IMU Attitude Fault Detection via GNSS and Flight Data Comparison
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Solution Overview
Problem
Conventional aircraft systems face challenges in accurately determining which inertial measurement unit (IMU) is providing faulty attitude data when one of the remaining IMUs degrades during flight, leading to bias errors and a need for timely fault detection.
Innovation Solution
The system employs transversely mounted dual Global Navigation Satellite System (GNSS) antennas to estimate roll and combines angle of attack data with flight path angle to estimate pitch, comparing these estimates against IMU calculations to identify and alert the flight crew of faulty IMUs by exceeding predetermined thresholds.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If redundant IMUs are installed to provide confirmation of correct readings, then reliability is improved, but the ability to detect and identify faulty IMUs deteriorates when one IMU degrades with bias error
Solution Approach 1:
The system introduces an intermediary fault detection mechanism that compares attitude data from multiple IMUs against expected physical relationships (such as the relationship between pitch, roll, and heading rates). This intermediary comparison process identifies faulty IMUs by detecting inconsistencies in the data, allowing the system to maintain reliability even when one IMU degrades with bias error.
2Reliability
If three IMUs are used to provide attitude solutions, then reliability is improved, but the complexity of determining which IMU is faulty worsens when one IMU degrades
Solution Approach 1:
The system implements feedback by continuously monitoring attitude data from all IMUs and comparing it against expected physical relationships. When an IMU degrades, the feedback mechanism detects the inconsistency and provides information about which specific IMU is faulty, reducing the complexity of fault identification while maintaining the reliability benefits of using three IMUs.
Data Source
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Figure 1B
Figure 2A
AI summary
Systems and methods for attitude fault detection in an inertial measurement unit (IMU) are disclosed. In one embodiment, an avionics system comprises: an IMU configured to produce a calculated pitch solution, a calculated roll solution, or both; a monitor coupled to the IMU and configured to produce an estimated pitch solution, an estimated roll solution, or both; a comparator, wherein the comparator determines the difference between the calculated pitch solution and the estimated pitch solution, the difference between the calculated roll solution and the estimated roll solution, or both; and a display device communicatively coupled to the comparator; wherein the display device receives a warning message from the comparator when the difference between the calculated pitch solution and the estimated pitch solution is greater than a pitch threshold, or when the difference between the calculated roll solution and the estimated roll solution is greater than a roll threshold, or both.