Vehicle Speaker Control Using Voice Coil State Estimation
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Solution Overview
Problem
Conventional active noise control systems in vehicles face limitations in efficiently eliminating noise due to speaker non-linearity, distortion, and temperature variations, which affect audio quality and noise control performance, especially in handling low-frequency components and small speaker sizes.
Innovation Solution
A sound control device and method that measures drive signals to a speaker, estimates the state of the voice coil including displacement and temperature, and adjusts input signals to correct bias, prevent non-linearity, and extend the speaker's output range, thereby improving active noise control and audio quality.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Adaptability or versatility
If the speaker is controlled to output the noise control signal outside the output range of the speaker, then the noise control signal can be output to eliminate low-frequency noise, but the low-frequency components of the noise control signal are distorted and output or noise control performance of other frequency band signals deteriorates due to non-linearity or saturation of the speaker
Solution Approach 1:
The system estimates the voice coil state (displacement and temperature) before outputting the noise control signal to the speaker. By performing this estimation in advance, the system can determine whether the speaker is operating within its linear range and adjust the noise control signal accordingly to prevent distortion and saturation, thereby maintaining noise control performance across all frequency bands
Solution Approach 2:
The system uses a model of the speaker to estimate the voice coil state based on the drive signal, creating a feedback loop that monitors speaker operation. This feedback mechanism allows the system to detect when the speaker approaches saturation or non-linear operation and adjust the noise control signal to maintain optimal performance, preventing distortion of low-frequency components and preserving performance in other frequency bands
2Volume of moving object
If the size of the speaker is reduced, then the speaker can be installed in limited vehicle space, but the non-linear distortion increases
Solution Approach 1:
The system changes the operating parameters of the speaker by monitoring and adjusting for voice coil temperature and displacement. By estimating these parameters in real-time, the system can compensate for the increased non-linear distortion inherent in smaller speakers, maintaining audio quality and noise control performance despite the reduced speaker size
Solution Approach 2:
The system implements a feedback mechanism that estimates the voice coil state based on the drive signal and speaker model. This feedback allows the system to detect and compensate for non-linear distortion in real-time, enabling smaller speakers to operate more linearly and reducing harmful distortion products even though the speaker size is reduced for space constraints
3Device complexity
If the audio system simply mixes the noise control signal and the audio signal without considering speaker limitations, then the system complexity is reduced, but it may be difficult to efficiently eliminate noise or may cause a new problem
Solution Approach 1:
The system performs preliminary estimation of the voice coil state before mixing and outputting the noise control signal and audio signal. This preliminary action allows the system to identify potential issues with speaker operation and adjust the signals accordingly, ensuring efficient noise elimination without causing distortion or other problems, while adding minimal complexity to the signal processing chain
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 solution enhances the performance of active noise control and audio quality by adjusting input signals based on voice coil states, preventing distortion, and extending the speaker's output range, ensuring effective noise cancellation and maintaining audio quality across varying conditions.
Implementation Method 1
a voice coil of the speaker
Data Source
AI summary
A sound control device mounted in a vehicle and control method include measuring a drive signal input to a speaker, wherein the drive signal is generated in response to an input signal including at least one of a noise control signal and an audio signal, estimating a state of a voice coil of the speaker including at least one of displacement and temperature of the voice coil, based on the drive signal and a model of the speaker, and adjusting the input signal based on the state of the voice coil.