Variable Step-Size Active Noise Control for Vehicle Stability
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Solution Overview
Problem
Active noise control systems face instability and noise generation when acoustics change or unexpected noise occurs, leading to ineffective cancellation of undesired sounds, particularly at low frequencies, due to fixed step-size adaptations that can result in extreme operating states.
Innovation Solution
The system employs a variable step-size adaptation method using the Filtered-x Least Mean Squares (FxLMS) algorithm with a Normalized-FxLMS variant, along with frequency-dependent and adaptive step-size criteria to control filter updates, ensuring stability and optimal noise cancellation across dynamic vehicle conditions.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Device complexity
If fixed step-size adaptation is used in active noise control, then the system is simple to implement, but the system becomes unstable and generates noise when acoustics change or unexpected noise occurs
Solution Approach 1:
The patent implements dynamic step-size adaptation where the step-size parameter is continuously adjusted based on real-time system performance monitoring. When instability is detected (e.g., error signal exceeds threshold), the step-size is automatically reduced to restore stability. This dynamic adjustment resolves the contradiction by making the adaptation algorithm responsive to changing acoustic conditions while maintaining simplicity through rule-based control.
Solution Approach 2:
The system incorporates feedback mechanisms that monitor the error signal and system behavior, then use this information to adjust the step-size parameter. The feedback loop detects when the system approaches instability and triggers step-size reduction, ensuring reliable operation under varying acoustic conditions without requiring complex predictive models.
2Use of energy by moving object
If fixed step-size adaptation is used, then the algorithm is computationally efficient, but the system converges to extreme operating states that amplify noise rather than cancel it
Solution Approach 1:
The system uses feedback monitoring of the error signal to detect when noise amplification is occurring. When the error signal exceeds a predetermined threshold or shows signs of divergence, the feedback mechanism triggers a step-size reduction, preventing the system from converging to extreme operating states that generate harmful noise.
Solution Approach 2:
The patent implements preventive measures by setting threshold levels and monitoring system behavior before instability occurs. When approaching critical conditions, the step-size is reduced in advance to cushion against potential noise amplification, preventing harmful effects before they manifest.
3Speed
If the system quickly converges to extreme operating states, then the system responds rapidly to acoustic changes, but the system pushes into instability and generates destructive noise
Solution Approach 1:
The system dynamically adjusts the step-size parameter based on real-time conditions, allowing rapid convergence when stable and reducing step-size when approaching instability. This dynamic control enables the system to respond quickly to acoustic changes while preventing convergence to extreme states that generate destructive noise.
Solution Approach 2:
The patent changes the step-size parameter dynamically based on system behavior and acoustic conditions. By adjusting this critical parameter in response to error signal levels and convergence progress, the system achieves both rapid response and stability, avoiding the generation of destructive noise while maintaining fast adaptation capability.
Data Source
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AI summary
A system and method (referred to as the system) that actively reduces noise in a vehicle. The system generates one or more control output signals to drive multiple loudspeakers; and adapts multiple control coefficients of a control filter based on multiple secondary path transfer functions. The secondary path transfer functions model the acoustic paths between each loudspeaker and multiple microphones. The multiple control coefficients are time varying and frequency dependent and the rate the plurality control coefficients adapt is based on an adaptive step size based on one or more step size criteria.