Speaker Vibration Sensing With Dual Magnetic Sensors
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Solution Overview
Problem
Existing speakers lack accurate detection of vibrating part movement, leading to sound distortion and potential damage due to excessive amplitude, and existing feedback control systems are limited in range and rely on costly rare earth magnets.
Innovation Solution
A speaker design using two magnetic sensors to detect the magnetic field from a detection magnet, determining the difference between their outputs to expand the range of accurate vibration detection, allowing for precise feedback control and preventing excessive vibration.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Measurement precision
If a single magnetic sensor is used to detect the magnetic field from a detection magnet, then the detection system is simple, but the range of vibrations that can be detected with high accuracy is limited
Solution Approach 1:
The single magnetic sensor is divided into two magnetic sensors (first magnetic sensor and second magnetic sensor) spaced apart in the vibration direction. This segmentation allows the system to detect magnetic field differences that correspond to the position of the detection magnet, thereby expanding the accurate detection range while maintaining measurement precision.
Solution Approach 2:
The solution transitions from a single-point detection (one magnetic sensor) to a distributed detection system (two magnetic sensors spaced apart). By introducing the spatial dimension of sensor separation, the system can determine the position of the detection magnet more accurately across a wider range of vibrations.
2Adaptability or versatility
If the detection magnet moves to a distant position above the magnetic sensor, then the magnetic sensor can detect a weaker magnetic field, but the detection accuracy decreases
Solution Approach 1:
By segmenting the detection system into two magnetic sensors spaced apart, the system can detect the difference in magnetic field strength at different positions. This allows accurate detection even when the detection magnet is at distant positions, as the differential measurement compensates for the weakened magnetic field signal.
3Device complexity
If feedback control is implemented using a single magnetic sensor, then the control system is simple, but it cannot distinguish whether the detection magnet is located above or below the sensor
Solution Approach 1:
The single magnetic sensor is segmented into two magnetic sensors positioned at different locations. By comparing the outputs of these two sensors, the system can determine the relative position of the detection magnet (above or below) based on the difference in magnetic field measurements, thereby recovering the lost position information.
Solution Approach 2:
The difference between the outputs of the two magnetic sensors serves as an intermediary signal that encodes the position information of the detection magnet. This differential signal allows the feedback control system to distinguish the magnet's position without requiring complex additional sensors.
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
Enhances the accuracy and range of vibration detection, reducing sound distortion and preventing damage to components by accurately controlling the vibrating part's movement.
Implementation Method 1
a magnetic sensor such as a giant magneto resistive (GMR) element is fixed onto a top plate, and a small second magnet is attached to an outer surface of a bobbin
Implementation Method 2
a magnetic drive part configured to make the vibrating part vibrate; a voice coil is wound around a bobbin
Data Source
Figure 1
Figure 2
Figure 3~4
AI summary
A speaker includes: a drive-and-support part having a frame; a vibrating part supported by the frame such that the vibrating part is able to vibrate; a magnetic drive part configured to make the vibrating part vibrate; a detection magnet provided in one of the drive-and-support part or the vibrating part; a first magnetic sensor and a second magnetic sensor provided in the other one of the drive-and-support part or the vibrating part, and configured to detect a magnetic field produced by the detection magnet; and a detection circuit configured to determine a difference between a first detection output of the first magnetic sensor and a second detection output of the second magnetic sensor. The first and second magnetic sensors are spaced apart from each other in a direction in which the vibrating part vibrates.