Engine-Order Noise Cancellation Stability Under Frequency Response Drift
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Solution Overview
Problem
Existing engine-order-cancellation (EOC) apparatuses experience instabilities due to variations in frequency responses of acoustic signal output and sensor devices, leading to undesired audible noise in the car cabin, which conventional methods fail to adequately address.
Innovation Solution
A method for operating EOC apparatuses that includes detecting instability through predefined conditions, applying a first measure to prevent further instability increase by controlling energy levels below a threshold, and a second measure to gradually decrease instability by adjusting operational parameters such as the forgetting factor and step size.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Object-affected harmful factors
If the EOC apparatus generates noise cancellation signals to cancel engine noise, then noise cancellation effectiveness is improved, but instability occurs causing audible noise in the car cabin
Solution Approach 1:
The patent implements a feedback mechanism that continuously monitors the stability of the EOC apparatus by comparing reference frequency responses with actual frequency responses. When instability is detected (when the difference exceeds a threshold), the system automatically adjusts or disables the noise cancellation signals for affected harmonic orders, preventing the generation of audible noise while maintaining noise cancellation when stable
Solution Approach 2:
The system dynamically adjusts its operation by continuously monitoring frequency response variations and adapting the noise cancellation signals in real-time. The apparatus transitions between active noise cancellation and disabled states based on stability conditions, and can gradually decrease instability through adaptive adjustment of operational parameters like forgetting factor and step size
2Object-affected harmful factors
If the EOC apparatus operates at maximum noise cancellation level, then noise cancellation effectiveness is improved, but instability increases due to too sensible tuning
Solution Approach 1:
The patent changes operational parameters (forgetting factor, step size) dynamically based on stability conditions. When instability is detected, the system adjusts these parameters to reduce the aggressiveness of the noise cancellation algorithm, allowing the system to operate at maximum effectiveness when stable and maintain reliability when conditions vary
3Object-affected harmful factors
If the EOC apparatus uses fixed tuning for noise cancellation, then noise cancellation effectiveness is improved at specific operating states, but adaptability to changing physical conditions deteriorates
Solution Approach 1:
The system transitions from fixed tuning to dynamic adaptation by continuously monitoring frequency responses and adjusting noise cancellation signals based on current operating conditions. The apparatus can detect changes in physical conditions (temperature, humidity, passenger load) through frequency response variations and adapt its cancellation strategy accordingly
Solution Approach 2:
The patent implements parameter changes by adjusting operational parameters (forgetting factor, step size) based on detected instability caused by changing physical conditions. This allows the system to maintain effectiveness across varying operating states while adapting to environmental changes
Data Source
Figure 1
AI summary
Method for operating an engine-order-cancellation ("EOC") apparatus (2) adapted to generate noise cancellation signals (3) for cancelling noise (4) generated by an engine (5) at atleast one specific harmonic order at a given operating state of the engine (5), the method comprising the steps of: -detecting an instability of the EOC apparatus (2), and -performing at least one measure to avoid a further increase of the detected instability of the EOC apparatus (2) and/or at least one measure to decrease the instability of the EOC apparatus (2).