Closed-Loop MEMS Gyroscope Self-Test via Segmented Signal Analysis
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Solution Overview
Problem
MEMS gyroscopes in closed-loop configurations face challenges in self-testing due to dependence on bias voltage stability and masked parameter variations, which can lead to false alarms and operational instability, especially in high loop gain scenarios.
Innovation Solution
A microelectromechanical gyroscope with a closed-loop configuration that includes a test signal generator and self-test analyzer, capable of generating test input signals synchronized with primary motion signals and extracting test output signals to determine the validity of operating parameters, thereby enabling reliable self-testing during normal operation.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Measurement precision
If a closed-loop system is used to enhance gyroscope performance, then measurement precision and robustness are improved, but the system becomes heavily dependent on bias voltage stability and masked parameter variations that can lead to false alarms and operational instability
Solution Approach 1:
The patent segments the self-test function into multiple independent test modes (open-loop self-test and closed-loop self-test) that can be selectively executed. The test signal generator creates separate test signals for different operational conditions, allowing the system to test specific parameters without requiring continuous operation in a single mode. This segmentation enables reliable self-testing by isolating different test scenarios from each other and from normal operation.
Solution Approach 2:
The patent implements preliminary self-test actions by continuously monitoring system parameters and executing diagnostic tests before actual errors occur. The control circuit is configured to periodically perform self-tests during normal operation, detecting potential failures in advance. This preliminary detection capability allows the system to identify parameter drifts and component degradations before they lead to false alarms or operational instability.
2Loss of time
If continuous self-test is implemented in open-loop configuration, then rapid error identification is achieved, but the method is not well applicable for monitoring bias voltage levels in closed-loop configuration and requires additional dedicated self-test electrodes
Solution Approach 1:
The patent makes the existing sense electrodes multi-functional by enabling them to serve both normal sensing operations and self-test functions. The control circuit configures the sense electrodes to receive test signals during self-test modes and measurement signals during normal operation. This universal usage eliminates the need for separate dedicated self-test electrodes, reducing device complexity while maintaining continuous self-test capability for both open-loop and closed-loop configurations.
Solution Approach 2:
The patent implements dynamic reconfiguration of the electrode functions based on operational mode. The control circuit dynamically switches the sense electrodes between measurement mode and self-test mode, and adjusts the amplifier gain accordingly. This dynamic adaptability allows the same hardware to perform different functions optimally, enabling rapid error identification without requiring additional static test electrodes.
3Stability of the object's composition
If high loop gain is used to mask parameter variations and improve robustness, then minor variations are attenuated, but excessive variations in masked parameters may cause abrupt signal blockage and system instability
Solution Approach 1:
The patent applies partial self-testing by selectively monitoring only the most critical parameters that could lead to signal blockage or instability, rather than attempting to monitor all parameters continuously. The control circuit identifies key parameters such as amplifier gain and bias voltage levels that, if excessively varied, would cause system failure. By focusing self-test resources on these critical parameters, the system achieves effective protection against harmful variations without the complexity of complete parameter monitoring.
Solution Approach 2:
The patent implements feedback mechanisms where the results of self-tests are fed back to the control circuit, which then adjusts operational parameters to prevent instability. When parameter drifts are detected during self-testing, the control circuit can modify the loop gain or switch operational modes to maintain system stability. This feedback loop enables the system to respond to excessive parameter variations before they cause signal blockage or instability.
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
The solution allows for reliable self-testing in closed-loop configurations, reducing false alarms and ensuring timely identification of potential errors before they cause system instability, thus enhancing operational reliability and accuracy.
Implementation Method 1
a drive element suspended to the body for vibrational primary motion in a first direction
Implementation Method 2
a sense element coupled to the drive element to receive an orthogonal Coriolis force component in a second direction
Implementation Method 3
a sense circuit for outputting a sense signal that corresponds to forces acting on the sense element in the second direction, and for producing a sense feedback signal to control the vibrational secondary motion of the sense element
Data Source
Figure 1~2
Figure 3~4
Figure 5~6
AI summary
A closed-loop microelectromechanical gyroscope with a self- test function. At least one test input signal is generated from a signal of the vibrational primary motion and input during operation of the microelectromechanical gyroscope to the sense circuit.