Dynamic Loudspeaker Velocity Detection Using Back-EMF Signals
Find Innovative SolutionsGenerate Solutions
Solution Overview
Problem
Existing methods for velocity detection in dynamic loudspeakers are hindered by mutual inductance, noise from capacitor size discrepancies, and time delays and noise from integration circuits, leading to inaccurate velocity measurements.
Innovation Solution
Employing a sensing structure with operational amplifiers to emulate mathematical equations for velocity calculation, using resistors, inductors, and capacitors to derive and stabilize the velocity signal, and integrating feedback for accurate alignment with system input.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Measurement precision
If an auxiliary coil is utilized to detect the velocity of the speaker cone, then velocity detection is enabled, but mutual inductance arises between the auxiliary and voice coils resulting in measurement errors
Solution Approach 1:
The patent extracts the velocity detection function from the mechanical domain (auxiliary coil) and relocates it to the electrical domain by utilizing the existing voice coil and measuring the back EMF voltage, thereby eliminating mutual inductance interference entirely
Solution Approach 2:
The patent introduces back EMF voltage as an intermediary quantity that indirectly represents velocity without requiring direct mechanical coupling or additional coils, thus avoiding mutual inductance problems while maintaining measurement capability
2Ease of operation
If a capacitor-based approach is used for detecting the velocity of the speaker cone, then the detection method is straightforward, but the minute size of the sensor capacitor leads to substantial noise due to the considerable difference in size between the environmental capacitor and the sensor capacitor
Solution Approach 1:
The patent replaces the mechanical/electrical capacitor-based velocity detection system with an electromagnetic-based system that measures back EMF voltage, eliminating the noise problem associated with small capacitor sizes while maintaining operational simplicity
3Measurement precision
If a piezoelectric accelerometer is affixed to the loudspeaker cone to measure and compute the velocity, then velocity can be detected through acceleration measurement and integration, but the presence of non-zero mass in the piezoelectric accelerometer results in a time delay in the transmission of velocity to the sensor
Solution Approach 1:
The patent replaces the mechanical piezoelectric accelerometer system with an electrical measurement system that directly measures back EMF voltage proportional to velocity, eliminating the need for mass-based sensing and integration operations that cause time delays
Solution Approach 2:
The patent measures velocity directly through back EMF voltage without requiring sequential operations (acceleration measurement followed by integration), thereby eliminating the time delay inherent in multi-step processing
4Measurement precision
If a piezoelectric accelerometer with integration circuit is used to calculate velocity from acceleration, then velocity can be computed, but the integration circuit can introduce noise, thereby impairing the accuracy of the system
Solution Approach 1:
The patent extracts the velocity measurement function from the integration circuit and relocates it to the electromagnetic sensing domain by measuring back EMF voltage, thereby eliminating the noise-generating integration circuit entirely
Solution Approach 2:
The patent uses back EMF voltage as an intermediary that directly represents velocity without requiring integration operations, thereby eliminating the noise introduced by integration circuits while maintaining velocity calculation capability
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
Achieves precise velocity detection and feedback, reducing distortion to several decimal places, enabling high-fidelity sound production.
Implementation Method 1
When applying voltage across a motion conductor within magnetic field, it forces the conductor to move. The voltage across the motion conductor can be represented as um=R*i+L*di/dt+Kv; where R is the conductor's resistance, L is the inductance, i is the current, v is the velocity, and K is a constant in linear magnetic field.
Data Source
AI summary
Velocity detection is the crucial step for motion feedback and control. A dynamic loudspeaker can be conceptualized as a motion conductor within magnetic field. This invention calculates the velocity of a motion conductor, uses operational amplifier to emulate the calculation and realize the velocity detection.