Frequency Readout Gyroscope with Coriolis Coupled Modes
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Solution Overview
Problem
Current MEMS gyroscopes face limitations in power consumption and drift, making them unsuitable for widespread adoption in battery-powered devices and navigation systems, as they require high power for low noise amplification due to the significant difference in motion amplitudes between drive and sense axes.
Innovation Solution
The development of a direct frequency readout gyroscope utilizing a mechanical resonator with Coriolis-coupled modes, featuring a resonator with sensing and actuating means, sustaining circuitry, phase and frequency control circuitry, and output circuitry, which operates in Quadrature Frequency Modulated (QFM) and Lissajous Frequency Modulated (LFM) modes to maintain constant velocity amplitudes and phase differences, reducing power consumption and drift.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Measurement precision
If high amplitude vibrations are used in the drive axis to enable angular rate sensing, then sensitivity is improved, but power consumption increases due to the need for low noise amplification in the sense readout circuitry
Solution Approach 1:
The patent replaces the conventional mechanical vibration-based sensing with a resonant oscillation system that operates at its natural frequency. The resonator is excited to oscillate at its resonant frequency, and angular rate is sensed through Coriolis coupling between orthogonal modes of oscillation. This resonance-based approach improves sensitivity while reducing the power required compared to forcing high amplitude vibrations at non-resonant frequencies.
Solution Approach 2:
The patent changes the operating parameters by tuning the resonator to operate at its natural resonant frequency rather than forcing vibrations at arbitrary frequencies. By matching the drive frequency to the resonator's natural frequency, the system achieves maximum oscillation amplitude with minimum input energy, thereby improving sensitivity while reducing power consumption.
2Measurement precision
If the amplitude of motion in the sense direction is made larger to improve measurement capability, then measurement precision is improved, but the device complexity increases due to the need for additional amplification circuitry
Solution Approach 1:
The patent replaces the need for complex low noise amplification circuitry with a mechanical resonance-based sensing approach. By operating the resonator at its natural frequency and using Coriolis coupling between orthogonal modes, the system generates measurable signals directly from the mechanical motion without requiring extensive electronic amplification, thereby reducing readout circuitry complexity.
Solution Approach 2:
The patent utilizes mechanical vibration at the resonator's natural frequency to generate the sensing signal. The Coriolis force induced by angular rate creates a coupling between orthogonal vibration modes, producing a measurable displacement in the sense direction that can be detected with simple capacitive sensing, eliminating the need for complex amplification circuitry.
3Volume of moving object
If conventional MEMS gyroscope designs are used to achieve compact size, then device miniaturization is achieved, but drift performance deteriorates
Solution Approach 1:
The patent employs mechanical vibration at the resonator's natural frequency to enable compact MEMS gyroscope design. By utilizing the resonator's inherent oscillation modes and Coriolis coupling, the system achieves accurate angular rate sensing in a miniaturized form factor while maintaining low drift performance through resonance-based sensing that is less susceptible to noise and environmental disturbances.
Solution Approach 2:
The patent changes the operating parameters by tuning the resonator to operate at its natural resonant frequency, which enables compact design while maintaining performance. The resonant operation provides high Q-factor sensing that reduces drift, and the natural frequency is determined by the physical dimensions of the resonator, allowing for miniaturization without sacrificing drift performance.
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 results in a low-power, low-drift MEMS gyroscope that overcomes the limitations of previous designs by maintaining constant velocity amplitudes and phase differences, enhancing sensitivity and stability while reducing power consumption and drift, making it suitable for battery-powered devices and navigation systems.
Implementation Method 1
a mechanical resonator with Coriolis-coupled modes
Data Source
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AI summary
A frequency readout gyroscope is provided, having 2 or 3 axes, in which the frequency of the carrier associated with the oscillation of the proof mass changes while the amplitude stays constant. The invention departs from conventional gyroscopes which rely on measuring transducer sense axis displacement (amplitude modulation) to determine angular input rate. The invention utilizes what could be termed a form of frequency modulation, such as evaluating frequency phase difference between the axes of modulation. Examples include gyroscopes having either a quadrature or Lissajous FM mode of operation, in which angle random walk contribution from the electronics is reduced by approximately two orders of magnitude.