Vehicle Localization System Using Reradiated GNSS and Coded Targets
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Solution Overview
Problem
Current GPS-based vehicle location systems for vehicles on guideways, such as trains, face inaccuracies in station stops and tunnel navigation due to insufficient precision and satellite signal unavailability in tunnels, leading to high costs for alternative solutions like RFID and inductive loop systems.
Innovation Solution
A secondary positioning system that synchronizes GPS signals using GNSS receivers, transmitters, coded targets, and proximity sensors to provide accurate location information in tunnels by retransmitting GPS signals and using on-board databases, allowing continuous GPS signal reacquisition upon exiting the tunnel.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Ease of manufacture
If GPS signals are used for vehicle positioning on guideways, then the system cost is reduced, but the positioning accuracy becomes insufficient for precise station stops and location determination
Solution Approach 1:
The positioning system is segmented into multiple independent components: GPS receivers for general positioning, proximity sensors for detecting coded targets, and dead reckoning systems for intermediate positioning. Each component operates independently but contributes to the overall positioning accuracy, allowing the system to achieve high precision without requiring expensive unified infrastructure
Solution Approach 2:
Coded targets are introduced as intermediary objects placed at known locations along the guideway. These passive targets mediate between the GPS system and the vehicle positioning system, providing reference points that enhance positioning accuracy without requiring active transponders or expensive infrastructure
2Device complexity
If traditional GPS systems are used in tunnels, then the system complexity is reduced, but GPS signal availability becomes zero due to satellite obstruction
Solution Approach 1:
The system performs preliminary positioning using GPS signals and coded target detection before entering the tunnel. The dead reckoning system is pre-configured with the vehicle's position and velocity, allowing it to continue providing position estimates throughout the tunnel without requiring signal penetration or complex tunnel infrastructure
Solution Approach 2:
The vehicle-mounted system uses its own motion sensors and dead reckoning capabilities to self-determine position within tunnels. The system serves itself by continuously integrating velocity measurements from onboard sensors, eliminating the need for external signal sources or complex tunnel-based infrastructure
3Reliability
If RFID transponders are installed along the guideway to provide positioning in tunnels, then the positioning reliability is improved, but the hardware cost and system complexity increase significantly
Solution Approach 1:
The system replaces expensive, active RFID transponders with inexpensive, passive coded targets that can be simple visual or electromagnetic patterns. These targets are much cheaper to manufacture and install, yet provide sufficient positioning information when detected by the vehicle-mounted proximity sensors
Solution Approach 2:
The active electronic components (transponders and readers) are extracted from the guideway infrastructure and relocated to the vehicle. The guideway itself remains passive with only simple coded targets, significantly reducing infrastructure costs while maintaining positioning functionality through vehicle-mounted active sensors
4Measurement precision
If inductive loop communication systems are used for positioning, then the positioning accuracy is improved, but the installation cost and system complexity increase
Solution Approach 1:
The system replaces complex inductive loop cable installations with simpler optical or electromagnetic coded targets. These targets can be painted on the guideway surface or mounted as simple panels, eliminating the need for expensive cable installation while providing sufficient detection capability for vehicle-mounted sensors
Applied Scientific Principles
This section explains which scientific principles are used to turn an abstract innovation direction into a practical engineering solution.
Function Achieved in This Case
Enables accurate and cost-effective train positioning in tunnels and on guideways by combining reradiated GPS signals with proximity sensor data, ensuring precise location determination and minimizing reacquisition delays upon exiting tunnels.
Implementation Method 1
at least one GNSS receiver placed at one or more strategic locations in view of navigation satellites; a GNSS receiver on the vehicle for picking up GNSS signals directly from the navigation satellites
Implementation Method 2
GNSS transmitters for retransmitting received GNSS signals along an obscured portion of the guideway
Implementation Method 3
a proximity sensor on the vehicle for detecting the coded targets
Data Source
Figure 1~3
Figure 4
AI summary
A localization system for a vehicle running on a guideway including portions obscured from satellite view has a number of GNSS receivers placed at strategic locations along the guideway in view of navigation satellites. GNSS transmitters retransmit received GNSS signals along an obscured portion of the guideway. Coded targets are placed at known locations along the guideway. A GNSS receiver on the vehicle picks up GNSS signals directly from the navigation satellites or retransmitted from the GNSS transmitters when on an obscured portion of the guideway. A proximity sensor on the vehicle detects the coded targets. An on-board computer synchronizes the location obtained from the GNSS signals with the location obtained from the proximity sensor. The vehicle is thus able to determine its position even in an obscured portion, such as a tunnel.