• 한국전자파학회논문지
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• 제7권1호
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• pp.1-14
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• 1996

본 논문은 임펄스 잡음 환경하에서 전자파 장해의 유형에 따른 M-ary PSK 통신시스템의 오율성능을 분석하였다 M-ary PSK 신호로는 BPSK와 QPSK 신호를 대상으로 하였으며 방해파의 유형으로는 가우스파, 정현파, 구형파의 세가지 형태에 대해 고찰하였다. 검토한 결과 장해의 정도는 가우스, 정현, 구형 방해파 순서로 시스템의 성능이 열화됨을 알 수 있었다. 따라서 가우스파의 장해환경이 가장 큰 영향을 미치므로 시스템 설계시 전자파 장해의 영향올 고려할 경우, 가우스파를 기준으로 하는 것이 안전하고 신뢰할 수 있는 시스템 설계가 됨을 알 수 있었다. 한편 임펄스 잡음이 강한 환경에서는 방해파 성분이 약해진다고 해도 임펄스 잡음에 의해서 시스템의 성능이 심한 열화를 받음을 알 수 있었다. 따라서 임펄스 잡음은 통신시스템의 성능열화에 지배적인 요인이 됨을 확인할 수 있었다.

• 한국전산유체공학회지
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• 제6권2호
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• pp.22-31
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• 2001

The two-dimensional unsteady incompressible viscous flow behind rectangular bluff bodies between two parallel plates was analyzed numerically. The steady state flow and the vortex flow behind rectangular bluff bodies in the channel were investigated for two regimes i.e., the laminar(Re = 100, 300, 500) and the turbulent flows(Re = 10⁴∼10/sup 6/). The vortex shedding was generated by a physical disturbance(6%) numerically imposed at the rear of the bluff bodies for a short time. It was observed that the perturbed flow became periodic after a transient period. And in the case of unsteady inflow, the sinusoidal pulsatile flow was applied as the inlet condition in the turbulent flow of Reynolds number of 1.0×10/sup 5/. FLUENT code was employed to solve the problems. The power-law scheme was used to get stable linearized equations and the PISO algorithm was applied to finding the solution of them.

• 조명전기설비학회논문지
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• 제14권5호
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• pp.43-49
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• 2000

MH 랭프의 전자식 안정기에서 발생하는 음향공명의 감소를 위한 새로운 제어 방법올 제시한다. 주파수 가변 공전 인버터를 해석하고 전달함수를 구한다. 안정기의 전류제어기로 적분길를 채용한다. 램프전력 교란 및 주파수 확산을 이용하며 음향공명올 감소시키 위해 전류제어기 입력에 200[Hz] 정현파를 부가하여 램프 전류를 진폭 변조시킨다.MH 250[W] 램프를 대상으로 변조도에 따른 램프의 아크 안정성을 조사하고 제안된 진폭변조에 의한 음향공명 감소법 및 전류 제어기 설계법의 타당성을 확인하였다.

• 대한전기학회논문지:전력기술부문A
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• 제48권3호
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• pp.278-285
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• 1999

This paper utilizes the method of Q-parameterization control to design a controller which solves the problem of imbalance in magnetic bearing systems. There are two methods to solve this problem using feedback controal. The first method is to compensate for the imbalance forces by generating opposing forces on the bearing surface (imbalance compensation). The second method is to make the rotor rotate around its axis of inertia (automatic balancing);in this case no imbalance forces will be generated. In this paper we deal with only imbalance compensation. The free parameter of the Q-parameterization controller is chosen such that these goals are achieved. After the introduction of a model of the magnetic bearing system, we explain the Q-parameterization controller design of the magnetic bearing system with emphasis on the rejection of sinusoidal disturbance for imbalance compensation design. The design objectives are formulated as a linear equations in the controller free paramete Q. Finally, simulation and experimental results are presented and showed the robustness and effectiveness of the proposed controllers.

• 소음진동
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• 제8권5호
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• pp.964-973
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• 1998

본 논문에서 자기 축수 시스템의 부상과 불평형 보상 제어기를 제안한다. 특정한 동작속도에서 불균형 진동과 부상을 제어하기위해 우리는 이산시간 Q 매개변수화 제어를 사용한다. 회전자의 속도가 p=0일 때, 회전소도와 같은 주파수로 회전자의 불균형은 없다. 그래서 부상을 만들기 위해 우리는 제어기가 z=1의 단위원에서 극점을 가지는 Q매개변수화 Q를 선택한다. 그러나 회전자의 속도가 p$\neq$0일 때, 회전속도와 같은 주파수로 정현파의 외란이 존재하게 된다. 그래서 이 외란의 점근적인 소멸을 하기위해 Q 매개화변수 제어기 자유 변수 Q가 제어기가 어떠한 회전속도 p에 대한 z=expjpTs에 있는 단위 원에서 극점을 가지도록 선택된다. 첫째로, 우리는 이 연구에서 적용된 실험적인 구성을 소개한다. 두 번째로, 우리는 차분 방정식의 형태로 자기축수 시스템의 수학적인 모델을 제안한다. 세 번째로 우리는 제안된 이산 시간 Q매개변수화 제어기 설계방법을 설명한다. 제어기의 자유 매개변수 Q는 안정한 전달함수가 된다고 가정한다. 네 번째로, 우리는 설계목적을 만족하는 자유 매개변수가 복잡한 최적문제를 풀기보다는 선형 방정식을 구함으로서 만족될 수 있다. 마지막으로 몇 개의 시뮬레이션과 실험적인 결과가 제언된 제어기를 평가하기 위해 구해진다. 획득된 결과는 회전설계 속도에서의 불균형 진동을 제어하는 제안된 제어기의 효과를 나타낸다.

• 한국소음진동공학회:학술대회논문집
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• 한국소음진동공학회 2009년도 추계학술대회 논문집
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• pp.231-239
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• 2009

The filtered-x LMS (FX-LMS) algorithm has been applied to the active noise control (ANC) system in an acoustic duct. This algorithm is designed based on the FIR (finite impulse response) filter, but it has a slow convergence problem because of a large number of zero coefficients. In order to improve the convergence performance, the step size of the LMS algorithm was modified from fixed to variable. However, this algorithm is still not suitable for the ANC system of a short acoustic duct since the reference signal is affected by the backward acoustic wave propagated from a secondary source. Therefore, the recursive filteredu LMS algorithm (FU-LMS) based on infinite impulse response (IIR) is developed by considering the backward acoustic propagation. This algorithm, unfortunately, generally has a stability problem. The stability problem was improved by using an error smoothing filter. In this paper, the recursive LMS algorithm with variable step size and smoothing error filter is designed. This recursive LMS algorithm, called FU-VSSLMS algorithm, uses an IIR filter. With fast convergence and good stability, this algorithm is suitable for the ANC system in a short acoustic duct such as the intake system of an automotive. This algorithm is applied to the ANC system of a short acoustic duct. The disturbance signals used as primary noise source are a sinusoidal signal embedded in white noise and the chirp signal of which the instantaneous frequency is variable. Test results demonstrate that the FU-VSSLMS algorithm has superior convergence performance to the FX-LMS algorithm and FX-LMS algorithm. It is successfully applied to the ANC system in a short duct.

• Journal of Power Electronics
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• 제18권5호
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• pp.1545-1554
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• 2018

This paper proposes a modified control strategy to improve the performance of three-phase four-leg shunt active power filters (APFs) for the compensation of three phase unbalanced loads. Unbalanced current cannot be obtained accurately by a harmonic detector due to the lower frequency. The proposed control strategy eliminates conventional harmonic detectors by directly regulating the source current. Therefore, the computational complexity is greatly reduced and the performance of the APF is improved. A mathematic model has been developed based on the source currents. The corresponding controllers have been designed based on the sinusoidal internal model principle. The proposed control strategy can guarantee excellent compensation performance and stable operation after an extreme disturbance such as a short circuit fault. In addition, the proposed technique can selectively compensate specific harmonics. A 50kVA prototype APF is implemented in the laboratory to validate the feasibility and performance of the proposed control strategy.

• 한국소음진동공학회논문집
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• 제22권2호
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• pp.146-155
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• 2012

The filtered-x LMS(FX-LMS) algorithm has been applied to the active noise control(ANC) system in an acoustic duct. This algorithm is designed based on the FIR(finite impulse response) filter, but it has a slow convergence problem because of a large number of zero coefficients. In order to improve the convergence performance, the step size of the LMS algorithm was modified from fixed to variable. However, this algorithm is still not suitable for the ANC system of a short acoustic duct since the reference signal is affected by the backward acoustic wave propagated from a secondary source. Therefore, the recursive filtered-u LMS algorithm(FU-LMS) based on infinite impulse response(IIR) is developed by considering the backward acoustic propagation. This algorithm, unfortunately, generally has a stability problem. The stability problem was improved by using an error smoothing filter. In this paper, the recursive LMS algorithm with variable step size and smoothing error filter is designed. This recursive LMS algorithm, called FU-VSSLMS algorithm, uses an IIR filter. With fast convergence and good stability, this algorithm is suitable for the ANC system in a short acoustic duct such as the intake system of an automotive. This algorithm is applied to the ANC system of a short acoustic duct. The disturbance signals used as primary noise source are a sinusoidal signal embedded in white noise and the chirp signal of which the instantaneous frequency is variable. Test results demonstrate that the FU-VSSLMS algorithm has superior convergence performance to the FX-LMS algorithm and FX-LMS algorithm. It is successfully applied to the ANC system in a short duct.

• Korean Journal of Acupuncture
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• 제26권3호
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• pp.27-42
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• 2009

Objectives : The vestibular system detects head movement and serve to regulate and maintain the equilibrium and orientation of the body. It is known that the vestibular imbalance leads to vestibular symptoms such as nausea, vomiting, vertigo and postural disturbance. The objectives of the present study were to examine a modification of the dynamic activities of medial vestibular nucleus (MVN) neurons following electroacupuncture (EA) of GB43 (Hyepgye). Methods : In Sprague-Dawley rats weighing $250{\sim}300g$, dynamic responses induced by sinusoidal whole body rotation about vertical axis at 0.2 Hz were observed in MVN of rats during EA of GB43 (Hyepgye) with 0.2 ms, 40 Hz and $600{\pm}200{\mu}A$. Also, expression of cFos protein was observed 2 hours after EA for 30 mins. Results : In dynamic response of vestibular neuron, the excitatory or inhibitory responses of gain were predominant in the ipsilateral MVN neurons during EA but not predominant in the contralateral MVN. Most neurons showing decreased gain were classified to inhibitory responses of spontaneous firing discharge during EA and ones showing increased gain were classified to excitatory response of spontaneous firing discharge during EA. Also, EA of the left GB43 (Hyepgye) for 30 mins produced the expression of cFos protein in MVN, inferior olive (IO) and solitary tract nuclei (SOL). Spatial expressions of cFos protein were predominant in the contralateral MVN, ipsilateral IO and bilateral SOL. Conclusion : These results suggest that the excitability of MVN neurons was influenced by EA of GB43 (Hyepgye) and EA may be related to the convergence on MVN.

• Korean Journal of Acupuncture
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• 제25권3호
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• pp.117-135
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• 2008

Objectives: It is known that the vestibular imbalance leads to vestibular symptoms such as nausea, vomiting, vertigo and postural disturbance. Since the non-labyrinthine inputs from the limbs and viscera converge on the vestibular nucleus neurons receiving signal from peripheral vestibular endorgan, acupuncture to the periphery may influence the activities of vestibular nuclear neurons and produce a therapeutic effect on the vestibulacr symptoms. The present study was to examine a modification and characteristics of the static and dynamic activities of medial vestibular nucleus (MVN) neurons following electroacupuncture (EA) of GB43' acupoint. Methods: In 54 Sprague-Dawley adult male rats weighing 250${\sim}$300g, spontaneous firing discharges and dynamic responses induced by sinusoidal whole body rotation about vertical axis at 0.2 Hz were observed in MVN of rats during EA of GB43' acupoint, located between the left 4th and 5th toe, which is the territory of sural and peroneal nerves, with 0.2 ms, 40 Hz and 600${\pm}$200 ${\mu}A$. Results: EA of the left GB43' acupoint induced modifications of spontaneous firing rates in 45% of MVN neurons recorded, and the percentage of modified neurons was 44% in type I, 52% in type II and 46% in non-type neurons. The excitatory or inhibitory responses of spontaneous firing discharges were predominant in the ipsilateral MVN neurons during EA. The excitatory response was abolished after EA but the inhibitory response was prolonged after EA in the ipsilateral MVN. The neurons of MVN showing modified spontaneous firing discharges by EA showed lower frequency (${\geq}$10 spikes/sec) of mean spontaneous firing rates than non affected ones. Conclusion: These results suggest that the neuronal activities of MVN neurons were influenced by EA of GB43' acupoint and the effects of EA may be related to the convergence of the peripheral vestibular inputs and ascending somatosensory inputs on MVN.