• Proceedings of the Korean Society of Precision Engineering Conference
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• 2005.06a
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• pp.284-288
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• 2005

This paper proposes the direct detection method of phase angle for the power source, which is based on the PLL method. The proposed method using a bidirectional photo-coupler is used to directly detect the zero crossing of phase voltage and calculate the angular frequency in the controller based on a M/T algorithm. Through the method, the additional installation space in the traditional method using a potential transformer can be minimized and it can be easy to design. The paper presents straightforward schematic circuits, design and experimental results.

• Journal of Korea Multimedia Society
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• v.8 no.1
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• pp.56-61
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• 2005

In this thesis, propose speech period and pitch detection for continuous speech recognition. This mathod is distinguishes between vowel and consonant to frame unit in continuous speech, for distinguishable voice. Powerful extraction of speech period could threshold energy make use of input signal to real noise environment. Also algorithm of this method distinguish between vowel and consonant at the same time in voice make use of zero crossing rate and short time energy to extractible speech period.

• Proceedings of the KIEE Conference
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• 1987.07b
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• pp.1360-1363
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• 1987

Two edge detection methods are devised and tested. First one makes use of mean-difference between two connected regions after bimodal thresholding within a local window. It appears experimentally to provide reduced edge width maintaining good connectivity. It seems due to the use of the threshold obtained from a larger neighborhood. Second one uses additionally the gradient information to detect approximate zero crossing points of second directional derivative. This provides edges thinned nearly to one pixel width.

• Proceedings of the KIEE Conference
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• 1988.07a
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• pp.709-712
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• 1988

Ultrasonic Doppler Diagnostic System utilizes the Doppler effect for measurement of blood velocity. The sign of the Doppler frequency shift represents blood flow direction. CW(Continuous-Wave) Doppler System uses quadrature detection and phase rotation method to produce simultaneous independent audio and velocity signals for forward and reverse blood flow direction in the time-domain, had been fabricated. But time-domain analyzing such as audio evaluation and zero- crossing detection for instantaneous and mean frequnecy measurement do not provide both an accurate and quantitative result. Therefore, it is necessary to adopt frequency-domain technique to improve system performance. In this paper, we describe a unit which is composed of CW Doppler System and real-time spectrum analyzer (installed TMS 32010 DSP Chip). This unit shows time-dependent spectrum variation and mean velocity of Blood signal.

• Proceedings of the KIPE Conference
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• 2008.06a
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• pp.91-93
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• 2008

In this paper, novel phase angle following algorithm for the single phase grid-connected inverter is proposed. Gird-connected inverter needs phase angle detection for synchronization grid voltage with the inverter output. In case of single phase grid-connected inverter, zero crossing detection and virtual 2-phase PLL using digital all pass filter or digital low pass filter are used conventionally. But these methods have a weakness for harmonics, noises and ripples. The proposed method of PLL achieve DFT(Discrete Fourier Transform) using Goertzel algorithm. It can extract fundamental voltage of grid. As a results, it can obtain phase angle using digital all pass filter without effect of harmonics, noises and ripples. Simulation results are presented to demonstrate the effectiveness of the proposed algorithm.

• Proceedings of the IEEK Conference
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• 2006.06a
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• pp.887-888
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• 2006

In this paper, we devised mac-yule detection system which provide resting state mac-yule. The devised system composed of signal transformation part, signal processing part, and PC based display part. Hardware part consisit of PPG, ECG, EEG, EMG, and RSP. Also, software system consist of bio-signal processing software which detecting mac-yule. EEG-$\alpha$, $\beta$ wave analysis algorithm that use wavelet transformation, RSP detecting algorithm which used zero-crossing method.

• Journal of the Institute of Convergence Signal Processing
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• v.11 no.3
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• pp.183-188
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• 2010

In this paper we propose a detection method of the medial axis of the continuous stripes on the LoG scale-space. Our method detects the medial axis of continuous stripes iteratively by varying the scale of LoG operator. Small-scale LoG operator detects two +/- pole pairs centered on the edge positions of stripe by the zero-crossing detection. The more increase the scale of LoG scale-space, the more close two poles to the medial axis of stripe. The medial axis of continuous stripe is the position where two poles is overlapped. The proposed method detected robustly the medial axis of continuous stripes stronger than the thinning methods used to binary image.

• Journal of Electrical Engineering and Technology
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• v.11 no.1
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• pp.157-166
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• 2016

In this paper, a new sag and peak voltage detector is proposed for a single-phase inverter using delta square operation. The conventional sag detector is from a single-phase digital phase-locked loop (DPLL) that is based on d-q transformations using an all-pass filter (APF). The d-q transformation is typically used in the three-phase coordinate system. The APF generates a virtual q-axis voltage component with a 90° phase delay, but this virtual phase cannot reflect a sudden change in the grid voltage at the instant the voltage sag occurs. As a result, the peak value is drastically distorted, and it settles down slowly. A modified APF generates the virtual q-axis voltage component from the difference between the current and the previous values of the d-axis voltage component in the stationary reference frame. However, the modified APF cannot detect the voltage sag and peak value when the sag occurs around the zero crossing points such as 0° and 180°, because the difference voltage is not sufficient to detect the voltage sag. The proposed algorithm detects the sag voltage through all regions including the zero crossing voltage. Moreover, the exact voltage drop can be acquired by calculating the q-axis component that is proportional to the d-axis component. To verify the feasibility of the proposed system, the conventional and proposed methods are compared using simulations and experimental results.

• Proceedings of the IEEK Conference
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• summer
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• pp.237-243
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• 2004

A multichannel smart sound sensor capable to detect and identify sound events in noisy conditions is presented in this paper. Sound information extraction is a complex task and the main difficulty consists is the extraction of high­level information from an one-dimensional signal. The input of smart sound sensor is composed of data collected by 5 microphones and its output data is sent through a network. For a real time working purpose, the sound analysis is divided in three steps: sound event detection for each sound channel, fusion between simultaneously events and sound identification. The event detection module find impulsive signals in the noise and extracts them from the signal flow. Our smart sensor must be capable to identify impulsive signals but also speech presence too, in a noisy environment. The classification module is launched in a parallel task on the channel chosen by data fusion process. It looks to identify the event sound between seven predefined sound classes and uses a Gaussian Mixture Model (GMM) method. Mel Frequency Cepstral Coefficients are used in combination with new ones like zero crossing rate, centroid and roll-off point. This smart sound sensor is a part of a medical telemonitoring project with the aim of detecting serious accidents.

• The Transactions of the Korean Institute of Power Electronics
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• v.12 no.1
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• pp.9-18
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• 2007

This paper proposes the modeling of sensorless drive system using 120 degree conduction method for IPM (Interior Permanent Magnet) BLDC motors and analyzes characteristics of the terminal voltage that is used to detect the rotor position. This paper shows that the ZCP (Zero-Crossing Point) of the measured terminal voltage used In sensorless control is ahead of that of the back EMF of IPM motors because they have a saliency. This research also analyzes that the amount of position detection error is related to saliency, rotor speed, and load condition. In addition, this paper shows that motors have bigger advance angles than we have expected because the ZCP of terminal voltage precedes the actual ZCP, and under operation conditions such as heavy load and high speed it may generate abnormal currents that flow toward opposite direction after phase current becomes zero.