Vehicle Positioning Using Virtual Transponder Footprints
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Solution Overview
Problem
Current systems, such as the Transcore system, provide insufficient positioning accuracy for trains stopping at platforms, with a nominal accuracy of +/-400 mm, due to asymmetrical transponder footprints and potential electromagnetic interference, which is inadequate for precise station stops.
Innovation Solution
The method involves detecting signals from groups of transponders spaced apart, identifying a point with a known geometric relationship to their footprints, and computing the vehicle's position by matching this relationship, using the midpoint or other geometric points between the footprints, rather than bisecting the TI Lock signal, thereby improving detection accuracy.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Measurement precision
If the TI Lock signal is bisected to determine position, then positioning accuracy improves, but the assumption of symmetry is violated leading to centre deviation errors
Solution Approach 1:
The patent creates a virtual transponder at a calculated position between two physical transponders. This virtual transponder's footprint is synthesized by combining signals from the two physical transponders, allowing position determination without relying on the symmetry of individual transponder footprints. The virtual footprint approach copies the essential measurement function while eliminating the symmetry dependency.
Solution Approach 2:
The patent explicitly addresses and accommodates the asymmetry in transponder footprints by using pairs of transponders and calculating a virtual midpoint. Instead of assuming symmetry as the Transcore system does, the invention uses the known asymmetry characteristics to determine that the virtual transponder positioned at the midpoint between two physical transponders provides more reliable positioning data.
2Area of stationary object
If transponders are spaced further apart, then detection coverage increases, but positioning accuracy between transponders decreases
Solution Approach 1:
The patent divides the detection space into segments defined by pairs of transponders. Each pair creates a localized measurement zone where the virtual transponder provides high-accuracy positioning. By segmenting the track into such zones with overlapping coverage, the system achieves both wide detection coverage and high positioning accuracy within each segment.
Solution Approach 2:
The virtual transponder acts as an intermediary element that bridges the gap between two physical transponders. It provides continuous positioning information in the space between transponders, effectively extending the accurate measurement capability beyond the immediate vicinity of physical transponders while maintaining high precision.
3Productivity
If electromagnetic interference is present, then signal reliability decreases, but the system must continue operating
Solution Approach 1:
The patent uses feedback from multiple transponders to continuously monitor and adjust position determination. By comparing signals from pairs of transponders and using the virtual transponder concept, the system can detect anomalies caused by electromagnetic interference and rely on the redundant measurement paths to maintain accurate positioning despite individual signal disruptions.
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
This approach reduces positioning errors to +/-250 mm, effectively improving accuracy and minimizing the impact of footprint asymmetry and interference, while allowing for precise location determination and travel direction assessment.
Implementation Method 1
detecting signals from groups of transponders located beside the guideway as the vehicle moves along the guideway
Data Source
AI summary
A method of determining the position of a vehicle moving along a guideway is disclosed wherein signals from groups of transponders located beside the guideway are detected as the vehicle moves along the guideway to create a footprint in the time domain corresponding to the time the vehicle is in communication with that transponder. The transponders of each group are spaced a known distance apart from each other. An estimate of the position of the moving vehicle is computed by matching the point in the time domain that bears the same geometric relationship to the footprints corresponding to the transponders of the group to a point in the spatial domain that bears a known geometric relationship with the transponders of each group.