Multi-axis MEMS Accelerometer Symmetrical Proof Mass Design
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Solution Overview
Problem
Conventional multi-axis MEMS accelerometers face challenges in reducing stress sensitivity and size for integration into smaller devices, such as mobile phones and wearable electronics, while maintaining accurate acceleration measurement across multiple axes.
Innovation Solution
The design incorporates a Z-axis proof mass with two pairs of electrodes and a symmetrical arrangement of X-axis and Y-axis accelerometer subcomponents within the perimeter of the Z-axis proof mass, allowing for independent rotation and reduced mechanical coupling, which enhances symmetry and minimizes stress-induced deformations, thereby improving sensitivity and size reduction.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Volume of moving object
If the accelerometer size is reduced for integration into smaller devices, then the device compactness is improved, but the stress sensitivity increases due to reduced structural symmetry and increased mechanical coupling
Solution Approach 1:
The patent applies asymmetry principle in reverse (maintaining symmetry) by designing the Z-axis proof mass with symmetrical electrode placement and arranging X-axis and Y-axis accelerometer subcomponents symmetrically within the Z-proof mass perimeter. This symmetrical configuration compensates for the reduced overall size by ensuring balanced stress distribution, thereby reducing stress sensitivity even in a compact form factor.
Solution Approach 2:
The patent implements nesting by placing the X-axis and Y-axis accelerometer subcomponents within the perimeter of the Z-axis proof mass structure. This nested arrangement allows multi-axis acceleration sensing in a compact volume while maintaining structural integrity and reducing mechanical coupling between axes, thereby addressing both size reduction and stress sensitivity concerns.
2Device complexity
If multiple accelerometer subcomponents are integrated into a single structure, then the device complexity is reduced, but the stress-induced deformations increase due to mechanical coupling between subcomponents
Solution Approach 1:
The patent applies segmentation by providing separate Z-axis proof masses for different quadrants (first and second Z-proof masses) while arranging them symmetrically. The X-axis and Y-axis accelerometer subcomponents are also segmented and positioned within the perimeters of respective Z-proof masses. This segmented yet symmetrical design reduces mechanical coupling and stress-induced deformations while maintaining integration benefits.
Solution Approach 2:
The patent maintains symmetry in the arrangement of multiple accelerometer subcomponents. The first and second Z-proof masses are positioned symmetrically, and the X-axis and Y-axis subcomponents are arranged symmetrically within the perimeters. This symmetrical configuration ensures balanced stress distribution across all subcomponents, reducing stress-induced deformations while achieving integration.
3Measurement precision
If the Z-axis proof mass is made larger to increase inertial torque for sensitivity, then the measurement precision is improved, but the overall device size increases
Solution Approach 1:
The patent places the X-axis and Y-axis accelerometer subcomponents within the perimeter of the Z-axis proof mass, creating a nested configuration. This allows the Z-proof mass to maintain sufficient size for adequate inertial torque and sensitivity, while the nested subcomponents utilize the available space efficiently, preventing overall device size increase.
Solution Approach 2:
The patent arranges the first and second Z-proof masses symmetrically with respect to multiple axes (first axis, second axis, third diagonal axis, and fourth diagonal axis). This multi-axial symmetrical arrangement optimizes the spatial distribution of mass, maintaining high inertial torque for sensitivity while achieving compact overall dimensions through efficient three-dimensional space utilization.
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 enables efficient detection of acceleration across multiple axes with reduced stress sensitivity and smaller size, effectively addressing the limitations of conventional MEMS accelerometers by maintaining high inertial torque and symmetry, thus enhancing the accelerometer's performance in smaller devices.
Implementation Method 1
maintaining high inertial torque
Implementation Method 2
the first plurality of electrodes and the second plurality of electrodes are symmetrical about each of the first axis
Data Source
AI summary
Implementations of an accelerometer component may include: a first Z proof mass rotatable about a first axis and coupled to an anchor, the first Z proof mass including a first plurality of electrodes. Implementations may include a second Z proof mass rotatable about the first axis and coupled to the anchor, the second Z proof mass including a second plurality of electrodes. An X-axis accelerometer subcomponent may be located within a perimeter of the first Z proof mass, and a Y-axis accelerometer subcomponent may be located within a perimeter of the second Z proof mass. The first plurality of electrodes and the second plurality of electrodes may be symmetrical about each of the first axis, a second axis perpendicular to the first axis, a third axis diagonal to the first axis and second axis, and a fourth axis diagonal to the first axis and second axis.