Rail Vehicle Drive Torque Control for Wheelset Torsional Vibration
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Solution Overview
Problem
Torsional vibrations in rail vehicle wheelsets cause damage and reduce passenger comfort, and existing solutions either increase weight and cost or require additional sensors and components, while operating in micro-slip leads to tractive effort loss.
Innovation Solution
Identify specific slip speed and friction coefficient combinations that trigger torsional vibrations, define a restricted zone in the friction diagram to avoid these conditions, and adjust drive torque to exit this zone quickly, using slip controllers to manage torque adjustments.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If the wheelset is dimensioned to reduce torsional vibrations, then vibration damage is reduced, but weight and cost increase
Solution Approach 1:
The invention changes the operating parameters (drive torque, slip speed) to avoid the restricted zone where torsional vibrations occur, rather than changing the physical dimensions of the wheelset. This allows the same wheelset design to operate without vibrations by controlling it to stay out of the harmful parameter range.
2Measurement precision
If sensors and evaluation units are added to detect torsional vibrations, then vibration detection capability is improved, but device complexity increases
Solution Approach 1:
The invention takes preliminary action by defining the restricted zone in advance based on friction characteristics, and controlling the drive to avoid entering this zone. This preventive approach eliminates the need for sensors to detect vibrations after they occur, as the control system prevents the conditions that would generate vibrations in the first place.
Solution Approach 2:
The invention uses feedback by continuously monitoring the current operating point (drive torque, slip speed) and comparing it with the restricted zone boundaries. The control system adjusts the drive torque based on this feedback to ensure the operating point remains outside the restricted zone, thereby preventing torsional vibrations without requiring additional sensors.
3Reliability
If mechanical dampers are installed to reduce vibration amplitude, then vibration reduction is achieved, but weight and maintenance costs increase
Solution Approach 1:
The invention converts the potentially harmful restricted zone into a beneficial control parameter. By identifying and avoiding the restricted zone where vibrations occur, the system prevents harm before it occurs, eliminating the need for corrective measures like dampers and their associated costs.
4Reliability
If the rail vehicle operates exclusively in micro-slip with low traction, then torsional vibrations are avoided, but tractive effort is reduced
Solution Approach 1:
The invention makes the operating mode dynamic by allowing the vehicle to operate in different slip regimes (micro-slip or macro-slip) depending on the current operating conditions and the location of the operating point relative to the restricted zone. This dynamic adaptation enables the system to maintain high tractive effort when safe, while avoiding vibrations when necessary.
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
Prevents torsional vibrations by rapidly avoiding triggering conditions, reducing the need for additional components and maintaining vehicle safety and simplicity, while avoiding detection delays and potential damage.
Implementation Method 1
The wheelset axle acts as a torsional spring between the two wheel discs
Implementation Method 2
The friction characteristic of a rail vehicle describes the dependence of the coefficient of friction μ on the slip or the slip speed S... and thus the friction conditions between the wheel and the rail
Data Source
Figure 1
AI summary
To reduce or prevent torsional vibrations in wheelsets, a restricted zone is defined in the friction diagram of a rail vehicle. If a current operating point lies within this restricted zone, the drive torque control cycles through a predefined sequence, thus largely preventing prolonged operation within the restricted zone.