Adaptive Notch Filter Research Articles

A Complex Adaptive Notch Filter

A complex adaptive notch filter is developed, for tracking single-sided (a.k.a. analytic or complex) tones immersed in background noise. A complex all-pass based realization is pursued which inherits useful properties from its real counterpart: independent tuning of the notch frequency and attenuation bandwidth, easy realization of the complementary band-pass filter, unbiased frequency estimation, and faster convergence and tracking than a gradient descent algorithm.

Time-varying AR modeling and adaptive IIR notch filter for anti-jamming DSSS receiver

Using Time-Varying AR (TVAR) model and adaptive notch filter is a new method for the non-stationary jammer suppression in Direct Sequence Spread Spectrum (DSSS). The performance of TVAR model for Instantaneous Frequency (IF) estimation will be affected by some factors such as basis functions. 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 Signal-to-Interference plus-Noise Ratio (SINR) of correlation output to the narrowband 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.

Robust Adaptive Frequency Estimation of Three-Phase Power Systems

An algorithm based on the concept of an adaptive notch filter is proposed for the frequency estimation of three-phase power signals. The algorithm permits direct estimation of frequency and its rate of change for power system signals. The proposed method uses the information of all three-phase signals together. The structure, mathematical formulation, and theoretical stability analysis of the proposed technique are presented, and its performance is studied in a variety of scenarios where three-phase power signal attributes such as frequency and amplitude undergo variations over time. This study confirms the desirable transient and steady-state performances of the proposed algorithm. In contrast to the conventional three-phase PLL-based frequency estimator, the proposed method is less sensitive to distortions such as harmonics and interharmonics and is not sensitive to unbalanced system conditions.

An Adjustable Model Reference Adaptive Control for a Flexible Launch Vehicle

Flexibility and aeroelastic behaviors in large space structures can lead to degradation of control system stability and performance. The model reference adaptive notch filter is an effective methodology used and implemented for reducing such effects. In this approach, designing a model reference for adaptive control algorithm in a flight device such as a launch vehicle is very important. In this way, the vibrations resulting from the structure flexibility mostly affects the pitch channel, and its influences on the yaw channel are negligible. This property is used and also the symmetrical behavior of the yaw and pitch channels. In this paper, by using this property and also the symmetrical behavior of the yaw and pitch channels, a new model reference using identification on the yaw channel is proposed. This model behaves very similar to the rigid body dynamic of the pitch channel and can be used as a model reference to control the vibrational effects. Simulation results illustrated applies the proposed algorithm and considerably reduces the vibrations in the pitch channel. Moreover, the main advantage of this new method is the online tuning of the model reference against unforeseen variations in the parameters of the rigid launch vehicle, which has not been considered in the previous works. Finally, robustness of the new control system in the presence of asymmetric behavior is investigated.

A Shunt Power Conditioner Operated by a Simplified Version of the Gauss-Newton Algorithm

This paper introduces a developed simplified version for the recursive Gauss-Newton algorithm for extraction and mitigation of the stationary current quality problems such as current harmonics and current fluctuation. Adaptive notch filters are newly utilized for supplying the Gauss-Newton algorithm with the required values of frequencies for current disturbances such as non-characteristic harmonics, inter-harmonics and sub-harmonics. Also, this paper exhibits the mitigation results for current harmonics and fluctuation problems by using a shunt power conditioner. Moreover, in this paper the ramp-comparison current controller, linear current controller, is employed to operate the mitigation device. The effectiveness of the developed extraction technique associated with the employed current controller for the shunt power conditioner is verified by simulation results using MATLAB/SIMULINK.

A Synchronization Design for UWB-Based Wireless Multimedia Systems

Multi-band orthogonal frequency-division multiplexing (MB-OFDM) ultra-wideband (UWB) technology offers large throughput, low latency and has been adopted in wireless audio/video (AV) network products. The complexity and power consumption, however, are still major hurdles for the technology to be widely adopted. In this paper, we propose a unified synchronizer design targeted for MB-OFDM transceiver that achieves high performance with low implementation complexity. The key component of the proposed synchronizer is a parallel auto-correlator structure in which multiple ACF units are instantiated and their outputs are shared by functional blocks in the synchronizer, including preamble signal detection, time-frequency code identification, symbol timing, carrier frequency offset estimation and frame synchronization. This common structure not only reduces the hardware cost but also minimizes the number of operations in the functional blocks in the synchronizer as the results of a large portion of computation can be shared among different functional blocks. To mitigate the effect of narrowband interference (NBI) on UWB systems, we also propose a low-complexity ACF-based frequency detector to facilitate the design of (adaptive) notch filter in analog/digital domain. The theoretical analysis and simulation show that the performance of the proposed design is close to optimal, while the complexity is significantly reduced compared to existing work.

A study on adaptive notch filter using exponential all‐pass transfer function

AbstractWe propose an adaptive notch filter that realizes the phase shift of the all‐pass filter by the expression of Fourier sine series. The method of controlling the weights of the all‐pass filter formed by IIR filters is well known. However, these adaptive notch filters have not been put to practical use due to the peculiar stability problems of IIR filters and the problem of determining the degree of the IIR filter. The proposed adaptive notch filter is always stable since the all‐pass filter is formed by exponential filters. Furthermore, the adaptive algorithm is a simple gradient‐based algorithm and convergence of weights is guaranteed. The degree of the all‐pass filter depends only on the required steepness of the elimination characteristic and does not depend on the number of narrowband signals that are to be eliminated. Furthermore, the proposed method is suitable for practical use because the elimination characteristic is hardly influenced by a broadband signal added to the narrowband signal. The analytical results and a rigorous verification of the above features by computer simulation are presented. © 2010 Wiley Periodicals, Inc. Electron Comm Jpn, 93(5): 8–14, 2010; Published online in Wiley InterScience (www.interscience.wiley.com). DOI 10.1002/ecj.10256

Processing of Harmonics and Interharmonics Using an Adaptive Notch Filter

A method for real-time detection and extraction of individual harmonic and interharmonic components in a power signal with potentially time-varying characteristics is presented. The proposed method, which is based on the concept of adaptive notch filter (ANF), adaptively decomposes the measured power signal into its constituting components independent of where their frequencies are located. The algorithm provides instantaneous values of the various estimated frequency components in addition to the values of their frequencies, amplitudes, and phase angles. The structure and mathematical formulation of the proposed technique, including guidelines for its parameter tuning, are presented and its performance is studied in a variety of scenarios where the power signal attributes, such as fundamental frequency and amplitude, undergo variations over time. This study confirms the desirable transient and steady-state performances of the proposed method. Compared with its recently proposed counterpart, the proposed method of this paper obviates the need for using a phase-locked loop (PLL), and hence, offers a more simplified structure which makes it more attractive from an implementation point of view.

Unbiased plain gradient algorithm for a second-order adaptive IIR notch filter with constrained poles and zeros

This article proposes an unbiased plain gradient algorithm for a second-order adaptive IIR notch filter with constrained poles and zeros. The proposed algorithm employs removing a dominant parameter that produces inherent bias. By using this technique, the performances are improved with slight expense in computational complexity. In this paper, theoretical analysis for deriving the estimations of bias and mean square error (MSE) at steady state are presented in closed form. Moreover, the stability bound of the algorithm is also derived. To confirm the analytical results, the computer simulations are provided to corroborate the effectiveness of the proposed algorithm. Furthermore, the performances of the algorithm are also compared with the plain gradient (PG) and modified plain gradient (MPG) algorithms.

Selective Compensation Strategies for the 3-phase Cascaded Multilevel Active Power Filter using ANF-based Sequence Decoupling Scheme

A new control strategy for the 3-phase multilevel cascaded H-bridge (CHB) active power filter is presented. The selective compensation of load side reactive and harmonic components is adopted to reduce the current controller bandwidth. The adaptive notch filters (ANFs) are utilized at the d-axis and q-axis of the load side currents to extract the positive- and negative-sequence components of individual harmonic component. The theoretical derivations of the ANF-based sequence decoupling scheme is outlined, followed by the design issues of the current regulators and the dc-link voltage controllers. Simulation results under balanced and unbalanced load conditions with transient load disturbances are presented for verification. The validity of the proposed control scheme is validated by the simulation results. Ill. 10, bibl. 11 (in English; summaries in English, Russian and Lithuanian).

New Coning Error Compensation Method Using Direct Signal Estimation

AbstractThis paper proposes new coning mitigation algorithm based on the signal processing technique. For accurate attitude calculation of inertial navigation system, the coning error mitigation is a key part of attitude computation. Many researchers have used gyro outputs to calculate higher-order correction terms. But these results have a performance limit because they assume the signals to be polynomials. The proposed algorithm detects and estimates the sinusoidal components from gyro measurements. If coning signals occur in gyro measurements, a sinusoidal signal can be estimated using adaptive notch filtering, and higher-order correction terms can be calculated from parameters of this estimated signal. The proposed algorithm can properly operate on a vehicle with continuous and steady oscillations. Simulation results show that the direct compensation algorithm worked efffectively.

Unbalance Vibration Control and Experiment Research of Magnetically Suspended Flywheels

Rotor imbalance can lead to synchronous disturbances of magnetically suspended flywheel (MSFW),and reduce the attitude control accuracy and the load accuracy of spacecrafts.An open-loop bearing force compensation method is proposed to attenuate the unbalance vibration.The control goal is to inhibit the synchronous section of bearing forces,the dynamics of rotor is set up,and the characters of rigid rotor imbalance are analyzed.A displacement stiffness force compensation mechanism and two switches for open and closed loop control and displacement stiffness force compensation control are added to the adaptive notch filter to inhibit the unbalance vibration of bearing forces.The method is suitable for the MSFW property of crossing critical speed frequently,especially for magnetically suspended reaction wheel (MSRW).Simulation and experiment results demonstrate that the method has good inhibitory effect on the unbalance vibration of flywheel rotor in the whole speed range.

Acceleration Harmonic Cancellation of Electro-hydraulic Servo Shaking Table

Nonlinearities are inherent in electro-hydraulic servo shaking table. Some nonlinearities are dead zone of servo valve, backlash and friction between joints, and friction in hydraulic cylinder. Nonlinearities cause harmonic distortion of the output acceleration signal corresponding to a sinusoidal input. On the basis of extensive studies on literature related to dead zone, backlash and friction compensation scheme, an adaptive harmonic suppression strategy based on adaptive notch filter technology is proposed. The task is accomplished by generating reference signals with frequency to be suppressed from the output. According to the error between the input acceleration and the feedback acceleration, the weights of filter are adjusted on-line by least mean square adaptive filtering algorithm in real-time. The reference inputs are weighted by the adaptive filter in such a way that it closely matches the harmonic. The output of the adaptive filter is a harmonic replica and is injected to the fundamental signal such that the output harmonic is suppressed, and the total harmonic distortion is greatly reduced. The above course is used as a basis for the development of adaptive harmonic cancellation algorithm.

Novel adaptive IIR filter for frequency estimation and tracking [DSP Tips&Tricks

In many applications, a sinusoidal signal may be subjected to nonlinear effects in which possible harmonic frequency components are generated. In such an environment, we may want to estimate (track) the signal's fundamental frequency as well as any harmonic frequencies. Using a secondorder notch filter to estimate fundamental and harmonic frequencies is insufficient since it only accommodates one frequency component. On the other hand, applying a higher-order infinite impulse response (IIR) notch filter may not be efficient due to adopting multiple adaptive filter coefficients. In this article, we present a novel adaptive harmonic IIR notch filter with a single adaptive coefficient to efficiently perform frequency estimation and tracking in a harmonic frequency environment. Furthermore, we devise a simple scheme to select the initial filter coefficient to insure algorithm convergence to its global minimum error.

ADAPTIVE FREQUENCY ESTIMATION WITH LOW SAMPLING RATES BASED ON ROBUST CHINESE REMAINDER THEOREM AND IIR NOTCH FILTER

In this paper, based on an adaptive IIR notch filter and a robust Chinese remainder theorem (CRT), we propose an adaptive frequency estimation algorithm from multiple undersampled sinusoidal signals. Our proposed algorithm can significantly reduce the sampling rates and provide more accurate estimates than the method based on adaptive IIR notch filter and sampling rates above the Nyquist rates does. We then present simulation results to verify the performance of our proposed algorithm for both stationary and nonstationary signals.

Adaptive Compensation for Reaction Force With Frequency Variation in Shaking Table Systems

This paper presents an adaptive control methodology of a shaking table system for earthquake simulators. In the system, reaction forces generated by a specimen deteriorate the table motion performance, resulting in lower control accuracy in seismic tests. In particular, in cases of excitation tests for structures (power facilities, large vehicles, etc.) including motors with periodic rotation, the reaction force as a disturbance is excited with a specific frequency during their actual operations. In addition, the variation of the rotational frequency in the motor causes the variation of frequency in the disturbance. In order to compensate for the disturbance, therefore, an adaptive feedback compensator is designed to improve the disturbance suppression capability, by applying an adaptive notch filter to identify the frequency in an online manner. The proposed control approach has been verified by experiments using a prototype of a shaking table system.

Current Harmonic Compensation by a Single-Phase Shunt Active Power Filter Controlled by Adaptive Neural Filtering

This paper presents a single-phase shunt active power filter (APF) for current harmonic compensation based on neural filtering. The shunt active filter, realized by a current-controlled inverter, has been used to compensate a nonlinear current load by receiving its reference from a neural adaptive notch filter. This is a recursive notch filter for the fundamental grid frequency (50 Hz) and is based on the use of a linear adaptive neuron (ADALINE). The filter's parameters are made adaptive with respect to the grid frequency fluctuations. A phase-locked loop system is used to extract the fundamental component from the coupling point voltage and to estimate the actual grid frequency. The current control of the inverter has been performed by a multiresonant controller. The estimated grid frequency is fed to the neural adaptive filter and to the multiresonant controller. In this way, the inverter creates a current equal in amplitude and opposite in sign to the load harmonic current, thus producing an almost sinusoidal grid current. An automatic tuning of the multiresonant controller is implemented, which recognizes the largest three harmonics of the load current to be compensated by the APF. The stability analysis of the proposed control system is shown. The methodology has been applied in numerical simulations and experimentally to a properly devised test setup, also in comparison with the classic sinusoidal current control based on the P-Q theory.

Deployable space structure control using adaptive predictive controller with notch filter

The present study addresses the adaptive predictive controller with adaptive notch filter for the tip position control of a deployable space structure model. An adaptive notch filter is designed to estimate multiple bending mode frequencies of the deployable manipulator and to minimize the effect of bending vibration. The results show that the adaptive predictive controller with adaptive notch filter is quite effective controlling the tip position of a deployable space structure under poor modeling information.

Adaptive Mode-Suppression and Disturbance-Rejection Scheme With Application to Disk Drives

The goal of a track-following controller for a disk drive is to maintain as close to perfect tracking as possible. Better tracking allows for more data to be stored on a single disk. There are several factors which make this control problem difficult, such as high-frequency resonant modes, unknown disturbances, and a preset sampling rate. The resonant modes of a disk drive are often uncertain and vary between units and can also lie near or beyond the Nyquist frequency. Suppressing these modes can be difficult. However, a multirate adaptive notch filter and adaptive bandwidth controller is proposed to suppress these resonant modes. A robust online estimator that estimates the mode frequencies is used to allow the multirate adaptive notch filter to track the disk drive's modes. By adding a multirate scheme to the adaptive notch filter, it can suppress modes at higher frequencies, which are close to or beyond the Nyquist frequency of the preset sampling rate. As the multirate adaptive notch filter tracks the plant mode frequencies, the adaptive bandwidth controller ensures that stability and performance requirements are satisfied by using the online estimate of the mode frequencies. An adaptive disturbance rejector is added to the adaptive mode-suppression scheme and broken into two parts: a part to suppress the repeatable runout and another to attenuate the residual disturbance by using a neural model. Both parts are adapted online and combined with the mode-suppression scheme to ensure good disturbance rejection even in the presence of unknown or changing resonant modes. Simulation results with a hard disk drive as the application are included and show that the adaptive mode-suppression scheme is able to maintain stability and better performance than a nonadaptive counterpart for an uncertain resonant-mode frequency. When combined with the adaptive disturbance-rejection scheme, stability is maintained and an improvement of as much as 14.3% in 3sigma is seen. This improvement in tracking can allow for data to be stored more densely on a single disk, providing larger storage media for the same size of disk drive.

A Single-Phase Shunt Active Power Filter for Current Harmonic Compensation by Adaptive Neural Filtering

This paper presents a single-phase shunt active power filter for current harmonic compensation based on neural filtering. The shunt active filter, realized by a current controlled inverter, has been used to compensate a non-linear current load by receiving its reference from a neural adaptive notch filter. This is a recursive notch filter for the fundamental grid frequency (50 Hz.) and is based on the use of a linear adaptive neuron (ADALINE). Current control of the inverter has been done by a multiresonant controller. In this way the inverter creates a current equal in amplitude and opposite in sign to the load harmonic current, thus creating an almost sinusoidal grid current. The methodology has been applied in numerical simulations and experimentally on a properly devised test setup.