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RISS 인기검색어
- 검색키워드
- 저자 : 최철형(Chul-Hyung Choi) (검색결과 4 건)
- 무료
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태아 ECG 추출 기능을 가지는 모바일 심전도 측정 시스템 설계
최철형(Chul-Hyung Choi),김영필(Young-Pil Kim),김시경(Si-Kyung Kim),유정봉(Jeong-Bong You),서봉균(Bong-Gyun Seo) 대한전기학회 2017 전기학회논문지 Vol.66 No.2
In this paper, the abdomen ECG(AECG) is employed to measure the mother’s ECG instead of the conventioanl thoracic ECG measurement. The fetus ECG signal can be extracted from the AECG using an algorithm that utilizes the mobile fetal ECG measurement platform, which is based on the BLE (Bluetooth Low Energy). The algorithm has been implemented by using a replacement processor processed directly from the platform BLE instead of the large statistical data processing required in the ICA(Independent component analysis). The proposed algorithm can be implemented on a mobile BLE wireless ECG system hardware platform to process the maternal ECG. Wireless technology can realize a compact, lowpower radio system for short distance communication and the IOT(Intenet of Things) enables the transmission of real-time ECG data. It was also implemented in the form of a compact module in order for mothers to be able to download and store the collected ECG data without having to interrupt or move the logger, and later link the module to a computer for downloading and analyzing the data. A mobile ECG measurement prototype is manufactured and tested to measure the FECG for pregnant women. The experimental results verify a real-time FECG extraction capability for the proposed system. In this paper, we propose an ECG measurement system that shows approximately 91.65% similarity to the MIT database and the conventional algorithm and SNR performance about 10% better.
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FFD와 로봇 팔을 이용한 3D 가발 형상 제작 시스템
최철형(Chul-Hyung Choi),세이푸르(Saifur Rahman),김시경(Si-Kyung Kim),박인덕(In-Deok Park),김영필(Young-Pil Kim) 한국정보기술학회 2018 한국정보기술학회논문지 Vol.16 No.1
In this paper, we propose a new method to automatically make 3D wigs by replacing existing manual wig manufacturing system. To obtain the existing 3D head image, there is a method using a laser and an infrared ray. However, since both methods use light, it is difficult to measure the correct head by the hair. In this paper, we propose a contact type measurement method which has no problem in actual head shape processing even when there is hair. The 3D wig making method of this paper first establishes seven representative landmark points for the head shape and creates a standard 3D head shape which is an ideal head shape. Using the robotic arm designed in this paper, 3D position information of five measurement points is extracted and the 3D head of the subject is generated using the FFD(Free Form Deformation) algorithm based on the corresponding data. As a result of the implemented method, there was an error of 1.1 ~ 5.6% compared between actual head and subject. The proposed technique has the advantage of making the customized wig quickly and efficiently by taking only five 3D contact measurement points of the subject.
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적응형 필터와 가변 임계값을 적용하여 잡음에 강인한 심전도 R-피크 검출
세이푸르(MD Saifur Rahman),최철형(Chul-Hyung Choi),김시경(Si-Kyung Kim),박인덕(In-Deok Park),김영필(Young-Pil Kim) 한국산학기술학회 2017 한국산학기술학회논문지 Vol.18 No.12
심전도(ECG) 신호에서 R-피크를 추출하는 기법에 대하여 많은 연구가 진행 되어 왔으며, 다양한 방법으로 구현되어 왔다. 그러나 이러한 검출 방법 대부분은 실시간 휴대용 심전도 장치에서 구현하기가 복잡하고 어려운 단점이 있다. R-피크 검출을 위해서는 심전도 데이터에 대하여 베이스라인 드리프트 및 상용전원 잡음 제거 등의 적절한 전처리 및 후가공이 필요하며, 특히 적응형 필터를 활용한 기법에서는 적절한 임계값을 선택하는 것이 중요하다. 적응형 필터의 임계값을 추출하는 방식에서는 고정형(Fixed) 및 적응형(adaptive)으로 구분할 수 있다. 고정 임계 값 추출 방식은 고정된 임계값 보다 낮은 값의 입력이 들어오는 경우에 R-피크 값을 감지하지 못하는 경우가 있으며, 적응 임계값 추출 방식은 때때로 잡음에 의한 잘못된 임계값을 도출하여, 다른 파형(P혹은 T파)의 피크를 감지하는 경우도 나타난다. 본 논문에서는 계산상의 복잡성이 적고, 코드구현이 단순하면서도 잡음에 강인한 R-피크 검출 알고리즘을 제안한다. 제안된 방식은 앞서 설명한 임계값 추출 문제를 해결하기 위해서, 적응형 필터를 사용해, 심전도 신호에서 베이스 라인 드리프트 제거를 하여 적절한 임계값을 계산하도록 한다. 그리고 필터 처리된 심전도 신호의 최소 값과 최대 값을 사용하여 적절한 임계값이 자동으로 추출 되도록 한다. 그런 다음 심전도 신호로부터 R-피크를 검출하기 위해 임계값 아래에서 ‘neighborhood searching’ 기법이 적용된다. 제안된 방법은 R-피크 검출의 정확도를 향상시키고, 계산 량을 줄여 검출 속도가 보다 빨라지도록 하였다. 다음으로 R-피크 값이 검출 되면, R-R interval 등의 값을 이용해 심박 수를 계산할 수 있도록 한다. 실험결과 심박 수 검출 정확도와 감도가 약 100%로 매우 높았음을 확인할 수 있었다. There have been numerous studies on extracting the R-peak from electrocardiogram (ECG) signals. However, most of the detection methods are complicated to implement in a real-time portable electrocardiograph device and have the disadvantage of requiring a large amount of calculations. R-peak detection requires pre-processing and post-processing related to baseline drift and the removal of noise from the commercial power supply for ECG data. An adaptive filter technique is widely used for R-peak detection, but the R-peak value cannot be detected when the input is lower than a threshold value. Moreover, there is a problem in detecting the P-peak and T-peak values due to the derivation of an erroneous threshold value as a result of noise. We propose a robust R-peak detection algorithm with low complexity and simple computation to solve these problems. The proposed scheme removes the baseline drift in ECG signals using an adaptive filter to solve the problems involved in threshold extraction. We also propose a technique to extract the appropriate threshold value automatically using the minimum and maximum values of the filtered ECG signal. To detect the R-peak from the ECG signal, we propose a threshold neighborhood search technique. Through experiments, we confirmed the improvement of the R-peak detection accuracy of the proposed method and achieved a detection speed that is suitable for a mobile system by reducing the amount of calculation. The experimental results show that the heart rate detection accuracy and sensitivity were very high (about 100%).
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Flyback Converter Active Balancing BMS 적용 유 · 무에 따른 리튬폴리머 이차전지 가용시간 분석
김영필(Young-Pil Kim),최철형(Chul-Hyung Choi),고석철(Seok-Cheol Ko),김시경(Si-Kyung Kim) 대한전기학회 2017 전기학회논문지 Vol.66 No.5
In this paper, the run time of Li-polymer secondary cell with and without Active Balancing BMS is analyzed. The Active Balancing System using Flyback Converter with two-way power control facility, his designed for optimal characteristics of balancing. The run time of Li-polymer secondary cell is drastically increased employing the Flyback Convert Active Balancing BMS. The run time performance of Li-polymer secondary cell with or without Flyback Converter Active Balancing BMS is analyzed with the discharging and charging experiment of Li-polymer secondary cell.
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