Dissimilar GNSS Modules for High Integrity Landing
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Solution Overview
Problem
Current GLS systems are not capable of achieving the high integrity level required for category III aircraft approaches, as they lack sufficient mechanisms to detect and prevent undetected erroneous outputs, particularly due to shared faults between dual-channel systems that do not guarantee independence and can result in undetected errors.
Innovation Solution
A GLS system with dissimilar master and slave GNSS modules, where each module processes and compares guidance data, using an integrity test to detect faults based on predetermined thresholds and eliminating common sources of error, ensuring that differences in outputs exceed a predetermined variance threshold, thereby preventing undetected errors.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If a dual-channel GNSS system is used to improve integrity, then the reliability improves, but common faults between channels can cause undetected errors
Solution Approach 1:
The patent implements dissimilar GNSS modules where the first and second modules have different hardware configurations, processing algorithms, or satellite constellation selections. This asymmetry ensures that common faults affecting identical channels will manifest differently across the dissimilar modules, enabling detection through comparison while maintaining high reliability requirements for category III approaches.
2Device complexity
If a single-channel GNSS receiver is used, then the device complexity is reduced, but the integrity risk cannot meet category III requirements
Solution Approach 1:
The patent divides the single GNSS reception function into two independent modules (first GNSS module and second GNSS module), each capable of independent signal processing and guidance data generation. This segmentation allows the system to meet category III integrity requirements through redundant monitoring while maintaining relatively simple individual module designs.
3Ease of manufacture
If dual-channel GNSS modules with identical architecture are used, then the ease of manufacture improves, but the ability to detect common faults is reduced
Solution Approach 1:
The patent deliberately introduces asymmetry between the two GNSS modules through different hardware configurations, processing methods, or satellite selection criteria. This ensures that manufacturing standardization does not lead to identical failure modes, allowing the comparison mechanism to detect common faults that would otherwise remain undetected in symmetric architectures.
Data Source
AI summary
Device for receiving radio-navigation signals, for aiding the piloting of an aircraft, comprising a first master GNSS module and a second slave GNSS module which are dissimilar, the first master GNSS module comprising a first means for processing radio-navigation signals and a first means for computing guidance data (Xg), the second slave GNSS module comprising a second means for processing radio-navigation signals and a second means for computing guidance data (Xg) on the basis of the measurements provided by the said second means for processing signals, each GNSS module furthermore comprising a comparison means for comparing between the outputs Xg1,Xg2 of the said first and second means for computing guidance data, suitable for executing the following integrity test:|Xg1−Xg2|>Kg·√{square root over (Variance(Xg1−Xg2))}and for inferring an integrity defect if the said integrity test is satisfied.