Angular Acceleration Sensor Beam With Stress Concentration Holes
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Solution Overview
Problem
Existing angular acceleration sensors face challenges in achieving both a wide detection band and a high signal-to-noise (S/N) ratio due to the trade-off between sensitivity and resonant frequency, as modifying the beam design to increase resonant frequency reduces sensitivity and vice versa, and external stress from the housing or temperature unevenness can degrade signal quality.
Innovation Solution
The design includes a beam with a width-direction protrusion and through-holes, where the detection element is positioned to concentrate stress efficiently, and the beam is connected to the fixed portion and weight in a way that minimizes unwanted stress transmission, maintaining rotational balance and increasing sensitivity and precision.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Speed
If the beam width is increased to increase resonant frequency, then the resonant frequency is improved, but the sensitivity is reduced due to reduced deflection
Solution Approach 1:
The beam is designed with non-uniform width, featuring a wider middle portion and narrower end portions. This local variation in geometry allows the middle portion to have high resonant frequency while the end portions maintain high deflection for sensitivity. The detection element is positioned at the middle portion where stress concentration occurs, enabling it to detect angular acceleration effectively despite the overall increased beam width.
2Speed
If the beam width is increased to obtain a wide detection band, then the detection band is improved, but the S/N ratio is reduced due to increased stress transmission from the fixed portion
Solution Approach 1:
The beam's non-uniform width design creates a middle portion with higher width that acts as a stress isolation zone. This local geometric feature prevents stress from the fixed portion from being transmitted to the detection element, thereby maintaining a high S/N ratio even with increased beam width for wide detection band.
Solution Approach 2:
The middle portion of the beam with larger width serves as an intermediary structure between the fixed portion and the detection element. It mechanically decouples the stress transmission path, allowing the detection element to be isolated from unwanted stress while still detecting the intended angular acceleration signals.
3Measurement precision
If through-holes are formed in the beam to reduce rigidity and increase sensitivity, then the sensitivity is improved, but the resonant frequency is reduced
Solution Approach 1:
Through-holes are extracted from the end portions of the beam to reduce rigidity locally. This extraction of material from specific locations (end portions) allows increased deflection and sensitivity without significantly affecting the overall resonant frequency, as the middle portion maintains sufficient structural integrity.
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 allows for a wide detection band and high S/N ratio by efficiently concentrating stress on the detection element, reducing unwanted stress transmission, and maintaining high sensitivity and precision in detecting angular acceleration.
Implementation Method 1
The detection element is disposed in the beam and detects stress due to deflection of the beam along the planar surface
Implementation Method 2
The weight is elastically supported on the fixed portion by the beam
Data Source
AI summary
An angular acceleration sensor includes a planar surface extending along an X-Y plane, a fixed portion, a weight, a beam, and piezoresistors. The weight is supported by the fixed portion. The beam extends along an Y-axis and is connected to the fixed portion and the weight. The beam includes through-holes extending therethrough in a Z-axis direction and protrusions protruding in an X-axis direction. The positions of the piezoresistors in the Y-axis direction overlap those of the through-holes and are displaced from those of the width-direction protrusions.