Rail Vehicle Positioning Using Speed Signal Processing
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Solution Overview
Problem
GPS-based position determination systems for rail vehicles are ineffective in underground metro rail networks, necessitating an alternative method for accurately determining the geographic location of rail vehicles without relying on GPS signals.
Innovation Solution
A method and system that utilize on-board speed sensors to record and process linear speed signals, identify stationary periods, calculate distances traveled between known stopping locations, and match these distances with stored route data to determine the vehicle's position, incorporating a pattern recognition algorithm for accurate location identification.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Measurement precision
If GPS-based position determination is used, then position accuracy is improved in above-ground environments, but the system becomes inapplicable in underground metro rail networks
Solution Approach 1:
The patent introduces an intermediary system consisting of ground-based transponders and on-board sensors that act as mediators between the vehicle and the positioning function. Since GPS signals cannot penetrate underground, this intermediary system provides alternative signal paths through the tunnel environment, enabling position determination where GPS fails.
Solution Approach 2:
The patent replaces the electromagnetic wave-based GPS system with a mechanical measurement system using on-board sensors (accelerometers, gyroscopes, odometers) that directly measure physical quantities like acceleration, angular velocity, and wheel rotation. This mechanical substitution enables positioning in environments where electromagnetic signals are blocked.
2Device complexity
If GPS signals are used for position determination, then system complexity is reduced, but the system becomes unreliable in GPS-denied environments
Solution Approach 1:
The patent creates a universal positioning system that can operate in both above-ground and underground environments. The on-board computer integrates multiple sensor inputs and can switch between GPS-based positioning (when available) and inertial/sensor-based positioning (when GPS is unavailable), making the system reliable across diverse environments without requiring separate systems.
3Adaptability or versatility
If on-board sensors are used to determine position without GPS, then environmental adaptability is improved, but measurement precision may be affected by signal processing complexity
Solution Approach 1:
The patent implements feedback mechanisms where the on-board computer continuously processes sensor data, compares calculated positions with expected positions based on route information, and adjusts measurements accordingly. This feedback loop helps correct drift errors in inertial measurements and maintains positioning accuracy over time.
Solution Approach 2:
The system performs preliminary actions by pre-storing detailed route information including track geometry, station locations, and signal characteristics. This preliminary data is used to predict expected sensor readings and validate real-time measurements, improving accuracy by comparing actual measurements against known reference information.
Data Source
AI summary
A method of determining the geographical position of a rail vehicle travelling on a defined route that has a number of known stopping locations separated by known distances. The method comprises steps of: recording a linear speed signal of the vehicle; processing the linear speed signal to identify a plurality of preceding stationary periods when linear speed equals zero, including a last stationary period, and to calculate the distance traveled between the plurality of preceding stationary periods; comparing the calculated distances with the known distances between stopping locations, to match the last identified stationary period to a corresponding one of the known stopping locations and identify the direction of travel of the rail vehicle; and determining the geographical position of the rail vehicle by processing a portion of the speed signal obtained since the last identified stationary period, to calculate the distance traveled from the corresponding stopping location.