• Proceedings of the Korean Society for Noise and Vibration Engineering Conference
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• 2008.04a
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• pp.525-528
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• 2008

The dynamic range of MR damper is the most important characteristics for the usage of semi-active control system. The damping force can be increased by simply decresing the orifice gap in the traditional oil damper, but it deteriorate the dynamic range in MR damper. In this paper, the multi-stage electro-magnetic core is suggested to maintain the performance of MR damper with a large damping force. The MR damper with 3 stage core is designed and manufactured for testing and analysis.

• Journal of the Korean Society for Railway
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• v.8 no.4
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• pp.361-366
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• 2005

The high investment is necessary for the new high speed lines. So the KRRI has been interested in the possibility of upgrading the existing line in order to speed up the train in the conventional lines. The pantograph in train is indispensable in order to supply the electrification equipments with power in safe. The pantograph and the overhead wire form a dynamic coupled system and they affect each other through the contact force. Unfortunately, as the operational speed of a train increases, the vibration of the pantograph and the overhead wire also increases. This may lead to a zero contact force between the pantograph head and the overhead wire, which can results in the loss of contact, arching and abrasion. If the arching and spark happen between the pantograph and the overhead catenary system, the EMI(electro magnetic interface) and noises may occur. After all, the quality of current collection is deteriorated. This paper describes the dynamic response between the pantograph and catenary system by the numerical simulations and presents the LQ-servo controller to reduce the contact force variation

• Structural Engineering and Mechanics
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• v.9 no.2
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• pp.111-126
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• 2000

Truss type structures are attractive to a variety of engineering applications on earth as well as in space due to their high stiffness to mass ratios and ease of construction and fabrication. During the service life, an individual member of a truss structure may lose load carrying capacity due to many reasons, which may lead to collapse of the structure. An analytical and computational procedure has been developed to study the response of truss structures subject to member failure under static and dynamic loadings. Emphasis is given to the dynamic effects of member failure and the propagation of local damage to other parts of the structure. The methodology developed is based on nonlinear finite element analysis technique and considers elasto-plastic material nonlinearity, postbuckling of members, and large deformation geometric nonlinearity. The pseudo force approach is used to represent the member failure. Results obtained for a planar nine-bay indeterminate truss undergoing sequential member failure show that failure of one member can initiate failure of several members in the structure.

• 제어로봇시스템학회:학술대회논문집
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• 2003.10a
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• pp.1146-1151
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• 2003

Pneumatic servo valve is an electro-mechanical device which change electric signals to a proper pneumatic signals, that is, flowrate and pressure. In this study, a pneumatic servo valve was designed and each simulation was conducted on any variation in the flowrate depending upon the magnetic force of the linear force motor and the displacement of the spool. And permanent magnet was used as a material for the plunger of the servo valve. Thereby, a low electrical power consumption type coil was desinged. And a modeling for the coil design was conducted by using the magnetic circuit. also, the feasibility of the modeling was verified by using a commercial magnetic field analysis program. The designed and fabrication of the spool and sleeve, position sensor, servo controller and the dynamic characteristic verified by the experiment.

• Journal of Mechanical Science and Technology
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• v.17 no.12
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• pp.1949-1960
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• 2003

This paper presents vibration and noise control of flexible structures using squeeze mode electro-rheological mounts. After verifying that the damping force of the ER mount can be controlled by the intensity of the electric fild, two different types of ER squeeze mounts have been devised. Firstly, a small size ER mount to support 3 kg is manufactured and applied to the frame structure to control the vibration. An optimal controller which consists of the velocity and the transmitted force feedback signals is designed and implemented to attenuate both the vibration and the transmitted forces. Secondly, a large size of ER mount to support 200 kg is devised and applied to the shell structure to reduce the radiated noise. Dynamic modeling and controller design are undertaken in order to evaluate noise control performance as well as isolation performance of the transmitted force. The radiated noise from the cylindrical shell is calculated by SYSNOISE using forces which are transmitted to the cylindrical shell through two-stage mounting system.

• Journal of the Korean Society for Precision Engineering
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• v.17 no.3
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• pp.39-46
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• 2000

In this paper, the analysis of dynamic characteristics and performance investigation of the ER damper are investigated. The ER damper is based on a double rod actuator and an electric field are applied to the moving electrode composed of cylinder and piston. The performance of the ER damper is length of piston electrode field and its velocities. The experimental and calculated results show that the characteristic of the ER damper varies with the magnitude of the electric field.

• Transactions of the Korean Society for Noise and Vibration Engineering
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• v.15 no.12 s.105
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• pp.1355-1360
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• 2005

Periodic structures can be applied as a MEMS(micro-electro-mechanical system) sensor or actuator due to low energy loss and wideband frequency response. The dynamic behavior of a mistuned periodic structure Is dramatically changed from that of a perfectly tuned periodic structure. The effects of mistuning, coupling stiffness, and driving point on the forced vibration responses of a simple periodic structure ate investigate4 through numerical simulations. On the basis of that, one can design effective and reliable MEMS components using periodic structures.

• Proceedings of the KIEE Conference
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• 2009.04b
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• pp.97-99
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• 2009

In this paper, a new type of electromagnetic actuator, an electro magnetic force driving actuator (EMFA) is developed and analyzed, applicable to air circuit breaker (ACB). Transient analysis is performed in order to obtain the dynamic characteristics of the EMFA. The distribution of static magnetic flux is obtained using the finite element method (FEM). The coupled problems of electrics and mechanics governing equations are solved using the time difference method (TDM). Also according to interception rate of each contactor, investigation about load condition of contactor spring is conducted, applied it to three-link system. And comparison about dynamic characteristics of three-link simulation and experiment data are performed.

• Proceedings of the KSR Conference
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• 2008.06a
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• pp.1903-1908
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• 2008

This paper presents a characteristics of linear induction motor considering airgap variation for railway transit in order to achieve high performance of the vehicle. The operating principle of a LIM(Linear induction motor) is identical to a rotary induction motor. Space-time variant magnetic fields are generated by the primary part across the airgap and induce the electro-motive force(EMF) in the secondary part, a conducting sheet. This EMF generates the eddy currents, which interact with the airgap flux and so produce the thrust force known as Loren's force. Even though the operating principal is exactly same as a rotary motor, the linear motor has a finite length of the primary or secondary parts and it causes static and dynamic end-effect which is the discontinuous airgap flux phenomenon. This end-effect causes the deterioration of the system performance, especially in high-speed operation. Another problem is that construction tolerance restricts the minimum airgap in order to prevent a collision between the primary part and the secondary reaction plate. More over, as the airgap length is getting smaller, the attraction force between the primary part and secondary parts is getting larger dramatically and the attraction force would be another friction against propulsion. Therefore, it is necessary to figure out the characteristics of linear induction motor considering airgap variation in order to achieve high performance of the vehicle. The dynamic model of LIM taking into account end-effects is derived. Then the modified mechanical load equation considering the effect of the attraction and thrust force according to the airgap variation is analyzed. The simulation results are presented to show the effect of the LIM according to the airgap variation.

• The Transactions of the Korean Institute of Electrical Engineers P
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• v.60 no.2
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• pp.82-90
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• 2011

The small precision spindle motors in the high value-added products including the visible home appliances such as DLP projector require not only the energy conversion devices but also high efficiency, low vibration and sound operation. However, the spindle motors using the conventional ball bearing and sintered porous metal bearing have following problems, respectively: the vibration by the irregularity of balls and the short motor life cycle by the ball's abrasion and higher sound noises by dry contact between shaft and sleeve. In this paper, it is proposed that the spindle motor with a fluid dynamic bearing is suitable for the motor to drive the color wheel of the DLP(digital lightening processor) in the visible home appliances. The proposed spindle motor is composed of the fluid dynamic bearing with both the radial force and the thrust force. The fluid dynamic bearing is solved by the finite element analysis of the mechanical field with the Reynolds equations. The magnetic part of spindle motor, which is a type of Brushless DC Motor, is designed by the electro-magnetic field analysis coupled with the Maxwell equation. And the load capacity and the friction loss of fluid dynamic bearing are analyzed to bearing clearance variation by the fabrication error in designed motor. The design of the proposed motor is implemented by the load torque caused by the eccentricity and the unbalance of the fluid dynamic bearing when the motors are fabricated in error. The prototype of the motor with the fluid dynamic bearing is manufactured, and experiment results show the vibration, sound, and phase current at no load and color wheel load of the motors in comparison. The high performance characteristics with the low vibration, the low acoustic noise and the optimal mechanical structure are verified by the experimental results.