Design and experimental investigation of a semi-active eddy-current vibration damper for precision instrument transportation

Abstract

Broadband, non-stationary vibration during road transportation poses a significant risk to the structural integrity and operational accuracy of precision instruments, while fixed damping cannot simultaneously provide effective resonance suppression and high-frequency vibration isolation. To address this limitation, a semi-active plate-type eddy-current vibration isolation platform with adjustable damping was developed. The platform employs a hybrid magnetic-field configuration in which permanent magnets provide baseline damping and electromagnets provide the controllable damping component. Key structural parameters were investigated using electromagnetic finite-element analysis, and a dynamic model incorporating a multi-magnet coupling correction was established. On this basis, a frequency-band-based semi-active damping strategy with response-dependent gain adjustment was implemented. The resulting damper provided an adjustable equivalent damping coefficient of 229.55–332.15 N (m s−1)−1, corresponding to a damping ratio of 0.28–0.41. For the tested eddy-current-damped conditions, the discrepancy between the simulated and experimental transmissibility remained within 2.0%, and the dominant resonance of the prototype occurred at approximately 6.2 Hz. Under 2–200 Hz broadband random excitation, the semi-active system achieved an acceleration GRMS of 2.2071 g, which was 50.7% lower than the excitation GRMS and 34.82% and 18.25% lower than those obtained without additional eddy-current damping and with fixed maximum damping, respectively. These results show that frequency-dependent eddy-current damping regulation can alleviate the trade-off between resonance suppression and vibration isolation, providing a viable prototype-level approach for broadband vibration protection of precision instruments during transportation.