Active Engine Noise Reduction with Harmonic Output Limiting
Find Innovative SolutionsGenerate Solutions
Solution Overview
Problem
Engine harmonic cancellation systems in motor vehicles can become unstable, leading to loud and noticeable noise artifacts due to changes in the vehicle cabin's transfer function, causing loudspeaker output gains to become positive and diverge.
Innovation Solution
Estimating engine harmonic noise levels based on vehicle engine operation signals like RPM and torque, and limiting the output of transducers to the minimum necessary to cancel these noise levels, preventing the system from producing sound louder than the engine noise.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If the adaptive filter output is applied to transducers to cancel engine noise, then noise cancellation effectiveness is improved, but system stability deteriorates when transfer function changes occur
Solution Approach 1:
The patent applies preliminary anti-action by implementing a stability monitor that proactively detects transfer function changes and a gain limiter that pre-restrains transducer output gains before they can diverge. This preventive approach counteracts potential instability before it manifests as noise artifacts, allowing the system to maintain reliability while preventing stability deterioration.
Solution Approach 2:
The patent implements feedback mechanisms through the stability monitor that continuously monitors system conditions and provides information to the gain limiter. This feedback loop enables the system to detect transfer function changes and adjust transducer gains dynamically, maintaining both noise cancellation effectiveness and system stability under varying operating conditions.
2Reliability
If transducer output gains are increased to improve noise cancellation, then noise cancellation effectiveness is improved, but noise artifacts increase when system becomes unstable
Solution Approach 1:
The gain limiter applies preliminary anti-action by pre-restraining transducer output gains based on monitored stability conditions. When transfer function changes are detected, the gain limiter proactively limits the gains before they can become positive and cause divergent oscillations, thereby preventing noise artifacts while maintaining effective noise cancellation within safe gain boundaries.
Solution Approach 2:
The patent applies parameter changes by dynamically adjusting transducer output gain parameters based on stability monitor feedback. The system changes gain parameters from potentially high values that improve cancellation to limited values that prevent artifacts, adapting the gain parameter to operating conditions to balance cancellation effectiveness with artifact prevention.
3Reliability
If the system operates without output limiting to maintain noise cancellation performance, then noise cancellation effectiveness is improved, but system shutdowns occur due to instability
Solution Approach 1:
The patent applies beforehand cushioning by implementing protective measures (stability monitor and gain limiter) that cushion the system against instability-induced shutdowns. These measures provide a safety buffer that allows the system to continue operating through transfer function changes and gain variations that would otherwise cause divergence and forced shutdowns, extending continuous operation duration.
Solution Approach 2:
The feedback mechanism enables continuous operation by continuously monitoring system stability and providing real-time adjustments. When instability conditions are detected, the feedback loop triggers gain limiting that prevents divergence, allowing the noise cancellation system to maintain operation continuously without shutdowns while preserving cancellation effectiveness within stable operating parameters.
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
This approach minimizes audible artifacts from system instability, allowing the engine harmonic cancellation system to operate without shutting down and reducing noise artifacts like voice echoes and afterglow, while making tuning for instability easier and less risky.
Implementation Method 1
The sound is acoustically opposite to the undesirable engine sounds that are to be canceled. The adaptive filter can alter the magnitude and/or the frequency of the input signal.
Implementation Method 2
one or more transducers that produce sound (i.e., loudspeakers). The sound is acoustically opposite to the undesirable engine sounds that are to be canceled.
Data Source
AI summary
A device and method that is configured to operate an active noise reduction system for a motor vehicle, where there is an active noise reduction system input signal that is related to the vehicle engine operation, and where the active noise reduction system comprises one or more adaptive filters that output noise reduction signals that are used to drive one or more transducers with their outputs directed to reduce engine noise. The engine harmonic noise level is estimated from the input signal that is related to the vehicle engine operation, and the output of the transducers is limited based on the estimate of the engine harmonic noise level.