• Journal of KSNVE
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• v.10 no.5
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• pp.769-774
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• 2000

The purpose of the work is to present successful applications of a modified wavelet shrinkage method for the accurate and fast estimation of a transfer function. Although the experimental process of determining a transfer function introduces not only Gaussian but also non-Gaussian noises, most existing estimation methods are based only on a Gaussian noise model. To overcome this limitation, we propose to employ a modified wavelet shrinkage method in which L1 -based median filtering and L2 -based wavelet shrinkage are applied repeatedly. The underlying theory behind this approach is briefly explained and the superior performance of this modified wavelet shrinkage technique is demonstrated by a numerical example.

• Journal of Power Electronics
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• v.1 no.2
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• pp.127-132
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• 2001

This paper describes two different systems which can compensate harmonic currents generated in a power system. As non-linear loads increase gradually in industry fields, harmonic current generated in the electric power network system also increases. Harmonic current makes a power network current distorted and generates heat, vibration and noise in the power machinery. Many approaches have been applied to compensate harmonic currents generated in the power system. Among various approaches, in this paper, two kinds are compared and evaluated. They are flywheel compensators bases on secondary excitation of WRIM(wounded rotor induction motor) and SCIM(squirrel cage induction motor). Both systems have a common structure. They use a flywheel as an energy storage device and use PWM inverters. The main differences are the size and rating of the converter used.

• Journal of the Korean Society for Railway
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• v.4 no.1
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• pp.16-22
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• 2001

This paper describes two different systems which can compensate harmonic currents generated in the power system. As non-linear loads increase gradually in industry fields, harmonic current generated in the electric power network system also increases. Harmonic current makes a power network current distorted and generates heat, vibration, noise in the power machinery. Many approaches have been applied to compensate harmonic currents generated in the power network system. Among various approaches, in this paper, two kinds of approaches are compared and evaluated. They are flywheel compensator based on secondary excitation of wounded rotor induction motor(WRIM) and primary excitation of squirrel cage induction motor(SCIM). Both systems have a common structure. They use a flywheel as a energy storage device and use PWM inverters.

• Journal of Institute of Control, Robotics and Systems
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• v.22 no.4
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• pp.247-252
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• 2016

In this paper, we propose a new defect detection technology for micro-defect on the surface of steel products. Due to depth and size of microscopic defect, slop of surface and vibration of strip, the conventional optical method cannot guarantee the detection performance. To solve the above-mentioned problems and increase signal to noise ratio, a novel retro-schlieren method that consists of retro reflector and knife edge is proposed. Moreover dual switching lighting method is also applied to distinguish uneven micro defects and surface noise. In proposed method, defective regions are represented by a black and white pattern. This pattern is detected by a defect detection algorithm with Gabor filter. Experimental results by simulator for sample defects of cold rolled steel show that the proposed method is effective.

• Proceedings of the Earthquake Engineering Society of Korea Conference
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• 1999.04a
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• pp.202-216
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• 1999

To control the motion of building structures under earthquakes their response should be measured first by various sensors and transformed into the control forces using some control algorithms. Of many control algorithms linear quadratic control is widely used as it is easy to implement and analyze. However the algorithms has the disadvantage that it needs the real-time measurements of all state variables(i.e, building's displacements and velocities) which are difficult to achieve for the building structures under earthquakes. Thus the practical algorithms employing output feedback are developed. In this paper LQG algorithm is used for the control of the building model with an active mass driver. The building's acceleration is used to obtain the control gain and the Kalman filter gain. The LQG control strategy is verified with the experimental study on the one-storybuilding model equipped with the active mass driver. This paper demonstrates experimentally the efficacy of the LQG algorithm based on the active mass driver system in reducing the response of seismically excited buildings.

• Proceedings of the KIPE Conference
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• 2002.11a
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• pp.7-11
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• 2002

This paper proposes an APF(Active Power Filter) with WRIM(Wounded Rotor Induction Motor) controlled by sliding mode which can compensate harmonic currents generated in a power system. As non-linear loads increase gradually in industry fields, harmonic current generated In the electric power network system also increases. Harmonic current makes a power network current distorted and generates heat, vibration and noise In the power machinery, Many approaches have been applied to compensate harmonic currents generated in the power system. Among various control strategy, in this paper, a sliding mode controlled systems is designed and evaluated. This is a flywheel compensator based on secondary excitation of WRIM(wounded rotor induction motor) with SMC(sliding mode controller). The proposed system uses a flywheel as an energy storage device. The designed control scheme is verified through simulation.

• Journal of the Korean Society for Nondestructive Testing
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• v.27 no.6
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• pp.483-500
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• 2007

Emerging sensor-based structural health monitoring (SHM) technology can play an important role in inspecting and securing the safety of aging civil infrastructure, a worldwide problem. However, implementation of SHM in civil infrastructure faces a significant challenge due to the lack of suitable sensors and reliable methods for interpreting sensor data. This paper reviews recent efforts and advances made in addressing this challenge, with example sensor hardware and software developed in the author's research center. It is proposed to integrate real-time continuous monitoring using on structure sensors for global structural integrity evaluation with targeted NDE inspection for local damage assessment.

• Journal of KSNVE
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• v.9 no.2
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• pp.265-272
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• 1999

A LMS algorithms has been widely used for an adaptive filter algorithm in active noise control systems. But this algorithm has poor convergence and it is very difficult to select optimal convergence parameters in this algorithm. In this paper, a fuzzy LMS algorithm where the convergence parameters are computed using a fuzzy logic controller was proposed. A proposed algorithm was applied to active noise control system in HVAC(central Heating Ventilation and Air Conditioning) ducts. The experimental ducts and experimental apparatus were designed and manufactured for experiments, and the modelling of the experimental ducts was also performed for computer simulations. Computer simulations and experiments were performed to show the effectiveness of a proposed algorithm.

• Proceedings of the KAIS Fall Conference
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• 2007.11a
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• pp.334-336
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• 2007

본 연구에서는 엘리베이터 카로 전달되는 수직방향의 진동을 억제하기 위하여 MR댐퍼를 장착한 시스템을 제안하고 시스템의 지배방정식을 도출하였다. MR댐퍼에 공급되는 전류에 의하여 엘리베이터 시스템의 응답특성을 관찰하였다. MR댐퍼에 공급되는 전류의 세기가 증가할수록 MR댐퍼의 감쇠력이 증가하여 엘리베이터 시스템의 가속도가 빠르게 줄어드는 것을 확인하였다.

• Journal of Digital Contents Society
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• v.17 no.2
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• pp.71-79
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• 2016

This study is intended to compare the performances of sound source localization methods used for stable automobile control by improving voice recognition rate in automobile environment and suggest how to improve their performances. Generally, sound source location estimation methods employ the TDOA algorithm, and there are two ways for it; one is to use a cross correlation function in the time domain, and the other is GCC-PHAT calculated in the frequency domain. Among these ways, GCC-PHAT is known to have stronger characteristics against echo and noise than the cross correlation function. This study compared the performances of the two methods above in automobile environment full of echo and vibration noise and suggested the use of a median filter additionally. We found that median filter helps both estimation methods have good performances and variance values to be decreased. According to the experimental results, there is almost no difference in the two methods' performances in the experiment using voice; however, using the signal of a song, GCC-PHAT is 10% more excellent than the cross correlation function in terms of the recognition rate. Also, when the median filter was added, the cross correlation function's recognition rate could be improved up to 11%. And in regarding to variance values, both methods showed stable performances.