Theoretical and experimental performance analysis of a novel rotating hybrid excitation eddy current damper

The eddy current damper offers several advantages over traditional viscous fluid dampers, including the absence of oil leakage, high temperature stability, and easy control. Until now, the utilization of an electromagnet and permanent magnet as a magnetic field source in the eddy current damper with rotational motion has not been effectively considered. Therefore, this paper proposes a novel rotating hybrid excitation eddy current damper (RHE-ECD) and elucidates its structural design and operational principles. The damping synergy mechanism is achieved through the implementation of a ball screw mechanism, while the hybrid control of the damper is accomplished by strategically arranging two types of magnetic field sources. The permanent magnet serves as a fixed magnetic field source, maintaining the passive damping capability of the damper, while the electromagnet adjusts the magnetic field according to the current, providing an initial level of adjustability. The expression for the damping coefficient of eddy currents in a single magnetic field source was derived based on Faraday's law of electromagnetic induction, and the theoretical analysis examined the influence of various parameters on the damping coefficient. Subsequently, a series of performance tests were conducted on the RHE-ECD prototype to investigate the relationship between the maximum damping force of the damper and loading speed as well as loading current under different operating conditions. Finally, a comparison was made between experimental results and simulation results to validate the accuracy of finite element simulation method. The research demonstrates that the RHE-ECD, designed in this paper, exhibits excellent energy dissipation performance. The hysteresis curve is relatively comprehensive, while the friction force and inertia force are negligible. When the axial velocity of the damper is below 15.71 mm/s, there exists a linear relationship between the eddy current damping force and the cutting magnetic induction line speed of the conductor disk. The prototype's eddy current damping coefficients at 0 A and 10 A currents are determined to be 681kN center dot s/m and 1133kN center dot s/m respectively. Moreover, as the electromagnet loading current increases, the maximum eddy current damping force also increases following a quadratic relationship according to fitting results. The experimental results of the prototype for the eddy current damper are consistent with the simulation results, except for a few minor discrepancies. Except for a few data points, the maximum error falls within 20 %, thereby validating the accuracy of the finite element simulation method.