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Development of a Compact-size and Wireless Surface EMG Measurement System
Wonkeun Youn,Jung Kim 제어로봇시스템학회 2009 제어로봇시스템학회 국제학술대회 논문집 Vol.2009 No.8
This paper proposes a compact-size and a wireless surface EMG(electromyography) measurement system of a noninvasive type. The limitations of the current EMG sensor system include its large size , and the necessity of a wire. Therefore, this study focused on the development of a compact size preamplifier and wireless EMG measurement system. The EMG described herein is comprised of a preamplifier including an electrode for the measurement of the EMG signal, a main amplifier for signal processing, DSP(digital signal processor) processor for A/D conversion and digital signal processing, and a Bluetooth module for wireless communication. EMG signal obtained by the developed system results in better signal-to-noise ratio (SNR) compared to commercially available EMG system. This SNR of the developed system can be attributed to repeated signal processing on analog circuit and DSP, which reduces the size of the developed system. In our power spectral density, the EMG signal was distributed between approximately 20Hz and 400Hz. A Compact size and wireless surface EMG measurement system with high SNR can be useful for providing subjects comfort and consequently controlling external prosthesis.
Wonkeun Youn,고하윤,Hyungsik Choi,Inho Choi,Joong-Hwan Baek,Hyun Myung 제어·로봇·시스템학회 2021 International Journal of Control, Automation, and Vol.19 No.2
This paper proposes a novel complete navigation system for autonomous flight of small unmanned aerial vehicles (UAVs) in GPS-denied environments. The hardware platform used to test the proposed algorithm is a small, custom-built UAV platform equipped with an onboard computer, RGB-D camera, 2D light detection and ranging (LiDAR), and altimeter. The error-state Kalman filter (ESKF) based on the dynamic model for low-cost IMU-driven systems is proposed, and visual odometry from the RGB-D camera and height measurement from the altimeter are fed into the measurement update process of the ESKF. The pose output of the ESKF is then integrated into the open-source simultaneous location and mapping (SLAM) algorithm for pose-graph optimization and loop closing. In addition, the computationally efficient collision-free path planning algorithm is proposed and verified through simulations. The software modules run onboard in real time with limited onboard computational capability. The indoor flight experiment demonstrates that the proposed system for small UAVs with low-cost devices can navigate without collision in fully autonomous missions while establishing accurate surrounding maps.
ATM 상에서 멀티미디어 지향 오류 제어 기법의 성능 분석
최원근(Wonkeun Choi),안순신(Sunshin An) 한국정보과학회 1999 정보과학회논문지 : 시스템 및 이론 Vol.26 No.7
멀티미디어 통신에서 통신 성능에 관련된 요구 사항들은 QoS 매개 변수들로서 서술된다. QoS매개 변수들에서 중요한 매개 변수 중의 하나가 전송 신뢰성이다. QoS 매개 변수로서의 신뢰성은 오류 감지, 보고 그리고 정정 기법으로 정의된다. 하지만 기존의 오류 제어 기법들은 멀티미디어 데이타의 통합된 관점을 고려하지 않았다. 그래서 우리는 MEC(multimedia-oriented error control)라고 명명된 오류 제어 기법을 제안하였다. [1] 본 논문에서는 MFC기법의 성능을 조사하였다. 성능평가 결과는 MEC기법이 기존의 오류 제어 기법보다도 낮은 전송지연 (lower delay)과 호손율 (blocking probability)을 갖는다는 것을 볼 수 있었다. 결국 제안된 MEC기법은 수송 프로토콜에게 유연성과 높은 성능을 갖도록 해준다. Communication performance requirements are described as QoS parameters in multi-media communication. One of the important QoS parameters is the reliability of the transfer. As a QoS parameter, the reliability defines error detection, report and correction mechanisms. Conventional error control mechanisms, however, do not consider the integrated viewpoint of multimedia data. So we have proposed the MEC(multimedia-oriented error control). [1] In this paper, we have investigated the performance evaluation of the MEC. The results show that the MEC mechanism provides lower transfer delay and blocking probability than those of the conventional error recovery mechanism. Therefore, the proposed MEC mechanism makes the transport protocol have the flexibility and high performance.
인간-기계 인터페이스를 위한 근육 진동 신호 기반 팔꿈치 굽힘 힘 예측
윤원근(Wonkeun Youn),김정(Jung Kim) 대한기계학회 2009 대한기계학회 춘추학술대회 Vol.2009 No.11
The mechaomyography (MMG) is generated by the muscle surface oscillations due to pressure waves originating from the lateral expansion of the contracting muscle fibers. Since MMG signals reflect important aspect of muscle activities including the number and firing rates of recruited motor units (MUs). MMG signals could be utilized for predicting the exerted force by skeletal muscles. The objectives of this study were to investigate the feasibility of predicting isometric force from MMG signals and to explore the effect of muscle fatigue in performance of the force prediction. MMG signals from three contributed muscles during isometric elbow flexion were recorded as well as the force at wrist. Artificial neural network (ANN) with muscle fatigue compensation model were constructed and trained using the MMG signals collected for each subject, It was found that the isometric elbow flexion force could be accurately predicted by proposed methods, based on the values of normalized root mean square error (NRMSE) and the correlation coefficient (CC), with the performance of the ANN with fatigue compensation model being significantly better (NRMSE = 0.106±0.049, CC= 0.918±0.083) that those of its ANN (NRMSE = 0.160±0.045, CC= 0.710±0.211).
차원근 ( Wonkeun Cha ),이향숙 ( Hyangsook Lee ) 한국로지스틱스학회 2020 로지스틱스연구 Vol.28 No.2
Bonded Goods Caretaker is a qualified person certified by the state who must necessarily be employed by bonded area operator (including bonded warehouse, bonded factory, duty-free shop, etc.) to run a bonded area. Bonded Goods Caretaker is also a professional person in charge of bonded goods who, being possessed of expertise, partially performs the duties of customs officers by commission with regard to the control of bonded goods. Currently, however, without grades given on such qualification and with poor means to enhance professionalism such as supplement education, he is even forced to hold other posts concurrently, which is legally prohibited. Accordingly, this study is aimed to propose an improvement plan on the system of bonded goods caretaker. First, factors related to an improvement plan were drawn by reviewing foregoing studies and survey was conducted by composing these factors with four categories and twenty-two subcategories. Workers at bonded area (operator, person in charge, bonded goods caretaker, customs officers) were surveyed and through response to the questions, rankings for improvement factors were drawn. Next, additional analysis was conducted via one-way ANOVA for each subcategory on whether there was difference in perceiving importance among bonded area workers. It is expected that the results of this study could be used to improve conditions for bonded goods caretakers and enhance their professionalism, independence, etc. through policy proposals related to bonded goods caretaker system.
Chung, Wonkeun,Jung, Hyunchul,Lee, Chang Hun,Kim, Sung Hyun American Scientific Publishers 2012 Journal of nanoscience and nanotechnology Vol.12 No.7
<P>In this study, the yellow emitting cubic structure of Sr0.95Zn0.05Se:Eu2+ phosphors were prepared by high temperature solid state reaction. The Sr0.95Zn0.05Se:Eu2+ phosphors exhibited strong excitation intensity under 400-460 nm region, and broad band emission appeared at around 545-600 nm due to the d-f transition of Eu2+. To enhance the red emission, HDA/TOP/TOPO capped CdSe/ZnS NCs were synthesized via fast nucleation and slow growth method. The narrow emission peak was located at 615 nm with 69% of high quantum yield. Bright white emission was generated by combining a 460 nm InGaN LED chip with CdSe/ZnS NCs and Sr0.95Zn0.05Se:Eu2+ hybrid phosphors. The fabricated white LEDs showed warm white light with acceptable CIE chromaticity coordinate variation from (0.343, 0.255) at 20 mA to (0.335, 0.250) at 50 mA. The addition of CdSe/ZnS NCs contributed to the extension of white light spectrum by supplement of the red region. The color rendering index was largely enhanced from 41.7 to 79.7 compared to the Sr0.95Zn0.05Se:Eu2+ based phosphors white LED.</P>
Spray pyrolysis prepared yellow to red color tunable Sr1-xCaxSe:Eu2+ phosphors for white LED.
Chung, Wonkeun,Jung, Hyunchul,Lee, Chang Hun,Kim, Jihyun,Kim, Sung Hyun Optical Society of America 2012 Optics express Vol.20 No.12
<P>The spherical and submicron size of Sr1-xCaxSe:Eu2? phosphors were successfully prepared by ultrasonic spray pyrolysis. The phosphors adopted a cubic structure, and the replacement of Sr2? with Ca2? decreased the lattice parameter. The Sr1-xCaxSe:Eu2? showed broad and strong excitation under 420-460 nm blue light, and the emission band could be tuned from 565 to 607 nm by increasing the Ca2? ratio in the host lattice. In addition, the doping of Zn2? into Sr2? or Ca2? enhanced the emission intensity with a small red shift due to the change in crystal field strength and nephelauxetic effects. The warm and high CRI of white LED was achieved using blue LED pumped with blending phosphors of 612 nm emitting Ca?.??Zn?.?2Se:Eu2? and 565 nm emitting YAG. The correlated color temperatures and CRI were 4719.2K, and 86.3, respectively, and an acceptable color variation was also observed at operating currents ranging from 20 to 70 mA.</P>