• 전력전자학회:학술대회논문집
• /
• 전력전자학회 2009년도 정기총회 및 추계학술대회 논문집
• /
• pp.209-211
• /
• 2009

A digital grid synchronization technique is needed for distributed generation system to make output current sinusoidal even if the grid voltage is distorted by harmonics. In this paper, a digital grid synchronization technique based on adaptive notch filter is proposed. The analysis of proposed technique is performed through the consideration of grid synchronization technique based on PLL and FLL, and the validity of the proposed method was confirmed by simulation results.

• 대한의용생체공학회:의공학회지
• /
• 제31권2호
• /
• pp.170-175
• /
• 2010

A method of measuring heart rate using photoplethysmograph(PPG) signal during exercise is proposed. PPG's are composed of strong base tones and their harmonics, and the strong base tones are trackable by the adaptive notch filter (ANF) which adjusts its coefficients to minimize the output power. The proposed heart rate measurement algorithm continuously notches the frequency component with the maximum power in the measured PPG, so that the fundamental frequency corresponding to heart rate is traced. We also presents methods of detecting degeneration and impulsive noise blocks to minimize the coefficient fluctuation. Experiments were conducted using real PPG signals captured during exercise. Results showed that the proposed algorithm is capable of consistently tracking the heart rate embedded in the noisy PPG's.

• Composites Research
• /
• 제14권1호
• /
• pp.39-46
• /
• 2001

본 논문에서는 신경망 제어기를 이용하여 복합재 보의 적응 다중 모드 진동 제어에 관한 실험적 연구를 수행하였다. 신경망 제어기는 계산량이 많기 때문에 실시간 적용에 어려움이 따른다. 본 논문에서는 진동 신호를 모드별로 분리하기 위한 적응 노치 필터를 제안하였다. 연결 강도의 개수가 적어서 계산량이 적은 두 개의 신경망 제어기를 이용하여 각 모드의 제어력을 계산하였다. 끝단 질량의 위치의 차이로 인해 고유 진동수가 다른 두 시편 A, B에 대하여 적응 노치 필터와 신경망 제어기를 이용한 적응 진동 제어를 수행한 결과, 두 경우 모두 효과적으로 진동 제어가 이루어졌다. 이러한 결과로 시스템 파라미터의 변환에 대한 신경망 제어기의 적응 진동 제어 성능을 확인할 수 있다.

• 제어로봇시스템학회:학술대회논문집
• /
• 제어로봇시스템학회 1997년도 한국자동제어학술회의논문집; 한국전력공사 서울연수원; 17-18 Oct. 1997
• /
• pp.321-324
• /
• 1997

In this paper, Active Noise Control(ANC) algorithm is proposed based on the estimated frequency estimator of the reference signal. The conventional feedforward ANC algorithms should measure the reference and use it to calculate the gradient of the squared error and filter coefficients. For ANC systems applied to aircrafts and passenger ships, engines from which reference signal is usually measured is so far from seats where main part of controller is placed that the scheme might be difficult to implement or very costly. Feedback ANC algorithm which doesn't need to measure the reference uses the error signal to update the filter and is sensitive to unexpected transient noise like a sneeze, clapping of hands and so on The proposed algorithm estimates frequencies of the desired signal in real time using adaptive notch filter. New frequency estimation algorithm is proposed with the improved convergence rate, threshold SNR and computational simplicity. Reference is not measured but created with the estimated frequencies. It has strong similarity to the conventional feedback control because reference is made from error signal. Enhanced error signal is used to update the controller for better performance under the measurement noise and impact noise. The proposed ANC algorithm is compared with the conventional feedback control.

• International Journal of Aeronautical and Space Sciences
• /
• 제13권4호
• /
• pp.491-498
• /
• 2012

A Ground Based Augmentation System (GBAS) is an enabling technology for an aircraft's precision approach based on a Global Navigation Satellite System (GNSS). However, GBAS is vulnerable to interference, so effective GNSS interference detection and mitigation methods need to be employed. In this paper, an intentional GNSS interference detection and characterization algorithm is proposed. The algorithm uses Automatic Gain Control (AGC) gain and adaptive notch filter parameters to classify types of incoming interference and to characterize them. The AGC gain and adaptive lattice IIR notch filter parameter values in GNSS receivers are examined according to interference types and power levels. Based on those data, the interference detection and characterization algorithm is developed and Monte Carlo simulations are carried out for performance analysis of the proposed method. Here, the proposed algorithm is used to detect and characterize single-tone continuous wave interference, swept continuous wave interference, and band-limited white Gaussian noise. The algorithm can be used for GNSS interference monitoring in an excessive Radio Frequency Interference environment which causes loss of receiver tracking. This interference detection and characterization algorithm will be used to enhance the interference mitigation algorithm.

• 한국소음진동공학회:학술대회논문집
• /
• 한국소음진동공학회 2000년도 추계학술대회논문집
• /
• pp.443-448
• /
• 2000

In this paper, we propose a novel adaptive feedforward controller for periodic disturbance and noise cancellation, with a frequency tracking capability. It can be added to an existing feedback control system without altering the original closed-loop characteristics, which is based on adaptive algorithm. We introduce novel algorithm "Constrained AFC(adaptive feedforward controller) algorithm" that increase the convergence region regardless of the delay in the closed loop system. In the algorithms, coefficients of the controller are adapted using the residuals of constrained structure which are defined in such a way that the coefficients become time invariant. The proposed algorithm not only estimate the magnitude and phase of the tonal disturbance and noise but also track the frequency of the tone, which changes in quasi-static manner. The frequency tracking algorithm uses the instantaneous frequency approach based on Hilbert transform. A number of computer simulations have been carried out in order to demonstrate the effectiveness of proposed method under various conditions.

• 대한의용생체공학회:의공학회지
• /
• 제25권4호
• /
• pp.315-321
• /
• 2004

본 연구에서는 다채널 디지털 보청기에서 적용될 수 있는 적응 궤환 제거 알고리즘을 제안하였다. 제안된 적응궤환 제거기는 궤환 검출을 위한 적응 노치 필터와 궤환 제거를 위한 NLMS (normalized least mean square) 적응필터로 구성되어 있다. 제안된 적응 궤환 제거 알고리즘을 다채널 보청 알고리듬과 결합하였다. 다채널 보청 알고리즘은 MDCT (modified discrete cosine transform) 필터뱅크를 이용하여 주파수 대역별 청력 손실을 보상하도록 구성하였다. 제안된 알고리즘을 포함한 완성된 보청 알고리즘의 성능을 컴퓨터 시뮬레이션을 통해 평가하였으며 상용 DSP보드를 이용하여 실시간 구현을 확인하였다.

• 한국음향학회:학술대회논문집
• /
• 한국음향학회 2001년도 추계학술발표대회 논문집 제20권 2호
• /
• pp.245-248
• /
• 2001

Howling을 억제하기 위하여 Howling의 원인인 피드백 신호를 적응 필터로 소거하는 방법이 연구되어왔다. 이 방법은 적응 필터로 피드백 경로의 전달함수를 추정하고, 입력 신호에서 피드백 신호를 소거하는 것이다. 그러나, Open-100p 이득이 평탄하고 시스템의 Group-delay가 짧은 Howling의 경우에는, 현재 다른 분야에서 사용되고 있는 Howling 억제 기법을 이용하는 것은 어렵다. 따라서, 본 연구에서는 적응 Notch 필터를 이용하여 Howling을 억제하는 방법을 제안, 평가하고, 또한, 이득 여유를 증가시키기 위한, Notch 필터의 설계 방법에 관해서 검토한 후, 시뮬레이션을 통해 그 타당성을 입증하고자 한다.

• 대한전자공학회:학술대회논문집
• /
• 대한전자공학회 2000년도 ITC-CSCC -2
• /
• pp.673-676
• /
• 2000

Adaptive Fourier analysis of sinusoidal signals in noise is of essential importance in many engineering fields. So far, many adaptive algorithms have been developed for this purpose. In particular, a filter bank based algorithm called constrained notch Fourier transform of its cost-efficiency and easily controllable performance. However, its performance deteriorates when the signal frequencies are not uniformly spaced. This paper proposes, at first, a new structure for the CNFT, referred to as modified CNFT (MCNFT), to compensate the performance degeneration of the CNFT for noisy sinusoidal signals with non-uniformly spaced frequencies. Next, a detailed performance analysis for the MCNFT is conducted. Closed form expression of steady-state mean square error (MSE) for the discrete Fourier coefficients (DFCs) is derived. Extensive simulations are presented to demonstrate the improved performance of the MCNFT and the validity of the analytical results.

• 한국전자파학회논문지
• /
• 제23권7호
• /
• pp.848-851
• /
• 2012

많은 레이다 시스템들이 주파수 밴드를 공유하여 동시에 운용될 때, 레이다 시스템 간 간섭은 불가피하게 발생한다. 간섭이 레이다 성능을 저하시킬 수 있기 때문에 간섭의 억제는 레이다 시스템에서 중요한 문제이다. 본 논문에서 STFT와 적응형 대역 저지 필터를 이용하여 간섭을 탐지하고 제거하는 방법을 제안하였다. 실제 FMCW 레이다를 이용하여 제안된 방법의 성능을 검증하였다.