Railway Axle Speed Tracking via Adhesion Observer
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Solution Overview
Problem
Modern railway vehicles face a significant reduction in traction and braking capacity when all axles enter a slipping phase due to degraded adhesion conditions, as maintaining a 'dead' axle to accurately measure speed leads to a loss of traction and braking capability.
Innovation Solution
Implementing a method that uses an adhesion observer and a torque control system to dynamically maintain axles on the peak adhesion curve, allowing for accurate speed tracking and maximum adhesion utilization during traction and braking, thereby recovering the use of 'dead' axles for improved traction and braking capacity.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Measurement precision
If a dead axle is maintained to accurately measure vehicle speed during slipping conditions, then speed measurement precision is improved, but traction and braking capacity deteriorates
Solution Approach 1:
The system dynamically adjusts the torque applied to each axle based on real-time adhesion conditions. During slipping conditions, the control system actively modulates torque to maintain axles on the peak adhesion curve, transitioning from a static dead axle configuration to a dynamic control regime where torque is continuously adjusted to optimize both speed measurement and traction/braking performance
Solution Approach 2:
The invention changes the operating parameters of the axles by actively controlling the torque applied to each axle. Instead of maintaining a fixed dead axle state, the system varies the torque parameter in real-time based on adhesion observer feedback, allowing axles to operate at optimal points on the adhesion curve that balance speed tracking accuracy with maximum traction and braking capacity
2Force
If all axles are used for traction and braking in degraded adhesion conditions, then traction and braking capacity is improved, but speed measurement accuracy deteriorates
Solution Approach 1:
The system implements a feedback mechanism where an adhesion observer continuously monitors the adhesion conditions and provides real-time information to the control system. This feedback loop enables the control system to adjust torque application on each axle to maintain optimal operating points, ensuring that speed measurement accuracy is preserved even when all axles are actively engaged in traction and braking operations
Solution Approach 2:
The adhesion observer acts as an intermediary that decouples the conflicting requirements of maximum traction/braking capacity and accurate speed measurement. By providing real-time adhesion condition information, it enables the control system to coordinate torque application across all axles while maintaining at least one axle in a state suitable for accurate speed tracking, thus mediating between the two opposing objectives
Data Source
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AI summary
The method comprises the steps of generating speed signals indicating the angular speed (co) of the wheels (W) of said at least one controlled axle (A); estimating, as a function of such angular speed (ω), the value of the adhesion (μ) in the contact area of the wheels (W) of such axle (A) and the rails, using an adhesion observer (1201) and computing the value of the speed slip (δ) of the wheels (W) of such controlled axle (A), generating signals representative of the derivative (dμ÷dδ) of said adhesion (μ) as a function of the slip (δ) of the wheels (W) of such axle (A); generating a driving signal (C(Tj+1)) for torque control devices (1205) controlling the torque applied to the wheels (W) of such axle (A), by means of an adaptive control (1204) of the derivative signals (dμ÷dδ) as a function of an error signal (e((Tj+1)) indicative of the difference between the value of the derivative (dμ÷dδ) and a predetermined reference value so as to reduce and keep such difference substantially at zero; applying the driving signal (C(Tj+1)) to said torque control means (1205) and therefore computing the vehicle speed as the linear advance speed of such at least one controlled axle (A).