Traditional Notch Filter Research Articles

Adaptive control of an amplified piezoelectric-driven micropositioning stage based on notch filter structure inspiration and neural network online tuning

Abstract Piezoelectric-driven flexure micro/nanopositioning stages often exhibit a low-damping resonance mode, which can easily excite mechanical resonance during high-speed movement, and significantly impact the control system’s stability, control bandwidth, and trajectory tracking accuracy. To mitigate the reliance on the precise modeling of stage dynamics inherent in current resonant controllers, an adaptive control method based on a back propagation (BP) neural network was designed to suppress resonance in real-time. First, a piezoelectric-driven flexure micro/nanopositioning stage system was constructed. Next, a feedback controller similar to a notch filter was designed, with bilinear transformation applied based on the system’s inherent parameters to determine the initial values. Finally, the designed adaptive control method was tested through trajectory tracking experiments using a triangular wave signal. The experimental results showed that, when tracking the triangular wave signal, the maximum tracking error was reduced by 74.62% compared to proportional-integral (PI) control alone and by 69.91% compared to proportional integral control combined with a traditional notch filter. The tracking results demonstrate a significant improvement in the stage’s stability and tracking accuracy.

Application of an improved wide–narrow-band hybrid ANC algorithm in a large commercial vehicle cabine

In recent years, active noise reduction technology has become a research hotspot. However, most active noise reduction technologies are developed based on passenger vehicles and are not implemented in large commercial vehicles. The large commercial vehicle sound field space is large, the traditional active noise reduction method is difficult to implement. In order to explore this problem, this paper proposes an improved active noise control method for commercial vehicles: (1) based on the traditional notch filter, a notch FxLMS algorithm based on speed smoothing is proposed; (2) on the basis of the traditional wire–narrowband hybrid ANC algorithm, the reference signal weighting technology is introduced into the wide-band subsystem, and the notch FxLMS algorithm based on speed smoothing is used as the narrowband subsystem, so as to propose an improved wire-narrowband hybrid ANC algorithm. With the help of MATLAB, the simulation model of the designed algorithm is established, and the collected commercial vehicle test noise data is used as the reference signal to simulate and verify the proposed algorithm. The results show that the proposed method has certain practicability.

A Current Harmonic Suppression Method for PMSM Based on Harmonic Prediction Adaptive Notch Filter

The adaptive filters (ANF) have been commonly used in current harmonic suppression. However, the digital delay will narrow the stability region and its harmonic suppression performance will be deteriorated at high-speed region. To overcome this problem, this paper proposed two modified ANF. Combining with the deadbeat current (DBC) controller, the effect of digital delay on ANF is analyzed. A simple one step harmonic prediction method (OSPANF) is proposed to replace the traditional steepest gradient method (SGM). Based on the OSPANF, the current can be controlled stably in the high-speed area and the harmonic suppression effect is better than the traditional notch filter. Through bode diagram analysis, OSPANF will have a harmonic amplification peak near the set notch frequency, which may bring additional disturbances. Thus, a two steps prediction adaptive notch filter (TSPANF) is implemented. Through the Experimental results, it can be proved that the proposed TSPANF method has better harmonic suppression effect in the high-speed area than OSPANF and the stability region of the proposed two methods is larger than the traditional method.

Modified Variational Mode Decomposition for Power Line Interference Removal in ECG Signals

Power line interferences (PLI) occurring at 50/60 Hz can corrupt the biomedical recordings like ECG signals and which leads to an improper diagnosis of disease conditions. Proper interference cancellation techniques are therefore required for the removal of these power line disturbances from biomedical recordings. The non-linear time varying characteristics of biomedical signals make the<strong> </strong>interference removal a difficult task without compromising the actual signal characteristics. In this paper, a modified variational mode decomposition based approach is proposed for PLI removal from the ECG signals. In this approach, the central frequency of an intrinsic mode function is fixed corresponding to the normalized power line disturbance frequency. The experimental results show that the PLI interference is exactly captured both in magnitude and phase and are removed. The proposed approach is experimented with ECG signal records from MIT-BIH Arrhythmia database and compared with traditional notch filtering.

Modified Variational Mode Decomposition for Power Line Interference Removal in ECG Signals

Power line interferences (PLI) occurring at 50/60 Hz can corrupt the biomedical recordings like ECG signals and which leads to an improper diagnosis of disease conditions. Proper interference cancellation techniques are therefore required for the removal of these power line disturbances from biomedical recordings. The non-linear time varying characteristics of biomedical signals make the<strong> </strong>interference removal a difficult task without compromising the actual signal characteristics. In this paper, a modified variational mode decomposition based approach is proposed for PLI removal from the ECG signals. In this approach, the central frequency of an intrinsic mode function is fixed corresponding to the normalized power line disturbance frequency. The experimental results show that the PLI interference is exactly captured both in magnitude and phase and are removed. The proposed approach is experimented with ECG signal records from MIT-BIH Arrhythmia database and compared with traditional notch filtering.

High-bandwidth control of piezoelectric steering mirror for suppression of laser beam jitter

Laser beam steering or pointing, which stabilizes the beam direction, is critical in many areas, such as optical communication systems, astronomy and directed-energy systems etc. However, the disturbances including atmospheric turbulence and mechanical jitter on platform may degrade the pointing accuracy. A proportional-integral (PI) feedback control commonly has been used in the track loop with a fast steering mirror. To compensate dynamic disturbance effectively, the laser beam steering control system must have a larger bandwidth than the disturbance bandwidth. But the control bandwidth is limited by the noise of the sensor, computing latency, and the light energy. So, a simple proportional-integral (PI) feedback controller of a piezoelectric fast steering mirror (PFSM) can only compensate the broadband disturbance of the atmospheric turbulence, but cannot effectively compensate a larger amplitude narrowband jitter because of the low control bandwidth. Moreover, when the control bandwidth is tuned to high, the mechanical resonance of the PFSM can cause the instability of the system. An improved dual two-order filter assisted high-bandwidth control algorithm to improve the pointing accuracy and error attenuation capability is proposed. This method can control a PFSM for suppression of laser beam jitter. The influence of filter parameters on frequency characteristics is analyzed, and then, a practical design method is proposed. The dual two-order filter can combine the characteristics of traditional notch filter and two-order low-pass filter, and can also obtain any desired amplitude in the interesting frequency ragion with little influence on the others. The principle of the proposed filter for suppressing the mechanical resonance of the PFSM and the narrowband disturbance is elaborated. And then, the different dual two-order filters are designed according to the frequency content of the PFSM and the narrowband disturbance. Finally, the proposed dual two-order filter assisted PI control algorithm and classic PI control algorithm are compared with each other. Experimental results show that, in the same conditions, the pointing accuracy of the proposed two-order filter assisted PI control algorithm is nearly 5 times better than that of the classic PI control algorithm, and the error attenuation bandwidth is one time higher. It also indicates that the proposed algorithm does not need an additional sensor; it is simple and effective for the suppression of the mechanical resonance of a PFSM and that of the narrowband disturbance, hence it improves the system error attenuation bandwidth and the beam pointing accuracy.

Resonance suppression method based on digital filter for servo system

According to mechanical resonance problem in flight simulation servo system( turntable system),the principles of resonance suppression about traditional notch filter and second-order low-pass filter were analyzed. Afterwards the two-second resonance suppression digital filter was proposed. The two-second digital filter combines the characteristics of traditional notch filter and second-order low-pass filter,and it can suppress the resonance point and the anti-resonance point at the same time. Through theoretical analysis and simulation combination,the principle of the two-second digital filter restraining the resonance point and the anti-resonance point simultaneously was explained. The experiments were also conducted,in which above all filters were joined into the turntable system respectively. Experimental results show that,the proposed filter ensures high tracking precision meanwhile effectively widens the bandwidth of the servo system.

Simulation of Adaptive Filter Based on LMS Algorithm in Simulink

The paper introduces the principle and structure of adaptive filter based on LMS algorithm, studies a design scheme of a single frequency adaptive notch filter, and simulates its working procedure by using the Simulink simulation tool. The simulation results show that the adaptive notch filter based on LMS algorithm has the better convergence and the smaller steady-state error than traditional notch filter in the appropriate parameter.