Accelerometer Raised Pads Isolate Strain Hysteresis
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Solution Overview
Problem
Accelerometers face hysteresis issues due to forces and thermal strains during construction, leading to inaccurate acceleration measurements as the physical structure changes, making it difficult to return to a null position.
Innovation Solution
The use of raised pads with pad flexures between the proof mass and the support structure to mechanically isolate the proof mass from strains, allowing for better isolation during construction and reducing hysteresis by minimizing contact and strain impact, which can be adjusted or removed post-construction for further isolation.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If the accelerometer is directly mounted to the support structure during construction, then the assembly is simpler and more rigid, but thermal strains and forces from stators bend the stators and create hysteresis in the acceleration measurement
Solution Approach 1:
Raised pads are introduced as intermediary elements between the accelerometer and the support structure. These pads serve as mechanical mediators that prevent direct contact and strain transmission from the stators to the accelerometer during construction and operation, thereby eliminating hysteresis while maintaining assembly simplicity
Solution Approach 2:
The support structure is segmented into multiple raised pads distributed around the accelerometer perimeter. This segmentation allows each pad to independently support the accelerometer while distributing thermal and mechanical strains, preventing concentrated stress that would cause stator bending and measurement hysteresis
2Measurement precision
If raised pads are used to isolate the accelerometer from stator strains, then hysteresis is reduced and measurement accuracy improves, but the device complexity increases due to additional components
Solution Approach 1:
The raised pads are merged with the support structure as integral features rather than separate components. This integration eliminates the need for additional fasteners or mounting hardware, reducing assembly complexity while maintaining the isolation function that prevents hysteresis and improves measurement precision
3Stability of the object's composition
If the accelerometer is compressed between stators during construction, then the assembly is more compact and stable, but the compression forces create strain in the accelerometer and epoxy bond joints leading to hysteresis
Solution Approach 1:
The raised pads provide beforehand cushioning by creating a compliant interface between the rigid stators and the accelerometer. This cushioning effect absorbs compression forces during assembly while maintaining stable positioning, preventing strain accumulation in epoxy bond joints that would otherwise lead to hysteresis and measurement inconsistency
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 approach enhances the accuracy of acceleration measurements by reducing hysteresis and bias instabilities, providing a more stable and cost-effective accelerometer assembly with improved mechanical isolation and reduced calibration needs.
Implementation Method 1
a flexure configured to flexibly connect the proof mass to the support structure
Implementation Method 2
The strains in the accelerometer assembly may accumulate due to thermal coefficient of expansion mismatches
Data Source
Figure 1
Figure 2
Figure 3~5B
AI summary
Techniques of manufacturing an accelerometer as disclosed herein include positioning an accelerometer between a first stator and a second stator, and the accelerometer comprises a plurality of features. In some examples, the plurality of features include a proof mass, a support structure defining a plane and configured to support the proof mass, a flexure configured to flexibly connect the proof mass to the support structure, and a plurality of raised pads, the plurality comprising at least one raised pad positioned between the flexure and an exterior of the support structure, wherein the at least one raised pad is configured to be isolatable. Techniques of manufacturing the accelerometer as disclosed herein further include compressing the first stator and the second stator onto the accelerometer, attaching a bellyband to the first stator and the second stator, and isolating the at least one raised pad.