Frequency Multiplexed Vibratory Gyroscope Self-Calibration
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Solution Overview
Problem
Coriolis vibratory gyroscopes face challenges in continuous self-calibration, particularly in measuring bias without redundant sensors or predetermined calibration inputs, and existing methods are inadequate for handling time-varying biases and are not continuous.
Innovation Solution
A Coriolis vibratory gyroscope with a resonant structure exhibiting degeneracy in its modal structure, where one mode is maintained at resonance frequency and the second mode is modulated in amplitude at a dither frequency, allowing for continuous bias measurement by demodulating signals to separate rotation rate and bias signals.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Measurement precision
If mode reversal or mode switching is used for calibration, then calibration can be performed, but the calibration is not continuous and updates are discrete in time
Solution Approach 1:
The patent applies frequency multiplexing to enable continuous calibration by simultaneously operating multiple modes at different frequencies. The first mode operates at a first frequency while the second mode operates at a second frequency, allowing continuous bias measurement without discrete switching, thus resolving the contradiction between measurement precision and calibration speed.
Solution Approach 2:
The patent dynamically assigns different frequencies to different modes during operation. The system can switch between frequency assignments based on operational requirements, enabling continuous adaptation and calibration without stopping the gyroscope, thereby achieving both precise bias measurement and continuous calibration capability.
2Measurement precision
If redundant sensors are used for self-calibration, then continuous bias measurement is possible, but device complexity and cost increase
Solution Approach 1:
The patent makes a single gyroscope sensor perform multiple functions by operating it in different frequency-multiplexed modes. The same physical sensor measures both rotation rate and bias continuously by analyzing signals at different frequencies, eliminating the need for redundant sensors while maintaining measurement precision.
Solution Approach 2:
The patent changes the operating frequency parameter of the resonator to enable different measurement functions. By operating the resonator at different frequencies (first frequency for rotation rate, second frequency for bias), a single sensor can extract multiple measurement information, reducing device complexity while maintaining measurement capability.
3Reliability
If physical input axis switching is used for calibration, then bias compensation can be performed, but device performance is disrupted and calibration is not continuous
Solution Approach 1:
The patent dynamically switches between frequency modes rather than physically switching input axes. This dynamic frequency assignment allows the gyroscope to maintain continuous operation and performance while performing calibration, as the frequency switching can be done without disrupting the physical sensing function.
Solution Approach 2:
The patent maintains continuous useful action by performing calibration through frequency multiplexing rather than physical axis switching. The gyroscope continues to sense rotation continuously while bias compensation is performed through signal processing of frequency-separated modes, ensuring uninterrupted device 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
Enables continuous, fast self-calibration of bias without redundant sensors, effectively addressing time-varying biases and improving device performance by accurately separating rotation rate and bias signals.
Implementation Method 1
a first mode is maintained at resonance frequency and simultaneously a second mode is maintained at the resonance frequency modulated in amplitude at a dither frequency
Implementation Method 2
the second mode is maintained at the resonance frequency modulated in amplitude at a dither frequency
Implementation Method 3
When the device rotates about a particular body-fixed axis, the resulting Coriolis forces acting on the body's vibrating mass elements excite a different resonant mode. The rate at which energy is transferred to this second mode is a measure of the rotation rate about the sensitive axis.
Implementation Method 4
A first mode output is demodulated at the resonance frequency to output a signal proportional to a sum of a rotation rate of the gyroscope and the measurement bias of the gyroscope. A second mode output is demodulated first at the resonance frequency and then at the dither frequency to output a signal proportional to a difference of the measurement bias of the gyroscope and the rotation rate of the gyroscope.
Data Source
AI summary
A Coriolis vibratory gyroscope having a resonator with at least a first and a second n=2 vibratory modes of same resonance frequency in a resonator plane; first and second sensing circuits for generating first and second sense signals in response to a motion of the resonator along a major axis of the first and second vibratory modes; a first drive circuit for driving the resonator in the first vibratory mode with a first drive signal; a second drive circuit for simultaneously driving the resonator in the second vibratory mode with a second drive signal; wherein said first signal has a first frequency equal to a resonant frequency of said resonator in said first vibratory mode, and said second signal has the same frequency as the first signal, modulated in amplitude with a second frequency.