GNSS-IRS Hybrid Navigation System for Category III Approach Integrity
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Solution Overview
Problem
Current aircraft piloting aid systems, particularly those using GNSS for precision approach phases, face challenges in maintaining signal integrity and continuity, especially in low visibility conditions, due to limitations in existing multimode receivers and the high cost and maintenance requirements of ILS and MLS systems.
Innovation Solution
A GNSS-IRS hybrid system with GBAS or SBAS augmentation, utilizing existing multimode receivers and inertial reference systems, is implemented to provide redundant and fault-tolerant guidance signals, ensuring integrity and continuity by realigning inertial data with accurate GNSS information and switching to inertial data when GNSS integrity is compromised.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If ILS or MLS systems are used for precision approach operations, then guidance signal integrity and continuity are maintained, but the cost and maintenance requirements increase significantly
Solution Approach 1:
The patent combines GNSS positioning data with inertial reference system data to create a hybrid navigation solution. The GNSS/IRS hybrid system merges satellite-based positioning with inertial navigation to achieve category III precision approach capabilities without requiring expensive ILS or MLS ground infrastructure, thereby reducing system complexity and cost while maintaining guidance integrity and continuity
Solution Approach 2:
The multimode receiver is designed to perform multiple functions: it can operate in both ILS/MLS modes and GNSS mode, and can provide guidance for multiple approach categories (I, II, and III). This multi-functionality allows the system to replace specialized ILS/MLS equipment while maintaining the required guidance performance across different operational scenarios
2Device complexity
If existing multimode receivers are used for GLS operations, then equipment costs are reduced, but the continuity and integrity of guidance signals are compromised
Solution Approach 1:
The system implements monitoring and alerting functions that detect GNSS signal integrity issues before they compromise navigation accuracy. By continuously monitoring satellite geometry, signal quality, and positioning accuracy, the system can alert operators to potential problems and switch to inertial navigation in advance, preventing guidance failures and maintaining continuity
Solution Approach 2:
The inertial reference system acts as an intermediary backup when GNSS signals are compromised. The hybrid system uses the IRS to maintain navigation accuracy when GNSS availability or integrity is insufficient, effectively mediating between the cost-effective GNSS solution and the reliability requirements for category III operations
3Device complexity
If GNSS data is used alone for precision approach, then system cost is reduced, but accuracy and reliability deteriorate due to external disturbances
Solution Approach 1:
The navigation system uses a composite approach by combining GNSS data with inertial reference system data. This composite navigation solution leverages the strengths of both systems: GNSS provides long-term accuracy and position verification, while the IRS provides short-term precision and immunity to signal disturbances, achieving category III accuracy requirements at lower cost than traditional ILS/MLS systems
Data Source
AI summary
A function for generating guidance data from the GNSS data and the inertial data (IRS1) with integrated fault detection is distributed on the inertial reference units and the digital processing boards of said multimode receivers. Application to an augmented GLS guidance mode for category I to III approach operations.