Application of Electromagnet Using Magnetization or Demagnetization for Magnetic Damper

In this paper the authors develop a new type of a hybrid magnetic damper which has a variable damping force generated by hybrid electromagnets. The hybrid electromagnet is composed of a ferrite core combined with a rare-earth magnet. The damper can make the damping coefficient increasing from neutral value with magnetized field, or otherwise decreasing it with demagnetized field. It has also a fail-safe mechanism under an electrically malfunction. In order to determine the magnetic damping coefficients created by eddy current depend on a shape of a magnet and a conductive disk, it is accurately calculated by using an arc shape. For investigating about dynamic properties, resisting force characteristics are measured by using a vibration actuator. In experimental results, the damper has a damping coefficient which is proportional to current squared increasing and decreasing from neutral value. Seismic response simulations of one-degree-of-freedom system with the hybrid damper are calculated using LQR control. The effects of vibration suppression are confirmed numerically.