• Journal of Positioning, Navigation, and Timing
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• v.3 no.4
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• pp.155-161
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• 2014

The purpose of this study is to develop precise point positioning (PPP) algorithms based on GLONASS code-pseudorange, verify their performance and present their utility. As the basic correction models of PPP, we applied Inter Frequency Bias (IFB), relativistic effect, satellite antenna phase center offset, and satellite orbit and satellite clock errors, ionospheric errors, and tropospheric errors that must be provided on a real-time basis. The satellite orbit and satellite clock errors provided by Information-Analytical Centre (IAC) are interpolated at each observation epoch by applying the Lagrange polynomial method and linear interpolation method. We applied Global Ionosphere Maps (GIM) provided by International GNSS Service (IGS) for ionospheric errors, and increased the positioning accuracy by applying the true value calculated with GIPSY for tropospheric errors. As a result of testing the developed GLONASS PPP algorithms for four days, the horizontal error was approximately 1.4 ~ 1.5 m and the vertical error was approximately 2.5 ~ 2.8 m, showing that the accuracy is similar to that of GPS PPP.

• Journal of Sensor Science and Technology
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• v.28 no.5
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• pp.323-328
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• 2019

Recently, a sound wave phase meter (SWPM) that can directly measure the pressure waveform of sound waves in free space has been reported, and the development of educational experimental equipment using this meter is in progress. One of the main advantages of using this meter is that wavelengths can be obtained directly from the crests and troughs of the measured pressure waveforms in space without expensive equipment. However, there are times when the measurement wavelength does not exactly match the actual wavelength value, and the pressure waveform differs from the actual shape. This study was conducted to identify and analyze the causes of such errors occurring in SWPM. As a result, it was found that wavelength errors occur when the propagation direction of sound waves and the measurement direction of SWPM do not coincide. It has also been found that an error in the pressure waveform is generated when the induction and sound wave signal outputs from the SWPM interfere with each other to produce a composite signal. We have shown that we can develop educational experimental equipment by suggesting ways to reduce such errors.

• Proceedings of the KIEE Conference
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• 1999.07e
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• pp.2431-2433
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• 1999

Phase errors of arrayed waveguide degrade the performance of AWG router, especially for dense WDM system. So it is necessary to measure the phase error and to compensate. The analysis method of the interference signal from the low coherence interferometer to measure the path length difference phase error is studied. The interference signal generated assuming the intentional path length difference errors of 0.1$\sim$0.4${\mu}m$ are analyzed and the results show that the path length difference phase error of ${\Delta}L$ within ${\pm}14^{\circ}$ of sampling phase error can be accurately measured.

• Journal of Information Processing Systems
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• v.13 no.1
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• pp.83-94
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• 2017

Near-field source localization algorithms are very sensitive to sensor gain/phase response errors, and so it is important to calibrate the errors. We took into consideration the uniform linear array and are proposing a blind calibration algorithm that can estimate the directions-of-arrival and range parameters of incident signals and sensor gain/phase responses jointly, without the need for any reference source. They are estimated separately by using an iterative approach, but without the need for good initial guesses. The ambiguities in the estimations of 2-D electric angles and sensor gain/phase responses are also analyzed in this paper. We show that the ambiguities can be remedied by assuming that two sensor phase responses of the array have been previously calibrated. The behavior of the proposed method is illustrated through simulation experiments. The simulation results show that the convergent rate is fast and that the convergent precision is high.

• Proceedings of the KIEE Conference
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• 1998.11a
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• pp.220-222
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• 1998

This paper presents a method, which develops an ability of Zero-phase Overcurrent Relay. Zero-phase current is very useful factor of Fault decision in Protect Relaying system. Actually, the setting-point value of Designed Relay, using Zero-phase current, is fixed. So in the case of deciding fault, Fixed setting-point value is not suitable for changing Load. and cause errors in Distributions system. For solving this problem, This paper proposes the Changed setting point value Algorithm, which can be adaptive for changing Distributions system using Zero-phase current r.m.s. indexes. The results of simulation under Load changing and High impedance fault show that proposed algorithm is useful for changing Distributions system and decreasing errors.

• The Journal of Korean Institute of Information Technology
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• v.17 no.10
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• pp.57-63
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• 2019

Motion errors which are caused by several reasons, non-ideal path, errors of navigation systems, and radar system errors, have to be corrected. Motion compensation methods can compensate the motion error, but not exactly. To correct these residual errors, several autofocus methods are invented. A popular method is phase gradient autofocus (PGA). PGA does not assume specific circumstances, such as isolated point targets and shapes of errors. PGA is an iterative and adaptive method, so that the processing time is the main problem for the real time processing. In this paper, the improved method to select targets for PGA is proposed to reduce processing time. The variances of image pixels are used to select targets with high SNR. The processing of PGA with these targets diminishes the processing time and iterations effectively. The processed results with real radar data, obtained by flight tests, show that the proposed method compensates errors well, and reduce working time.

• The Bulletin of The Korean Astronomical Society
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• v.41 no.1
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• pp.74.2-74.2
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• 2016

It is important to know how well observation errors are removed in the calibration process prior to ensuing scientific research. In mm-VLBI observations, a radio wave suffers from an atmospheric propagation delay due to the rapid change of atmospheric refraction. It makes phases of VLBI correlation output fluctuate rapidly, which essentially decreases the coherence of phases and reduces the integration time. Consequently, it is challenging to achieve a high signal-to-noise ratio and enhance the quality of scientific output. Among the causes of the atmospheric propagation delay, water vapor in the troposphere is the most decisive factor to affect phase errors in the high frequency range (> 10GHz). It is expected to have the non-dispersive characteristic that enables to introduce new calibration strategy, Frequency Phase Transfer (FPT). This new method utilizes low frequency phases to compensate phase errors in high frequency bands. In addition, Korean VLBI Network (KVN) which benefits from the simultaneous 4-channels (22/43/86/129 GHz) observations is ideal to probe FPT performance. In order to evaluate FPT performance of KVN, we present the results of FPT phase analysis and discuss its performance.

• Journal of the Korean housing association
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• v.27 no.6
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• pp.137-144
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• 2016

In modular architecture, manufacturing drawing which includes whole information for modular unit production is essential since works for modular unit have to be performed in manufacturing factory not construction field. Although the manufacturing drawing is important as known it is insufficient to utilize the manufacturing drawing in modular architecture project and this makes modular unit low-quality with re-work and work time delay. To prevent low-quality modular unit caused by insufficient manufacturing drawing, in this research firstly manufacturing drawing's current situation and error cases in manufacturing phase of past modular housing project were analyzed, and correlation between reduction of errors occurance frequency and improving manufacturing drawing was verified. Secondly manufacturing drawing improvement factors were deducted in interior, furniture, mechanical work phase which errors' occurance rate is high and the way of deducting manufacturing drawing lists and contents were suggested with light-weight work as an example in case of new type of errors occurance. A series of research process can contribute to good-quality modular unit by errors reduction. As a result of research, about half of errors occurance can be reduced with suggested manufacturing drawing improvement factors. And the manufacturing drawing process can contribute to modular production which have uniform quality.

• The Transactions of the Korean Institute of Power Electronics
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• v.22 no.6
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• pp.496-503
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• 2017

This study proposes a high-performance current control algorithm for a diode-bridge-type single-phase boost power factor correction (PFC) converter. The conventional asynchronous single-phase current controllers that directly control AC-type current tend to be accompanied by steady-state errors due to their poor dynamic characteristics for the transient-state, which can be attributed to bandwidth limitations and phase delays. In the proposed algorithm, an ideal current control with minimal phase delays and steady-state errors can be achieved by using a virtual DQ synchronous reference frame and by controlling the synchronous reference frame excluding the frequency component in the single-phase system. The performance of the conventional asynchronous single-phase current controller is compared with that of the proposed algorithm through simulation and experiments, and the results have confirmed the superiority of the latter.

• Proceedings of the KIPE Conference
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• 2014.11a
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• pp.87-88
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• 2014

The paper presents a novel phase locked loop(PLL) control method for robust three-phase thyristor dual converters under sag, notch, and phase loss conditions. This method is applied to three line to line voltages of grid to derive three phase angle errors from three separated single-phase PLLs. They can substitute for abnormal phase to guarantee the synchronization in the various grid fault conditions. The performance of novel PLL with moving average method is verified through simulations.