MEMS Accelerometer Layout for Double Differential Error Cancellation
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Solution Overview
Problem
Existing MEMS sensors face challenges in achieving double differential detection and self-testing, leading to incomplete cancellation of common mode errors due to the use of a single rotor mass design, which affects accuracy and reliability, especially in safety-critical applications.
Innovation Solution
A MEMS sensor design featuring multiple independent differential sensor elements anchored within a common anchoring area, allowing for double differential detection and self-testing by minimizing mechanical stress through symmetric anchoring and orthogonal suspension axes, thereby enhancing error compensation and operational reliability.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Device complexity
If a single rotor mass design is used, then the device complexity is reduced, but the measurement precision deteriorates due to incomplete cancellation of common mode errors
Solution Approach 1:
The single rotor mass is segmented into multiple independent rotor masses (at least two), each capable of independent movement. This segmentation enables multiple differential sensor elements to be formed, allowing for double differential detection that effectively cancels common mode errors while maintaining manageable device complexity through modular architecture.
Solution Approach 2:
Multiple independent differential sensor elements are merged within a common anchoring area, sharing common anchor structures and suspension mechanisms. This merging approach enables double differential detection by combining the outputs of multiple sensor elements, achieving superior error cancellation and measurement precision without proportionally increasing overall device complexity.
2Reliability
If multiple independent differential sensor elements are used, then the reliability is improved through self-testing capability, but the device complexity increases
Solution Approach 1:
The multiple independent differential sensor elements perform self-testing by monitoring each other's operation. The symmetric anchoring and orthogonal suspension axes enable the sensor elements to detect anomalies in each other, providing built-in self-diagnosis and self-testing capability that enhances reliability without requiring external testing equipment or complex control systems.
Solution Approach 2:
Orthogonal suspension axes are employed for the multiple rotor masses, creating asymmetric orientations that enable independent detection along different axes. This asymmetric design allows for comprehensive self-testing capability where each sensor element can monitor the operational status of others, improving reliability while maintaining clear functional differentiation.
3Ease of manufacture
If asymmetric anchoring is used, then the ease of manufacture is improved, but the measurement precision deteriorates due to mechanical stress-induced errors
Solution Approach 1:
The anchoring structure employs symmetric anchoring within a localized common anchoring area, concentrating the anchor structures in a specific region. This local symmetry ensures that mechanical stress is distributed uniformly across all sensor elements in the anchoring area, minimizing stress-induced measurement errors while maintaining ease of manufacture through localized symmetric fabrication processes.
Solution Approach 2:
The anchoring configuration uses symmetric geometric parameters and material properties for all anchor structures within the common anchoring area. By maintaining consistent anchoring parameters (dimensions, materials, orientations) across all sensor elements, the design achieves uniform mechanical stress distribution, eliminating precision errors while simplifying the manufacturing process through parameter standardization.
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 stress-induced errors and enables effective double differential detection and self-testing, ensuring accurate operation and reliability, particularly in safety-critical applications by ensuring similar mechanical stress across all sensor elements.
Implementation Method 1
When external forces are applied to the accelerometer, the rotor mass moves against the forced direction due to an inertial force
Implementation Method 2
The movement causes capacitance variations between interdigitated comb fingers which form pairs of parallel plate capacitors
Implementation Method 3
the rotor mass and the springs, which allow the rotor mass to move
Data Source
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AI summary
The present invention relates to A MEMS sensor with movable and fixed components for measuring linear acceleration. The MEMS sensor includes at least two mutually independent differential sensor elements disposed inside a common frame structure providing walls for hermetic sealing of the MEMS sensor. The mutually independent differential sensor elements are pairwise configured to perform double differential detection of linear acceleration. The MEMS sensor comprises a common anchoring area to which the at least two pairwise arranged differential sensor elements are anchored. The common anchoring area is located at the centroid of the pairwise configured differential sensor elements. A self-test capability of the MEMS sensor is also provided.