• Proceedings of the Korean Society for Noise and Vibration Engineering Conference
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• 2003.05a
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• pp.985-990
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• 2003

With the rotational speed of the hard disk drive (HDD) increased, the low frequency structural vibration induced by the unbalance force gives rise to the structure home noise of the personal computer, and finally degrades the noise quality. As the unbalance of the hard disk drive is decided by the mechanical assembly allowance between clamping and platter disk, there is limit to control this unbalance by the improved assembly method. To improve the noise and vibration performance of PC, basically the unbalance of HDD needs to be measured absolutely and reduced during the stage of the disk assembly. This study introduces the HDD unbalance measurement methods of the absolute magnitude based on the mobility concept, and the unbalance location information with the acceleration orbit.

• Journal of Institute of Control, Robotics and Systems
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• v.18 no.10
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• pp.947-954
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• 2012

Sand scorpions are nocturnal animals to mostly use tactile senses to detect their prey. It has been reported that sand scorpions have high vibration sensitivity for their prey-localizing behavior. We tested vibration experiments in the sand with microphone sensors to model the sand scorpion's behavior and a time-difference model was applied to find the direction of a vibration source. Using the information of the arrival time of the vibration signal to reach each leg position, we can find the location of the vibration source.

• International Journal of Railway
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• v.6 no.3
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• pp.95-106
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• 2013

Earthborne vibrations are induced by construction operation such as pile driving, roadbed compaction, and blasting and also by transit activities such as truck and trains. The earthborne vibration creates the stress waves traveling outward from the source and can structurally damage nearby buildings and structures in the forms of direct damage to structure and damage due to dynamic settlement. The wave propagation characteristics depends on impact or vibration energy, distance from the source, and soil characteristics. The aim of this paper is to provide a comprehensive review on the mechanistic of earthborne vibration and the current practice of vibration control and mitigation measures. The paper describes the state of knowledge in the areas of: (1) mechanics of earthborne vibration, (2) damage mechanism by earthborne vibration, (3) calculation, prediction of ground vibration, (4) the criteria of vibration limits, (5) vibration mitigation measures and their performance, and (6) the current practice of vibration control and mitigation measures.

• Journal of the Semiconductor & Display Technology
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• v.21 no.4
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• pp.59-64
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• 2022

Vibration is one of the factors that degrades the performance of equipment and measurement equipment used in high-tech industries such as semiconductors and display. The vibration isolator is classified into passive type and active type. The passive vibration isolator has the weakness of insufficient vibration isolation performance in the low frequency band, so an active vibration control system that can overcome these problems is used recently. In this paper, PID controller is used to control the active vibration isolator. Methods for setting the gain of the PID controller include the Zeigler-Nichols method, the pole placement method. These methods have the disadvantage of requiring a lot of time or knowing the system model accurately. This paper proposes the gain auto tuning method of the active vibration isolator applied with the PSO algorithm, which is an optimization algorithm that is easy to implement and has stable convergence performance with low calculations. It is expected that it will be possible to improve vibration isolation performance and reduce the time required for gain tuning by applying the proposed PSO algorithm to the active vibration isolator.

• Proceedings of the Korean Society of Marine Engineers Conference
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• 2006.06a
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• pp.35-36
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• 2006

This study is mainly concerned with vibration control of L-type reciprocating air compressor by a dynamic vibration absorber. The dynamic vibration absorber of reciprocating air compressor was designed for constant revolution running condition. For the review, Vibration test was conducted for the performance appraisal of installed dynamic vibration absorber in the reciprocating air compressor. As a result of the test, the performance of dynamic vibration absorber was satisfactory.

• Proceedings of the Computational Structural Engineering Institute Conference
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• 2004.04a
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• pp.57-64
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• 2004

Stay cables, such as are used in cable-stayed bridges, are prone to vibration due to their low inherent damping characteristics. Several methods have been proposed and implemented to mitigate this problem, though each has its limitations. Recently some studies have shown that semiactive dampers can potentially achieve performance levels nearly the same as comparable active devices with few of the detractions. This paper presents the results of a study to evaluate the performance of semiactive dampers for mitigating the vibration of stay cables. Moreover, a number of recently proposed semiactive control algorithms are formulated for use with shear mode MR damper to compare the efficiency of each algorithm through numerical simulation. Numerical simulation considers a stay cable excited by shaker and controlled by shear mode MR dampers. In simulation, the response with a semiactive damper is found to be dramatically reduced compared to the uncontrolled case. Furthermore, it is verified that the algorithm based on Lyapunov control theory is very efficient in mitigating the cable vibration.

• Proceedings of the Acoustical Society of Korea Conference
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• spring
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• pp.223-226
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• 2000

Currently a multichannel system for virtual 3-D sound rendering is under development. Robust sound image formation and smooth real time interactivity are main design Points. The system utilizes VBAP algorithm as virtual sound image positioning. Overall system settings can be easily configured. We developed software, RIMA. as a driving Program of the system. At this stage, it is possible to position virtual sound images at arbitrary positions in three-dimensional space. The characteristics of the system are discussed. The system has been applied to the KAIST Bicycle Simulator to generate the virtual sound field.

• Journal of the Society of Naval Architects of Korea
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• v.32 no.1
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• pp.94-102
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• 1995

The active control system of structural vibration using a hydraulic actuator is developed. The developed system consists of three parts : a hydraulic unit, an actuator unit and a control unit. Structural vibration is sensored by the accelerometer attached to the structure and reduced by the optimally controlled motion of active mass giving anti-phase inertia force to the structure. It is experimentally confirmed that the vibration level of model structure is reduced to about 1/6 by the developed active control system.

• The KSFM Journal of Fluid Machinery
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• v.15 no.2
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• pp.36-40
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• 2012

Pitch control of wind turbine is activated above rated wind speed for the purpose of rated power regulation. When we design pitch controller, its gain-scheduling is essential due to nonlinear characteristics of aerodynamic torque. In this study, 2-mass model including a vibration mode of drive-train for a 2 MW wind turbine is considered and pitch control with gain-scheduling using a linearization analysis of the nonlinear aerodynamic torque is applied. Some simulation results for the pitch gain-scheduling under step wind speed are presented and investigated. It is shown that gain-scheduling in pitch control is important especially in the region of high wind speeds when there exists a vibration mode of drive-train.

• Structural Monitoring and Maintenance
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• v.5 no.1
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• pp.15-38
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• 2018

Negative stiffness dampers (NSDs) have been proven an efficient solution to vibration control of stay cables. Although previous studies usually assumed a linear negative stiffness behavior of NSDs, many negative stiffness devices produce negative stiffness with nonlinear behavior. This paper systematically evaluates the impact of nonlinearity in negative stiffness on vibration control performance for stay cables. A linearization method based on energy equivalent principle is proposed, and subsequently, the impact of two types of nonlinear stiffness, namely, displacement hardening and softening stiffness, is evaluated. Through the Hilbert transform (HT) of free vibration responses, the effects of nonlinear stiffness of an NSD on the modal frequencies, damping ratios and frequency response functions of a stay cable is also investigated. The HT analysis results validate the accuracy of the linearization method.