Acceleration Sensor Coupling Portion Noise Suppression
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Solution Overview
Problem
Existing acceleration sensors face issues with noise characteristics deterioration due to manufacturing variations, particularly in brown noise, which affect the signal-to-noise ratio and detection accuracy, especially when frequency characteristics between movable portions differ.
Innovation Solution
The acceleration sensor design incorporates a coupling portion that aligns the frequency characteristics of two movable bodies with different rotational moments, forming a single structural body to suppress noise characteristics deterioration, while maintaining high detection sensitivity and reducing manufacturing variations' influence.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Measurement precision
If a pair of movable portions with different rotational moments are provided to suppress sensitivity of other axes, then detection accuracy is improved, but manufacturing variations cause frequency characteristic variations and noise characteristics deteriorate
Solution Approach 1:
The patent merges the first movable body and second movable body into a single integrated structure where the movable portions are coupled together. This combining approach allows the system to maintain the axis-suppressing functionality while sharing common structural characteristics that reduce manufacturing variations and stabilize frequency characteristics, thereby improving noise performance.
Solution Approach 2:
The patent introduces a coupling portion with specific spring constant characteristics to adjust and equalize the frequency characteristics of the movable portions. By changing the mechanical coupling parameters, the system compensates for manufacturing variations and stabilizes the overall frequency response, reducing brown noise while preserving the differential measurement capability.
2Measurement precision
If multiple movable portions with different rotational moments are used to improve detection accuracy, then sensitivity to other axes is suppressed, but frequency characteristic variations occur due to manufacturing variations
Solution Approach 1:
By integrating multiple movable bodies into a unified structure with shared support elements and coupling portions, the patent reduces the number of independent manufacturing processes. This merging ensures that all movable portions experience the same manufacturing conditions, thereby reducing frequency characteristic variations while maintaining the necessary rotational moment differences for axis suppression.
Solution Approach 2:
The coupling portion acts as an intermediary element that mechanically links the movable portions and transmits common vibrations while allowing differential responses. This intermediary structure ensures that manufacturing variations affect all movable portions equally, thereby canceling out in the differential measurement while preserving the axis-suppressing functionality.
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 configuration enhances the signal-to-noise ratio, improves detection accuracy, and reduces manufacturing costs by minimizing the impact of variations, resulting in a more reliable acceleration sensor.
Implementation Method 1
Each movable portion includes a first movable portion and second movable portion that are provided with a swinging axis interposed therebetween and have different rotational moments around the swinging axis. When acceleration in the Z-axis direction is applied, each movable portion swings in a seesaw manner around the swinging axis due to a difference in a rotational moment
Implementation Method 2
capacitance between each first movable portion and each first fixed electrode and capacitance between each second movable portion and each second fixed electrode are displaced in opposite phases. For that reason, the acceleration in the Z-axis direction can be measured based on an amount of change (differential) in capacitance
Data Source
AI summary
An acceleration sensor includes a substrate, a first movable body that includes a first movable portion and a second movable portion having a rotational moment around a first swinging axis smaller than that of the first movable portion, a second movable body that includes a third movable portion and a fourth movable portion having a rotational moment around a second swinging axis smaller than that of the third movable portion, a first fixed electrode that is disposed on the substrate and faces the first movable portion, a second fixed electrode that faces the second movable portion, a third fixed electrode that faces the third movable portion, a fourth fixed electrode that faces the fourth movable portion, and a coupling portion that couples the first movable body and the second movable body.