Vehicle Position Uncertainty Control Near Wayside Devices
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Solution Overview
Problem
Existing vehicle control systems, such as Positive Train Control (PTC) systems, face challenges in accurately determining the location of the leading edge of a vehicle due to errors in GPS signals, track data, wheel size, and wheel slip/slide, leading to uncertainties that can result in erroneous stop or proceed commands.
Innovation Solution
A vehicle control system that includes a control circuit onboard the vehicle to receive wayside signals and leading edge signals, calculating position uncertainty and determining whether a wayside device is within this uncertainty to accurately control vehicle movement.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Measurement precision
If GPS signals and positioning systems are used to determine vehicle location, then vehicle positioning capability is provided, but position accuracy deteriorates due to signal errors, track data errors, wheel size errors, and wheel slip/slide
Solution Approach 1:
The system performs preliminary actions by continuously calculating position uncertainty ahead of time using multiple error sources (GPS accuracy, track data accuracy, wheel size accuracy, wheel slip/slide) before making control decisions. This allows the vehicle control system to proactively determine when position uncertainty exceeds thresholds and take preventive actions, rather than reacting after errors accumulate.
Solution Approach 2:
The system implements feedback by continuously monitoring position uncertainty and using it to adjust vehicle control decisions. The calculated position uncertainty feeds back into the control logic to determine whether to proceed with movement commands or halt operations, creating a closed-loop system that adapts to changing position accuracy conditions.
2Measurement precision
If multiple error sources are considered in position calculation, then position uncertainty is reduced, but system complexity increases
Solution Approach 1:
The system segments the position uncertainty calculation into distinct components corresponding to different error sources: GPS signal accuracy, track data accuracy, wheel size accuracy, and wheel slip/slide. Each component is calculated and combined separately, allowing the system to manage complexity by treating each error source as an independent module rather than a monolithic calculation.
3Measurement precision
If position uncertainty calculation is performed continuously, then control accuracy is improved, but computational load increases
Solution Approach 1:
The system applies partial action by calculating position uncertainty only to the extent necessary for safe operation. Rather than continuously recalculating all error components at maximum precision, the system determines when position uncertainty exceeds predetermined thresholds and adjusts control decisions accordingly, performing calculations at the necessary level of detail without excessive computational overhead.
Data Source
AI summary
An apparatus for determining position uncertainty of a vehicle in proximity to a wayside device, the apparatus comprises a control circuit located on-board a vehicle comprising a leading edge. The control circuit is configured to receive a wayside signal from a wayside device positioned along a route to be traveled by the vehicle and receive a leading edge signal from a positioning system. The wayside signal represents a location of the wayside device. The leading edge signal represents a location of the leading edge of the vehicle. The control circuit is configured to determine a distance between the leading edge of the vehicle based on the leading edge signal received from the positioning system and the location of the wayside device associated with the wayside signal, calculate a position uncertainty of the leading edge of the vehicle, and determine whether the wayside device is within the position uncertainty.