• Journal of Institute of Control, Robotics and Systems
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• v.15 no.11
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• pp.1076-1079
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• 2009

This article deals with an optical image stabilizer which moves an image sensor in the direction of cancelling the vibration caused by hand shaking to prevent a photographed image from blurring. The ball-guide way method adopted as a transfer device of the image sensor is easy to be manufactured because of its simple structure and is suitable to minimize the friction between mechanisms, but has weakness of a chance of physical defect such as groove and rising. In case that the movement of the transfer device equipped with the image sensor is blunted because a ball is stuck in defects of guide way, the performance of the image stabilizer falls down drastically. We propose a method to prevent the transfer device from blunting by applying artificial vibration. At this time, the artificial vibration should be designed under consideration of dynamic characteristics and specifications of the system to be discriminated from the vibration caused by hand shaking.

• Proceedings of the Korean Society for Noise and Vibration Engineering Conference
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• 2008.04a
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• pp.569-574
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• 2008

Nowadays, the equipment for a semiconductor process is required to raise accuracy and productivity. Therefore, the natural frequency of the equipment has been lowered because it has been precise, rapid, large, and light. In order to improve the efficiency of production, it is necessary for the equipment to increase the operation speed, which causes inevitable vibration problems. In this paper, influence analysis of ball-screw in the equipment and evaluation method for the vibration on the base are presented based on the analyses of dynamic characteristics for the mechanical structure through the modal test.

• Proceedings of the Korean Society for Noise and Vibration Engineering Conference
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• 2004.05a
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• pp.304-307
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• 2004

To reduce the structure-born sound by floor impact source in an apartment building, it is necessary to identify the relationship between floor impact sound and vibration. Various impact sources which were made by a bang machine and an impact ball were used for measurement of impact sound and vibration. The experimental results show that the linear relationship between floor impact sound and vibration was in existence despite of various floor impact sources.

• Transactions of the Korean Society for Noise and Vibration Engineering
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• v.13 no.10
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• pp.805-812
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• 2003

This paper presents a method to investigate the characteristics of a ball bearing and the dynamics of a HDD spindle system due to temperature variation. Finite element model is developed for the rotating and stationary parts of a HDD spindle system separately to determine their thermal deformations by using ANSYS, a finite element program. Then, the relative position of the rotating part with respect to the stationary part is determined by solving the equilibrium equation of the contact force between upper and lower ball bearings. The validity of the proposed method is verified by comparing the theoretical natural frequencies of a HDD spindle system with the experimental ones before and after temperature variation. It shows that the elevated temperature results in the increase of contact angle and the decrease of bearing deformation, contact force and bearing stiffness, which result in the decrease of the natural frequencies of a HDD spindle system.

• Transactions of the Korean Society of Mechanical Engineers A
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• v.29 no.7 s.238
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• pp.955-963
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• 2005

This research investigates dynamic characteristics of a linear motion (LM) guide through a experimental result and theoretical analysis. The stiffness in the LM guide is determined by the preloading due to the minus clearance between the ball bearing and the contact surface and it can be derived by Hertzian contact theory and the nonlinear motion of equation. The vibration analysis is performed using Lagrange equations and its result agrees with the experiment result. Using the sensitivity analysis on design parameters such as the contact angles of ball bearings and the eccentricity of mass center, the variation of the natural frequencies can be predicted.

• Proceedings of the Korean Society for Noise and Vibration Engineering Conference
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• 2003.05a
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• pp.578-584
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• 2003

This paper presents a method to investigate the characteristics of a ball bearing and the dynamics of a HDD spindle system due to temperature variation. Finite element model is developed fer the rotating and stationary parts of a HDD spindle system separately to determine their thermal deformations by using ANSYS, a finite element program. Then, the relative position of the rotating part with respect to the stationary part is determined by solving the equilibrium equation of the contact force between upper and lower ball bearings. The validity of the proposed method is verified by comparing the theoretical natural frequencies of a HDD spindle system with the experimental ones before and after temperature variation. It shows that the elevated temperature results in the increase of contact angle and the decrease of bearing deformation, contact force and bearing stiffness, which result in the decrease of the natural frequencies of a HDD spindle system.

• Proceedings of the Korean Society for Noise and Vibration Engineering Conference
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• 2005.11a
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• pp.808-811
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• 2005

To use the impact ball as a new standard floor impact source, the objective and subjective properties of the impact bali were investigated. The results showed that not only the objective properties of the impact ball such as the Impact force exposure level, mechanical impedance but also the psychological parameters were more similar to those of the human impact than the bang machine. In addition, most of the subjects chose the impact bail sound as the most similar sound to the human impact sound in the auditory experiment.

• Physical Therapy Korea
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• v.17 no.4
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• pp.26-34
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• 2010

The purpose of this study was to compare the trunk and lower extremity muscle activity induced by six different conditions floor, intensity 0, 1, 3, 5 of whole body vibration (WBV), and Swiss ball during bridging exercise. Surface electromyography (EMG) was used to measure trunk and lower extremity muscles activity. Ten elderly women were recruited from Hong-sung Senior Citizen Welfare Center. The collected EMG data were normalized using reference contraction (during floor bridging) and expressed as a percentage of reference voluntary contraction (%RVC). To analyze the differences in EMG data, the repeated one-way analysis of variance was used. A Bonferroni's correction was used for multiple comparisons. The study showed that EMG activity of the rectus abdominis, external oblique, internal oblique, erector spinae and rectus abdominis muscles were not significantly different between six different conditions of during bridging exercise (p>.05). However, there were significantly increased EMG activity of the rectus femoris (p=.034) in the WBV intensity 0, 1, 3, and 5 conditions compared with the floor bridging condition. EMG activity of the medial gastrocnemius were significantly increased in the WBV intensity 0, 1, 3, 5 and Swiss ball conditions compared with the floor bridging condition. Future studies are required the dynamic instability condition such as one leg lifting in bridging.

• Proceedings of the Korean Society for Noise and Vibration Engineering Conference
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• 2014.04a
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• pp.528-529
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• 2014

• Transactions of the Korean Society of Machine Tool Engineers
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• v.14 no.3
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• pp.8-15
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• 2005

A new measuring method for tool deflection has been developed when sculptured surface is processed in ball-end milling. Since the vibration due to cutting forces has low frequencies, an electromagnetic sensor is used for measuring the exact vibration displacement. The amplitude and direction of vibration displacement during the cutting process is presented as orbital plot. In this study, it assumes that the vibration displacement is proportional to the length of cutting chip. Therefore, tool deflection is calculated by summing up the vibration displacement of unit chip length for engaged chip length. In addition, computer programs has been developed to predict the deflection of tools when machining sculptured surface. This developed program predicts the tool deflection per block of NC data, so that it can easily identify the parts which have the possibility of machining errors.