figure 8

Root locus of the closed loop system showing the stability of the system when the filter gain is properly chosen

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Figure 9

Schematic showing the dimensions of the beam

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Figure 10

Layout of the experimental system

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Figure 11

Effect of varying the filter frequency on the frequency response

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Figure 12

Effect of varying the filter damping ratio on the frequency response

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Figure 13

Linear and nonlinear time response of the beam before and after control

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Figure 14

Experimentally measured and predicted frequency response of second mode for controlled system compared to the case of passive eddy current damping and no added damping

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Figure 15

Experimentally measured and predicted frequency response of first mode for controlled system compared to the case of passive eddy current damping and no added damping

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Figure 16

Experimentally measured and predicted frequency response of the beam before and after passive-active control of the first two modes

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Figure 17

Measured and predicted time response of the beam vibrating at its first bending mode with the controller turned on at 1.0s

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Figure 18

Measured and predicted time response of the beam vibrating at its second bending mode with the controller turned on at 0.5s

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Figure 19

Initial displacement response of the beam with passive damping and passive-active damping

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Figure 1

Schematic of conductive material passing through a magnetic field and the generation of eddy currents

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Figure 2

Cantilever beam in magnetic field generated by permanent magnet

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Figure 3

Magnetic field and the eddy currents induced in the cantilever beam

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Figure 4

Schematic demonstrating the effect of the imaginary eddy currents

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