Loudspeaker Diaphragm State Estimation via Adaptive Filtering
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Solution Overview
Problem
Conventional methods for estimating loudspeaker diaphragm state in portable devices are bulky, difficult to install, costly, and limited by rated power, which restricts sound pressure and output power due to the need for sensors.
Innovation Solution
An adaptive filtering method is used to adjust the weight values of a diaphragm displacement model, estimating relative displacement and speed to determine the driving voltage, reducing the number of parameters and simplifying the model for accurate and efficient loudspeaker state estimation.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Measurement precision
If sensors are used to detect diaphragm displacement and speed, then measurement precision is improved, but device complexity and cost increase
Solution Approach 1:
The patent replaces physical sensors (mechanical detection system) with an electrical measurement system. By measuring the voltage across the voice coil and using the known relationship between voltage, current, and diaphragm motion in the electromagnetic field, the system estimates diaphragm displacement and speed without physical sensors. This substitution eliminates sensor installation complexity while maintaining measurement capability.
Solution Approach 2:
The patent introduces an intermediary measurement approach by using the voice coil voltage as a proxy for direct diaphragm measurement. Instead of measuring diaphragm position directly with sensors, the system measures the electrical parameter (voltage) that is directly related to diaphragm state through the electromagnetic coupling, thereby inferring diaphragm displacement and speed indirectly.
2Reliability
If rated power is limited to protect diaphragm, then reliability is improved, but output power and sound pressure decrease
Solution Approach 1:
The patent implements a feedback control mechanism by continuously estimating diaphragm displacement from voltage measurements and using this information to control the driving signal. The system monitors the estimated diaphragm state and adjusts the input power accordingly, allowing operation near but not exceeding the maximum safe displacement limit. This feedback loop enables the system to operate at higher power levels safely by preventing diaphragm overload.
Solution Approach 2:
The patent transitions from a static power limit (fixed rated power) to a dynamic power control system. By continuously estimating diaphragm displacement and adjusting the driving voltage in real-time based on the estimated state, the system can dynamically optimize power output while maintaining diaphragm safety. This allows the loudspeaker to operate at higher average power levels than a fixed rated power would permit.
3Productivity
If adaptive filtering is used to adjust model parameters, then productivity is improved, but calculation complexity increases
Solution Approach 1:
The patent applies adaptive filtering selectively to only the necessary model parameters (weight values in the diaphragm displacement model) rather than adjusting all parameters. By focusing the adaptation process on specific critical parameters that have the greatest impact on estimation accuracy, the system achieves good model convergence without the computational burden of optimizing all parameters simultaneously.
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 allows for accurate and efficient estimation of loudspeaker diaphragm displacement and voltage, increasing output power and sound pressure while minimizing the need for sensors, making it suitable for practical applications in portable devices.
Implementation Method 1
Loudspeakers can produce sound by driving diaphragms to vibrate through an electromagnetic field that is generated by an electromagnetic coil
Implementation Method 2
adjusting a weight value of a diaphragm displacement model by adaptive filtering until an error between an estimated value of a driving voltage of a loudspeaker and a measured value of the driving voltage is less than a predetermined threshold
Data Source
AI summary
A loudspeaker diaphragm state estimation method includes: adjusting a weight value of a diaphragm displacement model by adaptive filtering until an error between an estimated value of a driving voltage of a loudspeaker and a measured value of the driving voltage is less than a predetermined threshold; estimating a diaphragm relative displacement of the loudspeaker according to the diaphragm displacement model corresponding to a final determined weight value; determining a diaphragm relative speed at a next moment based on an input current, a product value of a vector determined by an estimated value of a diaphragm relative speed and an estimated value of a diaphragm relative displacement, and a weight value vector obtained at a present moment; and determining an estimated value of the driving voltage using the estimated value of the diaphragm relative speed, the input current, and a DC impedance of the loudspeaker at the present moment.