• Proceedings of the Korean Society for Noise and Vibration Engineering Conference
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• 2004.11a
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• pp.1005-1011
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• 2004

Squeeze film dampers (SFDs) have been commonly used to effectively enhance the dynamic behavior of the rotating shaft supported by rolling element bearings. However, due to the recent trends of high operating speed, high load capacity and light weight in rotating machinery, it is becoming increasingly important to change the dynamic characteristics of rotating machines in operation so that the excessive vibrations, which may occur particularly when passing through critical speeds or unstable regions, can be avoided. Semi-active type SFDs using magneto-rheological fluid (MR fluid), which responds to an applied magnetic field with a change in rheoloaical behavior, are introduced in order to find its applications to rotating machinery as an effective device attenuating unbalance responses. In this paper, a semi-active SFD using MR fluid is designed, tested and identified by means of linear analysis to investigate the capability of changing its dynamic properties such as damping and stiffness. Furthermore, the proposed device is applied to a rotor system to investigate its potential capability for vibration attenuation: an efficient method for selecting the optimal location of the proposed damper is introduced and control algorithm that could improve the unbalance response properties of a flexible rotor is also proposed.

• Transactions of the Korean Society of Automotive Engineers
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• v.9 no.1
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• pp.189-197
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• 2001

This paper presents hysteresis models of damping forces of a magneto-rheological (MR) damper which is applicable to a middle-sized passenger vehicle. After manufacturing a cylindrical type of the MR damper, its field-dependant damping force and hysteresis behavior are experimentally evaluated. Three different models ; Bingham model, Bouc-Wen model and Polynomial model are provided to predict the hysteretic damping force. The damping force characteristics predicted from three different models are compared with the measured results under various excitation conditions.

• Journal of Power System Engineering
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• v.13 no.1
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• pp.26-32
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• 2009

This study is about roll characteristics evaluation to show the advantage of using MR(magneto-rheological) dampers for steering of a SUV(sports utility vehicle). Roll characteristics is very important to observe the roll-propensity of the SUV. ADAMS/Car program was used to simulate the basic steering motion, using 63 D.O.F. vehicle model. Sky-Hook and Ground-Hook control algorithms were used as a semi-active suspension system controller. The roll characteristics from the steering motion were compared between the simulation results from the semi-active suspension system and the passive suspension system.

• Proceedings of the KSME Conference
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• 2004.11a
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• pp.619-624
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• 2004

This paper applies the fuzzy logic controller to a semiactive seat suspension system in order to obtain the better ride comfort in constraint of specific rattle space. The seat suspension system used for this research is a scissors-type one with the MR (Magnetic Rheological) fluid damper. Since a seat suspension system with a driver can not be exactly modeled, it is effective to control with the fuzzy logic controller. The rule was carefully tuned to effectively reduce the vibration transmitted to a driver. The on-road ride was realized on a hydraulic excitor and the result shows that the fuzzy controller has reduced the vibration of a seat suspension system compared to the continuous skyhook controller.

• Proceedings of the Korean Society for Noise and Vibration Engineering Conference
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• 2007.11a
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• pp.369-374
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• 2007

This paper presents yaw vibration control performances of railway vehicle featuring controllable magnetorheological damper. A cylindrical type of MR damper is devised and its damping force is evaluated by considering fluid resistance and MR effect. Design parameters are determined to achieve desired damping force level. The MR damper model is then incorporated with the governing equations of motion of the railway vehicle which includes vehicle body, bogie and wheel-set. Subsequently, computer simulation of vibration control via proportional-integral-derivative (PID) controller is performed using Matlab. Various control performances are demonstrated under external excitation by creep force between wheel and rail.

• Transactions of the Korean Society for Noise and Vibration Engineering
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• v.18 no.5
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• pp.524-532
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• 2008

This paper presents yaw vibration control performances of railway vehicle featuring controllable magnetorheological damper. A cylindrical type of MR damper is devised and its damping force is evaluated by considering fluid resistance and MR effect. Design parameters are determined to achieve desired damping force level. The MR damper model is then incorporated with the governing equations of motion of the railway vehicle which includes vehicle body, bogie and wheel-set. Subsequently, computer simulation of vibration control via proportional-integral-derivative(PID) controller is performed using Matlab. Various control performances are demonstrated under external excitation by creep force between wheel and rail.

• Proceedings of the Korean Society for Noise and Vibration Engineering Conference
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• 2008.04a
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• pp.957-962
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• 2008

This paper presents vibration control performances and stability evaluations of railway vehicle featuring controllable magnetorheological (MR) damper. The MR damper model is developed and then incorporated with the governing equations of motion of the railway vehicle which includes vehicle body, bogie and wheel-set. A cylindrical type of MR damper is devised and its damping force is evaluated by considering fluid viscosity and MR effect. Design parameters are determined to achieve desired damping force level applicable to real railway vehicle. Subsequently, computer simulation of vibration control and stability analysis is performed using Matlab Simulink.

• Transactions of the Korean Society for Noise and Vibration Engineering
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• v.18 no.7
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• pp.732-740
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• 2008

This paper presents vibration control performances and stability evaluations of railway vehicle featuring controllable magnetorheological(MR) damper. The MR damper model is developed and then incorporated with the governing equations of motion of the railway vehicle which includes vehicle body, bogie and wheel-set. A cylindrical type of MR damper is devised and its damping force is evaluated by considering fluid viscosity and MR effect Design parameters are determined to achieve desired damping force level applicable to real railway vehicle. Subsequently, computer simulation of vibration control and stability analysis is performed using Matlab Simulink.

• Transactions of the Korean Society for Noise and Vibration Engineering
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• v.26 no.2
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• pp.165-171
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• 2016

A prosthetic knee for above-knee (AK) amputee is categorized into passive and active type. The passive prosthetic knee is generally made by elastic material. Although AK amputee can easily walk by using passive prosthetic leg, knee joint motions are not similar to ordinary persons. The active prosthetic leg can control the knee angle owing to the actuator and microprocessor. However, the active type is not cost-effective and the stability may be lost due to the malfunction of sensors. In order to resolve these disadvantages of passive and active type, a semi-active prosthetic knee which can control the knee angle is proposed in this work. The proposed semi-active one requires a less input energy but provides active type performance. In order to achieve this goal, in this work, a semi-active prosthetic knee using magneto-rheological (MR) damper for AK amputees is designed. The MR damper can support the weight of body by using less energy than actuator of active prosthetic. It can control knee angle by inducing the magnetic field at the time of stance phase. This salient characteristic is evaluated and presented in this work.

• Proceedings of the Korean Society for Noise and Vibration Engineering Conference
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• 2009.04a
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• pp.581-586
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• 2009

This paper presents an optimal design of magnetorheological(MR) damper based on analytical methodology and finite element analysis. The proposed MR damper consists of MR valve and gas chamber. The MR valve is constrained in a specific volume and the optimization problem identifies geometric dimensions of the valve structure that maximize the pressure drop of the MR valve or damping force of the MR damper. In this work, the single-coil annular MR valve structure is considered. After describing the schematic configuration and operating principle of MR valve and damper, a quasi-static model is derived based on Bingham model of MR fluid. The magnetic circuit of the valve and damper is then analyzed by applying the Kirchoff’s law and magnetic flux conservation rule. Based on the quasi-static modeling and the magnetic circuit analysis, the optimization problem of the MR valve and damper is built. The optimal solution of the optimization problem of the MR valve structure constrained in a specific volume is then obtained and compared with the solution obtained from finite element method.