MEMS Gyroscope Self-Test via Quadrature Error Compensation
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Solution Overview
Problem
MEMS gyroscope sensors face challenges in accurately detecting angular motion due to quadrature error caused by imperfect elastic connections, and there is a need for self-testing to ensure proper operation, especially in safety-critical applications where reliability is paramount.
Innovation Solution
A self-testing scheme that utilizes the quadrature error compensation functionality to excite the sensing mass by opening the control loop, applying an additional force, and sensing the resulting quadrature error, with fault detection performed by comparing the in-phase and quadrature phase components of the error signal to expected values.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Measurement precision
If quadrature error compensation is used to improve measurement precision, then the sensing accuracy is improved, but the device complexity increases due to additional control loops and compensation mechanisms
Solution Approach 1:
The gyroscope performs self-testing by utilizing its own quadrature error compensation control loop to generate test signals and detect faults. The sensing mass is excited through the quadrature error compensation mechanism, and the resulting responses are processed by the existing signal processing circuits to identify operational faults without requiring external test equipment.
Solution Approach 2:
The quadrature error compensation control loop serves dual purposes: it compensates for quadrature errors during normal operation and simultaneously functions as a test signal generator for self-diagnosis. The same electrodes and control circuits used for error compensation are repurposed to excite the sensing mass during fault detection modes.
2Reliability
If self-testing is implemented to improve reliability, then fault detection capability is improved, but the ease of operation deteriorates due to additional testing procedures and control requirements
Solution Approach 1:
The system performs self-diagnosis automatically without requiring external intervention or specialized test equipment. The control circuitry autonomously switches between normal operation mode and self-test mode, excites the sensing mass through the quadrature error compensation mechanism, and processes the resulting signals to detect faults internally.
Solution Approach 2:
The self-testing is performed periodically or on-demand by switching the quadrature error compensation control loop between closed-loop compensation mode and open-loop test mode. During self-test, the control loop is opened to allow uncompensated excitation of the sensing mass, and the resulting responses are measured and analyzed for fault detection.
3Measurement precision
If the control loop is opened for self-testing to improve fault detection accuracy, then the measurement precision is improved, but the stability of the object's composition deteriorates due to disruption of the closed-loop control system
Solution Approach 1:
The system periodically switches between closed-loop compensation mode and open-loop self-test mode. During self-testing, the control loop is temporarily opened to enable accurate fault detection through uncompensated excitation responses. After completion of the self-test, the control loop is reclosed to restore stable compensation operation. This periodic switching allows both accurate fault detection and stable normal operation.
Solution Approach 2:
Before opening the control loop for self-testing, the system prepares by switching to open-loop mode and applying test signals through the quadrature error compensation electrodes. This preliminary action ensures that the sensing mass is properly excited and the test conditions are established before actual fault detection measurements are taken, minimizing disruption to overall system stability.
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 method effectively detects faults and ensures proper operation of the MEMS gyroscope sensor by accurately identifying deviations in the quadrature error signal, enhancing reliability in safety-critical applications.
Implementation Method 1
In the case of a rotation of the structure with respect to a predetermined gyroscope axis with an angular velocity, the sensing mass is subjected to a Coriolis force proportional to the angular velocity itself.
Implementation Method 2
A change in capacitance with respect to the sensing mass is sensed in order to detect the angular motion (rotation).
Implementation Method 3
applying an electrostatic force on the sensing mass to cancel quadrature error
Data Source
AI summary
A microelectromechanical system (MEMS) gyroscope sensor has a sensing mass and a quadrature error compensation control loop for applying a force to the sensing mass to cancel quadrature error. To detect fault, the quadrature error compensation control loop is opened and an additional force is applied to produce a physical displacement of the sensing mass. A quadrature error resulting from the physical displacement of the sensing mass in response to the applied additional force is sensed. The sensed quadrature error is compared to an expected value corresponding to the applied additional force and a fault alert is generated if the comparison is not satisfied.