Active Vibration Noise Control Device Filter Coefficient Stability
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Solution Overview
Problem
Existing active vibration noise control devices face issues with cyclic abnormal sounds and increased vibration noise due to phase errors in the transfer function caused by secular changes in the speaker, leading to continuous fluctuations in filter coefficients.
Innovation Solution
An active vibration noise control device that includes a basic signal generating unit, an adaptive notch filter, a microphone for error detection, a reference signal generating unit, a filter coefficient updating unit, an amplitude calculating unit, and an attenuating unit that attenuates the control signal when the amplitude exceeds a threshold, thereby stabilizing the filter coefficient and preventing abnormal sound occurrences.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If the adaptive notch filter continuously updates the filter coefficient to minimize the error signal, then the noise cancellation effectiveness is improved, but cyclic abnormal sounds and vibration noise increase due to phase errors in the transfer function
Solution Approach 1:
The system uses feedback from the microphone to detect the cancellation error and continuously updates the filter coefficient through the filter coefficient updating unit. This feedback mechanism allows the system to adapt to changes in the transfer function while monitoring for abnormal conditions, resolving the contradiction by enabling effective noise cancellation while detecting when cyclic abnormal sounds occur.
Solution Approach 2:
The system changes the parameter (filter coefficient) dynamically to minimize the error signal. When the amplitude of the filter coefficient exceeds the threshold, indicating phase error and potential cyclic abnormal sound, the system intervenes to prevent further parameter changes that would worsen the condition, thus maintaining noise cancellation effectiveness while preventing harmful cyclic sounds.
2Adaptability or versatility
If the filter coefficient is continuously updated based on the error signal, then the adaptation to transfer function changes is improved, but the filter coefficient fluctuates excessively causing vibration noise increase
Solution Approach 1:
The feedback mechanism monitors the amplitude of the filter coefficient through the amplitude calculating unit. When the amplitude exceeds the threshold, the system detects excessive fluctuation and prevents further updates, thus maintaining adaptability to genuine transfer function changes while stabilizing the filter coefficient to prevent vibration noise.
Solution Approach 2:
The system dynamically adjusts the filter coefficient parameter based on the error signal, but introduces a threshold-based constraint that limits parameter changes when amplitude exceeds the threshold. This resolves the contradiction by allowing necessary adaptation while preventing excessive fluctuations that cause vibration noise.
3Object-generated harmful factors
If the control signal is attenuated to suppress cyclic abnormal sounds, then the harmful sound is reduced, but the noise cancellation effectiveness decreases
Solution Approach 1:
The system takes preliminary anti-action by detecting when the amplitude of the filter coefficient exceeds the threshold, indicating the onset of cyclic abnormal sound. By preventing further filter coefficient updates at this stage, the system suppresses the harmful sound before it fully develops, while maintaining noise cancellation effectiveness through controlled attenuation rather than complete suppression.
Solution Approach 2:
The system changes the state of the filter coefficient updating process based on the amplitude threshold. When the threshold is exceeded, the system prevents parameter changes that would worsen the cyclic abnormal sound, while allowing controlled operation to maintain noise cancellation effectiveness. This resolves the contradiction by selectively managing parameter updates based on system state.
Data Source
AI summary
An active vibration noise control device is preferably used for canceling a vibration noise by making a speaker generate a control sound. Concretely, the active vibration noise control device includes an attenuating unit which attenuates a control signal generated by an adaptive notch filter, and provides the attenuated control signal to the speaker, when amplitude of a filter coefficient is larger than a threshold. Therefore, it is possible to suppress continuous ups and downs of the filter coefficient during an occurrence of an abnormality. Hence, it becomes possible to appropriately suppress an occurrence of a cyclic abnormal sound and an increase in the vibration noise during the occurrence of the abnormality.