Z-axis Gyroscope with Asymmetric Truncated Triangular Suspender

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Solution Overview

Problem

Z-axis MEMS gyroscopes face challenges in preventing coupling between primary and secondary oscillation modes due to manufacturing asymmetries and external vibrations, which affect the accuracy of angular rotation measurements.

Innovation Solution

The design incorporates piezoelectric drive and sense transducers placed on a suspender with a truncated triangular shape surrounding the oscillating proof mass, allowing for independent primary and secondary oscillation modes by optimizing the shape and placement of peripheral suspenders to minimize coupling effects.

Engineering Contradictions & Design Principles

VSEngineering Contradiction Analysis

1Measurement precision

If proof masses are suspended by suspenders to allow both primary and secondary oscillation modes, then the gyroscope can detect angular rotation, but coupling between primary and secondary modes occurs due to manufacturing asymmetries

Engineering Contradiction:

Improveangular rotation detection accuracyVSAvoidmode coupling resistance

Core Design Contradiction:

Measurement precisionVSReliability

Solution Approach 1:

The suspender is designed with an asymmetric truncated triangular shape where the three legs have different lengths. This intentional asymmetry creates different stiffness characteristics for primary mode oscillation versus secondary mode oscillation, allowing the suspenders to be more compliant in the primary mode direction while providing greater resistance to secondary mode coupling, thereby reducing spurious signals from manufacturing asymmetries

Inventive Principle:

Principle #4Asymmetry

Solution Approach 2:

The suspenders are configured with non-uniform properties along their length, with each leg having different dimensions and attachment points. The truncated triangular geometry creates local variations in stiffness and flexibility, allowing the suspender to selectively allow primary oscillation while restricting secondary oscillation coupling at specific locations

Inventive Principle:

Principle #3Local quality

2Reliability

If multiple pairs of proof masses are used to cancel external vibrations, then robustness against disturbances improves, but coupling between primary and secondary oscillation modes increases

Engineering Contradiction:

Improvevibration resistanceVSAvoidoscillation signal accuracy

Core Design Contradiction:

ReliabilityVSMeasurement precision

Solution Approach 1:

The asymmetric suspender configuration creates inherent differences in how each proof mass pair responds to external vibrations versus primary oscillation. The different leg lengths cause external vibration disturbances to affect each mass differently, enabling differential cancellation while the asymmetric stiffness pattern ensures that primary oscillation signals are transmitted more uniformly, reducing mode coupling

Inventive Principle:

Principle #4Asymmetry

3Ease of manufacture

If conventional suspension arrangements are used, then manufacturing is simpler, but coupling between primary and secondary modes cannot be prevented

Engineering Contradiction:

Improvesuspender fabrication simplicityVSAvoidoscillation mode independence

Core Design Contradiction:

Ease of manufactureVSMeasurement precision

Solution Approach 1:

The suspender is segmented into three distinct legs of different lengths, each contributing differently to the overall mechanical properties. This segmentation allows independent optimization of each leg's contribution to primary mode compliance versus secondary mode resistance, achieving mode decoupling through the collective behavior of segmented elements while maintaining a single integrated suspender structure that can be manufactured using standard MEMS processes

Inventive Principle:

Principle #1Segmentation

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 configuration enhances the robustness of the gyroscope by reducing the leakage of kinetic energy from primary to secondary modes and effectively cancels out external vibrations, improving the accuracy of angular rotation measurements.

Implementation Method 1

driven into a primary oscillation mode by piezoelectric drive transducers

Methodology Applied

Scientific EffectPiezoelectric effect: Piezoelectric Effect

Implementation Method 2

piezoelectric sense transducers...configured to detect the secondary oscillation mode

Methodology Applied

Scientific EffectPiezoelectric effect: Converse Piezoelectric Effect

Implementation Method 3

suspended from a first peripheral suspender...configured to flexibly allow oscillating drive motion and sense motion at a desired resonant frequency

Methodology Applied

Scientific EffectElasticity: Elasticity

Implementation Method 4

If the gyroscope undergoes angular rotation about the z-axis, the resulting secondary oscillation induced by the Coriolis force

Methodology Applied

Scientific EffectCoriolis force: Coriolis Force

Data Source

PatentUS11280610B2Piezoelectric z-axis gyroscope

Publication Date: 2022.03.22 MURATA MFG CO LTD

AI summary

The disclosure describes a z-axis gyroscope where a proof mass is suspended from a peripheral suspender and a central suspender. The peripheral suspender forms a truncated triangle around the proof mass, and the central suspender extends through the truncated corner of the triangle formed by the peripheral suspender. The proof mass is driven into a primary oscillation mode by one or more piezoelectric drive transducers located on the peripheral suspender. One or more piezoelectric sense transducers located on the base of the peripheral suspender are configured to detect the secondary oscillation mode of the proof mass.