Development of a new passive-active magnetic damper for vibration suppression

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\u27s 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\u27s motion and the radial magnetic flux was used to passively suppress the beam\u27s 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 ASME