• Journal of the Korean Society for Precision Engineering
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• v.20 no.5
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• pp.171-179
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• 2003

An Amplitude Proportional Friction Damper (APFD) is considered in order to improve the characteristics of Coulomb friction damper. The frictional force is proportional to the amplitude in APFD system and the system is non-linear as is Coulomb damper system. A free vibration analysis on the 1-DOF system has made to demonstrate the characteristics of the APFD system. The results show that APFD system has similar damping characteristics to the viscous damper. Also, the solution for the response of a base-excited system with APFD is developed through the application of a Fourier series to represent the frictional force of APFD. It is assumed that no stick-slips occur during any portion of the steady-state oscillation.

• Proceedings of the KSME Conference
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• 2001.11a
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• pp.495-500
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• 2001

Because of resonance between natural frequency of the second floor base for IPB(Isolated Phase Bus) duct supports in a power plant and operation frequency of the turbine, there was high amplitude vibration on IPB duct. To reduce vibration of IPB duct, Firstly it was set a FEM model to seek the mode shape for the concrete structure. Secondly, it was carried out dynamic analysis for the FEM model. Lastly, because the natural frequency of the concrete structure could not be changed, it was changed supports position for the IPB duct near to beams. It resulted in reducing vibration of IPB duct.

• Proceedings of the Korean Society for Noise and Vibration Engineering Conference
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• 2000.06a
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• pp.472-478
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• 2000

The vibration of the hard disk drive (HDD) systems, which comprises flexible disks, flexible shafts, bearings, and base structures, are analyzed by a finite element method (FEM) to cope with complicated coupling effects between them. The natural frequencies and mode shapes of the uncoupled, axial and bending coupled vibrations are calculated. Modal testing of the HDD systems is performed to validate the finite element analysis (FEA) results. Good agreement was obtained between the computed and experimental results. Sizing design sensitivity analysis (DSA) of the system was performed with the thickness of base structure and bearing stiffness as design variables. The DSA results tell how can I increase or decrease eigenvalue of the system effectively.

• Transactions of the Korean Society for Noise and Vibration Engineering
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• v.26 no.4
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• pp.365-374
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• 2016

The underwater radiated noise can be reduced by decreasing the structure borne noise of the on-board equipment. Therefore, the structure borne noise of the onborad installed equipment is strongly restricted by ROK navy with MIL-Std 740-2. Usually, the vibration transmissibility from the equipment to the hull of the ship is dependent on its mount characteristics. Even though the double mount structure is proper to apply for ship board application rather than single mount, it is not widely applied due to the weight and volume resriction of the ship. Therefore, in this research, the base using sandwitch panel which can act as double mount structure is suggested and its noise reduction capacity is verified with analytic calculation as well as experiment.

• Journal of the Korean Society for Precision Engineering
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• v.20 no.2
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• pp.209-217
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• 2003

In this paper, the dynamic system modeling and the state sensitivity analysis of the spin-coater system are proposed for the reduction of the vibration. In the respect of modeling, the spin-coater system is considered to be composed of servomotor, spindle, supporting base and so on. Each component of model is combined and derived to 3 dimensional equations. The combined model is verified by experimental values of actual system in the frequency domain. By direct differentiation of the constraint equations with respect to kinematic design variables, such as eccentricity of spindle, moment of inertia, rotational stiffness and damping of supported base, sensitivity equations are derived to the verified state equations. Sensitivity of design variables could be used for vibration reduction and natural frequency shift in the frequency domain. Finally, dominant design variables are selected from the sensitivity analysis.

• Proceedings of the Korean Society for Noise and Vibration Engineering Conference
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• 1997.04a
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• pp.160-166
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• 1997

The spindle motor in a computer hard disk drive can be modeled as a rotor-bearing system supported by the base plate. Ball bearing is the crucial element to determine the stiffness of the spindle motor, and its design parameters and operating conditions determine the dynamic characteristics of the spindle motor. In the analysis of a rotor-bearing system with a short shaft like a spindle motor, the stiffness of the base plate as well as ball bearings must be considered accurately to analyze the dynamic charateristics of a spindle motor. In this paper, the lateral and the axial vibration of the spindle motor were analyzed by the transfer matrix method for the dual-shaft rotor-bearing model and by d.o.f lumped parameter model, respectively. The simulation results had good agreements with the experimental modal testing. The dynamic characteristics were fully investigated for the change of the major design parameters of the spindle motor, i.e. the preload of ball bearings and the rotational speed.

• Proceedings of the Korean Society for Noise and Vibration Engineering Conference
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• 2003.05a
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• pp.142-147
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• 2003

This paper is concerned with the experiment of vibration isolation device whit can cope with heave, pitch and roll type vibrations. This new device consists of S-shaped piezoceramic actuators supporting each corner of the plate. Small piezoceramic sensors are located at the middle of each side. This paper also presents the development and the movement of the system. The active control technique was also developed to cope with base excitation. Experimental results show that vibrations can be reduced by the new device in the case of base excitation of harmonic type.

• Journal of Institute of Control, Robotics and Systems
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• v.9 no.1
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• pp.82-89
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• 2003

A robust motion control method is proposed fur the point-to-point position control of a XY positioning system which consists of a base cart, elastic ben and moving mass. The horizontal motion controller consists of the feedforward controller to suppress the single mode vibration of the elastic beam and the feedback controller to get the high-accuracy positioning performance of the base cart. Input preshaping vibration suppression method based on system modeling with analytic frequency equation is proposed and integrated into the robust internal-loop compensator(RIC) to increase the robustness of the whole closed-loop system The vertical motion controller is proposed based on the dual RIC structure. Through experiments, it is shown that the proposed method can stabilize the system and suppress the vibration in the presence of uncertainties and disturbances.

• Proceedings of the Korean Society for Noise and Vibration Engineering Conference
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• 2000.06a
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• pp.1423-1428
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• 2000

• Structural Engineering and Mechanics
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• v.32 no.6
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• pp.755-770
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• 2009

This study proposes a new smart base isolation system that employs Magneto-Rheological Elastomers (MREs), a class of smart materials whose elastic modulus or stiffness can be varied depending on the magnitude of an applied magnetic field. It also evaluates the dynamic performance of the MRE-based isolation system in reducing vibrations in structures subject to various seismic excitations. As controllable stiffness elements, MREs can increase the dynamic control bandwidth of the isolation system, improving its vibration reduction capability. To study the effectiveness of the MRE-based isolation system, this paper compares its dynamic performance in reducing vibration responses of a base-isolated single-story structure (i.e., 2DOF) with that of a conventional base-isolation system. Moreover, two control algorithms (linear quadratic regulator (LQR)-based control and state-switched control) are considered for regulating the stiffness of MREs. The simulation results show that the MRE-based isolation system outperformed the conventional system in suppressing the maximum base drift, acceleration, and displacement of the structure.