Abstract:Inflatable space-based structures have become increasingly popular over the past three decades due to their minimal deployed mass and launch volume. To facilitate packaging of the satellite in the shuttle bay, the optical or antenna surface is in many cases a thin-film membrane. Additionally, because the structure holding the membrane is a lightweight and flexible inflated device, the membrane is subjected to a variety of dynamic loadings. For the satellite to perform optimally, the membrane structure must be … Show more
“…This concept used the magnet's axial flux induced by two oppositely poled magnets and has been studied by previous researchers [1][2][3][4] because of the desirable traits that this method has for magnetic braking. Sodano et al [16][17][18] proposed a new concept using the eddy currents induced in a conductive plate which oscillates through the magnetic poling axis as shown in Fig. 1(b).…”
Eddy currents are induced when a nonmagnetic, conductive material is moving as the result of being subjected to a magnetic field, or if it is placed in a time-varying magnetic field. These currents circulate in the conductive material and are dissipated, causing a repulsive force between the magnet and the conductor. With this concept, eddy current damping can be used as a form of viscous damping. The present study investigates analytically and experimentally the characteristics of eddy current damping when a permanent magnet is placed in a conductive tube. The theoretical model of eddy current damping as the result of a magnet in a copper tube is developed from electromagnetics and is verified from experiments. The experiments include a drop test whereby a magnet is dropped in a copper tube to measure the damping force in a steady-state, and a dynamic test is used to measure the same phenomenon in a dynamic-state. The drop test shows that the present model can accurately predict the force of steady-state damping. From the dynamic test, although predictability is not accurate at high excitation frequencies, the present model can be used to predict damping force at low excitation frequencies.
“…This concept used the magnet's axial flux induced by two oppositely poled magnets and has been studied by previous researchers [1][2][3][4] because of the desirable traits that this method has for magnetic braking. Sodano et al [16][17][18] proposed a new concept using the eddy currents induced in a conductive plate which oscillates through the magnetic poling axis as shown in Fig. 1(b).…”
Eddy currents are induced when a nonmagnetic, conductive material is moving as the result of being subjected to a magnetic field, or if it is placed in a time-varying magnetic field. These currents circulate in the conductive material and are dissipated, causing a repulsive force between the magnet and the conductor. With this concept, eddy current damping can be used as a form of viscous damping. The present study investigates analytically and experimentally the characteristics of eddy current damping when a permanent magnet is placed in a conductive tube. The theoretical model of eddy current damping as the result of a magnet in a copper tube is developed from electromagnetics and is verified from experiments. The experiments include a drop test whereby a magnet is dropped in a copper tube to measure the damping force in a steady-state, and a dynamic test is used to measure the same phenomenon in a dynamic-state. The drop test shows that the present model can accurately predict the force of steady-state damping. From the dynamic test, although predictability is not accurate at high excitation frequencies, the present model can be used to predict damping force at low excitation frequencies.
“…While this configuration is effective for magnetic damping, it is not functional for use as an actuator for providing dynamic energy to a structure. However, Sodano et al [11,12] recently developed an eddy current damping scheme that functioned such that forces were generated in the poling axis of the magnet rather than perpendicular to it as previous studies had done. The study modeled and experimentally demonstrated the placement of a permanent magnet in close proximity to a conductive structure vibrating along the poling axis of the magnet could induce damping levels as high as 35% of critical.…”
mentioning
confidence: 95%
“…Therefore the damping system developed by Sodano et al [11][12][13] can be modified to allow the permanent magnet to move relative to the structure such that forces are generated due to the motion of the magnet relative to the beam. The proposed eddy current excitation system will convert a traditional linear actuator into a non-contact actuator.…”
When a conductive material is subjected to a time changing magnetic field, eddy currents are induced in that structure. The eddy currents circulate inside the conductor resulting in a magnetic field that interacts with the applied field. The eddy current field is such that it opposes the change in flux resulting in a force between the source and conductor. The time changing magnetic field necessary to induce an electrometric force in the materials can be generated through a variety of different ways. In the present study, a permanent magnet will be mounted to the tip of an electromagnetic shaker such that the motion of the magnet relative to the structure will cause a time changing field and the formation of eddy currents. The actuator will be demonstrated to be beneficial due to its ability to apply actuation forces without contacting the structure. This study will show that the non-contact nature of the system eliminates mass loading and added stiffness which are downfalls of traditional excitation techniques. Additionally, it will be shown that the use of a non-contact device preserves the mode shapes of the structure, whereas a stinger results in distortions due to the added constraint. Using this concept, a model of the actuation system will be developed, allowing the beams response to be simulated. The actuation system will then be used to excite a cantilever beam to obtain the modal parameters without contacting the structure. The novel noncontact actuation system developed in this paper provides a new method performing vibration testing of on lightweight or flexible structures while preserving their dynamics.
“…The concept of the ECD used in the present study is presented in Figure 4 and is proposed by Sodano et al [14][15][16] and Bae et al [10]. The damping force ( ) in the (vertical) direction due to the eddy current in Figure 4 yields…”
Section: Modeling Of Eddy Current Dampingmentioning
confidence: 99%
“…Using this model, they have investigated the ECD damping characteristics and performed the simulation of the vibration suppression of a cantilever beam with Kwak's ECD. Sodano et al [14][15][16] proposed the new concept of ECD device to attenuate the vibration of a cantilevered beam. Cheng and Oh [17,18] studied multimode vibration suppression using a permanent magnet and a coil with a shunt circuit for semiactive control.…”
For a few decades, various methods of suppressing structural vibration have been proposed. The present study proposes and exploits an effective method of suppressing the vibration of cantilever plates similar to the solar panels of a satellite. Magnetically tuned mass dampers (mTMDs) are a tuned mass damper (TMD) with eddy current damping (ECD). We introduce the mTMD concept for the multimode vibration suppression of the cantilever plate. The design parameters of the mTMD are determined based on the parametric study of the theoretical four-degree-of-freedom model, which was derived for a cantilever plate with TMDs. Two TMDs are optimized for the first bending mode and first torsion mode of the plate, and they are verified analytically and experimentally. To increase the damping performance of the TMDs, ECD is introduced. Its damping ratios are estimated analytically and verified experimentally.
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