MEMS Sensor Gain Tuning for Vibration Immunity
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Solution Overview
Problem
Micro-electro-mechanical systems (MEMS) devices, such as gyroscopes, face issues with vibration sensitivity due to fabrication imperfections, leading to unwanted motions and bias errors in rotation rate measurements.
Innovation Solution
The method involves adjusting the gain of pick-off mechanisms, specifically by tuning the voltages applied to capacitive pick-offs, to reduce the output of sensor devices when they respond to stimuli other than the external stimulus of interest, thereby compensating for imperfections like capacitance mismatches, proof mass imbalances, and spring flexure asymmetries.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Measurement precision
If symmetric capacitor configuration is used to cancel common-mode motion, then measurement precision is improved, but manufacturing precision deteriorates due to unavoidable fabrication imperfections causing imperfect cancellation
Solution Approach 1:
The patent applies parameter changes by adjusting the gain of pick-off mechanisms to compensate for fabrication imperfections. Specifically, the gain adjustment modifies the electrical parameters of the read-out system to counterbalance the mechanical asymmetries introduced during fabrication, thereby maintaining measurement precision despite manufacturing variations
Solution Approach 2:
The patent implements feedback through a tuning process where the gain of pick-off mechanisms is adjusted based on the measured output of the sensor device. This feedback loop allows the system to detect and correct for common-mode motion errors caused by fabrication imperfections, improving the overall measurement accuracy
2Adaptability or versatility
If proof masses are made susceptible to multiple stimuli for comprehensive sensing, then adaptability is improved, but reliability deteriorates due to vibration sensitivity and bias errors
Solution Approach 1:
The patent extracts and isolates the harmful common-mode motion component from the measurement signal. By using pick-off mechanisms to detect and separate the unwanted vibration-induced motion from the desired rotation rate signal, the system can focus on measuring only the relevant stimulus while rejecting spurious inputs
Solution Approach 2:
The patent converts the harmful effect of vibration-induced common-mode motion into a useful calibration signal. By intentionally measuring the common-mode response through pick-off mechanisms, the system can identify and correct for fabrication imperfections, thereby improving reliability
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 effectively suppresses vibration sensitivity and reduces bias errors, enhancing the performance of MEMS devices for navigation applications by ensuring accurate rotation rate measurements.
Implementation Method 1
Micro-electro-mechanical systems (MEMS) devices and other sensor devices often use variable capacitive read-out techniques for measurements of motion of a proof mass or other structure in the device
Data Source
AI summary
A method for tuning one or more sensor devices is provided, wherein each sensor device comprises one or more proof masses configured to move in response to an external stimulus of interest, and the one or more proof masses are also susceptible to move in response to one or more stimuli other than the external stimulus of interest. Each sensor device also comprises one or more pick-off mechanisms respectively associated with each of the one or more proof masses. The one or more pick-off mechanisms is proportionally responsive to a motion of the sensor device. The method for tuning includes adjusting gain of one or more of the pick-off mechanisms to reduce an output of each sensor device when the one or more proof masses move in response to the one or more stimuli other than the external stimulus of interest.