MEMS Inertial Sensor Vibration Frequency Detection
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Solution Overview
Problem
Microelectromechanical system (MEMS) sensors, such as accelerometers and gyroscopes, face challenges in accurately distinguishing external vibrations from desired movements due to exposure to various vibration sources, which can interfere with their operation, especially during device start-up or mode transitions.
Innovation Solution
A method and system where MEMS inertial sensors generate a frequency scan signal pattern with periodic signal portions at various test frequencies, sense the movement of a proof mass, and correlate the sense signal with these patterns to identify the frequency of external vibrations, using processing circuitry to determine correlation values and identify the associated frequency, potentially with phase-shifted signals to mitigate alignment issues.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Adaptability or versatility
If MEMS sensors are exposed to various vibration sources during operation, then the sensor can detect diverse movements and orientations, but the sensor's ability to accurately distinguish external vibrations from desired movements deteriorates
Solution Approach 1:
The patent segments the vibration analysis into multiple frequency components by generating a frequency scan signal pattern with multiple periodic signal portions at different test frequencies. The processing circuitry correlates the sense signal with each periodic signal portion separately, dividing the complex vibration problem into manageable frequency-specific analyses. This allows the sensor to maintain versatility in detecting diverse movements while improving precision by analyzing each frequency component independently.
Solution Approach 2:
The patent applies partial action by selectively analyzing only specific frequency components of the vibration signal that are relevant to the application. Instead of processing the entire frequency spectrum equally, the system focuses computational resources on identifying vibrations at specific test frequencies through correlation with periodic signal portions, thereby improving measurement precision for targeted frequencies while maintaining overall detection capability.
2Productivity
If the sensor operates during device start-up or mode transitions, then the sensor can capture complex movements, but the accuracy of vibration detection deteriorates due to interference from various vibration types
Solution Approach 1:
The patent implements preliminary action by generating a frequency scan signal pattern before analyzing the sense signal. The processing circuitry prepares multiple periodic signal portions at different test frequencies in advance, then correlates these pre-prepared patterns with the sensed vibrations. This preliminary preparation of frequency reference patterns enables the sensor to maintain high detection accuracy during dynamic operational phases like start-up and mode transitions, while still capturing comprehensive movement data.
3Measurement precision
If the sensor uses correlation analysis with frequency scan patterns to identify vibration frequencies, then the measurement precision of vibration frequency improves, but the device complexity increases
Solution Approach 1:
The patent applies universality by designing the processing circuitry to perform multiple functions: generating frequency scan signal patterns, sensing proof mass movement, generating sense signals, and correlating signals to identify vibration frequencies. This multi-functional approach consolidates what could be separate complex subsystems into a unified processing unit, thereby improving frequency identification accuracy while minimizing the increase in overall device complexity.
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 allows for precise characterization and monitoring of external vibrations, enhancing the sensor's ability to distinguish background vibrations from desired movements, improving operational accuracy and reliability in diverse environments.
Implementation Method 1
one or more sense electrodes that sense a movement of the proof mass
Data Source
AI summary
A modified version of a MEMS self-test procedure is presented that can be used to detect the amplitude and frequency of an external vibration from an ambient environment. The method implements processing circuitry that correlates an output sense signal, s(t), with a plurality of periodic signal portions and a plurality of shifted periodic signal portions to generate a plurality of correlation values. A frequency associated with the external vibration is determined based on the plurality of correlation values.