Papers by Author: Soo Hun Lee

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Authors: Bong Suk Kim, Soo Hun Lee, Jun Ni, Jun Yeob Song
Abstract: The goal of system monitoring and diagnostics is to minimize economic losses, to increase stability, to maximize productivity, and to maintain product quality in manufacturing. The feature extraction from the signals acquired in rotating machine is required for performance evaluation, condition monitoring, and fault diagnostics. In this paper, we extracted the distinctive features from vibration signals gathered in rotor-bearing system during acceleration in order to monitor an abnormal condition by using various kinds of signal processing methods such as the Fast Fourier Transform, Short-Time Fourier Transform, Wigner-Ville Distribution, and Discrete Wavelet Transform.
Authors: Ki Hyun Kim, Dae Gab Gweon, Hyun Soo Jung, Soo Hun Lee, Min Sung Hong, Moon G. Lee
Abstract: Design of design of X-Y-Theta fine stage using VCM (voice coil motor) is presented in this paper. This fine stage is combined with linear DC motor. Long range, high speed and high precision of the stage is obtained by using dual servo control for laser micro/nano machining. A novel structure of VCM for the fine stage is proposed. The fine stage can have 3 DOF(X-Y-Theta) motion by four VCM actuators which are located on the same plane. The X-Y-Theta fine stage is designed to have high acceleration for high throughput. Based on the design, the stage is fabricated. The designed stage has the acceleration of 5m/s2 with 45kg total mass. In addition, this actuator is feedback controlled using HP laser interferometer. The reaction force between the coarse and fine stage of the dual servo is compensated by force compensator.
Authors: Jong Min Kin, Min Sung Hong, Bong Suk Kim, Soo Hun Lee
Abstract: In conventional machining, cutting conditions such as cutting speed, feed rate, and depth of the cut have great influence on the surface roughness. In micro machining, however, the surface shape is affected by not only the machining parameters mentioned earlier but also tool stiffness, system stability, and workpiece properties caused by the miniatured structure and cutting tool. Especially, in a micro-machine system, the difference between the cutting forces in the recursive cuts introduces the vibration easily. A high spindle causes instability of the system, increases the temperature in the cutting process, and also changes the tool’s shape. This study introduces a method to predict the surface shape of the workpiece based on the machining conditions in micro milling. The micro-milled surfaces in different machining conditions are predicted by a computer simulation including the vibration model and the simulated results show good agreement with the experimental results.
Authors: Bong Suk Kim, Soo Hun Lee, Jong Soo Kim, Jun Yeob Song
Abstract: The importance of evaluation and establishment during product development process, for the reliability and safety of mechanical system and parts, is getting increased in the field of mechanical and electronic industry. The object of this paper is to suggest the reliability assessment method for machine tools using failure mode analysis and to introduce two web-based analysis programs which save all data related to failure rate, failure mode, and failure component. In order to evaluate the reliability of machine tools, this paper takes three steps: the use of previous database, the failure rate estimation using failure history data, and the failure mode analysis using performance test.
Authors: Min Gi Kim, Won Woo Hwang, Soo Hun Lee
Abstract: As the home appliances are systemized, they have complicatedly assembled structure. It is reasonable to see the noise problem of home appliance in the viewpoint of system like vehicle and ship. There are various system analysis methods to resolve the noise problem [1-3]. To use system analysis methods, the system information like modal and path properties must be gathered and analyzed. But it takes many times to find out the system properties, so the simpler system analysis methods are needed. The coherence analysis method is useful as the system analysis method, since the method can identify the system property like the relationship between inputs and outputs directly and simply. In the paper, the partial coherence analysis is used for identification of the MISO system of washing machine, in which multi-input signals are vibration signals of motor bracket and an output signal is noise signal of washing machine. The relationship between the noise of washing machine and the vibration of the motor bracket in working status was identified and the parts of bracket closely correlated with noise were also proved by the relationship. And the noise of washing machine was controlled by redesigning the parts of bracket associated with the noise of washing machine based on the coherence function in octave band.
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