Capacitive MEMS Acceleration Sensor Asymmetric Mass Design
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Solution Overview
Problem
Existing capacitive MEMS tri-axis acceleration sensors face challenges in being both mechanically robust against external stresses and vibrations while maintaining a small size, with limitations in sensitivity and mass distribution leading to errors in measurement.
Innovation Solution
The capacitive micromechanical acceleration sensor design features spring structures and comb structures positioned to maximize moment of inertia and minimize mass, with asymmetric mass distribution and shared anchoring points for the rotor and stator electrodes, enhancing robustness and sensitivity while minimizing errors from mechanical stresses.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Area of moving object
If the spring structures are positioned close to the rotor electrode to minimize sensor area, then the sensor size is reduced, but the moment of inertia decreases leading to reduced sensitivity
Solution Approach 1:
The patent applies asymmetry by positioning the spring structures asymmetrically relative to the rotor electrode, specifically placing them as far from the signal generating rotor electrode as possible while maintaining asymmetric mass distribution. This asymmetric configuration maximizes the moment of inertia for a given sensor area, thereby improving sensitivity without requiring increased sensor size.
2Measurement precision
If mass is increased to achieve adequate deflection of the rotor electrode, then sensitivity improves, but the sensor becomes more sensitive to external vibrations and mechanical stresses
Solution Approach 1:
The patent applies preliminary action by strategically positioning the spring structures and asymmetric mass distribution before the sensor operates, such that the moment of inertia is maximized in advance. This pre-optimized configuration ensures adequate deflection with minimal mass, thereby improving sensitivity while simultaneously reducing sensitivity to external vibrations and mechanical stresses.
3Measurement precision
If the anchors are positioned far from the rotor and stator electrodes to reduce error signals, then measurement accuracy improves, but the mechanical robustness against external stresses decreases
Solution Approach 1:
The patent applies local quality by positioning the anchors close to the rotor and stator electrodes specifically in regions where they can provide mechanical support without significantly affecting the measurement. This localized anchoring strategy ensures mechanical robustness while minimizing the error signal generation, as the anchors are placed in optimal locations that balance both requirements.
4Stability of the object's composition
If symmetric mass distribution is used to balance the rotor electrode, then mechanical stability improves, but the sensor area increases and manufacturing cost rises
Solution Approach 1:
The patent applies asymmetry by using asymmetric mass distribution in the rotor electrode configuration. This asymmetric design achieves adequate mechanical stability through the optimized positioning of the asymmetric mass relative to the spring structures, while simultaneously reducing the sensor area and manufacturing complexity compared to symmetric designs.
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 results in a more robust, sensitive, and cost-effective capacitive micromechanical tri-axis acceleration sensor that is less sensitive to external vibrations and requires less mass for adequate deflection, reducing errors and maintaining mechanical stability.
Implementation Method 1
a first spring structure for movably anchoring the rotor electrode of the first sensor at the substrate and a second spring structure for movably anchoring the rotor electrode of the first sensor at the substrate
Implementation Method 2
capacitive micromechanical acceleration sensor
Data Source
AI summary
The invention relates to a capacitive micromechanical acceleration sensor comprising a first sensor (2), a second sensor (4), and a third sensor (5). The first sensor (2) comprises a rotor electrode (6) and stator electrode (7). The sensor comprises a first beam (8) that is connected to a rotor electrode support structure (19) and that is connected to the rotor electrode (6). The sensor comprises a second beam (12) that is connected to the rotor electrode support structure (19) and that is connected to the rotor electrode (6). The second sensor (4) is situated in a first space (17) circumscribed by the first beam (8), the first sensor (2), and the rotor electrode support structure (19).The third sensor (5) is situated in a second space (18) circumscribed by the second beam (12), the first sensor (2), and the rotor electrode support structure (19).