Active Vibration Noise Control Using Gradient-Based Frequency Correction
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Solution Overview
Problem
Conventional active vibration noise control apparatuses struggle to correctly correct the control frequency when external disturbances are present, leading to reduced noise reduction effectiveness due to inappropriate filter coefficient updates.
Innovation Solution
An active vibration noise control apparatus that generates a control signal based on cosine and sine wave signals and updates a correction value to decrease signal power of an error signal, using the relationship between signal power changes and correction value changes, to accurately correct the control frequency even in the presence of external disturbances.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Measurement precision
If the filter coefficient of the adaptive notch filter is updated based on the error signal, then the control frequency can be corrected to reduce vibration noise, but the filter coefficient is not updated appropriately when external disturbance is present
Solution Approach 1:
The patent extracts the influence of external disturbance from the error signal by calculating the gradient of the squared error signal with respect to the control frequency. This allows the system to identify and separate the component caused by frequency deviation from the component caused by external disturbance, enabling reliable filter coefficient updates even in the presence of external disturbance.
Solution Approach 2:
The patent introduces an intermediary variable (the gradient of the squared error signal) that mediates between the error signal and the filter coefficient update. This intermediary allows the system to indirectly estimate the frequency deviation while being less sensitive to external disturbance, thus improving the reliability of the update process.
2Productivity
If the control frequency is corrected based on filter coefficient change, then vibration noise reduction effect is improved, but the correction becomes inaccurate when external disturbance amplitude is comparable to cancellation error
Solution Approach 1:
The patent employs feedback by continuously monitoring the error signal and using its gradient with respect to control frequency to adjust the filter coefficient. This feedback mechanism allows the system to adaptively correct the control frequency based on the actual vibration noise reduction effect, while the gradient calculation provides a more accurate feedback signal that is less susceptible to external disturbance interference.
Solution Approach 2:
The patent changes the parameter used for correction from the raw error signal or filter coefficient change to the gradient of the squared error signal with respect to control frequency. This parameter transformation makes the correction process more robust to external disturbance, as the gradient provides a more reliable indication of the true frequency deviation even when external disturbance is present.
Data Source
AI summary
There are provided a control signal generation unit 120 that generates a control signal on the basis of a cosine wave signal and a sine wave signal whose frequencies are a control frequency identified according to a vibration noise source, and a correction value update unit that updates a correction value to a value for decreasing signal power of an error signal on the basis of a relationship between increase and decrease of the signal power of the error signal obtained from remaining vibration noise that remains after interference sound that is generated on the basis of the control signal and propagates through a secondary route interferes with vibration noise generated from the vibration noise source and increase and decrease of the correction value used for correction of the control frequency.