Nested Torsion-Plate Accelerometer for Low Cross Coupling
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Solution Overview
Problem
Existing accelerometers suffer from interference due to substrate deformation, affecting detection precision and stability.
Innovation Solution
The accelerometer design incorporates a substrate with anchor points, an external coupling unit, first and second torsion plates, and elastic components, along with in-plane and out-of-plane detection devices, featuring symmetrical torsion plates and capacitor plates to reduce cross coupling and enhance sensitivity and accuracy.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Measurement precision
If differential detection by forming a differential capacitance with seesaw structures is used, then acceleration detection is achieved, but cross coupling occurs and detection precision is affected
Solution Approach 1:
The accelerometer is divided into independent detection units for different axes. Each axis has its own proof mass and capacitor arrangement, allowing separate detection of accelerations in X, Y, and Z directions without mutual interference, thus eliminating cross coupling between axes
Solution Approach 2:
Capacitor plates are strategically positioned at specific locations around the proof mass to detect acceleration along particular axes. The local capacitance changes are measured at predetermined positions, enabling precise detection of acceleration in specific directions while ignoring interference from other directions
2Measurement precision
If seesaw structures are used for differential detection, then acceleration detection is achieved, but substrate deformation affects test results
Solution Approach 1:
The detection system extracts the measurement function from the substrate structure. The proof mass and capacitor plates are designed as separate components that can detect acceleration independently of substrate deformations, removing the harmful influence of substrate stress on measurement accuracy
Solution Approach 2:
The proof mass acts as an intermediary between the acceleration force and the capacitor plates. It translates acceleration into positional changes that are then detected by the capacitive sensing system, isolating the measurement process from direct substrate deformation effects
3Measurement precision
If rotation radius of torsion plates is increased, then sensitivity of acceleration detection is improved, but device complexity increases
Solution Approach 1:
Multiple detection systems are nested within a compact three-dimensional structure. The first and second proof masses are positioned at different locations and orientations, with their detection capacitors arranged in a nested configuration that maximizes the effective rotation radius while minimizing the overall device footprint
Solution Approach 2:
The detection system transitions from a two-dimensional planar arrangement to a three-dimensional configuration. Proof masses and capacitor plates are positioned in different spatial layers and orientations, effectively increasing the rotation radius and detection sensitivity without proportionally increasing the device's planar dimensions
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 design improves detection accuracy and stability by reducing cross coupling and enhancing sensitivity across multiple axes, particularly in the third direction, while maintaining robustness against substrate deformation.
Implementation Method 1
The external coupling elastic component is located between the first torsion plate and the external coupling unit, and is located between the second torsion plate and the external coupling unit, and is configured to provide elastic support for the external coupling unit
Implementation Method 2
The in-plane detection device includes a plurality of first capacitor plates and a plurality of second capacitor plates... respectively cooperate with the external coupling unit to form a first differential detection capacitor and a second differential detection capacitor
Implementation Method 3
The out-of-plane detection device includes a third capacitor plate, the third capacitor plate is respectively spaced apart from the first torsion plate and the second torsion plate in the third direction, and forms a third differential detection capacitor with the external coupling unit
Data Source
AI summary
An accelerometer includes a substrate. The substrate includes anchor points. An external coupling unit is annular and is parallel to the substrate. A first torsion plate is disposed on an inner side of the external coupling unit and is connected to the anchor points. Inner coupling beams are disposed on a side, close to the anchor points, of the first torsion plate. A second torsion plate is disposed on the inner side of the external coupling unit and is connected to the anchor points, the second torsion plate is connected to the first torsion plate through two of the inner coupling beams, the second torsion plate and the first torsion plate are mutually embedded, the first torsion plate and the second torsion plate are symmetrical about a first axis of symmetry. The accelerometer reduces cross coupling reduced, and accuracy and anti-interference performance of the accelerometer are improved.