• Proceedings of the Korean Society for Noise and Vibration Engineering Conference
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• 2001.11a
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• pp.46-51
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• 2001

To reach high areal density, less track pitch is expected and more servo bandwidth is required. One approach to overcoming the problem is by using dual stage servo system. In this system, a voice coil motor (VCM) is used as the primary stage while a milliactuator is used as the secondary stage. We have suggested new milliactuator based on the shear mode of piezoelectric elements to drive the head suspension assembly. In this paper, we introduce controller design method, PQ method. PQ method reduces the controller design problem for DISO(dual-input/single-output) systems to two standard controller design problems for SISO(single-input/single-output) problems. The first part of PQ method directly address the issue of actuator output contribution, and the second part allows the use of traditional loop shaping to achieve the overall system performance. This paper shows how to employ the PQ method to meet aggressive close-loop performance specifications for a disk drive system with a VCM and piezoelectric milliactuator.

• Transactions of the Korean Society for Noise and Vibration Engineering
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• v.17 no.10
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• pp.958-966
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• 2007

This study presents full vehicle dynamics model for the dynamic characteristic analysis of chassis parts which are suspension and brake system. This vehicle dynamics model is appled to kinematics and quasi-static analysis for each chassis part. In order to develop the vehicle dynamics model, the parameters of each chassis element part which are bush, spring and damper are measured by experiment. Also the wheel forces and moments of 6 DOF are measured at each wheel center. These data are applied to input parameter for vehicle dynamics model. And the verification of the developed model is achieved to comparison with the experimental force data of spring, trailing arm and assist arm by using the load response by strain gauge. These experimental force data are acquired by road test at event surfaces of P/G which are belgian and chuck holes roads.

• Proceedings of the Korean Society for Noise and Vibration Engineering Conference
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• 2003.05a
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• pp.1128-1133
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• 2003

A gas driven heat pump (GHP) core design comprises internal combustion engine, compressors incorporated to a cooling/heating system, rubber mountings and belt transmissions. Main excitation farces are generated by an engine, compressors themselves and belt fluctuation. It leads to high vibration level of the mount that can cause damage of GHP elements. Therefore an appropriate design of the mounting system is crucial in terms of reliability and vibration reduction. In this paper oscillation of the engine mount is explored both experimentally and analytically. Experimental analysis of natural frequencies and operational frequency response of the GHP engine mounting system enables to create simplified model for numerical and analytical investigations. It is worked out criteria f3r vibration abatement of the isolated structure. Influence of bracket stiffness between engine and compressors, suspension locations and damper performance is investigated. Ways to reduce excitation forces and improve dynamic performance of the engine-compressor mounting system are considered from these analyses. Implementation of the proposed approach permits to choose appropriate rubber mountings and their location as well as joining elements design A phase matching technique can be employed to control forces from main exciters. It enables to changing vibration response of the structure by control of natural modes contribution. Proposed changes lead to significant vibration reduction and can be easily utilized in engineering practice.

• Transactions of the Korean Society for Noise and Vibration Engineering
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• v.15 no.11 s.104
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• pp.1248-1254
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• 2005

L/UL(Load/unload) mechanism has been widely used in SFF(Small form factor) HDD because L/UL technology has many advantages such as an increase of areal density, reduction of power consumption and improvement of shock resistance. In this system, the most important design goal is no slider-disk contact and fast air-hearing breaking during L/UL process. To do so, we should consider many design parameters related to L/UL system. The ramp shape is the most dominant component among parameters which dramatically affect the L/UL performance. This paper makes an advanced ramp model using ANSYS/LS-DYNA. Through this FE model, this paper investigates the effect of initial ramp slope and location of air-bearing breaking. From the experiment for three different ramps, we also verify that experimental results agree with simulation results. We conclude that the ramp design should have small ramp slope at the moment which a suspension tap contacts with ramp and large ramp slope after air-bearing breaking in order to improve L/UL Performance.

• Proceedings of the Korean Society for Noise and Vibration Engineering Conference
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• 2005.11a
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• pp.330-336
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• 2005

This paper presents a method to analyze the vibration of a flexible spinning disk-spindle system with FDBs, flexible base structure and an actuator in a HDD by using the FEM. Finite element equations of each component of a HDD spindle system from the spinning flexible disk to the flexible base plate are consistently derived by satisfying the geometric compatibility in the internal boundary between each component. A global matrix equation obtained by assembling the finite element equations of each substructure is transformed to a state-space matrix-vector equation, and both damped natural frequencies and modal damping ratios are calculated by using the restarted Arnoldi iteration method. The validity of the proposed method is verified by comparing the simulated natural frequencies, mode shapes with the experimental results.

• Transactions of the Korean Society for Noise and Vibration Engineering
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• v.16 no.6 s.111
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• pp.619-626
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• 2006

Body-on-frame type vehicle has a set of frame bushes between body and frame for vibration isolation. Such frame bushes are important vibration transmission paths to passenger space for excitations during driving. In order to reduce the vibration level of passenger space, therefore, change of complex stiffness of the frame bushes is more efficient than modification of other parts of the vehicle such as body, frame and suspension. The purpose of this study is to reduce the vibration level for ride comfort by optimization of complex stiffness of frame bushes. In order to do this, a simple finite element vehicle model was constructed and complex stiffness of the frame bushes was set to be design variables. The objective function was defined to reflect frequency dependence of passenger ride comfort. Genetic algorithm and sub-structure synthesis were applied for minimization of the objective function. After optimization level at a position of interest on the car body was reduced by about 43.7 % in RMS value. Causes for optimization results are discussed.

• Proceedings of the Korean Society for Noise and Vibration Engineering Conference
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• 2004.11a
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• pp.121-124
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• 2004

In this paper, we address an active vibration control system, which suppresses the vibration engaged by magnetically levitated stage. The stage system consists of a levitating platen with four permanent magnetic linear synchronous motors in parallel. Each motor generates vertical force fer suspension against gravity and propulsion force horizontally as well. This stage can generate six degrees of freedom motion via the vertical and horizontal forces. In the stage system, which represents the settling-time critical system. the motion of the platen vibrates mechanically. We designed an active vibration control system for suppressing vibration due to the stage moving. The command feedforward with inertial feedback algorithm is used fer solving stage system's critical problems. The components of the active vibration control system are accelerometers for detecting stage table's vibrations, a digital controller with high precise signal converters, and electromagnetic actuators.

• Proceedings of the KSR Conference
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• 2011.10a
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• pp.1894-1904
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• 2011

The Light Rail Transit (LRT) System which has medium transport capacity between subway and bus(5,000-25,000 persons per hour) is the most advanced transportation system. It has many benefits, cheap construction, operational costs through driverless and flexible route planning. Also, the rubber tired AGT (K-AGT) of various LRT has a rubber wheels and side guide. The side guide type has an many advantages. but occur a vibration and friction noise through contact between guide rail and wheel. Most of point that decreased comport is vibration thorough the guide contact. In this paper, It is purpose to improve the maximum running speed of rubber tired AGT localization bogie which is currently developed from 70km/h to 80km/h. To satisfy comport index of railway vehicle that is required in performance test. we examined coefficient of bogie suspension which is designed.

• Transactions of the Korean Society of Mechanical Engineers A
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• v.31 no.7 s.262
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• pp.725-731
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• 2007

An air spring which is a part of the suspension system of automobiles is used to reduce and absorb the vibration and the noise. Main components of the air spring are a cord reinforced rubber bellows, a canister and a piston. The performance of the air spring are depended on configurations of rubber bellows, the angle and elastic modulus of cord. The finite element analysis are executed to predict and evaluate the load capacity and the stiffness. The design variables of air spring are determined to adjust the required specifications of the air spring. Several samples of the air spring are manufactured and experimented. It is shown that the results by finite element analysis are in close agreement with the test results.

• Transactions of the Korean Society of Automotive Engineers
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• v.15 no.6
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• pp.44-49
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• 2007

It is well known that the acoustic cavity inside the tire-wheel assembly contributes to vehicle interior noise. In this paper, we have performed acoustic and structural modal testings to investigate the influences of the acoustic cavity resonance on structural vibration characteristics for the tire in free-suspension and for the loaded tire. The testings have given us some findings, which are reported in this paper.