Active Vibration Noise Reduction With Adaptive Filter Updates
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Solution Overview
Problem
Existing active noise control devices face challenges in setting filter coefficients adaptively and improving convergence and stability, particularly when the sound pressure error is large or the microphone position changes, leading to complex convergence coefficient settings.
Innovation Solution
An active vibration noise reduction device that includes a speaker, microphone, control filter, and secondary path filter, which adaptively updates filter coefficients using an update amount derived from the error signal, step size parameter, and convolution between reference and secondary path filters, automatically adjusting the update amount based on the error signal magnitude.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Ease of operation
If a constant convergence coefficient is used when sound pressure error is large, then the control device is simple to operate, but the convergence speed is slow and stability is poor
Solution Approach 1:
The patent applies dynamics by making the convergence coefficient variable rather than constant. The coefficient automatically adapts based on the sound pressure error magnitude: using a first convergence coefficient when error is small and a second convergence coefficient when error is large. This dynamic adjustment resolves the contradiction by enabling both ease of operation (automatic adaptation) and fast convergence (larger coefficient when needed).
Solution Approach 2:
The patent changes the parameter of convergence coefficient based on the sound pressure error condition. By switching between different coefficient values according to error magnitude, the system achieves both operational simplicity (no manual tuning needed) and improved convergence performance (optimal coefficient selected automatically).
2Speed
If the convergence coefficient is increased to improve convergence speed, then the convergence speed improves, but the stability of residual noise characteristics deteriorates
Solution Approach 1:
The patent resolves this contradiction by conditionally changing the convergence coefficient parameter. When sound pressure error is small (stable condition), it uses a first convergence coefficient that maintains stability. When sound pressure error is large (unstable condition), it uses a second convergence coefficient that prioritizes convergence speed. This conditional parameter change allows the system to achieve both speed and stability at different stages.
Solution Approach 2:
The system dynamically adjusts the convergence coefficient based on real-time sound pressure error conditions, enabling the control device to switch between stability-oriented and speed-oriented modes automatically, thus resolving the trade-off between convergence speed and stability.
3Stability of the object's composition
If manual adjustment of convergence coefficient storage table is performed to improve stability, then stability improves, but the device complexity increases
Solution Approach 1:
The patent applies self-service by enabling the control device to automatically select and adjust convergence coefficients based on sound pressure error conditions without requiring manual configuration of a convergence coefficient storage table. The system self-adjusts by switching between predefined coefficient values, eliminating complex manual setup while maintaining stability.
Solution Approach 2:
The system uses feedback from the sound pressure error signal to automatically determine which convergence coefficient to apply. This feedback mechanism eliminates the need for complex manual tuning of storage tables, as the system automatically adapts based on real-time error conditions, thus reducing device complexity while improving stability.
Data Source
AI summary
An active vibration noise reduction device includes: a speaker that outputs a cancellation sound for canceling noise; a microphone that generates an error signal from the noise and the cancellation sound; a control filter configured to generate a control signal for controlling the cancellation sound from a reference signal; and a secondary path filter presenting an estimation value of a transfer function from the speaker to the microphone, wherein the control filter is configured to be adaptively updated by an update amount obtained by multiplying the error signal, a step size parameter calculated based on the error signal, and a result of convolution between the reference signal and the secondary path filter.