Integrated 3-Axis Accelerometer with Nested Teeter-Totter Proof Mass
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Solution Overview
Problem
Conventional three-axis accelerometers with multiple independent proof masses are too large and expensive, and those using a single solid proof mass for all directions are susceptible to mechanical stress and cross-talk, leading to poor performance and accuracy issues.
Innovation Solution
A single mass integrated three-axis accelerometer design featuring a laterally-moving x-y axis proof mass with an embedded teeter-totter z-axis proof mass, mechanically coupled with torsional springs, reducing mechanical cross-talk and z-axis offset errors, and providing in-plane symmetry.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Measurement precision
If multiple independent proof masses are used for each sensing direction, then measurement precision is improved, but device complexity and footprint increase
Solution Approach 1:
The patent merges multiple independent proof masses into a single integrated proof mass structure. The x-y axis proof mass and z-axis proof mass are combined into one monolithic structure, reducing the number of separate components while maintaining the ability to measure acceleration in multiple directions. This integration reduces device complexity and footprint while preserving measurement precision through the coupled motion detection capabilities.
Solution Approach 2:
The single integrated proof mass serves multiple functions by detecting acceleration in both x-y directions and z-direction simultaneously. The proof mass structure is designed to respond to forces in multiple orientations, making it a multi-functional sensing element that replaces what would traditionally require separate dedicated proof masses for each axis, thereby reducing overall device complexity.
2Device complexity
If a single solid proof mass is used for all directions, then device complexity is reduced, but mechanical cross-talk and stress interfere with measurement precision
Solution Approach 1:
The single integrated proof mass is segmented into functionally distinct regions: an x-y axis proof mass portion and a z-axis proof mass portion. These segments are mechanically coupled through torsional springs that allow independent motion detection for each axis while maintaining structural integration. This segmentation enables the single proof mass to behave as multiple independent sensing elements, reducing mechanical cross-talk and stress interference while preserving measurement precision.
Solution Approach 2:
Torsional springs serve as intermediary elements between the x-y axis proof mass and z-axis proof mass. These springs mechanically couple the two portions while allowing them to move independently in their respective directions. The torsional springs act as mediators that transmit force while isolating the motion paths, preventing direct mechanical interference and cross-talk between the x-y and z-axis sensing directions.
3Measurement precision
If conventional three-axis accelerometer constructions are used, then measurement capability is achieved, but footprint is larger than necessary
Solution Approach 1:
The z-axis proof mass is nested within or integrated with the x-y axis proof mass structure. The nested configuration allows the z-axis sensing functionality to be embedded within the footprint of the x-y axis proof mass, eliminating the need for separate dedicated space for the z-axis proof mass. This nesting approach significantly reduces the overall footprint while maintaining full three-axis measurement capability.
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 minimizes mechanical cross-talk and z-axis offset errors, improving accuracy and reducing the footprint of the accelerometer, making it more suitable for smaller applications while maintaining performance.
Implementation Method 1
the proof mass(es) often oscillate in response to the acceleration
Implementation Method 2
The vertically-moving mass is mechanically coupled to the laterally-moving mass with one or more torsional springs
Implementation Method 3
the laterally-moving mass is mechanically coupled to one or more anchors or supports with one or more laterally-moving springs
Implementation Method 4
The displacement and/or oscillation frequency of the proof mass(es) is measured using capacitive sensing techniques
Implementation Method 5
These accelerometers generally utilize proof masses springedly coupled to a substrate, which are displaced in response to experiencing acceleration
Data Source
AI summary
A three-axis accelerometer includes a single, integrated mass including at least one lateral (x-y) proof mass and at least one vertical (z) proof mass. The vertical proof mass is arranged as a teeter-totter mass, which is located within the lateral proof mass. The vertical proof mass is mechanically coupled to the lateral proof mass with one or more torsional springs, and the lateral proof mass is mechanically coupled to one or more anchors with one or more lateral springs. The at least one vertical proof mass may be symmetrically positioned about one or more axes of the three-axis accelerometer, so that the 3-axis accelerometer has in-plane symmetry. The three-axis accelerometer may be less susceptible for mechanical cross-talk or noise and may provide a smaller packaged solution for sensing acceleration in three directions.