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고속 BLDC 전동기 센서리스 구동에서 역기전력 신호의 노이즈와 샘플링 주기가 미치는 영향
서은정(Eunjeong Seo),이강석(Kangseok Lee),이우택(Wootaik Lee) 한국자동차공학회 2013 한국자동차공학회 부문종합 학술대회 Vol.2013 No.5
The purpose of this paper is to analyze effects of back-EMF(Electro Magnetic Force) signal noise and sampling period for Brushless DC(BLDC) motor sensorless drives at high speed. A typical zero crossing detection method detects zero crossing point using change of back-EMF polarity. Using this method, back-EMF signal noise and sampling period are the cause of performance degradation at high speed, because the number of back-EMF samples to detect zero crossing is small. Therefore the effects are analyzed by simulation on high performance BLDC motor drives at high speed.
BLDC 고속 센서리스 구동의 ZCP 추정 오차 저감을 위한 Programmable Low Pass Filter 설계
서은정(Eunjeong Seo),이강석(Kangseok Lee),이우택(Wootaik Lee) 대한전기학회 2014 전기학회논문지 Vol.63 No.1
This paper presents a design method of programmable low pass filter(PLPF) which reduce an estimation error of a zero crossing point(ZCP) for a high speed brushless DC(BLDC) motor drive. BLDC motor sensorless drive is possible by estimation of ZCP. The ZCP estimated by detecting a change of back-EMF polarity has the estimation error because noises exist on the measured back-EMF. Therefore a calculated commutation timing using the ZCP is inaccurate. And the inexact commutation timing leads to ripples of 3-phase current and degradation of drive performance. This paper proposes the design method of the PLPF to overcome these problems. First, a speed calculated a inaccurate period of the ZCP is analyzed in the frequency domain. Then, the PLPF that has varying cut-off frequency according to change of the speed is designed on the frequency analysis result. The proposed method is verified by the experiment.
학술지“환경교육”논문 분석을 통한 학교 환경교육 연구 동향 고찰
황세영(Seyoung Hwang),서은정(Eunjeong Seo),이리나(Rina Lee),홍인영(Inyoung Hong) 한국환경교육학회 2012 環境 敎育 Vol.25 No.2
The purpose of this study was to review the research trends in school environmental education. We analyzed 383 research papers that specifically focused on the school context which were 66% of the total number (N=577) published in this journal between 1990~2011. We defined the characteristics of review and developed a review method by examining previous review studies in this area. The review framework for school environmental education research was devised in terms of seven research areas: 1) Theories and objectives of school environmental education, 2) Environmental awareness, attitude and behavior, 3) Current issues in environmental education in the school context, 4) Instructions and programs, 5) National Curriculum, 6) Environmental education contents, and 7) Teacher professionalism. In this paper, we present dominant features within each category with focus on the overall trends of research methods and themes. Finally, we discuss research issues emerging out of the empirical analysis for considering the value of research for enhancing the quality of environmental education in schools.