Adaptive Filter Divergence Control in Vehicle ANC Systems
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Solution Overview
Problem
Active noise cancellation systems, such as those used in vehicles for engine order cancellation and road noise cancellation, are prone to instability due to adaptive filter divergence, leading to noise boosting and other undesirable behaviors.
Innovation Solution
A method is introduced to detect divergence in adaptive filters by analyzing filter coefficients and modifying their properties, including deactivating the ANC system, resetting coefficients, or increasing leakage values, to maintain stability and performance.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If adaptive filters are used in ANC systems to cancel noise, then noise cancellation performance is improved, but filter divergence occurs leading to instability and noise boosting
Solution Approach 1:
The patent implements a divergence detection mechanism that continuously monitors filter coefficients and provides feedback to the adaptive filter controller. When divergence is detected, the system adjusts the filtering process by modifying the adaptive filter's operation, thereby maintaining stability while preserving noise cancellation performance.
Solution Approach 2:
The patent modifies parameters of the adaptive filter based on divergence detection. Specifically, it changes the filtering process parameters (such as step size, leakage values, or convergence criteria) in response to detected divergence conditions, allowing the system to recover from unstable states while maintaining effective noise cancellation.
2Productivity
If adaptive filters continuously adapt to minimize noise, then noise cancellation effectiveness increases, but the system becomes susceptible to divergence and instability
Solution Approach 1:
The system uses feedback from divergence detection to control the adaptive filtering process. The adaptive filter controller receives divergence information and adjusts its operation accordingly, creating a closed-loop system that maintains effectiveness while preventing runaway adaptation that leads to divergence.
Solution Approach 2:
The patent introduces dynamic control of the adaptive filter based on real-time divergence conditions. The filtering characteristics are dynamically adjusted according to the operational state, allowing the system to adapt aggressively when stable and conservatively when divergence is detected, thus balancing effectiveness and stability.
Data Source
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AI summary
A active noise cancellation (ANC) system may include an adaptive filter divergence detector for detecting divergence of the one or more controllable filters as they adapt, based on various temporal or frequency domain amplitude characteristics. Upon detection of a controllable filter divergence, the ANC system may be deactivated, or certain speakers may be muted. Alternatively, the ANC system may modify the diverged controllable filters to restore proper operation of the noise cancelling system. This may include adjusting a leakage value of an adaptive filter controller.