• 제목/요약/키워드: frequency-phase method

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신체 성분 분석을 위한 다 주파수 생체전기 임피던스 분석 시스템 구현 (Implementation of Multiple Frequency Bioelectrical Impedance Analysis System for Body Composition Analysis)

  • 김성철
    • 한국산학기술학회논문지
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    • 제13권11호
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    • pp.5403-5408
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    • 2012
  • 본 논문에서는 신체 성분 분석을 위한 다주파수 생체전기 임피던스 분석법에 대하여 소개하고 이를 기반으로 다주파수 생체전기 임피던스 분석 시스템을 구현하고 그 과정 및 결과를 제시하였다. 시스템의 구성요소들을 다주파수 교류 신호 발생부, 위상 신호 검출부, 전압 신호 검출부, 제어부, 입 출력부, 전극부, 전원부로 구분하여 설명하고, 구체적으로 구현 기법을 소개하였다. 체성분 데이터의 임상적 의의를 검토하고자 세계 최고 수준의 기술을 적용하여 높은 재현도와 고정밀도의 데이터를 제공하는 전문가용 체성분 분석기로 측정한 데이터와 비교 검토하고 두 측정치간의 상관관계를 구한 결과 시스템에 의한 체성분 분석은 상당히 높은 재현성을 나타낸다고 할 수 있다.

ELINT 장비용 광대역 초고속 고정밀 주파수 합성기 설계 및 구현 (Design and Implementation of Wideband Ultra-Fast High Precision Frequency Synthesizer for ELINT Equipment)

  • 이규송;전계익;오승엽
    • 한국전자파학회논문지
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    • 제20권11호
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    • pp.1178-1185
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    • 2009
  • 본 논문은 2.5 MHz 간격으로 광대역 주파수를 발생하며 응답 시간이 400 nsec 이하인 초고속 이산(discrete) 주파수 합성기를 제안한다. 제안한 주파수 합성기는 고정 주파수 위상 제어 루프(PLL)와 주파수 분배기를 이용해 16개의 기준 신호를 생성하고, 이들을 선택하여 주파수 혼합하는 방식으로 710~1,610 MHz내에서 2.5 MHz 간격의 이산 주파수 신호를 고속으로 생성한다. 제작된 주파수 합성기의 주파수 천이 응답 시간은 평균 350 nsec, 고조파를 비롯한 모든 불요파 신호는 -60 dBc 이하, 위상 잡음 특성은 -94 dBc/Hz @100 Hz, 출력 세기는 평균 21.5 dBm, 평탄도는 2.65 dB 이하로 측정되었다. 또한 주파수 천이 응답 속도를 측정하는 새로운 기법의 측정 방법이 제안되었다.

정전용량형 변위 센서 신호 처리 회로 개발 및 성능 평가 (Development of a Signal Conditioning Circuit for Capacitive Displacement Sensors and Performance Evaluation)

  • 김종안;김재완;엄태봉;강주식
    • 한국정밀공학회지
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    • 제24권9호
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    • pp.60-67
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    • 2007
  • A signal conditioning circuit for capacitive displacement sensors was developed using a high frequency modulation/demodulation method, and its performance was evaluated. Since capacitive displacement sensors can achieve high resolution and linearity, they have been widely used as precision sensors within the range of several hundred micrometers. However, they inherently have a limitation in low frequency range and some nonlinearity characteristics and so a specially designed signal conditioning circuit is needed to handle these properties. The developed signal processing circuit consists of three parts: linearization, modulation/demodulation, and nonlinearity compensation. Each part was constructed discretely using several IC chips and passive elements. An evaluation system for precision displacement sensors was developed using a laser interferometer, a precision stage, and a PID position controller. The signal processing circuit was tested using the evaluation system in the respect of resolution, repeatability, linearity, and so on. From the experimental results, we know that a highly linear voltage output can be obtained successfully, which is proportional to displacement and the nonlinearity of output is less than 0.02% of full range. However, in the future, further investigation is required to reduce noise level and phase delay due to a low-pass filter. The evaluation system also can be applied effectively to calibration and evaluation of precision sensors and stages.

자동변속기 장착 차량의 아이들 셰이크 진동 성능 개선 대책에 대한 고찰 (Investigations on Improvement of Vehicle Design Feature on Idle Shake with Automatic Transmission)

  • 최천;서명원;김영진
    • 한국자동차공학회논문집
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    • 제8권4호
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    • pp.110-120
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    • 2000
  • In order to improve the vibration characteristics of mid sized passenger car automatic transmission at idle experimental and theoretical studies have been carried out. Idle shake in "D" range occurs by various reasons such as characteristics of body bending resonance between subsystems and engine mounts etc. Using full vehicle finite element analyses and modal tests we introduce the way to reduce the idle shake in the early design stage. It shows that the exciting forces are the 2nd order torque and force of engine. A powertrain system modes in "D" range are entirely effected by the additional boundary conditions of drive line. As a result the frequencies of subsystems are arranged to be lined up at the idle frequency range in order to avoid the resonances with subsystems To reduce the idle shake mounts of radiator are tuned to act as a dynamic damper to 1st bending frequency of the body. In addition a hydraulic mount which is optimized by Phase Shift Method is applied to the rear engine mount.e rear engine mount.

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Multi-band imaging of the H2O and SiO masers around the late-type stars using KVN

  • Yun, Youngjoo;Cho, Se-Hyung;Dodson, Richard;Rioja, Maria J.
    • 천문학회보
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    • 제40권2호
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    • pp.35.2-35.2
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    • 2015
  • We present the results of simultaneous observations of the H2O and SiO masers emitted from the circumstellar envelopes (CSEs) of the late-type stars. These observations have been carried out at the four frequency bands (K, Q, W and D bands) using KVN to apply the source frequency phase referencing (SFPR) analysis to the maser lines. We obtain the relative positions between the H2O and the SiO maser spots by using the SFPR method, which are very important to study the physical links between the inner and the outer parts of the CSEs of the late-type stars. The relative positions between the SiO maser spots of the different transitions are also obtained very accurately, which are very crucial to investigate the pumping mechanism of the SiO maser lines. From our results, the capability of the simultaneous multi-band observation of KVN is proved to be powerful to study the complicated physical environments of the CSEs and the stellar evolution of the late-type stars.

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Model Predictive Control for Shunt Active Power Filter in Synchronous Reference Frame

  • Al-Othman, A.K.;AlSharidah, M.E.;Ahmed, Nabil A.;Alajmi, Bader. N.
    • Journal of Electrical Engineering and Technology
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    • 제11권2호
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    • pp.405-415
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    • 2016
  • This paper presents a model predictive control for shunt active power filters in synchronous reference frame using space vector pulse-width modulation (SVPWM). The three phase load currents are transformed into synchronous rotating reference frame in order to reduce the order of the control system. The proposed current controller calculates reference current command for harmonic current components in synchronous frame. The fundamental load current components are transformed into dc components revealing only the harmonics. The predictive current controller will add robustness and fast compensation to generate commands to the SVPWM which minimizes switching frequency while maintaining fast harmonic compensation. By using the model predictive control, the optimal switching state to be applied to the next sampling time is selected. The filter current contains only the harmonic components, which are the reference compensating currents. In this method the supply current will be equal to the fundamental component of load current and a part of the current at fundamental frequency for losses of the inverter. Mathematical analysis and the feasibility of the suggested approach are verified through simulation results under steady state and transient conditions for non-linear load. The effectiveness of the proposed controller is confirmed through experimental validation.

A New Approach to Direct Torque Control for Induction Motor Drive Using Amplitude and Angle of the Stator Flux Control

  • Kumsuwan, Yuttana;Premrudeepreechacharn, Suttichai;Toliyat, Hamid A.
    • Journal of Electrical Engineering and Technology
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    • 제3권1호
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    • pp.79-87
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    • 2008
  • This paper proposes the design and implementation of a direct torque controlled induction motor drive system. The method is based on control of decoupling between amplitude and angle of reference stator flux for determining reference stator voltage vector in generating PWM output voltage for induction motors. The objective is to reduce electromagnetic torque ripple and stator flux droop which result in a decrease in current distortion in steady state condition. In addition, the proposed technique provides simplicity of a control system. The direct torque control is based on the relationship between instantaneous slip angular frequency and rotor angular frequency in adjustment of the reference stator flux angle. The amplitude of the reference stator flux is always kept constant at rated value. Experimental results are illustrated in this paper confirming the capability of the proposed system in regards to such issues as torque and stator flux response, stator phase current distortion both in dynamic and steady state with load variation, and low speed operation.

CDGPS를 위한 LSAST 미지정수 추정기법 개선에 관한 연구 (A study on improving LSAST ambiguity resolution for CDGPS)

  • 이기훈
    • 한국항공우주학회지
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    • 제34권5호
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    • pp.74-80
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    • 2006
  • 1980년대부터 민간에 개방된 GPS는 C/A코드의 도달시간을 측정하여 위치를 계산하고, 반송파의 도플러 주파수를 측정하여 속도를 계산한다. 위치정확도를 향상시키기 위하여 공통오차를 제거하는 DGPS 기법과 반송파 위상을 이용하여 수cm 내의 정확도를 가질 수 있는 CDGPS 기법이 1990년대부터 개발되기 시작하였다. 본 논문에서는 CDGPS를 위해 LSAST 미지정수 추정기법을 개선하여 계산효율 및 신뢰도를 높이고, 단일 주파수 GPS 수신기를 이용하여 움직이는 항체의 상대위치를 수cm 내의 정확도로 측정한 실험결과를 INS의 위치와 비교하여 제시한다. 이러한 결과는 추후 정밀관성항법장치, 무인자율주행, 측지 및 정밀지도제작 등에 유용하게 쓰일 수 있다.

직렬 변압기를 이용한 고정밀 자동전압조절기 (High precision Automatic Voltage Regulator by using series transformer)

  • 장뢰;이화춘;정태욱;남해곤;남순열;박성준
    • 전력전자학회:학술대회논문집
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    • 전력전자학회 2008년도 하계학술대회 논문집
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    • pp.574-576
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    • 2008
  • Now there are two types Non-contact compensation AC automatic voltage regulator (A.V.R). One is transformer compensation regulator, whose principle is the combination of multiple compensation transformers, do the compensation by turning on and off the connections of the transformer through the multi-full bridge circuit. This method removed the mechanical drive and contacts, which increases the life and the dynamic performance of the A.V.R. However, the compensation is multilevel, and it needs many compensation transformers and switches, the circuit is complex, the compensation precision is low. Another type is PWM switch AC regulator, whose principle is getting the AC voltage from the input, then induce the AC compensation voltage through commutating and high frequency PWM transforming, and phase tracking. Here the compensation is step-less, the compensation precision is high, and the response is fast. But the circuit is complex, and it needs an inverse compensation transformer, which is difficult to realize high-power applications. In this paper, it shows an Automatic Voltage Regulator which use high frequency PWM inverter do compensation. This A.V.R has the function as the custom-power, which make the performance of the power supply in a high level.

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회전자 바 개방과 회전자 편심에 의한 단삼 유도 전동기의 전기 및 기계적 특성 해석 (Electromechanical Characteristics of a Squirrel Cage Induction Motor due to Broken Rotor Bars and Rotor Eccentricity)

  • 박상진;장정환;장건희;이용복;김창호
    • 대한전기학회논문지:전기기기및에너지변환시스템부문B
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    • 제51권8호
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    • pp.425-433
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    • 2002
  • This research investigates the electromechanical characteristics of a sing1e-phase squirrel cage induction motor due to broken rotor bars and rotor eccentricity. Numerical analysis is performed by solving the nonlinear time-stepping finite element equation coupled with the magnetic field equation, circuit equation and mechanical equation of motion. It shows that the asymmetry of magnetic flux due to the broken rotor bars and rotor eccentricity introduce a change in the stator current, torque, speed, magnetic force and vibration of a rotor at the same time. However, even in the existence of rotor eccentricity, 3 broken rotor bar introduces a dominant change in the magnetic force and rotor displacement, i.e., beating phenomenon in time domain and sideband frequencies in frequency spectra, respectively.