Active Noise Cancellation Filter Adjustment for Vehicle Stability
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Solution Overview
Problem
ANC systems face instability and noise boosting due to deviations in the modeled transfer characteristics of secondary paths from actual paths in vehicle environments, caused by changes in vehicle geometry, passenger count, or component variations.
Innovation Solution
An active noise cancellation system with adaptive filter controllers that adjust step size and leakage parameters based on noise reduction ratio comparisons to thresholds, using LMS algorithms to stabilize the system and minimize noise boosting.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If the ANC system uses fixed filter parameters based on modeled transfer characteristics, then the system structure is simple, but noise boosting and instability occur when the actual secondary path deviates from the modeled path
Solution Approach 1:
The patent implements dynamic adjustment of filter parameters (step size and leakage) based on real-time monitoring of noise reduction ratio. The system transitions from fixed parameters to dynamically adaptive parameters that respond to changing vehicle conditions, passenger configurations, and component variations, thereby maintaining stability without requiring complex reconfiguration mechanisms.
Solution Approach 2:
The system continuously monitors the noise reduction ratio and uses this feedback to adjust the step size and leakage parameters. When the noise reduction ratio indicates potential instability or noise boosting, the system automatically reduces the step size parameter. This closed-loop feedback mechanism ensures reliability while keeping the overall system structure relatively simple.
2Adaptability or versatility
If the ANC system adapts to varying vehicle conditions (passenger count, geometry changes, component variations), then noise cancellation performance is maintained, but system complexity increases
Solution Approach 1:
The patent changes the parameters of existing filter components (step size and leakage) rather than introducing entirely new adaptive mechanisms. By adjusting these parameters based on noise reduction ratio thresholds, the system adapts to varying vehicle conditions while maintaining a relatively simple structure that builds upon the existing LMS algorithm framework.
Solution Approach 2:
The system employs dynamic parameter adjustment where the step size and leakage values are modified in real-time based on operational conditions. This allows the ANC system to adapt to passenger count changes, geometry variations, and component tolerances without requiring a completely redesigned complex adaptive architecture.
3Reliability
If the step size parameter is reduced to prevent noise boosting, then system stability improves, but convergence speed of the adaptive filter decreases
Solution Approach 1:
The system dynamically adjusts the step size parameter based on real-time noise reduction ratio monitoring. During normal operation, a larger step size enables faster convergence. When instability or noise boosting is detected, the step size is reduced to ensure stability. This dynamic approach allows the system to achieve both fast convergence and stability without being constrained by a fixed parameter choice.
Solution Approach 2:
The system periodically monitors the noise reduction ratio and adjusts parameters accordingly. This periodic feedback allows the filter to converge quickly during stable periods while intervening to reduce step size only when necessary to prevent noise boosting, thereby achieving both fast convergence and stability over time.
Applied Scientific Principles
This section explains which scientific principles are used to turn an abstract innovation direction into a practical engineering solution.
Function Achieved in This Case
The system effectively limits noise boosting and maintains stability by dynamically adjusting filter parameters, enhancing noise cancellation performance across varying vehicle conditions.
Implementation Method 1
ANC systems generally cancel or reduce unwanted noise by generating cancellation sound waves to destructively interfere with the unwanted audible noise. Destructive interference results when noise and 'anti-noise,' which is largely identical in magnitude but opposite in phase to the noise, reduce the sound pressure level (SPL) at a location.
Data Source
AI summary
An active noise cancellation (ANC) system is provided with at least one loudspeaker to project anti-noise sound within a passenger cabin of a vehicle in response to receiving an anti-noise signal and at least one microphone to provide an error signal indicative of noise and the anti-noise sound within the passenger cabin. An adaptive filter controller is programmed to filter the error signal to obtain a noise reduction ratio, and to adjust a step size and/or leakage parameter based on a comparison of the noise reduction ratio to a noise threshold. A controllable filter generates the anti-noise signal based on the adjusted step size and/or leakage parameter.