MEMS Gyroscope Quartet Mass Vibration Noise Rejection
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Solution Overview
Problem
Microelectromechanical (MEMS) gyroscopes face challenges in accurately measuring angular rotation due to external vibrations, which can cause noise in the output signal, especially at frequencies below 50 kHz, leading to sensitivity issues and energy leakage in single-mass designs, and require robustness against both linear and rotational vibrations.
Innovation Solution
A microelectromechanical gyroscope design featuring a quartet of Coriolis masses centered around a quartet center point, with elongated mass elements coupled to each Coriolis mass, allowing for detection of secondary oscillation modes while resisting undesired oscillations through a central synchronization and suspension arrangement that provides structural support and synchronization.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Device complexity
If a single proof mass is used in the gyroscope, then the device complexity is reduced, but the output signal becomes very noisy when external vibrations are present at frequencies close to the operating frequency
Solution Approach 1:
The single proof mass is segmented into multiple proof masses (typically four) arranged in a specific configuration. This segmentation allows the system to distinguish between useful Coriolis signals and vibration noise by analyzing the relative movements of multiple masses, thereby improving output signal quality while maintaining manageable device complexity through modular architecture.
Solution Approach 2:
Multiple proof masses are used as copies of the single mass concept, where each mass experiences the same vibration environment but their relative positions and movements provide differential information. This copying approach enables noise rejection through differential measurement while keeping each individual mass simple in structure.
2Reliability
If the operating frequency is increased above 50 kHz, then the robustness against vibrations is improved, but the sensitivity of the gyroscope becomes very low and quadrature signals become prominent
Solution Approach 1:
The system changes the operating parameters by using multiple proof masses with specific mass values and arrangements. This allows the gyroscope to maintain high sensitivity at lower frequencies while achieving robustness against vibrations through the differential measurement capability provided by the multi-mass configuration, avoiding the need to operate at excessively high frequencies.
Solution Approach 2:
The system uses differential measurement techniques that provide implicit feedback about the vibration environment and Coriolis effects. By continuously monitoring the relative positions and movements of multiple proof masses, the system can reject vibration-induced signals and maintain accurate measurements across a broader frequency range without sacrificing sensitivity.
3Device complexity
If a one-mass gyroscope is used, then the device complexity is reduced, but energy leakage from the drive mode occurs due to reaction forces
Solution Approach 1:
The single driven mass is segmented into multiple masses that can be driven in a coordinated manner. This segmentation allows the system to distribute the drive forces and reaction forces across multiple masses, reducing energy leakage from any single mass while maintaining the overall functionality of the gyroscope with manageable complexity.
4Reliability
If two or four proof masses oscillate in anti-phase, then the robustness against vibrations is improved through automatic cancellation, but the device complexity increases
Solution Approach 1:
The system segments the proof mass into multiple discrete masses (typically four) that can be independently positioned and controlled. This segmentation enables anti-phase oscillation patterns that automatically cancel vibration effects while keeping the overall device complexity manageable through modular design and standardized mass configurations.
Solution Approach 2:
The multiple proof masses are arranged in an asymmetric configuration relative to the drive mechanism, allowing them to experience different phase relationships during vibration. This asymmetric arrangement enables the masses to cancel vibration effects through differential movement while maintaining a relatively simple overall structure that does not require complex 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 enhances the signal-to-noise ratio by allowing Coriolis masses and elongated mass elements to oscillate in desired modes while resisting undesired oscillations, improving robustness and sensitivity, particularly in automotive applications where vibrations are prevalent.
Implementation Method 1
a quartet of Coriolis masses which are in their rest positions symmetrically arranged around a first quartet center point... Each elongated mass element is attached to the corresponding Coriolis mass with a connecting spring arrangement... allowing for detection of secondary oscillation modes while resisting undesired oscillations
Data Source
Figure 1~2a
Figure 2b~2c
Figure 2d
AI summary
A gyroscope with a Coriolis mass quartet which comprises four Coriolis masses which are in their rest positions symmetrically arranged around a quartet center point where a lateral axis crosses a transversal axis orthogonally in the device plane. The first and second Coriolis masses in the quartet are aligned on the lateral axis in their rest position, and the third and fourth Coriolis masses in the first Coriolis mass quartet are aligned on the transversal axis in their rest position. The gyroscope further comprises a first, second, third and fourth pair of elongated mass elements. The elongated mass elements which form the first pair are transversally aligned on opposite sides of the lateral axis outside of the first Coriolis mass. The elongated mass elements which form the second pair are transversally aligned on opposite sides of the lateral axis outside of the second Coriolis mass. The elongated mass elements which form the third pair are laterally aligned on opposite sides of the first transversal axis outside of the third Coriolis mass. The elongated mass elements which form the fourth pair are laterally aligned on opposite sides of the first transversal axis outside of the fourth Coriolis mass.