• 전기학회논문지
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• 제58권4호
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• pp.679-687
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• 2009

In this paper, a subband filtering and adaptive prediction technique for analyzing harmonics in power systems is presented. In this method, the filter banks are designed to decompose odd and even order harmonics separately. The adaptive prediction has been employed reduce the transient and white noise effect in time varying harmonics detecting and tracking. The frequencies and amplitudes of the decomposed harmonics are estimated by recursive algorithm. To demonstrate the performances of the developed technique, computer simulations to the signal with the time-varying frequency and THD are carried out.

• 전력전자학회논문지
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• 제5권2호
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• pp.192-199
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• 2000

본 논문은 고주파 유도 가열기의 전력조절을 위해 뉴로-퍼지 알고리즘을 이용하고, IGBT를 사용한 위상 전이 펄스변조(PSPM)와 주파수 추종 펄스변조(FEPM) 가 조절되는 공진 고주파 인버터를 응용한 유도가열기를 설명한다. 이는 실제로 산업 현장에서 20KHz~500KHz 유도 가열 및 유도 용해 전원장치용으로 쓰인다. 위상 전이 펄스변조 (PSPM) 정전력 조절 기술을 바탕으로 한 적응 주파수 추종기법은 스위칭 손실을 최소화하고 전력조절을 용이하게 하기 위해 소개되어졌다. 뉴로-퍼지제어기를 사용하여 만들어진 실험장치는 성공적인 논증과 토의가 되어졌다.

• 대한전기학회:학술대회논문집
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• 대한전기학회 1993년도 하계학술대회 논문집 A
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• pp.456-459
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• 1993

A new filter-bank is proposed in order to track center frequency of narrow bard signal. The filter-bark proposed here has a laster and a slave filter bark. The two barks are connected in series-parallel. The master filter bank which is made of traditional filter bank detects the center frequency roughly. And the performance for tracking center frequency is greatly improved by the slave filter bank which is based or energy-difference estimator. Computer simulations show that it achieves a good tracking accuracy.

• Smart Structures and Systems
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• 제13권2호
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• pp.203-217
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• 2014

Due to the shift in paradigm from passive control to adaptive control, smart tuned mass dampers (STMDs) have received considerable attention for vibration control in tall buildings and bridges. STMDs are superior to tuned mass dampers (TMDs) in reducing the response of the primary structure. Unlike TMDs, STMDs are capable of accommodating the changes in primary structure properties, due to damage or deterioration, by tuning in real time based on a local feedback. In this paper, a novel adaptive-length pendulum (ALP) damper is developed and experimentally verified. Length of the pendulum is adjusted in real time using a shape memory alloy (SMA) wire actuator. This can be achieved in two ways i) by changing the amount of current in the SMA wire actuator or ii) by changing the effective length of current carrying SMA wire. Using an instantaneous frequency tracking algorithm, the dominant frequency of the structure can be tracked from a local feedback signal, then the length of pendulum is adjusted to match the dominant frequency. Effectiveness of the proposed ALP-STMD mechanism, combined with the STFT frequency tracking control algorithm, is verified experimentally on a prototype two-storey shear frame. It has been observed through experimental studies that the ALP-STMD absorbs most of the input energy associated in the vicinity of tuned frequency of the pendulum damper. The reduction of storey displacements up to 80 % when subjected to forced excitation (harmonic and chirp-signal) and a faster decay rate during free vibration is observed in the experiments.

• 한국생산제조학회지
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• 제23권2호
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• pp.157-163
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• 2014

In this paper, a robust MRAC (model reference adaptive control) scheme is applied to control an electrohydraulic positioning system under various loads. The inverse dead-zone compensator in the control system cancels out the dead-zone response, and an integrator added to the controller provides good position-tracking ability. LQG/LTR (linear quadratic Gaussian control with loop transfer recovery) closed-loop model is used as the reference model for learning the MRAC system. LQG/LTR provides a systematic technique to design the linear controller that optimizes the objective function using some compromise between the control effort and the system performance in the frequency domain. Different external load tests are performed to investigate the effectiveness of the designed MRAC system in real time. The experimental results show that the tracking performance of the proposed system is highly accurate, which offers considerable robustness even with a large change in the load.

• 제어로봇시스템학회:학술대회논문집
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• 제어로봇시스템학회 2001년도 ICCAS
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• pp.76.3-76
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• 2001

In this paper, an adaptive disturbance compensation technique is used in a tracking problem, under which the tracking reference is unknown. Based on a simple disturbance observer that effectively estimates the low frequency components of disturbance, the feedforward compensation is applied in addition to the conventional feedback control. Under the proposed compensation method, sensitivity analysis is given to illustrate the effectiveness. Finally, the proposed method is applied to the tracking problem in an optical storage system.

• 대한전자공학회논문지SP
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• 제41권3호
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• pp.231-238
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• 2004

주파수 영역에서의 적응 신호처리는 입력의 자기 상관 행렬에 이산 퓨리에 변환(DFT Discrete Fourier Transform)을 이용할 때 거의 대각선화 되는 특성으로 인해 시간영역 적응필터보다 주파수 영역 적응 필터가 빠르게 적응한다. 본 논문에서는 변형된 이산 퓨리에 변환(MDFT: modified DFT)을 이용하여 주파수 영역 적응 필터를 설계함으로써 안정한 수렴 속도를 갖는 잡음 제거 시스템을 제안한다. 제안한 구조는 MDFT를 이용하여 연산수를 최소화하며, 안정한 수렴을 유지하면서 블록 없는 처리를 할 수 있고, 최적의 수렴 속도를 위해 입력 자기 상관 행렬에 MDFT를 사용해 근사적으로 대각화 시키고 시간적으로 변하는 스텝 크기를 정규화 하는 고속 적응 잡음 제거(HANR: high speed adaptive noise reduction) 알고리즘이다. HANR 알고리즘을 적용한 필터는 DFT변환법을 사용한 LMS방법(non-proposed)보다 30%정도의 속도 개선이 있다.

• 제어로봇시스템학회:학술대회논문집
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• 제어로봇시스템학회 1996년도 한국자동제어학술회의논문집(국내학술편); 포항공과대학교, 포항; 24-26 Oct. 1996
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• pp.173-176
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• 1996

The transient behavior of the complex-LMS adaptive filter is studied when the adaptive filter is operating on a fixed or sweeping complex frequency sine-wave signal. The first-order difference equation is derived for the mean weights and its closed form solution is obtained. The transient response is represented as a function of the eigenvectors and eigenvalues of input correlation matrix. The mean-square error of the algorithm is evaluated as well. An optimal convergence parameter and filter length can be determined for sweeping frequency sine-wave signals as a function of frequency change rate and signal and noise powers.

• 한국정밀공학회지
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• 제19권12호
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• pp.57-63
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• 2002

In this paper, the feedforward control with least mean square (LMS) adaptive algorithm is proposed and examined to reduce rotating error by runout of an active magnetic bearing system. Using eddy-current type gap sensor fur control, the electrical runout caused by non-uniform material properties of sensor target produces rotational error amplified in feedback control loop, so this runout should be eliminated to increase rotating accuracy. The adaptive feedforward controller is designed and examined its tracking and stability performances numerically with established frequency response function. The tested grinding spindle system is manufactured with a 5.5 ㎾ internal motor and 5-axis active magnetic bearing system including 5 eddy current gap sensors which have approximately 15 ~ 30 ${\mu}{\textrm}{m}$ of electrical runout. According to the experimental analysis, the error signal in radial bearings is reduced to less than 5 ${\mu}{\textrm}{m}$ when it is rotating up to 50,000 rpm due to applying the feedforward control for first order harmonic frequency, and vibration of the spindle base is also reduced about same frequency.

• 한국정보통신학회:학술대회논문집
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• 한국해양정보통신학회 2001년도 추계종합학술대회
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• pp.226-229
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• 2001

전파신호의 추적은 국방을 비롯한 다양한 분야에서 여러 가지 기술 발전을 이루고 있다. 특히 시간의 경과에 따라 변경되는 PRI 및 주파수를 갖는 전파에 대해서는 Adaptable한 추적 능력을 필요로 한다. 본 논문에서는 다양하게 변하는 PRI 및 주파수 변경 신호들에 대해 지능적으로 적응해 가면서 추적할 수 있는 추적 방식을 제안하고 이를 실험하였다. 제안된 방식은 신경회로망의 오차 역전과 알고리즘을 이용한 방법으로, 모의 전파 신호를 시간 구간으로 나누어 학습하였고 이에 대한 성능 테스트를 한 결과 제안된 방법이 전파 신호를 효율적으로 추적할 수 있음을 확인하였다.