• The Transactions of the Korean Institute of Electrical Engineers P
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• v.61 no.3
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• pp.111-115
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• 2012

Generally, brushless DC motor(BLDCM) driving system uses hall sensors or encoders as the mechanical position or speed sensor. It is necessary to achieve the informations of rotor position for driving trapezoidal type brushless DC motor without any position sensor. In this paper, the commutation signals are obtained without the motor neutral voltage, multistage analog filters, A/D converters, or the complex digital phase shift circuits which are indispensable in the conventional sensorless control algorithms. In the proposed method, in stead of detecting the zero crossing point of the nonexcited motor back electromagnetic force for the average motor terminal to neutral voltage, the commutation signal are extracted directly from the specific average line to line voltage with low-pass filter, adder and comparators circuit. In contrast to conventional methods, the neutral voltage is not need; therefore, the commutation signals are insensitive to the common mode noise. Moreover, the complex phase shift circuit can be eliminated. The effectiveness of the proposed method is verified through simulation results.

• Journal of Institute of Control, Robotics and Systems
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• v.5 no.4
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• pp.462-470
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• 1999

In this paper, we proposed a cross-couple controller for compensating nonlinear friction of the X-Y table of CNC machines. Due to the nonlinearity of the frictions, large contour errors, referred to as quadrant glitches, occur when each axis of the X-Y table makes a zero velocity crossing. To reduce the quadrant glitches the friction compensators and nonlinear friction observers for estimating Coulomb frictions are employed in the proposed method. A hyperbolic tangent function is used in reducing the magnitude of quadrant glitches and the CEM (Contour Error Model) is utilized for the estimation of the velocities. The performance of the proposed compensators is evaluated for several trajectories by computer simulations.

• Journal of the Korean Institute of Telematics and Electronics
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• v.15 no.6
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• pp.23-28
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• 1978

This paper describes a speech recognition system for ten isolated spoken digits. In this system, acoustic parameters such as zero crossing rate, log energy and three formant frequencies estimated by linear prediction method were extracted for classification and/or recognition purpose(s). The former two parameters were used for the classification of unvoiced consonants and the latter one for the recognition of vowels and voiced consonants. Promising recognition results were obtained in this experiment for ten digit utterances spoken by a male speaker.

• Proceedings of the Acoustical Society of Korea Conference
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• 1985.10a
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• pp.75-78
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• 1985

본 연구는 시간 영역의 parament를 이용하여 한국어 숫자음(영, 일, 이, 삼, 사, 오, 육, 칠, 팔, 구)을 인식했다. 입력 음성 신호 X(n)의 Beginning Point와 Ending point를 ZCR(Zero-crossing Rate), Magnitude, Energy, Autocorrelation을 이용 Beginning point와 Ending point를 구하고 자음부의 인식은 위 계수들을 이용하여 행했다. 또, 유성음 부분에서는 PARCOR(Partial Autocorrelation), LPC(Linear Predictive Coding)를 이용 모음부와 유성자음을 인식하여 모음을 6개 부류(ㅏ, ㅑ, ㅗ, ㅜ, ㅠ, ㅣ)로 구분 인식했다. 이 방법에 의하면 입력 음성 신호 X(n)의 B.P(Beginning Point)와 E.P(Ending Point)를 쉽게 추출 가능하며 또한 각 Parameter를 이용하여 94.4%의 인식율을 얻었다.

• The Journal of the Acoustical Society of Korea
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• v.21 no.8
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• pp.727-734
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• 2002

A simple algorithm for discriminating voiced sounds in a speech is proposed in this paper. In addition to low-frequency energy and zero-crossing rate (ZCR), both of which have been widely used in the past for identifying voiced sounds, the proposed algorithm incorporates pitch variation to improve the discrimination rate. Based on TIMIT corpus, evaluation result shows an improvement of 13% in the discrimination of voiced phonemes over that of the traditional algorithm using only energy and ZCR.

• Proceedings of the KIPE Conference
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• 2016.07a
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• pp.521-522
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• 2016

This paper presents a novel scheme to estimate the rotor position of a single-phase hybrid switched reluctance motor (HSRM). The proposed method uses the differential of back-EMF within a position region to estimate rotor position. By detecting the crossing-zero signal of back-EMF differential value, the minimum position of back-EMF corresponding to an absolute rotor position can be captured and used for position estimation four times in every mechanical rotation. In this way, a sensorless operation with adjustable turn on/off angle can be achieved without substantial computation. For the starting, two current comparators are adopted. The experimental verification using a prototype drive system is provided to demonstrate the viability of the proposed sensorless scheme.

• Proceedings of the KIPE Conference
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• 2016.07a
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• pp.433-434
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• 2016

전력계통은 안정된 전압과 주파수의 전력수급이 요구되는 가운데 발전기의 안정성은 주요 요소이다. 그런데 수차발전기 운전 중 부하 탈락 시 급격한 주파수 상승에 의한 발전기 과전압발생은 발전기 여자시스템의 제어신호인 전압실효값 오차에 기인한 것이다. 이런 오차를 최소화하고 발전기 전압을 안정시키기 위해 ZCP(Zero Crossing Point)와 FPGA를 이용한 주파수 검출영역 확장과 DFT(Discrete Fourier Transform) 알고리즘을 이용하여 안정된 전압실효값을 계산하는 기법을 설계하였다. 실험결과, 기존 57~63Hz 주파수 영역의 DFT 대비 확장된 30~90Hz 대역의 전압실효값 오차는 최대 24.68%에서 0.22%로 대폭 개선되었다.

• Proceedings of the KIPE Conference
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• 2011.11a
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• pp.169-170
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• 2011

PFC(Power Factor Correction) converters are commonly designed for CCM(Continuous Conduction Mode). However, DCM(Discontinuous Conduction Mode) appears in the input current near the ZCP(Zero Crossing Point) at light loads, resulting in input current distortion. It is caused by inaccurate average current values obtained in DCM. This paper studies a simple digital control scheme that can be operated in both CCM and DCM with minimal changes to the CCM average current control structure.

• The Journal of Korea Institute of Information, Electronics, and Communication Technology
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• v.2 no.1
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• pp.17-22
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• 2009

In this paper, we extract well-known parameters such as zero crossing rate(ZCR), low band energy(Band) and median frequency(MDF) from surface electromyogram (EMG), and compare to evaluate themselves as measures for fatigue. In experiments, 3 males and 3 females volunteered to participate in surface EMG recordings placed on the biceps brachii and each recording experiment continued until exhaustion.

• Proceedings of the KIEE Conference
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• 1990.11a
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• pp.428-431
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• 1990

This paper describes a pattern classification algorithm of QRS-complexes using significant point detection for extracting features of signals. Significant point extraction was processed by zero-crossing method, and decision function based on relational spectrum was used for pattern classification of the QRS-complexes. The hierarchical AND/OR graph was obtained by decomposing the signal, and by use of this graph, QRS's patterns were classified. By using the proposed algorithm, the accuracy of pattern classification and the processing speed were improved.