MEMS Resonator Electrostatic Springs Isotropic Stiffness

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Solution Overview

Problem

Conventional MEMS inertial angular sensors face challenges in achieving isotropic stiffness, leading to frequency anisotropy issues that affect the accuracy of gyroscope measurements, with existing solutions failing to adequately compensate for stiffness anisotropy in all directions.

Innovation Solution

The use of a resonator with multiple pairs of electrostatic springs positioned at specific angles to form right angles and symmetrical configurations, allowing for electrical adjustment of stiffness to compensate for both cosine and sine components of failing stiffness, thereby achieving isotropic stiffness in all directions.

Engineering Contradictions & Design Principles

VSEngineering Contradiction Analysis

1Manufacturing precision

If conventional MEMS machining methods are used for resonators, then manufacturing is simple and cost-effective, but frequency anisotropy reaches ±1% (±100 Hz) which is insufficient for precise gyroscopes requiring anisotropy below ±1 Hz

Engineering Contradiction:

Improvefrequency anisotropyVSAvoidresonator structure

Core Design Contradiction:

Manufacturing precisionVSDevice complexity

Solution Approach 1:

The patent replaces mechanical adjustment methods with electrical control through electrostatic springs. The electrostatic springs use electrical voltage to adjust stiffness characteristics, eliminating the need for complex mechanical adjustment mechanisms while achieving the required frequency anisotropy correction from ±1% to below ±1 Hz

Inventive Principle:

Principle #28Mechanics substitution (Replace mechanical system)

Solution Approach 2:

The patent changes the physical parameters of the resonator by introducing electrostatic springs that can dynamically adjust the stiffness matrix elements. By controlling the electrical voltage applied to these springs, the system can modify the resonator's mechanical properties to correct frequency anisotropy without changing the physical geometry

Inventive Principle:

Principle #35Parameter changes

2Measurement precision

If electrostatic springs are added to correct frequency anisotropy, then measurement precision improves, but device complexity increases due to additional components and control systems

Engineering Contradiction:

Improvegyroscope accuracyVSAvoidresonator structure

Core Design Contradiction:

Measurement precisionVSDevice complexity

Solution Approach 1:

The electrostatic springs serve multiple functions simultaneously: they provide mechanical support for the resonator mass, enable dynamic stiffness adjustment to correct frequency anisotropy, and can potentially serve as sensing elements. This multi-functionality reduces the need for separate components, thereby limiting the increase in device complexity while achieving improved gyroscope accuracy

Inventive Principle:

Principle #6Universality (Multi-functionality)

3Adaptability or versatility

If mechanical adjustment methods are used to balance the resonator, then manufacturing is simpler, but the solution cannot compensate for frequency anisotropy in all directions and requires individual stiffness adjustment of electrostatic springs

Engineering Contradiction:

Improveisotropic stiffness correctionVSAvoidadjustment mechanism

Core Design Contradiction:

Adaptability or versatilityVSDevice complexity

Solution Approach 1:

The patent implements dynamic adjustment capabilities through electrostatic springs that can be controlled in real-time during operation. This allows the system to adapt to different vibration orientations and correct frequency anisotropy in all directions dynamically, rather than relying on fixed mechanical adjustments that can only compensate for specific orientations

Inventive Principle:

Principle #15Dynamics

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 corrects frequency anisotropy in inertial angular sensors, enhancing the accuracy and precision of gyroscope measurements by ensuring uniform stiffness regardless of vibration orientation.

Implementation Method 1

The resonator comprises at least one mass suspended by mechanical springs and having a number N of pairs Pi (2≤i≤N) of electrostatic springs

Methodology Applied

Scientific EffectElectrostatic force: Electrostatics

Data Source

PatentUS11215456B2Resonator configured to be integrated into an inertial angular sensor

Publication Date: 2022.01.04 SAFRAN SA

AI summary

The invention concerns a resonator 1 configured to be integrated into an inertial angular sensor, said resonator 1 comprising at least one mass suspended by mechanical springs 5, a number N of pairs Pi (2≤i≤N) of electrostatic springs 50, said resonator 1 defining at least four axes of symmetry S1, S2, S3 and S4, characterized in that: each pair Pi consists of two electrostatic springs 50 each having a privileged axis of action, these electrostatic springs 50 being positioned so that their respective axes form a right angle; for at least one spring of one of the pairs and one spring of another pair, the angle formed by these two springs is equal to a predefined angle.