• Journal of the Korean Institute of Intelligent Systems
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• v.17 no.7
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• pp.875-880
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• 2007

Scientific challenges in the field of MR(magnetorheological) fluids and devices consist in the development of MR devices, the mathematical modeling and simulation of MR devices, and the development of (optimal) control algorithm for MR device systems. To take a maximum advantage of MR fluids in control applications a reliable mathematical model, which predicts their nonlinear characteristics, is needed. A inverse model of the MR device is required to calculate current(or voltage) input of MR damper, which generates required damping force. In this paper, we implemented test a bench for shear mode rotary MR damper and laboratory tests were performed to study the characteristics of the prototype shear-mode rotary MR damper. The direct identification and inverse dynamics modeling for shear mode rotary MR dampers using multi-layer neural networks are studied.

• Proceedings of the Earthquake Engineering Society of Korea Conference
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• 2002.03a
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• pp.417-423
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• 2002

Magnetorheological(MR) 댐퍼는 적은 용량의 전력을 사용하고 반응속도가 빠른 장점 때문에 구조물의 내진제어에 적당하여, 근래에 주목받고 있는 새로운 장치이다. MR 댐퍼는 반능동 제어 장치로써, 능동 질량감쇠기와는 다른 특성을 갖는다. 즉 필요한 제어력을 제어신호로 직접 생성해 낼 수 없는 대신에 MR 댐퍼의 입력전원을 제어하여 간접적으로 제어한다. 따라서 MR 댐퍼의 반능동 제어장치로써의 특성을 고려하는 효과적인 제어기법이 요구된다. 그러므로 본 연구에서는 지진에 대한 구조물의 응답을 줄이기 위해서, MR댐퍼를 제어할 수 있는 반능동 제어기법을 Lyapunov 안정성 이론을 바탕으로 제안하고자 한다. 제안방법을 검증하기 위해, 전단형 MR 댐퍼를 1층과 2층에 설치한 수치예제를 수행하였다.

• Journal of the Korean Institute of Intelligent Systems
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• v.17 no.5
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• pp.701-706
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• 2007

Recently, a number of researches about linear magnetorheological(MR) damper using valve-mode characteristics of MR fluid have sufficiently undertaken, but researches about rotary MR damper using shear-mode characteristics of MR fluid are not enough. In this paper, we performed vibration control of shear-mode MR damper for unlimited rotating actuator of mobile robot. Also fuzzy logic based vibration control for shear-mode MR damper is suggested. The parameters, like scaling factor of input/output and center of the triangular membership functions associated with the different linguistic variables, are tuned by genetic algorithm. Simulation results demonstrate the effectiveness of the fuzzy-skyhook controller for vibration control of shear-mode MR damper under impact force.

• Proceedings of the Korean Society of Precision Engineering Conference
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• 2013.05a
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• pp.739-740
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• 2013

• Proceedings of the KSME Conference
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• 2007.05a
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• pp.626-631
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• 2007

MR(Magneto-rheological) fluid is smart material that can be changed viscosity by controlling the magnetic field. MR damper with MR fluid can control damping force. It can be used extensively many engineering structures for reducing the effect of dynamic external disturbances. There are three kinds of MR dampers, such as valve mode, direct-shear mode and squeeze mode. In this study, design process of direct-shear mode MR damper with the MR fluid gap was developed. The parameters that used in the direct-shear mode MR damper Informed from the experiment of valve mode MR damper of Lord company. Magnetic analysis with finite element method was performed to find the optimal annular gap.

• Journal of the Korea institute for structural maintenance and inspection
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• v.14 no.4
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• pp.55-61
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• 2010

This paper is concerned with an experimental research to random vibration control caused by external loads specially in bridges which tend to be structurally flexible. Experimenting on a reduced structure modelled on Seohae Grand Bridge, we inflicted a reduced form of El-centro wave on the model structure to a proper proportion. On the center of its middle span, we placed a shear type MR damper which was to control its vibration and also acquire its structural responses such as displacement and acceleration at the same site. The experiments concerning controlling vibration were performed according to a variety of theories including un-control, passive on/off control, and Lyapunov stability theory. Its control performance was evaluated in terms of the peak absolute displacements, the peak absolute accelerations and the total power required to control the bridge which differ from each different experiment method. Among all the methods applied in this paper, case of Lyapunov control method turned out to be the most effective to reduces of displacement and acceleration. Also, this method could to decrease consuming of external power for vibration control. Finally, it was noteworthy that Lyapunov control method was specially effective in the vibration control employing a semi-active damper such MR damper.

• Journal of the Korea Academia-Industrial cooperation Society
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• v.15 no.3
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• pp.1247-1252
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• 2014

In the present study, sedimentation and shear stress of MR fluid are investigated to physical characteristics of MR fluid along temperature conditions. MR fluid is a suspension of micrometer-sized magnetic particles in a base liquid. Therefore, dispersion of MR fluid is important in the case of the design and optimization of the system using MR fluid. Due to sedimentation characteristics of MR fluid by magnetic particles, the sedimentation and shear stress of commercial MR fluid are investigated at $25^{\circ}C$ and $80^{\circ}C$ temperatures by using a forced convection oven and a viscometer. From experimental results, the sedimentation and shear stress are more affected by the temperatures of $80^{\circ}C$ than $25^{\circ}C$ and the mixing time of 5min than 10min. Shear stress by the applied current increases the shape of a quadratic equation and are lower 6-18% at $80^{\circ}C$ than $25^{\circ}C$.

• Journal of the Korea institute for structural maintenance and inspection
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• v.16 no.3
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• pp.60-66
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• 2012

This paper aims to constitute a feedback vibration control system using wireless sensor networks and experiment it on a model structure to verify its effectiveness. For the purpose, we set up a feedback vibration control system composed of a wireless input/output(I/O) sensor node based on bluetooth, a home-made shear type MR damper, a shaker which generates a constant size of sine wave, and a simple beam model structure. The vibration control experiment was performed by shaking the 1/4 point of beam with a shaker. At the moment of shaking, we controled the vibration with MR damper which was placed vertically on the center of beam. Simultaneously, by acquiring acceleration response at the 2/4 point of beam, we evaluated the effectiveness of control capability. The control command was set to send a voltage signal to MR damper when the acceleration response, acquired from the wireless I/O sensor node placed at the center of beam, was more than a certain amount. Although the realtime feedback vibration control system constituted in this paper is effective only within a limited command system, it has been proven that the system was able to effectively decrease the vibration of structure by generating a control command aimed for realtime purpose. The system also showed a possibility to be used as a structural response control system adapting a variety of semi-active control algorithm.

• Journal of the Korea institute for structural maintenance and inspection
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• v.15 no.1
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• pp.85-94
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• 2011

This paper is concerned to constitute a semi-active realtime feedback vibration control system and evaluate it through experiments in order to control in realtime the vibration externally generated, specially on the bridges which is structurally flexible. For the experiment of vibration control, we built a model bridge structure of Seohae Grand Bridge in a 1/200 reduced form and inflicted El-centro wave on the model structure also in a reduced force considering the lab condition. The externally excited vibration was to be controled by placing a shear type MR damper vertically on the center of bridge span, and the response (displacement and acceleration) of structure was to be acquired by placing LVDT and Accelerometer at the same time. As for the experiment concerning controlling vibration, a realtime feedback vibration control experiments were performed under each different condition largely such as un-control, passive on/off control, Lyapunov stability theory control, and Clipped-optimal control. Its control performance under different condition was quantitatively evaluated in terms of the peak absolute displacements, the peak absolute accelerations and the power required for control on the center of span. The results of experiments proved that the Lyapunov control and clipped-iptimal control were effective to decrease the displacement and acceleration of the structure, and also to decrease the power consumption to a great extent. Finally, the semi-active realtime feedback vibration control system constituted in this research was proven to be an effective way to control and manage the vibration generated on bridge structure.

• Journal of the Earthquake Engineering Society of Korea
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• v.23 no.2
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• pp.141-147
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• 2019

This research focuses on developing the Smart material with Grease adopted as a base oil to overcome a particle deposition caused by the MR fluid consisting of a silicon, which maximizing the characteristics and advantage of the MR fluid. By adopting the SMG fluid to a shear damper, this paper aimed to evaluate the control performance of it according to the variation of intensity of electric current(0 A, 0.5 A, 1.0 A, 1.5 A, 2.0 A, 2.5 A) and frequency(0.5 Hz, 1 Hz, 2 Hz). Subsequently, the usability of the SMG damper was analyzed by comparing the dynamic model of it to that of the other types of dampers(Power(Involution) Model, Bingham Model). As a result, DR, the performance indicator of semi-active damper, shows approximately 5 in a condition of 2 Hz. Also while confirming the excellent performance like the Power and the Bingham model, it raises the possibility to exploit it as the semi-active damper.