Asymmetric Torsion Beams in Inertial Sensors for Vibration Separation
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Solution Overview
Problem
Inertial sensors face a decrease in detection sensitivity due to unnecessary vibrations that occur at frequencies close to the desired detection frequency, caused by beams with the same shape and torsional spring constant, leading to coupling of unwanted vibrations with the intended detection signal.
Innovation Solution
The inertial sensor design features first and second beams with different shapes but the same torsional spring constant, which allows for a greater difference in frequency between the intended seesaw swing and unnecessary vibrations, thereby reducing the occurrence of unwanted vibrations and enhancing detection sensitivity.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Ease of manufacture
If beams with the same shape and torsional spring constant are used, then the structure is simple and easy to manufacture, but unnecessary vibrations occur at frequencies close to the detection frequency causing decreased detection sensitivity
Solution Approach 1:
The patent applies asymmetry by configuring the first and second beams with different shapes while maintaining the same torsional spring constant. Specifically, the beams have different widths or thicknesses, creating asymmetric geometric properties that shift the vibration frequencies of unnecessary modes away from the detection frequency, thereby eliminating harmful vibrations without compromising manufacturing simplicity
Solution Approach 2:
The patent changes the geometric parameters of the beams (such as width, thickness, or length) to create different shapes while carefully controlling the torsional spring constant to remain equal for both beams. This parameter adjustment allows the beams to have different natural frequencies, preventing resonance with the detection signal while maintaining structural balance
2Measurement precision
If beams with different shapes are used to increase frequency difference, then detection sensitivity is improved, but the manufacturing complexity increases
Solution Approach 1:
The patent introduces asymmetry in beam geometry (different widths or thicknesses) to create frequency separation between the detection mode and unwanted vibration modes. This asymmetric design is carefully controlled to maintain equal torsional spring constants, achieving the goal of improved detection sensitivity through frequency differentiation while keeping the structural complexity manageable
Solution Approach 2:
The patent applies local quality by making specific local modifications to the beam geometry (such as varying width or thickness in specific regions) rather than completely differentiating the entire beam structure. This localized approach creates the necessary frequency difference while minimizing overall structural complexity and maintaining manufacturing feasibility
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 effectively suppresses unnecessary vibrations, improving the detection sensitivity of the inertial sensor by increasing the frequency difference between the intended vibration and unwanted modes, thus preventing coupling and enhancing the accuracy of acceleration detection.
Implementation Method 1
a first beam and a second beam that link the fixed section to the movable element and are torsionally deformed by the swing motion of the movable element
Implementation Method 2
the capacitance between the first movable section and the first detection electrode and the capacitance between the second movable section and the second detection electrode change accordingly in opposite phases. The acceleration in the axis-Z direction can therefore be detected based on the changes in the capacitance.
Data Source
AI summary
An inertial sensor includes, provided that axes X, Y, and Z are three axes perpendicular to one another, a substrate, a fixed section fixed to the substrate, a movable element that swings around a swing axis extending along the axis Y, a first beam and a second beam that link the fixed section to the movable element and are torsionally deformed by the swing motion of the movable element, and a detection electrode that is disposed on the substrate and overlaps with the movable element in the plan view along the axis-Z direction, and the first beam and the second beams differ in shape from each other and have the same torsional spring constant.