MEMS Sensor Self-Test Using High-Frequency Noise Detection
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Solution Overview
Problem
Existing safety mechanisms for MEMS sensors, such as inertial sensors and gyroscopes, are complex and costly, and often trigger false alarms due to external excitation, complicating self-test functionality.
Innovation Solution
A noise-based safety mechanism is implemented by feeding a test signal at a frequency range above the sensor's signal frequency band, detecting a deliberately increased noise level, and comparing it to a threshold to determine sensor failures, using a fail counter for robustness.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If traditional safety mechanisms are implemented for MEMS sensors, then sensor failure detection capability is improved, but device complexity and cost increase
Solution Approach 1:
The sensor device performs self-testing by generating test signals internally and analyzing its own response. The electronic circuitry uses the sensor element itself as a test object, eliminating the need for external test equipment or complex separate safety systems. This self-service approach maintains reliability while minimizing added complexity and cost.
Solution Approach 2:
The sensor element serves dual purposes: it functions as both the operational sensor and the test object for safety verification. The same mechanical sensor element that measures physical parameters is also subjected to test signals to verify its proper operation. This multi-functionality reduces the need for separate dedicated test components.
2Reliability
If self-test functionality is added to ensure safety, then reliability is improved, but false alarms increase due to external excitation
Solution Approach 1:
The frequency spectrum is segmented into distinct bands: the operational frequency band for normal sensor signals and a separate test frequency band above the operational band. Test signals are applied at frequencies higher than any expected operational signals or external excitations. This frequency segmentation allows the safety mechanism to distinguish between normal operational variations (including external excitations) and actual sensor failures, preventing false alarms.
3Ease of manufacture
If safety features are built on electronic circuitry to minimize additional costs, then manufacturing cost is reduced, but ease of manufacture becomes more difficult
Solution Approach 1:
The safety testing functionality is merged with the existing operational electronic circuitry of the sensor device. The same electronic components that process operational sensor signals are also used to generate test signals and analyze test responses. This merging approach minimizes additional bill of materials costs and leverages existing manufacturing processes, making the safety features cost-effective to implement.
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 is simple, requires minimal additional resources, and effectively detects sensor failures without affecting performance or triggering false alarms, ensuring reliable operation.
Implementation Method 1
an input transducer configured to perform electrical to mechanical signal conversion
Implementation Method 2
an output transducer configured to perform mechanical to electrical signal conversion
Data Source
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AI summary
The present invention relates to a method and an apparatus for detecting a failure of a sensor device during operation of the sensor device. A test signal is generated in a first frequency band that is above a signal frequency band of the sensor device and fed into a sensor element of the sensor device. A set of samples is obtained, and a magnitude value is derived from said at least two consecutive samples at the first frequency band. The magnitude value is compared to a magnitude threshold value that defines a minimum for the magnitude value and if the magnitude value is below the magnitude threshold value, it is determined that an error has occurred in the sensor device.