Engine Harmonic Cancellation via Accelerometer and Adaptive Lookup Tables
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Solution Overview
Problem
Existing engine harmonic cancellation systems are ineffective due to dominance of road noise, limited adaptability, and reliance on microphones for feedback, which hampers accurate detection and rapid change capture of engine harmonics.
Innovation Solution
An engine harmonic cancellation system utilizing an accelerometer to generate a harmonic reference signal, a controller to mix it with a baseband signal from a look-up table, and speakers to produce a cancellation signal that destructively interferes with engine harmonics within a defined zone, with adaptive look-up tables to adjust for residual harmonics and rapid changes.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Measurement precision
If microphones are used for feedback in engine harmonic cancellation systems, then the system can detect residual harmonics, but the detection accuracy is hampered by road noise dominance and limited adaptability to rapid engine changes
Solution Approach 1:
The patent replaces acoustic sensors (microphones) with mechanical sensors (accelerometers) to detect engine harmonics. This substitution eliminates the problem of road noise dominance because accelerometers mounted on the engine block directly measure mechanical vibrations at the source, providing clear harmonic signals even during vehicle operation. The mechanical measurement approach enables accurate detection and rapid response to engine condition changes.
2Reliability
If traditional feedback control is used with microphones, then residual harmonics can be measured, but the system response is too slow to capture rapid changes in engine harmonics
Solution Approach 1:
The system uses accelerometers to directly measure engine vibrations at the source before they propagate into the cabin as audible noise. This preliminary detection at the generation point allows the control system to anticipate and cancel harmonics before they reach the passengers, enabling faster response to rapid engine changes and improving overall cancellation reliability.
3Adaptability or versatility
If the cancellation signal is generated without adaptive adjustment, then the system structure is simpler, but the system cannot adapt to rapid changes in engine conditions
Solution Approach 1:
The patent implements adaptive lookup tables that dynamically adjust cancellation parameters based on real-time engine operating conditions. The system continuously updates the lookup tables with measured harmonic data, enabling automatic adaptation to changing engine states without requiring complex real-time computation. This dynamic adaptation maintains high cancellatio effectiveness across varying engine conditions while keeping the overall system structure relatively simple.
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 effectively reduces engine harmonics by at least 3 dB within specific cancellation zones, improving adaptability and accuracy by using accelerometers for harmonic detection and adaptive look-up tables to manage rapid changes in engine conditions.
Implementation Method 1
an accelerometer disposed within a vehicle to detect a harmonic produced by an engine of the vehicle and to produce a harmonic reference signal representative of the harmonic
Implementation Method 2
a speaker disposed within the cabin and configured to receive the harmonic cancellation signal and to transduce the harmonic cancellation signal into an acoustic harmonic cancellation signal
Implementation Method 3
the harmonic cancellation signal is based, at least in part, on mixing the harmonic reference signal converted to baseband with a baseband signal output from a look up table
Data Source
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AI summary
An engine harmonic cancellation system includes an accelerometer disposed within a vehicle to detect a harmonic produced by an engine of the vehicle and to produce a harmonic reference signal representative of the harmonic; a controller configured to produce a harmonic cancellation signal that, when transduced into an acoustic signal, cancels the harmonic within at least one cancellation zone within a cabin of the vehicle, wherein the harmonic cancellation signal is based, at least in part, on mixing the harmonic reference signal converted to baseband with a baseband signal output from a look up table; and a speaker disposed within the cabin and configured to receive the harmonic cancellation signal and to transduce the harmonic cancellation signal into an acoustic harmonic cancellation signal, such that the harmonic is cancelled within the cancellation zone.