High G-Range Accelerometer Proof Mass with Recessed Damping
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Solution Overview
Problem
Existing high G-range accelerometers face challenges in achieving maximum bi-directional and symmetrical damping to accommodate acceleration ranges above several thousand G's, often requiring a compromise between sensitivity and measurement range, and are limited by economic and fabrication constraints.
Innovation Solution
A high G-range damped acceleration sensor is designed with a minimum mass proof mass and maximum surface area, utilizing squeezed gas films for damping and piezoresistive gages for signal conversion, and manufactured using Deep Reactive-Ion Etching (DRIE) technology to optimize bi-directional damping and suppress ringing.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Force
If the proof mass area is reduced to increase measurement range, then the maximum acceleration measurement range is improved, but the damping coupling to the damper is diminished linearly and the damping coefficient is reduced more strongly than linearly
Solution Approach 1:
The patent changes the geometric parameters of the proof mass by introducing recesses that reduce the overall area while maintaining the damping coupling through strategic placement of damping structures. This allows the proof mass to achieve both reduced area for high G-range and maintained damping effectiveness through the recess design that preserves coupling pathways.
Solution Approach 2:
The proof mass is segmented by introducing recesses that create distinct regions - the main body and the recess areas. This segmentation allows different portions of the proof mass to serve different functions: the main body provides the necessary mass for sensitivity while the recess areas facilitate damping coupling without requiring the entire surface area to be present.
2Force
If the measuring structure is stiffened to increase measurement range, then the maximum acceleration measurement range is improved, but the available damping of the proof mass is outrun and the coupling to the damper is reduced
Solution Approach 1:
The patent modifies the stiffness parameter of the measuring structure by introducing recesses that reduce the overall structural rigidity while maintaining sufficient stiffness for high G-range measurement. This controlled parameter change allows the structure to be stiff enough for high acceleration measurement but not so stiff that it outruns the damping capabilities.
Solution Approach 2:
The measuring structure is segmented by the recesses into distinct regions with different stiffness characteristics. The recess areas create compliance pathways that maintain damping coupling while the main structure retains sufficient stiffness for high G-range measurement, resolving the contradiction between stiffness and damping coupling.
3Reliability
If the proof mass area is maximized to maintain damping coupling, then the damping effectiveness is improved, but the measurement range is limited and the sensor size increases
Solution Approach 1:
The patent changes the area parameter by introducing recesses that reduce the proof mass area while maintaining damping effectiveness through strategic placement of damping structures in the recess areas. This allows the sensor to achieve high G-range measurement capability without sacrificing damping effectiveness.
Solution Approach 2:
The patent moves the damping function from the horizontal plane (requiring large proof mass area) to the vertical dimension by placing damping structures in the recess areas and using the air gap between the proof mass and substrate. This dimensional transition allows effective damping with reduced planar area, enabling high G-range measurement.
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
The design achieves effective bi-directional and symmetrical damping, allowing for accurate measurement of high-frequency accelerations while maintaining sensor sensitivity and minimizing size and cost constraints.
Implementation Method 1
utilizing squeezed gas films for damping
Implementation Method 2
piezoresistive gages for signal conversion
Data Source
Figure 1A~1B
Figure 2A
Figure 2B
AI summary
A new high G-range damped acceleration sensor is proposed with a proof mass optimized for maximized, bi-directional and symmetrical damping to accommodate acceleration ranges above and beyond several thousand G's. In order to achieve the maximum, bi-directional and symmetrical damping, the high G- range acceleration sensor is designed to have minimum amount of mass in the proof mass while maximizing its surface areas. Such high G-range damped acceleration sensor can be applied to any application in which damping (or suppression of ringing) is desired at quite high frequencies.