• Journal of the Korean Institute of Illuminating and Electrical Installation Engineers
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• v.13 no.4
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• pp.134-141
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• 1999

Ths paper describes on the stability improvement of output voltage control on the power suwJy for railway. On the transient states such as input voltage sudden change, the inpJt and output voltage beccxre unstable by L-C resonance occurred due to constant output voltage control. In this paper, the new clamping circuit for system stability is proposed, and control method using band attenuated filter and feed-forward terms is introduced. The propoesd damping circuit is composed with sma1l size R-L. Also, the 3 level PWM method is adopted to decrease distortion of output voltage. The output voltage is controlledl with variation under 10% without oscillation at transient states and have total hanmnic distortion under 3%.der 3%.

• Proceedings of the IEEK Conference
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• 2005.11a
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• pp.999-1002
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• 2005

This paper describes an improved Rate-Distortion Optimization Algorithm for JPEG2000. We proposed a new optimal constant setting method and rate allocation method to reduce execution time of the rate control. And we proposed hardware structure of the improved R-D opti. algorithm. Consequently, improved Rate-Distortion Optimization algorithm is faster than conventional rate control scheme in JPEG2000 standard and have nearly same performance.

• Proceedings of the KIEE Conference
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• 2006.11a
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• pp.237-239
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• 2006

The residual flux(${\psi}_r$) in transformer's iron cores cause the distortion of short-circuit current occasionally. And some considerable distortion effect on the validation of test results. To prevent this situation, there needs some suitable control of residual flux through the pretest. This paper deals with the how to control the residual flux in pretest and the comparison between the two test results which were obtained by different test method.

• Journal of Institute of Control, Robotics and Systems
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• v.15 no.10
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• pp.1021-1028
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• 2009

In this paper, a location identification for a cleaning robot using a camera shooting forward a room ceiling which kas three point landmarks is introduced. These three points are made from a laser source which is placed on an auto charger. A fisheye lens covering almost 150 degrees is utilized and the image is transformed to a camera image grabber. The widly shot image has an inevitable distortion even if wide range is coverd. This distortion is flatten using an image warping scheme. Several vision processing techniques such as an intersection extraction erosion, and curve fitting are employed. Next, three point marks are identified and their correspondence is investigated. Through this image processing and image distortion adjustment, a robot location in a wide geometrical coverage is identified.

• Journal of Institute of Control, Robotics and Systems
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• v.19 no.4
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• pp.290-298
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• 2013

Geomagnetic is refracted by building's wall and pillar. Therefore refracted geomagnetic is able to be used as feature point. In a specific space, a mobile device that is equipped with magnetic sensor array measures 3-axis magnetic field for each point. Magnetic field map is acquired by collecting the every sample point in the magnetic field. The measured magnetic field must be calibrated, because each magnetic sensor has a distortion. For this reason, sensor distortion model and sensor calibration method are proposed in this paper. Magnetic field that is measured by mobile device matches magnetic field map. Result of the matching is used for position estimation. This paper implements hardware system for position estimation method using magnetic field map.

• Journal of the Semiconductor & Display Technology
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• v.8 no.4
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• pp.7-13
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• 2009

The slender device(long length and thin width) manufactured by stereolithography process suffers from large curl distortion. This paper adapts two control parameters such as a critical exposure and a penetration depth. The measurement of the test parts dimension are carried out by reverse engineering method with the optical 3-dimensional measurement equipment. We investigate how each parameter contributes to the part accuracy and estimates the optimal set of parameters which minimizes the dimensional error of the test parts. Finally, As being an the RAM slot as being an example of the slender device, the RAM slot is made with the optimal values of control parameter and the results are investigated

• Proceedings of the KIEE Conference
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• 2000.07b
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• pp.1218-1220
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• 2000

A new control technique is proposed to reduce the distortion of UPS output voltage. The Load of UPS is rectifier which has many harmonics on its output current in many cases. The distortion of output voltage by the harmonics is repeated at the same position in one cycle. Therefore we can assume that the next cycle wave form would be similar to the previous one. The repeated error can be estimated and be compensated by the Multi controller at every sampling times.

• Journal of Communications and Networks
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• v.7 no.1
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• pp.65-75
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• 2005

In this paper, we consider a scenario in which the source has been offered QoS guarantees subject to token-bucket regulation. The rate of the source should be controlled such that it conforms to the token-bucket regulation, and also the distortion obtained is the minimum. We have developed an optimal scheduling algorithm for offline (like pre-recorded video) sources with convex distortion function and which can not tolerate any delay. This optimal offline algorithm has been extended for the real-time online source by predicting the number of packets that the source may send in future. The performance of the online scheduler is not substantially degraded as compared to that of the optimal offline scheduler. A sub-optimal offline algorithm has also been developed to reduce the computational complexity and it is shown to perform very well. We later consider the case where the source can tolerate a fixed amount of delay and derive optimal offline algorithm for such traffic source.

• Journal of Electrical Engineering and Technology
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• v.13 no.1
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• pp.362-371
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• 2018

This work proposes FPGA implementation of Carrier Disposition PWM for closed loop seven level diode clamped multilevel inverter in speed control of induction motor. VLSI architecture for carrier Disposition have been introduced through which PWM signals are fed to the neutral point seven level diode clamped multilevel using which the speed of the induction motor is controlled. This proposed VLSI architecture makes the power circuit to work better with reduced stresses across the switches and a very low voltage and current total harmonic distortion (THD). The output voltages, currents, torque & speed characteristics for seven level neutral point diode clamped multilevel inverter for AC drive was studied. It has observed the proposed scheme introduces less distortion and harmonics. The results were validated using real time results.

• 제어로봇시스템학회:학술대회논문집
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• 2003.10a
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• pp.789-792
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• 2003

Pipe inspection has a great importance to ensure safety for the nuclear power plant. In this paper, we designed visual inspection module for the tube internal, which diameter is 15${\sim}$20mm. And we made inspection module which consisted of CCD camera and light. And the relation between image and real world coordinate is established. Image processing is performed to calculate mapping parameter and analyze the size of defect. For the calculation of mapping parameter, experiment is performed using grid type test pattern. Acquired image is processed to extract image coordinate. Edge detection, thresholding, median filtering and morphology filtering is applied to extract grid pattern. Extracted image coordinate is used to calculate image to real world mapping. Lens distortion was considered and corrected to get exact data. Coordinate transformation data is provided for the users to recognize easily. Experiment was performed using grid type test pattern, we extracted lens distortion parameter and real coordinate of defect point. Radial distortion of lens was corrected but tangential distortion was not considered. As continuum to this study, the tangential distortion of lens is considered and improvement of analy zing technique for the tube internal be explored continuously.