Railway Vehicle Positioning via GNSS and Odometry Fusion
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Solution Overview
Problem
Current methods for real-time positioning of railway vehicles, such as traditional odometry and Global Navigation Satellite Systems (GNSS), face challenges in accuracy and cost, particularly in meeting the highest Safety Integrity Level (SIL4) standards, with high uncertainty and high installation and maintenance costs for balises, and inadequate protection levels from GNSS data.
Innovation Solution
A method and system that calculates a position interval for a railway vehicle by combining onboard GNSS signals with odometry data using an electronic control unit, which determines a maximum and minimum position and distance, and adjusts these values over time to refine the position interval, ensuring accurate and safe positioning within predefined intervals.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Measurement precision
If traditional odometry with balises is used for positioning, then measurement precision is improved, but device complexity and installation cost increase significantly
Solution Approach 1:
The patent introduces an intermediary computational process that combines GNSS position data with odometry measurements through a mathematical model. This intermediary layer reconciles the coarse GNSS data with the accumulating odometry error, achieving high positioning precision without requiring dense balise installation. The intermediary computation acts as a bridge between the two measurement systems.
Solution Approach 2:
The patent creates a virtual copy of the balise reference system through digital map coordinates and virtual reference points. Instead of physically installing numerous balises, the system replicates their positioning function through computational models and digital representations, significantly reducing physical infrastructure while maintaining measurement precision.
2Device complexity
If GNSS data alone is used for positioning, then device complexity is reduced, but measurement precision and safety level are insufficient for SIL4 standards
Solution Approach 1:
The patent merges GNSS positioning data with odometry measurements into a unified positioning solution. By combining these two independent measurement systems through a mathematical model, the system achieves both the simplicity of GNSS infrastructure and the precision required for SIL4 standards. The fusion of multiple data sources compensates for individual system weaknesses.
Solution Approach 2:
The system implements feedback by continuously comparing GNSS-derived positions with odometry-based positions and using the differences to adjust and refine the positioning estimate. This feedback mechanism allows the system to maintain high precision over long distances without additional infrastructure, as the system self-corrects based on the discrepancy between the two measurement methods.
3Measurement precision
If balise density is increased to maintain positioning accuracy over long distances, then measurement precision is improved, but installation and maintenance costs increase
Solution Approach 1:
The patent replaces expensive, permanent balise infrastructure with computationally intensive but economically cheaper methods. The system uses readily available GNSS receivers and standard odometry systems, processing data through sophisticated algorithms to achieve the same positioning function that would otherwise require costly balise installation and maintenance over long distances.
Data Source
AI summary
A method for calculating a location interval of a railway vehicle, including: calculating, at predefined and successive times: maximum and minimum positions reached by the vehicle as points on a digital map based on signals indicative of the absolute position of the vehicle; maximum and minimum distances travelled by the vehicle with respect to a reference point based on odometry; at a selected time adding: to the maximum and minimum positions at a time earlier than the selected time, the difference between values of the maximum distance at the selected and at the earlier times and the difference between values of the minimum distance at the selected and at the earlier times, thereby determining reference first maximum position and second minimum position. The advanced end of the interval is the most forward position between the first reference maximum position and the value of the maximum position at the selected time.