Common Proof Mass MEMS Accelerometer for Low-Noise Multi-Axis Detection
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Solution Overview
Problem
Conventional MEMS accelerometers require separate proof masses for detecting in-plane and out-of-plane acceleration, leading to larger size, increased power consumption, and reduced sensitivity, making them less suitable for low-noise applications.
Innovation Solution
A microelectromechanical system (MEMS) accelerometer design featuring a common proof mass that contributes to the detection of both in-plane and out-of-plane acceleration through differential sensing, utilizing butterfly modes for out-of-plane acceleration and common translational modes for in-plane acceleration, with tethers and couplers configured to promote these modes while minimizing noise.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Adaptability or versatility
If separate proof masses are used for detecting in-plane and out-of-plane acceleration, then the detection coverage is improved, but the device size and power consumption increase
Solution Approach 1:
The patent combines multiple proof mass portions (first, second, third, and fourth portions) into a single integrated proof mass structure that can detect both in-plane and out-of-plane acceleration. This merging eliminates the need for separate proof masses for different acceleration directions, thereby reducing device size while maintaining comprehensive detection capability.
Solution Approach 2:
The single proof mass is designed to perform multiple functions: it can detect in-plane acceleration through common translational modes and out-of-plane acceleration through butterfly modes. This multi-functionality allows one proof mass to replace what would traditionally require multiple separate proof masses, reducing overall device volume.
2Adaptability or versatility
If separate proof masses are used for detecting in-plane and out-of-plane acceleration, then the detection coverage is improved, but the power consumption increases
Solution Approach 1:
By merging multiple proof mass portions into a single integrated structure, the patent reduces the total number of moving components that require power for operation. The single proof mass can be actuated and sensed more efficiently than multiple separate proof masses, thereby reducing overall power consumption while maintaining the ability to detect acceleration in multiple directions.
Solution Approach 2:
The universal proof mass structure performs multiple detection functions (in-plane and out-of-plane acceleration detection) within a single component, eliminating the need to power multiple separate proof masses. This multi-functionality directly reduces power consumption while maintaining comprehensive detection coverage.
3Adaptability or versatility
If separate proof masses are used for detecting in-plane and out-of-plane acceleration, then the detection coverage is improved, but the sensitivity is reduced
Solution Approach 1:
The patent merges multiple proof mass portions into a single integrated structure where all portions contribute to both in-plane and out-of-plane acceleration detection. This merging allows the entire proof mass to participate in detecting all acceleration components, thereby improving sensitivity compared to having separate proof masses where only specific portions would detect specific directions.
Solution Approach 2:
The universal proof mass structure enables all proof mass portions to contribute to detecting both in-plane and out-of-plane acceleration simultaneously. This multi-functional design maximizes the effective sensing mass for each acceleration direction, improving measurement precision and sensitivity while maintaining comprehensive detection coverage.
4Volume of moving object
If a common proof mass is used for both in-plane and out-of-plane acceleration detection, then the device size is reduced, but the mode coupling between in-plane and out-of-plane detection may increase
Solution Approach 1:
The patent segments the common proof mass into distinct portions (first, second, third, and fourth portions) with specific geometric arrangements and connection configurations. This segmentation allows different portions to be optimized for different detection modes while maintaining structural integrity, thereby reducing unwanted mode coupling between in-plane and out-of-plane detection.
Solution Approach 2:
The patent applies local quality by configuring different portions of the proof mass with specific properties: some portions are optimized for in-plane detection while others are optimized for out-of-plane detection. The connections between portions are designed with specific stiffness characteristics to promote desired modes while minimizing coupling, allowing each local region to contribute optimally to its intended detection function.
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 results in a compact, low-power MEMS accelerometer with enhanced sensitivity, suitable for low-noise applications, as it allows a single proof mass to replace multiple masses and reduces noise susceptibility by enabling differential detection of multiple axes.
Implementation Method 1
Acceleration can be detected using capacitive sensors coupled to the proof mass
Implementation Method 2
Acceleration can be detected using capacitive sensors coupled to the proof mass
Implementation Method 3
In response to out-of-plane accelerations, some MEMS accelerometers may experience butterfly modes, where one proof mass portion rotates counterclockwise relative to an axis while at the same time another proof mass portion rotates clockwise relative to the same axis
Implementation Method 4
In response to in-plane acceleration, the proof mass portions may experience common translational modes, where the proof mass portions move in the plane along the same direction
Data Source
AI summary
Microelectromechanical system (MEMS) accelerometers are described. The MEMS accelerometers may include multiple proof mass portions collectively forming one proof mass. The entirety of the proof mass may contribute to detection of in-plane acceleration and out-of-plane acceleration. The MEMS accelerometers may detect in-plane and out-of-plane acceleration in a differential fashion. In response to out-of-plane accelerations, some MEMS accelerometers may experience butterfly modes, where one proof mass portion rotates counterclockwise relative to an axis while at the same time another proof mass portion rotates clockwise relative to the same axis. In response to in-plane acceleration, the proof mass portions may experience common translational modes, where the proof mass portions move in the plane along the same direction.