• Transactions of The Korea Fluid Power Systems Society
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• v.1 no.1
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• pp.17-22
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• 2004

The goal of this paper is to improve the position control performance of pneumatic rotary actuator with variable brake using Magneto-Rheological Fluid. The air compressibility and the lack of damping of the pneumatic actuator bring the dynamic delay of the pressure response and cause the oscillatory motion. In this study, a variable rotary brake comprising Magneto-Rheological Fluid is equipped to the joint of a pneumatic manipulator. Experiments of step response have proved that the transient response of the manipulator could be improved compared with that of the conventional control algorithm by using a phase plane switching control algorithm.

• Proceedings of the KIEE Conference
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• 2005.07d
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• pp.2962-2964
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• 2005

Magneto-Rheological (MR) fluid is suspension of fine magnetic particles in a liquid carrier such as silicon oil or water. MR fluid exhibits solid-like mechanical behavior into chain or clusters with high yield stress when magnetic field is applied to the particles. The response of MR fluids is very quick and reversible after removal of the field. MR Fluids have high yield stress (up to 5kPs) and operate in low voltage power supply. Recently, MR damper using MR fluids was open used in vibration control system such as structural devices, seat vibration controllers and helicopter rotor systems, but it is too big in size and heavy. Therefore, it is not appreciate to rehabilitation devices such as prosthetic limbs.

• Transactions of the Korean Society for Noise and Vibration Engineering
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• v.13 no.7
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• pp.517-523
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• 2003

This paper presents response property of the squeeze mode type mount using Magneto-Rheological fluid (MR fluid) . The MR mount for the isolation of multi-directional vibrations was constructed in this study. Both the mechanism and shape of the mount are the same as squeeze film dampers for a rotor system. In the present work, the performance of the mount was experimentally Investigated according to the magnetic field strength. The experimental results present that the MR mount can effectively reduce the vibration in a wide range of frequency by controlling the applied electromagnetic filed strength. Viscous damping and stiffness coefficients of the MR mount tend to be changed according to the variation of the applied currents In this study.

• Smart Structures and Systems
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• v.2 no.1
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• pp.61-80
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• 2006

The concept of structural vibration control is to absorb vibration energy of the structure by introducing auxiliary devices. Various types of structural vibration control theories and devices have been recently developed and introduced into mechanical systems. One of such devices is damper employing controllable fluids such as ElectroRheological (ER) or MagnetoRheological (MR) fluids. MagnetoRheological (MR) materials are suspensions of fine magnetizable ferromagnetic particles in a non-magnetic medium exhibiting controllable rheological behaviour in the presence of an applied magnetic field. This paper presents the modelling of an MRfluid damper. The damper model is developed based on Newtonian shear flow and Bingham plastic shear flow models. The geometric parameters are varied to get the optimised damper characteristics. The numerical analysis is carried out to estimate the damping coefficient and damping force. The analytical results are compared with the experimental results. The results confirm that MR damper is one of the most promising new semi-active devices for structural vibration control.

• Transactions of the Korean Society for Noise and Vibration Engineering
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• v.14 no.6
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• pp.470-477
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• 2004

This study shows the design process of a MR damper for semi-active suspension systems. Damping force characteristics of the designed damper was predicted through the flow analysis and magnetic analysis. The predicted results were compared with the experimental results and the initial design specification was modified according to the results.

• Transactions of The Korea Fluid Power Systems Society
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• v.3 no.1
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• pp.1-6
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• 2006

A servo actuator with a valve using MR (Magneto-Rheological) fluid is proposed for fluid control systems. The MR fluid is well known as a functional fluid whose apparent viscosity is controlled by the applied magnetic field strength. The pressure in the MR cylinder can be controlled by the applied magnetic field strength. Good points of the MR cylinder are more simple, compact and reliable structure than a conventional oil hydraulic cylinder. The experimental results show that the MR cylinder could be used as a servo actuator.

• Journal of the Korean Society of Manufacturing Process Engineers
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• v.8 no.1
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• pp.57-63
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• 2009

Magneto-Rheological(MR) fluid composes of a base fluid and ferromagnetic particles less than tens of micrometer size dispersed in the fluid. It is called as a smart material because its rheological properties are changable by a magnetic field. Its important applications are active devices such as controllable dampers and controllable clutches. The merit of those products is that their functional characteristics are controllable such that they enable active control strategies. This paper proposes an idea for machine tool applications of the MR fluid clutch as a safety device for power transmission. FEM has been used for magnetic field analyses and the results are compared with some former experiments. Some design syntheses of the MR clutches are suggested and hopefully considered that it may be an effective safety device for power transmission of machine tools.

• Journal of the Korea Academia-Industrial cooperation Society
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• v.1 no.2
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• pp.15-20
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• 2000

In this paper, hydraulic damper was studied to solve vibration problems of bridge, structures and several mechanic parts rising magnetic fluid. The damper was modeled using Magneto Rheological fluid and MR damper was manufactured on the basis of design drawing. To investigate the efficacy of magneto rheological phenomenon. experiments were performed on the several design parameters using Universal Testing Machine(UTM). Damping efficacy were examined by frequencies. displacement and electric currents through experiments.

• Proceedings of the Korean Society for Noise and Vibration Engineering Conference
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• 2001.11b
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• pp.739-744
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• 2001

In order to investigate the stability of magneto-rheological fluid based squeeze film damper (MR-SFD), its negative stiffness effect, which arises from magnetization of MR-SFD, is identified theoretically and experimentally. The analytical model of MR-SFD includes the magnetic circuit as well as the displacement stiffness associated with the squeeze mode of MRF. Extensive experiments are carried out to measure the magnetic attraction forces generated in the MR-SFD, with the excitation frequency and the eccentricity of the journal varied, which are controlled by an active magnetic bearing. The simulation and experimental results are found to be in good agreement. It is concluded that the negative stiffness effect dominates only in the low frequency region because its effect diminishes in the high frequency region due to the eddy-current loss.

• Transactions of the Korean Society of Mechanical Engineers A
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• v.30 no.10 s.253
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• pp.1305-1313
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• 2006

This paper presents an electromagnetic design methodology for the magneto-rheological (MR) fluid actuator. In order to improve the performance of the MR fluid actuator, the magnetic circuit including the MR fluid, the ferromagnetic material for flux path and the electromagnetic coil should be well designed, thereby the magnetic field intensity can be effectively supplied to the MR fluid. First of all, in order to improve the static characteristic, the length of the flux path is decreased by removing the unnecessary bulk of the yoke. Next, in order to improve the dynamic and hysteretic characteristics, the magnetic reluctance of the ferromagnetic material is increased by minimizing the cross section through which the flux passes. The effectiveness of the proposed design methodology is verified by the magnetic analysis and a series of basic experiments.