Vibratory Gyroscope Eigenmode Alignment
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Solution Overview
Problem
Resonant MEMS gyroscopes face misalignment issues during manufacturing or use, leading to frequency mismatch and bias signal errors due to misalignment of drive and sense modes with respect to physical electrodes, which complicates modal alignment and requires electrostatic transduction, narrow capacitive gaps, and large DC voltages.
Innovation Solution
Eigenmode operation method that adjusts excitation and readout scaling coefficients to maximize the drive readout signal and minimize the sense readout signal, allowing for modal alignment and dynamic tuning without the need for electrostatic transduction, thereby eliminating the requirement for narrow capacitive gaps and large DC voltages.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Measurement precision
If modal alignment is achieved through electrostatic transduction, then frequency mismatch is corrected, but the device requires narrow capacitive gaps and large DC voltages
Solution Approach 1:
The patent replaces electrostatic transduction (mechanical field-based alignment) with eigenmode operation (intrinsic vibrational mode matching). By operating at the natural eigenmodes of the gyroscope structure, modal alignment is achieved without requiring electrostatic actuation, thereby eliminating the need for narrow capacitive gaps and large DC voltages while maintaining frequency matching between drive and sense modes
Solution Approach 2:
The patent changes the operational parameters from electrostatically-tuned frequencies to intrinsic eigenmode frequencies. By designing the structure to operate at its natural vibrational modes, the system achieves modal alignment through structural design rather than electrostatic parameter adjustment, removing the requirement for precise capacitive gap control
2Reliability
If mode-matched operation is implemented, then signal-to-noise ratio is improved, but manufacturing misalignment causes frequency mismatch
Solution Approach 1:
The patent employs eigenmode operation where the gyroscope structure's own natural vibrational modes determine the operating frequencies. The structure serves itself by having its geometry and material properties define the resonant frequencies, making the system self-aligning and insensitive to manufacturing variations that would otherwise require precise manual or electrostatic adjustment
3Measurement precision
If electrostatic transduction is used for modal alignment, then frequency matching is achieved, but large DC voltages are required
Solution Approach 1:
The patent substitutes electrostatic transduction with direct eigenmode excitation. By using piezoelectric or other direct mechanical excitation methods that couple to the structural eigenmodes, the system achieves frequency matching without requiring large DC voltages to create electrostatic forces, thereby reducing power consumption and voltage requirements
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 achieves bias error cancellation, preserves electrical isolation of drive and sense modes, and allows for mode-matching of gyroscopes, improving signal-to-noise ratio and reducing specification requirements for interface circuitry.
Implementation Method 1
Resonant MEMS gyroscopes operate based on the transfer of energy between two vibration modes of the device due to Coriolis effect
Implementation Method 2
The device is excited at the resonance frequency of the primary drive mode
Implementation Method 3
If the resonance frequency of the sense mode matches that of the drive mode, the mechanical Q-amplification of the sense signal significantly improves the overall signal-to-noise ratio
Data Source
AI summary
Embodiments of the present disclosure can include a method of operating a vibratory gyroscope, the gyroscope comprising a plurality of excitation and readout electrodes, and defined by a first vibratory mode and a second vibratory mode, and the method comprising: introducing an input signal to a first pair of excitation electrodes; multiplying the input signal by scaling coefficients; applying these scaled input signals to a first pair of excitation electrodes; measuring output signals at the first and second pair of readout electrodes that correspond to the first and second vibratory modes respectively; multiplying the output signals by readout scaling coefficients to form scaled output signals, the sums of which provide first and second vibratory mode readout signals; and adjusting the scaling coefficients to maximize the first and minimize the second vibratory mode readout signals.