Teeter-Totter MEMS Accelerometer Anchor Displacement Tracking
Find Innovative SolutionsGenerate Solutions
Solution Overview
Problem
Microelectromechanical systems (MEMS) inertial sensors face challenges in accurately detecting in-plane accelerations due to distortions caused by anchor displacement, which can be misinterpreted as acceleration, leading to reduced sensitivity and linearity, especially under stress conditions like thermal variations.
Innovation Solution
The MEMS accelerometer design incorporates a teeter-totter configuration with a proof mass and counter-balance mass, using non-dedicated sense capacitors to detect both anchor displacement and acceleration, allowing for the cancellation of anchor displacement effects and enhancing sensitivity and linearity without dedicated sense capacitors for anchor tracking.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Measurement precision
If anchor displacement is detected using dedicated sense capacitors, then measurement precision is improved, but device complexity increases
Solution Approach 1:
The sense capacitors are designed to serve dual purposes: detecting both anchor displacement and acceleration simultaneously. The proof mass movement in response to acceleration creates capacitive changes that are detected by the same sense capacitors that detect anchor displacement, eliminating the need for separate dedicated sense capacitors for each function.
Solution Approach 2:
The patent combines the anchor displacement detection function and acceleration detection function into a single integrated sensing mechanism. The sense capacitors merge both detection functions by measuring capacitive changes caused by both anchor displacement and proof mass movement, reducing device complexity while maintaining measurement precision.
2Measurement precision
If anchor displacement effects are cancelled using teeter-totter configuration, then sensitivity is improved, but device complexity increases
Solution Approach 1:
The counter-balance mass is configured to offset the effects of anchor displacement on the proof mass. When the anchor displaces, the counter-balance mass moves in the opposite direction through the teeter-totter mechanism, canceling out the displacement effect and allowing the sense capacitors to detect only the acceleration-induced proof mass movement with enhanced sensitivity.
Solution Approach 2:
The teeter-totter configuration uses an asymmetric mechanical arrangement where the proof mass and counter-balance mass are positioned at different locations on the beam. This asymmetric design enables the counter-balance mass to effectively cancel anchor displacement effects while maintaining the ability to detect acceleration signals.
3Productivity
If dynamic range is enhanced without dedicated sense capacitors, then productivity is improved, but measurement precision deteriorates
Solution Approach 1:
The patent extracts the anchor displacement detection function from a separate dedicated sense capacitor and integrates it into the existing sense capacitor structure. By removing the need for dedicated anchor tracking capacitors and using the same sense capacitors for both acceleration and anchor displacement detection, manufacturing efficiency is improved while linearity is maintained through the teeter-totter cancellation mechanism.
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 effectively mitigates the impact of anchor displacement, increasing sensitivity and linearity, and allows for enhanced dynamic range without sacrificing linearity, making it suitable for various applications including automotive and wearable devices.
Implementation Method 1
Motion of the masses in response to acceleration and anchor displacement may be detected using capacitive sensors
Data Source
AI summary
A microelectromechanical system (MEMS) accelerometer is described. The MEMS accelerometer is arranged to limit distortions in the detection signal caused by displacement of the anchor(s) connecting the MEMS accelerometer to the underlying substrate. The MEMS accelerometer may include masses arranged to move in opposite directions in response to an acceleration of the MEMS accelerometer, and to move in the same direction in response to displacement of the anchor(s). The masses may, for example, be hingedly coupled to a beam in a teeter-totter configuration. Motion of the masses in response to acceleration and anchor displacement may be detected using capacitive sensors.