MEMS Gyroscope Drive Frequency Tuning via Non-Linear Springs
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Solution Overview
Problem
MEMS gyroscopes face challenges in matching resonant drive frequency (fdr) with resonant detection frequency (fdet) due to manufacturing limitations, requiring additional voltage on the detection side, which increases complexity and noise, and introduces parasitic mechanical mode vibrations.
Innovation Solution
The use of non-linear springs supported by tuners that can be pre-stressed with a trim voltage to modify the stress condition, allowing the resonant drive frequency to be tuned to match the resonant detection frequency without additional voltage on the detection side, utilizing a trim circuit and tuner systems connected to the springs.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Manufacturing precision
If additional voltage is applied to the detection side to tune fdet to match fdr, then the resonant frequencies can be matched, but the device complexity and noise increase
Solution Approach 1:
The patent extracts the frequency tuning function from the detection side and relocates it to the drive side. By applying trim voltage to the drive electrode rather than the detection electrode, the tuning function is separated from the detection path, eliminating the need for complex voltage conditioning on the detection side while maintaining frequency matching capability
Solution Approach 2:
The patent uses the drive electrode as an intermediary to achieve detection frequency tuning. Instead of directly applying trim voltage to the detection electrode, the system uses the drive electrode as a mediator that indirectly tunes the detection frequency by modifying the drive frequency, which couples to the detection path through the mechanical structure
2Manufacturing precision
If additional voltage is applied to the detection side to tune fdet, then frequency matching is achieved, but parasitic mechanical mode vibrations increase
Solution Approach 1:
The patent removes the source of parasitic vibrations by extracting the trim voltage application from the detection electrode and relocating it to the drive electrode. This eliminates the direct attractive force on the Coriolis mass that occurs when trim voltage is applied to detection electrodes positioned beneath the mass, thereby reducing parasitic mechanical mode vibrations
Solution Approach 2:
The patent converts the potentially harmful effect of trim voltage application into a beneficial outcome by changing where the voltage is applied. Instead of applying trim voltage to detection electrodes (which causes parasitic vibrations), the system applies it to the drive electrode, where the same voltage serves to tune the frequency without generating harmful mechanical modes
3Manufacturing precision
If separate sense and trim electrodes are provided, then frequency tuning is possible, but device complexity increases
Solution Approach 1:
The patent makes the drive electrode multi-functional by having it serve both as the drive electrode for exciting the Coriolis mass and as the trim electrode for frequency tuning. This eliminates the need for separate sense and trim electrodes, reducing device complexity while maintaining frequency tuning capability through the same electrode structure
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 enables effective matching of fdr with fdet without increasing noise or complexity, reducing parasitic vibrations by using non-linear springs and tuners to pre-stress the springs, thereby optimizing the signal-to-noise ratio.
Implementation Method 1
a plurality of non-linear springs supporting the mass
Implementation Method 2
a first tuner operably connected to the plurality of non-linear springs for modifying the stress condition of the plurality of non-linear springs in response to a trim voltage
Implementation Method 3
a mass drive component configured to drive the mass within a plane
Implementation Method 4
The out of plane rotation of the Coriolis mass thus changes a capacitance between the sense electrode and the Coriolis mass which provides an indication of the angular rate of rotation
Data Source
AI summary
A drive frequency tunable MEMS sensor in one embodiment includes a mass, a mass drive component configured to drive the mass within a plane, a plurality of non-linear springs supporting the mass a first tuner operably connected to the plurality of non-linear springs for modifying the stress condition of the plurality of non-linear springs in response to a trim voltage, and a trim circuit electrically coupled with the first tuner for providing the trim voltage.