Railway Vehicle Angular Velocity Bias Correction
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Solution Overview
Problem
Existing methods for measuring motion parameters of railway vehicles, such as velocity and distance, using wheel sensors and inertial units are often inaccurate due to wheel sliding and biases inherent in MEMS technology, leading to unreliable data.
Innovation Solution
A method that involves measuring instantaneous angular and acceleration velocities using sensors, determining biases by analyzing constant conditions, and calculating evaluated velocities and accelerations by subtracting these biases from measured values, thereby correcting for inaccuracies.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Measurement precision
If wheel sensors are used to measure velocity and distance, then measurement capability is provided, but measurement accuracy deteriorates due to wheel sliding during acceleration and braking phases
Solution Approach 1:
The patent introduces an intermediary processing system that combines data from multiple sensors (wheel sensors, inertial units, GPS) and uses bias determination algorithms to mediate between conflicting measurements. This intermediary layer filters out sliding errors by comparing measurements under known conditions (constant velocity, constant slope, constant curvature) and produces a corrected velocity signal that is more reliable than any single sensor alone.
2Measurement precision
If MEMS inertial units are used to measure angular velocity, then measurement capability is provided, but measurement accuracy deteriorates due to inherent biases in MEMS technology
Solution Approach 1:
The patent implements feedback mechanisms where the system continuously monitors measurements under known conditions (constant angular velocity, constant track slope, constant curvature) and uses this information to determine and correct biases. The corrected measurements are then fed back into the navigation calculation, creating a closed-loop system that progressively reduces bias errors and improves measurement reliability over time.
Solution Approach 2:
The system changes the operational parameters of the MEMS sensors by identifying periods when the vehicle is under specific conditions (constant velocity, constant slope, constant curvature) and using these parameter states to characterize and correct sensor biases. By analyzing sensor output under controlled parameter conditions, the system can separate true motion signals from sensor biases and produce corrected measurements.
3Measurement precision
If bias correction is implemented by analyzing constant conditions, then measurement accuracy improves, but system complexity increases due to additional processing requirements
Solution Approach 1:
The patent applies preliminary action by pre-establishing the conditions under which biases can be determined (constant velocity periods, constant slope sections, constant curvature segments) and preparing correction algorithms in advance. The system proactively identifies these conditions and performs bias characterization during these predetermined windows, rather than attempting real-time correction during all operating conditions, thereby simplifying the overall processing complexity.
Data Source
AI summary
A method for evaluating the angular velocity of a railway vehicle circulating on a track, the vehicle including an inertial unit including at least one angular velocity sensor, the method including measuring an instantaneous angular velocity provided by the sensor, determining the bias of the angular velocity measured around at least one axis, the velocity bias being taken as equal to the value of the angular velocity measured around this axis when the measured angular velocity is substantially constant for a predetermined period, and calculating the evaluated angular velocity, by subtracting from the measured angular velocity, the previously determined velocity bias.