Adaptive Notch Filter Research Articles

Adaptive Notch Filter Based Active Damping Control for Grid-Connected Inverter

The LCL filter is widely applied as interface between grid-connected inverter and grid due to the preferable high frequency attenuation characteristic. Under the condition of weak grid, impedance value of grid model cannot be ignored, the existence of grid impedance results in different LCL resonant frequencies, which will arise challenges of traditional active damping control. Based on the analysis of band pass filter using active damping control strategy, an adaptive active damping control is proposed in this paper by introducing the application of active notch filter, which can adjust the position of negative resonance point adaptively so as to manage sudden grid changes. Theoretical analysis and simulation results presented on the platform of grid-connected PV inverter system indicate the effectiveness and adaptability of this active damping strategy.

Self-tuning adaptive frequency tracker

An automatic gain tuning algorithm is proposed for a recently introduced adaptive notch filter. Theoretical analysis and simulations show that, under Gaussian random-walk type assumptions, the proposed extension is capable of adjusting adaptation gains of the filter so as to minimize the mean-squared frequency tracking error without prior knowledge of the true frequency trajectory. A simplified one degree of freedom version of the filter, recommended for practical applications, is proposed as well.

Steady-state analysis of a complex adaptive notch filter using modified gradient algorithm

Based on power spectral density (PSD) analytical technique, mean square error (MSE) (or variance) of the frequency estimate of a first-order complex adaptive IIR notch filter (ANF) using modified complex plain gradient (MCPG) algorithm is investigated in this paper. The steady-state expression for MSE is derived in closed form. A quantitative analysis for the estimation MSE has been carried out. It has been revealed that the MSE of frequency estimate is independent of an input frequency of a complex sinusoid. In addition, computer simulations are treated to corroborate the theoretical analysis and the relationships between MSE and system parameters are shown.

Adaptive Compensation Method of Position Estimation Harmonic Error for EMF-Based Observer in Sensorless IPMSM Drives

To improve the performance of sensorless interior permanent magnet synchronous motor (IPMSM) drives, a quadrature phase-locked loop (PLL) with an adaptive notch filter (ANF) is proposed for the model-based sliding-mode observer (SMO). The position estimation error with the sixth harmonic distortion caused by the inverter nonlinearity and the flux spatial harmonics is analyzed. The ANF based on adaptive noise canceling principle combined with the quadrature PLL is proposed to diminish the estimation harmonic error. This method can adaptively compensate the harmonics in the estimated electromotive force to eliminate the corresponding position estimation error. The estimated harmonic coefficients from the ANF can be continuously self-tuned using the least-mean-squares algorithm according to the estimated position information. The effectiveness of the proposed method is verified with the experimental results at a 2.2-kW IPMSM sensorless drive.

Low Complexity Adaptive Noise Canceller for Mobile Phones Based Remote Health Monitoring

Mobile phones are gaining acceptance to become an effective tool for remote health monitoring. On one hand, during electrocardiographic (ECG) recording, the presence of various forms of noise is inevitable. On the other hand, algorithms for adaptive noise cancellation must be shared by limited computational power offered by the mobile phones. This paper describes a new adaptive noise canceller scheme, with low computational complexity, for simultaneous cancellation of various forms of noise in ECG signal. The proposed scheme is comprised of two stages. The first stage uses an adaptive notch filters, which are used to eliminate power-line interference from the primary and reference input signals, whereas the other noises are reduced using modified LMS algorithm in the second stage. Low power consumption and lower silicon area are key issues in mobile phones based adaptive noise cancellation. The reduction in complexity is obtained by using log-log LMS algorithm for updating adaptive filters in the proposed scheme. A comprehensive complexity and performance analysis between the proposed and traditional schemes are provided. DOI: http://dx.doi.org/10.11591/ijece.v4i3.5534

A novel time varying signal processing method for Coriolis mass flowmeter

The precision of frequency tracking method and phase difference calculation method affects the measurement precision of Coriolis Mass Flowmeter directly. To improve the accuracy of the mass flowrate, a novel signal processing method for Coriolis Mass Flowmeter is proposed for this time varying signal, which is comprised of a modified adaptive lattice notch filter and a revised sliding recursive discrete-time Fourier transform algorithm. The method cannot only track the change of frequency continuously, but also ensure the calculation accuracy when measuring phase difference. The computational load of the proposed method is small with higher accuracy. Simulation and experiment results show that the proposed method is effective.

PERIODIC IMPULSIVE NOISE REDUCTION IN OFDM BASED POWER LINE COMMUNICATION

Different communication technologies are used for the transmission of information such as wireless communication, satellite communication etc. Power Line Communication (PLC) is one of the technologies using existing power cables for the transmission of information. Power cables are not designed for data transmission. So the PLC environment contains different types of noise. This paper presents a novel approach for removing periodic impulsive noise from OFDM based power line communication system. The noise is detected using periodic impulsive noise detection algorithm and the noise is filtered by using adaptive notch filter. An adaptive filter using LMS algorithm is also designed to suppress periodic impulsive noise. Then compare the Bit Error Rate (BER) of PLC system without noise filtering, with noise filtering using notch filter and with noise filtering using adaptive filtering based on LMS algorithm. Results show that the received data is same as that of input data which is transmitted. Simulation results shows that PLC system after noise filtering gives better results than PLC system without noise filtering.

A Robust Frequency Sampling Adaptive Notch Filter for Broadband Signals

SUMMARYAn adaptive notch filter composed of an exponential type all‐pass circuit has stable and the robust characteristics for broadband signals. In this paper, we propose a method of reducing the number of adaptive parameters and the adaptive algorithm using a frequency sampling adaptive filter with reduction of the phase shift samples. It is shown that a reduction of an order of magnitude or more is possible by use of the properties of a notch filter with small bandwidth.

Study on the Nonstationary jammer Suppression for DSSS Receiver

Using TVAR(Time Varying AR) model and adaptive notch filter is a new method for the non-stationary jammer suppression in DSSS(Direct Sequence Spread Spectrum). The performance of TVAR model for IF (Instantaneous Frequency) estimation will be affected by some factors such as basis functions. The DSSS (Direct Sequence Spread Spectrum) is sensitive to non-stationary jammer, especially the LFM (Frequency Modulation) jammer. Focusing on this problem, the optimal basis function of TVAR model for the IF estimation of the LFM signal is obtained in this paper. Besides the depth and width of notching, the phase properties of notch filter affect the SINR of correlation output to the narrow band jammer suppression in DSSS, in response to the problem the closed solution of correlation output SINR improvement has been derived when a single frequency jammer passes through direct IIR notch filter, and its performance has been compared with those of five coefficient FIR filters. Later, a novel method for LFM jammer suppression based on Fourier basis TVAR model and direct IIR notch filter is proposed. The simulation results show the effectiveness of the proposed method. DOI : http://dx.doi.org/10.11591/telkomnika.v12i4.4733

A fast, robust algorithm for power line interference cancellation in neural recording

Objective. Power line interference may severely corrupt neural recordings at 50/60 Hz and harmonic frequencies. The interference is usually non-stationary and can vary in frequency, amplitude and phase. To retrieve the gamma-band oscillations at the contaminated frequencies, it is desired to remove the interference without compromising the actual neural signals at the interference frequency bands. In this paper, we present a robust and computationally efficient algorithm for removing power line interference from neural recordings. Approach. The algorithm includes four steps. First, an adaptive notch filter is used to estimate the fundamental frequency of the interference. Subsequently, based on the estimated frequency, harmonics are generated by using discrete-time oscillators, and then the amplitude and phase of each harmonic are estimated by using a modified recursive least squares algorithm. Finally, the estimated interference is subtracted from the recorded data. Main results. The algorithm does not require any reference signal, and can track the frequency, phase and amplitude of each harmonic. When benchmarked with other popular approaches, our algorithm performs better in terms of noise immunity, convergence speed and output signal-to-noise ratio (SNR). While minimally affecting the signal bands of interest, the algorithm consistently yields fast convergence (<100 ms) and substantial interference rejection (output SNR >30 dB) in different conditions of interference strengths (input SNR from −30 to 30 dB), power line frequencies (45–65 Hz) and phase and amplitude drifts. In addition, the algorithm features a straightforward parameter adjustment since the parameters are independent of the input SNR, input signal power and the sampling rate. A hardware prototype was fabricated in a 65 nm CMOS process and tested. Software implementation of the algorithm has been made available for open access at https://github.com/mrezak/removePLI. Significance. The proposed algorithm features a highly robust operation, fast adaptation to interference variations, significant SNR improvement, low computational complexity and memory requirement and straightforward parameter adjustment. These features render the algorithm suitable for wearable and implantable sensor applications, where reliable and real-time cancellation of the interference is desired.

Diagnosis of broken rotor bars in induction motors based on harmonic analysis of fault components using modified adaptive notch filter and discrete wavelet transform

This paper proposes a method for fast and accurate detection of broken rotor bars (BRBs) in a three-phase squirrel cage induction motor. The fundamental component of the stator current signal is extracted using a linear time-invariant filter. The resultant residual signal which contains the harmonic components of the current is then used to detect the BRBs, by means of discrete wavelet transform (DWT). Since in experiment it is not possible to break the rotor bars while the motor is under load, finite element method and MATLAB/Simulink are employed to accurately demonstrate the behavior of the running machine as the BRB happens. To get more accuracy, differential evolution (DE) optimization algorithm is used to obtain the corresponding fault impedance for the rotor external circuit of the MATLAB model. Detail coefficients (DCs) of the wavelet decomposition are employed as the new fault indicators. Simulation results show that using DCs of the harmonic component signal rather than the actual current signal, leads to more distinctive fault signatures in the wavelet decomposition. The obtained results suggest that the proposed fault detection scheme can be employed as a highly reliable technique for diagnosing rotor bar failures in running machines.

Indirect Adaptive Attenuation of Multiple Narrow-Band Disturbances Applied to Active Vibration Control

In this brief, an indirect adaptive control methodology for attenuation of multiple unknown time varying narrow-band disturbances is proposed. This method is based on the real time estimation of the frequency of narrow-band disturbances using adaptive notch filters followed by the design of a controller using adjustable band-stop filters for the appropriate shaping of the output sensitivity function. A Youla-Kučera parametrization of the controller is used for reducing the computation load. This approach is compared on an active vibration control system with the direct adaptive control scheme based on the internal model principle proposed. Real time experimental results are provided.

CMF Signal Processing Method Based on Feedback Corrected ANF and Hilbert Transformation

Abstract In this paper, we focus on CMF signal processing and aim to resolve the problems of precision sharp-decline occurrence when using adaptive notch filters (ANFs) for tracking the signal frequency for a long time and phase difference calculation depending on frequency by the sliding Goertzel algorithm (SGA) or the recursive DTFT algorithm with negative frequency contribution. A novel method is proposed based on feedback corrected ANF and Hilbert transformation. We design an index to evaluate whether the ANF loses the signal frequency or not, according to the correlation between the output and input signals. If the signal frequency is lost, the ANF parameters will be adjusted duly. At the same time, singular value decomposition (SVD) algorithm is introduced to reduce noise. And then, phase difference between the two signals is detected through trigonometry and Hilbert transformation. With the frequency and phase difference obtained, time interval of the two signals is calculated. Accordingly, the mass flow rate is derived. Simulation and experimental results show that the proposed method always preserves a constant high precision of frequency tracking and a better performance of phase difference measurement compared with the SGA or the recursive DTFT algorithm with negative frequency contribution

Real-time estimation of respiratory rate from a photoplethysmogram using an adaptive lattice notch filter

BackgroundMany researchers have attempted to acquire respiratory rate (RR) information from a photoplethysmogram (PPG) because respiration affects the waveform of the PPG. However, most of these methods were difficult to operate in real-time because of their complexity or computational requirements. From these needs, we attempted to develop a method to estimate RR from a PPG with a light computational burden.MethodsTo obtain RR information, we adopt a sequential filtering structure and frequency estimation technique, which extracts a dominant frequency from a given signal. In particular, we used an adaptive lattice notch filter (ALNF) to estimate RR from a PPG along with an additional heart rate that is utilized as an adaptation parameter of our method. Furthermore, we designed a sequential infinite impulse response (IIR) notch filtering system (i.e., harmonic IIR notch filter) to eliminate the cardiac component and its harmonics from the PPG. We compared the proposed method with Burg’s AR modeling method, which is widely used to estimate RR from a PPG, using open-source data and measured data.ResultsBy using a statistical test, it was determined that our adaptive lattice-type respiratory rate estimator (ALRE) was significantly more accurate than Burg’s AR model method (p <0.0001). Furthermore, the ALRE’s tracking performance was better than that of Burg’s method, and the variances of its estimates were smaller than those of Burg’s method.ConclusionsIn short, our method showed a better performance than Burg’s AR modeling method for real-time applications.

PLL Based Digital Adaptive Filter for Detecting Interharmonics

Studies on the PLL (phase locked loop) based interharmonic measurements have been considerably increased recently. The method proposed in this study is a hybrid method based on the frequency analysis. The proposed method presents solutions for the leading problems about the interharmonic measurement, such as fundamental frequency shifting, spectral leakage, and picket-fence effect, using digital PLL and adaptive notch filter. In addition, a new approach is presented to solve the multizero crossing problem encountered in the analysis of the harmonic-interharmonic. Both simulative and field data tests have been performed to verify the effectiveness of the proposed method.

光雷一体化测量系统的谐振特性及组合补偿

To overcome the adverse effect of complicated resonant vibration resulting from the OE-radar integrative measuring system on a servo unit, a hybrid compensating method combined an adaptive notch filter and the feedback of observer filtering was proposed to restrain the resonant vibration. Firstly, the resonant characteristics of the system were analyzed according to the mechanical structure and tested frequency properties. It indicates that there are three kinds of primary resonant modes in the system, which is the radar antenna resonance, radar cabin resonance and the antenna high-order and bearing coupling resonance. The rule of resonant characteristics varying with an elevation angle was also obtained. Then, a compensating method to the complicated resonant vibration was discussed. The adaptive notch filter in series was applied to compensation of the radar antenna resonance and the radar cabin resonance, and the feedback of the Kalman observer filtering was used to restrain the antenna high-order and bearing coupling resonance. Experimental results indicate that all kinds of resonances are restrained effectively by the hybrid compensating method, the velocity close-loop bandwidth of servo unit is up to 115 rad/s, and the transient time of step response is 0.35 s. The method proposed can satisfy the system requirements for high bandwidth and stabilization.

A Novel Grid Synchronization PLL Method Based on Adaptive Low-Pass Notch Filter for Grid-Connected PCS

The amount of distributed energy resources (DERs) has increased constantly worldwide. The power ratings of DERs have become considerably high, as required by the new grid code requirement. To follow the grid code and optimize the function of grid-connected inverters based on DERs, a phase-locked loop (PLL) is essential for detecting the grid phase angle accurately when the grid voltage is polluted by harmonics and imbalance. This paper proposes a novel low-pass notch filter PLL (LPN-PLL) control strategy to synchronize with the true phase angle of the grid instead of using a conventional synchronous reference frame PLL (SRF-PLL), which requires a d-q-axis transformation of three-phase voltage and a proportional-integral controller. The proposed LPN-PLL is an upgraded version of the PLL method using the fast Fourier transform concept (FFT-PLL) which is robust to the harmonics and imbalance of the grid voltage. The proposed PLL algorithm was compared with conventional SRF-PLL and FFT-PLL and was implemented digitally using a digital signal processor TMS320F28335. A 10-kW three-phase grid-connected inverter was set, and a verification experiment was performed, showing the high performance and robustness of the proposal under low-voltage ride-through operation.

High Accuracy Attitude Control System Design for Satellite with Flexible Appendages

In order to realize the high accuracy attitude control of satellite with flexible appendages, attitude control system consisting of the controller and structural filter was designed. When the low order vibration frequency of flexible appendages is approximating the bandwidth of attitude control system, the vibration signal will enter the control system through measurement device to bring impact on the accuracy or even the stability. In order to reduce the impact of vibration of appendages on the attitude control system, the structural filter is designed in terms of rejecting the vibration of flexible appendages. Considering the potential problem of in-orbit frequency variation of the flexible appendages, the design method for the adaptive notch filter is proposed based on the in-orbit identification technology. Finally, the simulation results are given to demonstrate the feasibility and effectiveness of the proposed design techniques.

A novel adaptive Gaussian restoration filter for reducing periodic noises in digital image

Digital images can suffer from periodic noise, resulting in the appearance of repetitive patterns on the image data and quality degradation. In order to effectively reduce the periodic noise effects, a novel adaptive Gaussian notch filter is proposed in this paper. In the presented method, the frequency regions that correspond to noise are determined by applying a segmentation algorithm on the spectral band of the noisy image using an adaptive threshold. Then, a region growing algorithm tries to determine the bandwidth of each periodic noise component separately. Subsequently, proper Gaussian notch filters are used to decrease the periodic noises only at the contaminated noise frequencies. The proposed filter and some other well-known filters including the frequency domain mean and median filters and also the traditional Gaussian notch filter are compared to evaluate the effectiveness of the approach. The results in different conditions show that the proposed filter gains higher performance both visually and quantitatively with lower computational cost. Furthermore, compared with the other methods, the proposed filter does not need any tuning and parameter adjustments.

Front-End Narrowband Interference Mitigation for DS-UWB Receiver

Narrow band interference (NBI) suppression is one of major issues for ultra wideband (UWB) wireless communication system operating over huge spectrum occupied by narrow band wireless systems. In this paper, we propose an interference mitigation scheme based on complex-valued adaptive notch filter, which smartly exploits the substantial correlation difference of signals and removes the NBIs in UWB signal with noise by estimating the corresponding central frequencies. To obtain high speed convergence and maintain small signal distortion, a low complexity gradient algorithm for one-order basic adaptive notch filter cell is deduced. Considering that the data rate prior to despreading is extremely high, a novel time-division multiplexing (TDM) parallel approach for eliminating a single NBI is presented, which effectively simplify the hardware design especially in high speed digital signal processing. Based on the one-order basic adaptive notch filter cell, three different implementations including direct forms, linear cascade forms and TDM parallel cascade forms to eliminate multiple NBIs are developed and discussed. Theoretical analysis and simulation results indicate that the proposed scheme possesses the advantages of high convergence speed, small distortion and high stability. Furthermore, the propose scheme utilized as a preprocessing unit prior to despreading can considerably improve the interference tolerance margin of UWB systems, leading to it's suitable for the low complexity direct sequence (DS)-UWB receiver.