• Proceedings of the Korean Society for Noise and Vibration Engineering Conference
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• 2007.05a
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• pp.947-951
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• 2007

This paper is concerned with a new concept for the damper without neither a coil spring nor fluid. The new damper concept consists of the permanent magnets and the cylinder of the conducting material. The opposite pole magnets produces the repulsive forces and this is substituted for the coil spring. The relative motion between the magnets and conducting cylinder produces eddy currents thus resulting in the electromagnetic force, which turns out to be the damping force thus and is substituted for a damping fluid. This damper is called the eddy current damper(ECD). The important advantage of the proposed ECD is that it does not require the damping fluid and any external power and is non-contacting and relatively insensitive to temperature. In the present study, the proposed ECD was constructed and experiments were performed to investigate its dynamic characteristics. The experiments shows that the proposed ECD has the excellent damping ability.

• Smart Structures and Systems
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• v.22 no.6
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• pp.727-741
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• 2018

To mitigate vibrations, tuned mass dampers(TMD) are widely used for long span bridges or high-rise buildings. Due to some durability concerns, such as fluid degradation, oil leakage, etc., the alternative solutions, such as the non-contacted eddy current damping (ECD), are proposed for mechanical devices in small scales. In the present study, a new eddy current damping TMD (ECD-TMD) is proposed and developed for large scale civil infrastructure applications. Starting from parametric study on finite element analysis of the ECD-TMD, the new design is enhanced via using the permanent magnets to eliminate the power need and a combination of a copper plate and a steel plate to improve the energy dissipation efficiency. Additional special design includes installation of two permanent magnets at the same side above the copper plate to easily adjust the gap as well as the damping. In a case study, the proposed ECD-TMD is demonstrated in the application of a steel arch bridge to mitigate the wind-induced vibrations of the flexible hangers. After a brief introduction of the configuration and the installation process for the damper, the mitigation effects are measured for the ambient vibration and forced vibration scenarios. The results show that the damping ratios increase to 3% for the weak axis after the installation of the ECD-TMDs and the maximum vibration amplitudes can be reduced by 60%.

• Journal of the Korean Society for Aeronautical & Space Sciences
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• v.35 no.12
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• pp.1089-1094
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• 2007

This paper is concerned with a new concept for the damper without neither a coil spring nor fluid. The new damper concept consists of the permanent magnets and the cylinder of the conducting material. The opposite pole magnets produces the repulsive forces and this is substituted for the coil spring. The relative motion between the magnets and conducting cylinder produces eddy currents thus resulting in the electromagnetic force, which turns out to be the damping force and is substituted for a damping fluid. This damper is called the eddy current damper(ECD). The important advantage of the proposed ECD is that it does not require any damping fluid and any external power and is non-contacting and relatively insensitive to temperature. In the present study, the proposed ECD was constructed and the experiments were performed to investigate its dynamic characteristics. The experiments shows that the proposed ECD has the excellent damping ability.

• Transactions of the Korean Society for Noise and Vibration Engineering
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• v.21 no.12
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• pp.1091-1097
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• 2011

In the present study, TMD(tuned mass damper) with eddy current damping is proposed to suppress the vibration of a cantilever beam effectively. The advantages of TMD are that it is simple and its performance are excellent at any particular frequency. However, TMD may have the low performance at other frequency. To solve this problem and improve its performance, this study applies the eddy current damping to TMD. This TMD with ECD is named as MTMD(magnetically tuned mass damper). MTMD is designed for the vibration suppression of a cantilever beam. The mathematical modeling, simulation, and experiments of the cantilever beam with MTMD are performed. From analytic and experimental results, it can be concluded that the vibration suppression performance of MTMD are excellent.

• Structural Engineering and Mechanics
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• v.86 no.4
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• pp.573-587
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• 2023

A conventional tuned mass damper (TMD) provides a passive control option to suppress the structures' wind- or earthquake-induced vibrations. However, excessive displacements of the TMD raise concerns in the practical implementation. Therefore, this study proposes a novel TMD designed for and deployed on a high-rise sightseeing tower. The device consists of an integrated two-way slide rail mount and an eddy current damper (ECD) with a stroke control mechanism. This stroke control mechanism allows the damping coefficient to automatically increase when the stroke reaches a predetermined value, preventing excessive damper displacements during large earthquakes. The corresponding two-stage damping parameters are designed with a variable-thickness copper plate to enable the TMD stroke within a specified range. Thus, this study discusses the detailed design schemes of the device components in TMD. The designed two-stage damping parameters are also numerically verified, and the structural responses with/without the TMD are compared. As seen in the results, the proposed TMD yields effective control authority to limit the acceleration response within a comfort level. In addition, this TMD resolves the spatial availability for the damper movement in high-rise buildings by the controllable damping mechanism.

• Smart Structures and Systems
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• v.24 no.1
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• pp.15-26
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• 2019

Over the past decades, a great variety of dampers have been developed and applied to mechanical, aerospace, and civil structures to control structural vibrations. This study is focused on two emerging damper types, namely, eddy current dampers (ECDs) and electromagnetic damper (EMDs), both of which are regarded as promising alternatives to commonly-applied viscous fluid dampers (VFDs) because of their similar mechanical behavior. This study aims to enhance the damping densities of ECDs and EMDs, which are typically lower than those of VFDs, by proposing new designs with multiple improvement measures. The design configurations, mechanisms, and experimental results of the new ECDs and EMDs are presented in this paper. The further comparison based on the experimental results revealed that the damping densities of the proposed ECD and EMD designs are comparable to those of market-available VFDs. Considering ECDs and EMDs are solid-state dampers without fluid leakage problems, the results obtained in this study demonstrate a great prospect of replacing conventional VFDs with the improved ECDs and EMDs in future large-scale applications.

• Journal of the Korean Society for Aeronautical & Space Sciences
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• v.48 no.5
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• pp.355-361
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• 2020

Among these satellites, low - orbit small satellites with military characteristics require multi - target observation, and demand for high-resolution photographs and images is increasing. Fast maneuverability is the most important factor for high-resolution images and multi - target observations. However, in the case of a small satellites, it is possible to perform the attitude maneuver if it has high speed, but the residual vibration occurs when the attitude maneuver is completed and the next attitude maneuver is completed. In this study, to verify the vibration characteristics of the plate generated after attitude maneuver, an experimental fixture for simulating the attitude maneuver was fabricated and tested. In addition, Eddy Current Damper (ECD) using Eddy Current Brake system (ECB) is proposed as a passive damping method using permanent magnet to reduce vibration. A mathematical model was established to apply ECD and it was experimentally implemented according to the magnetic flux density and the air gap of the permanent magnet. One plate of four solar panels (plate) was specified, the residual vibration reduction performance after the test was verified experimentally.

• Transactions of the Korean Society for Noise and Vibration Engineering
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• v.24 no.9
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• pp.706-715
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• 2014

Recently, the medical community has been enthusiastically welcoming robots that are able to provide high-quality medical services across the board, including assisting the surgeons during surgeries. In response, many higher education institutions and research facilities started to conduct various experiments and studies about these robots. During such research, it was discovered that the arm of one particular robot type that is being developed to assist surgeries are prone to vibrate even from the weakest impact, in addition to other residual vibration problems. We attempted to reduce such dynamic response by using a MF-TMD that is produced by adding magnetic fluid to ECD. We verified the MF-TMD's performance by testing it within various frequency bands and attenuations. We then designed a cantilever that was structurally similar to the robot's arm. We attached the MF-TMD to this cantilever and conducted a pilot experiment, which validated our hypothesis that MF-TMD will reduce the robot arm's vibrations through its optimal damping ratio. Henceforth, we attached the MF-TMD to the robot arm in question and conducted a performance experiment in which we tuned the MF-TMD's frequency and damping factor to its optimal level and measured the vibrations of the arm. The experiment demonstrated that the vibrations that occurred whenever the arms rotated were significantly reduced.