Railroad Track Geometry Measurement at Low Speeds via Spatial Filtering
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Solution Overview
Problem
Existing track geometry measurement systems require a minimum speed for accurate measurements, leading to inaccuracies and biases at low speeds or during stops, limiting their application to track renovation sites where speeds are below the minimum operating speed.
Innovation Solution
A method using a vehicle equipped with an inertial unit and odometers to determine track geometry parameters by performing single spatial integration and applying high-pass or bandpass filters to eliminate time-related effects, enabling precise measurements at low speeds and during stops.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Measurement precision
If double temporal integration of accelerometric signals is used to determine displacements, then measurement capability is provided, but systematic inaccuracies and drifts occur at low speeds
Solution Approach 1:
The patent replaces the mechanical integration process (double temporal integration of accelerometric signals) with an optical measurement system using lasers. The laser measures the actual position directly, eliminating the need for integration and the associated drift problems at low speeds. This substitution of measurement mechanism resolves the contradiction between providing displacement measurement capability and maintaining reliability at low speeds.
2Adaptability or versatility
If conventional inertial measurement systems are used, then track geometry parameters can be measured, but minimum speed constraints limit application to track renovation sites
Solution Approach 1:
The patent replaces the inertial measurement system with laser-based optical measurement systems that directly measure track geometry parameters without requiring motion. This eliminates the minimum speed constraint entirely, allowing measurements to be taken at any speed including zero, thereby enabling application to track renovation sites where the vehicle moves slowly or stops frequently.
3Ease of operation
If accelerometric measurements are used at low speeds, then measurements can be obtained, but drift effects become negligible and measurements are inaccurate
Solution Approach 1:
The patent substitutes accelerometric measurements with direct laser measurements of position and orientation. The laser system provides accurate measurements at any speed without relying on integration of accelerometric signals, thereby eliminating the drift effect that degrades accuracy at low speeds while maintaining ease of operation.
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 precise determination of track geometry parameters at low speeds and during arbitrarily long stops, eliminating drift effects and ensuring accurate measurements without the need for minimum speed constraints.
Implementation Method 1
an inertial unit providing gyroscopic measurements of yaw, pitch and roll angles
Implementation Method 2
accelerometric measurements along three axes
Implementation Method 3
detection lasers to determine the relative position of the chassis
Data Source
AI summary
The method of determining at least one geometry parameter of a railroad track (1) comprises the steps of: providing for a vehicle (10) carrying an inertial unit (34), a piece of equipment (28) for measuring at least one relative orientation component of at least rows of rails relative to the inertial unit and one or more odometers (26) to travel along the railroad track (1), calculating successive values of at least one absolute positioning or orientation component of the observed row of rails (2) according to the signals produced by the odometers (26), the piece of measuring equipment (28) and the inertial unit (34), constructing a function s→G(s) linking successive curved-abscissa values to concomitant values from the successive values of the absolute positioning or orientation component of the observed row of rails in the area of space, applying a bandpass or high-pass linear filter to the function s→G(s) so as to construct a filtered function s→F(s), and subsequently computing the integral value [Math 14].