• Journal of the Korean Society for Precision Engineering
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• v.22 no.9 s.174
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• pp.69-76
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• 2005

The laser interferometer system such as HP5529A is one of the most powerful equipment fur measurement of the straightness error in precision stages. The straightness measurement system, HP5529A is composed of a Wollaston prism and a reflector. In this system, the straightness error is defined as relative lateral motion change between the prism and the reflector and computed from optical path difference of two polarized laser beams between these optics. However, rotating motion of the prism or the reflector used as a moving optic causes unwanted straightness error. In this paper, a compensation method is proposed for removing the unwanted straightness error generated by rotating the moving optic and an experiment is carried out for theoretical verification. The result shows that the unwanted straightness error becomes very large when the reflector is used as the moving optic and the distance between the reflector and the prism is far. Therefore, the prism must be generally used as the moving optic instead of the reflector so as to reduce the measurement error. Nevertheless, the measurement error must be compensated because it's not a negligible error if a rotating angle of the prism is large. In case the reflector must be used as the moving optic, which is unavoidable when the squareness error is measured between two axes, this compensation method can be applied and produces a better result.

• The Journal of Korean Institute of Electromagnetic Engineering and Science
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• v.21 no.1
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• pp.14-19
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• 2010

In this paper, an efficient algorithm is developed to perform target rotational motion compensation to achieve the clear inverse synthetic aperture radar(ISAR) image. The algorithm is based on a time-frequency technique. This algorithm provides an efficient method to resolve the blurring image caused by the time-varying behavior of the target scattering centers and leads to a well-focused ISAR image. Results demonstrate that the time-frequency techniques can improve the blurring ISAR image when an aircraft is in complex motion, such as maneuvering, rotation and acceleration.

• Journal of the Korea Institute of Information and Communication Engineering
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• v.15 no.4
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• pp.886-890
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• 2011

Induction motors are relatively cheap and rugged machines. For the vector control of induction motors, a position or speed sensor is needed. But a speed sensor increases motor cost and reduces reliability in harsh environment. Recently, many studies have been performed for sensorless speed control. This paper investigates an improved flux observer with the parameter error compensation for a sensorless induction motor. The proposed algorithm is verified through simulation and experiment.

• The Journal of Korean Institute of Electromagnetic Engineering and Science
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• v.29 no.4
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• pp.316-319
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• 2018

To detect the ground moving target, forward-looking SAR images obtained from the FMCW radar can be exploited. However, the quality of the SAR image is deteriorated due to the turbulence or fluctuation because of the flight path condition during the missile movement. We herein propose an entropy-minimizing autofocus method to compensate the motion error of forward-looking SAR. In particular, owing to the geometry of the forward-looking SAR, the motion error affects the SAR image in the two-dimensional (2D) form (azimuth and time axis). Therefore, we suggest a 2D autofocus method for the motion compensation.

• The Transactions of the Korean Institute of Power Electronics
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• v.14 no.1
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• pp.82-88
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• 2009

Low costed position sensor or sensorless control method is generally used in the motor control for home appliance because of the material cost and manufacture standard restriction. In conventional sensorless method, the stator resistance and back-EMF coefficient are varied by the motor speed and load torque variation. Therefore, position error occurred when the motor is operated by sensorless control method because of these variations. In this paper, the compensation method is proposed for sensorless position error using 2 hall sensors.

• Journal of Advanced Navigation Technology
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• v.8 no.2
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• pp.163-168
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• 2004

In this paper, we propose a frequency synchronization algorithm using characteristic of CAZAC sequence for HDR-WPAN and analyze the performance by signal constellation and EVM(error vector magnitude). The proposed frequency offset technique estimated each sample phase error of two sequences among 12 CAZAC sequences which have excellent autocorrelated characteristic. Estimated phase error is multiplied to each sample of next sequence for compensating the frequency offset. The remaining frequency offset after compensating it with two sequences has maximum 0.002 offsest ranges at each sample. The computer simulation proved that the permission of EVM value had satisfied in the case of DQPSK at 20[dB].

• Proceedings of the Korean Society of Precision Engineering Conference
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• 2007.11a
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• pp.25-26
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• 2007

• Proceedings of the Optical Society of Korea Conference
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• 2008.02a
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• pp.163-164
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• 2008

• Journal of the Institute of Electronics and Information Engineers
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• v.54 no.8
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• pp.107-114
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• 2017

In this paper, a novel power factor compensation system based on voltage-controlled method is proposed for 3-phase 4-wire power system. The proposed voltage-controlled power factor compensation system generates a reactive power required for compensation by applying a variable output voltage by a slidac to a capacitor. In conventional power factor compensation system using the capacitor bank method, the power factor compensation error occurs depending on the load condition due to the limited capacity of the capacitors. However, the proposed system compensates the power factor up to 100% without error. In this paper, we have developed a voltage-controlled power factor compensation system and a control algorithm for 3-phase 4-wire power system, and verify its performance through simulation and experiments. If the proposed power factor compensation system is applied to an industrial field, a power factor compensation performance can be maximized. As a result, it is possible to reduce of electricity prices, reduce of line loss, increase of load capacity, ensure the transmission margin capacity, and reduce the amount of power generation.

• Proceedings of the IEEK Conference
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• 2003.07c
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• pp.2811-2814
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• 2003

본 논문에서는 Sub-nano 수준의 위치정밀도와 분해능을 갖는 Piezo actuator 의 제어기 설계를 목적으로 하였다. 이산 시간 상태 공간에서의 Piezo actuator를 이용한 1 축 스테이지 드라이브 시스템 SISO 제어기를 설계하였다. Piezo actuator 의 소재 자체의 특성으로는 Hysteresis 가 있으며, 이는 정상상태에서 Piezo actuator 의 위치 오차를 발생하는 주요 원인이 된다. 제어기의 설계는 극점 배치 방법을 기본으로 하여 Hysteresis 에 대한 보상을 목적으로 적분제어방식과 외란 추정기를 각각 적용하였다. 모의실험을 통하여 제어기의 설계 및 시뮬레이션 하였으며, Hysteresis 에 대한 보상이 이루어짐을 보았고, 실험을 통하여 이를 증명하였다.