Experimental validation of an active eddy current vibration control scheme

Abstract

When a conductive material is subjected to a time changing magnetic field, eddy currents are formed in the conductor. These currents circulate inside the conductor such that a magnetic field is formed. This eddy current field then interacts with the applied field resulting in a dynamic force between the conductor and the magnetic source. The force can be considered dynamic because as the eddy currents circulate inside the conductor they are dissipated by the internal resistance of the conductor. Therefore, if a continuously changing field is not applied to the conductor the force will disappear. However, the eddy current forces can be utilized to form an actuator by applying a time changing current to an electromagnet that is in close proximity to a conductive material. This actuation method is easy to incorporate into the system and allows significant forces to be applied without every coming into contact with the structure. Therefore vibration control can be applied without inducing mass loading or added stiffness, which are downfalls of other methods. This manuscript will develop the concept and show that it can be accurately modeled and effectively used to control the vibration of a structure. This vibration control system will use a velocity feedback filter to actively modify the current applied to the coil. Using this system, experiments are performed on a cantilever beam showing the system can effectively suppress the each of the first five modes of vibration by upwards of 20dB.