MEMS Inertial Sensor Self-Test Modulation
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Solution Overview
Problem
Microelectromechanical (MEMS) inertial sensors experience changes in sensitivity and offset over time due to wear, requiring monitoring and compensation techniques, but existing methods are prone to interference and may not accurately detect sensor failures.
Innovation Solution
A MEMS inertial sensor design that includes self-test circuitry to apply spread spectrum and CDMA self-test signals, allowing for simultaneous operation and testing, with processing circuitry to identify sense and monitor signals and adjust measurements accordingly, minimizing interference and improving accuracy.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If test signals are injected into MEMS sensor components to monitor performance, then sensor reliability is improved, but measurement precision deteriorates due to interference with other measured signals
Solution Approach 1:
The patent segments the signal monitoring process by using separate sense electrodes dedicated to sensing and separate self-test electrodes dedicated to testing. This segmentation allows test signals and sense signals to be applied through different pathways, reducing interference between monitoring and measurement operations.
Solution Approach 2:
The patent introduces an intermediary signal processing approach where monitor signals from self-test electrodes are processed separately from sense signals. The processing circuitry handles test and measurement signals through different channels, using the monitor signal as an intermediate indicator of sensor health without directly interfering with the primary measurement function.
2Reliability
If compensation techniques are applied to maintain sensor operation, then sensor reliability is improved, but device complexity increases
Solution Approach 1:
The patent implements self-service through self-test electrodes and processing circuitry that automatically monitor sensor performance and generate compensation data. The system performs self-diagnosis and generates compensation information without requiring external testing equipment or complex external compensation systems, reducing overall device complexity while maintaining reliability.
Solution Approach 2:
The patent establishes a feedback loop where monitor signals from self-test operations are processed to generate compensation data that can be applied to maintain sensor accuracy. The processing circuitry continuously monitors sensor health and provides feedback for compensation, enabling automatic adaptation to sensor degradation without increasing operational complexity.
3Reliability
If monitoring techniques are utilized to detect sensor changes, then reliability is improved, but the system generates harmful interference with measured signals
Solution Approach 1:
The patent segments the electrode functions into distinct sense electrodes and self-test electrodes. This segmentation physically separates the pathways for measurement and monitoring, preventing test signals from interfering with sense signals and eliminating the harmful interference problem while maintaining reliable failure detection.
Solution Approach 2:
The patent extracts the monitoring function into a separate channel using dedicated self-test electrodes and processing circuitry. By taking out the monitoring operation from the primary sensing path and handling it through separate electronics, the system eliminates interference with measured signals while maintaining the ability to detect sensor changes and failures.
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
Enhances the ability to monitor and compensate for sensor changes, reduces interference, and effectively identifies potential errors or failures, ensuring accurate inertial measurements over the sensor's lifespan.
Implementation Method 1
at least one self-test electrode and self-test circuitry coupled to the at least one self-test electrode to apply a spread spectrum self-test signal to the at least one self-test electrode, wherein the self-test signal is at least partially transmitted through the at least one proof mass to generate a monitor signal
Data Source
AI summary
A MEMS inertial sensor may include drive electrodes that apply a drive signal to a suspended spring-mass system for measurement of an inertial linear or angular force and self-test electrodes that apply a self-test signal to the suspended spring-mass system for monitoring the characteristics of the suspended spring-mass system during operation. The self-test signal may be modulated by a spreading sequence that prevents interference with the self-test signal by vibrations and other disturbance signals. The self-test signals and drive signals may be modulated with CDMA code sequences to multiplex signals that are at least partially processed by a common sense path.