Rail Brake Friction Control for Consistent Stopping Distance
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Solution Overview
Problem
Existing braking systems for rail vehicles struggle with stochastic variations in braking distance due to varying friction conditions, particularly under adverse track conditions, which limits the ability to reduce train spacing and increase transport capacity.
Innovation Solution
A closed-loop control system for electrodynamic or electropneumatic braking systems that adjusts braking force based on real-time frictional contact and slip conditions, eliminating the need for separate emergency and service brake controls by continuously optimizing frictional engagement.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If separate brake control systems are used for emergency braking and service braking, then specific braking scenarios can be optimized, but the system complexity increases and switching points between systems must be predefined
Solution Approach 1:
The patent merges separate emergency braking and service braking control systems into a single unified friction-based brake control system. This unified system uses a single control logic that continuously adjusts braking force based on real-time friction conditions, eliminating the need for predefined switching points between different brake modes and reducing overall system complexity while maintaining optimized braking performance across all scenarios.
Solution Approach 2:
The friction-based brake control system is designed as a universal control mechanism that handles both emergency braking and service braking scenarios through a single control logic. The system adapts its braking force adjustments based on the current friction conditions and operational context, providing multi-functional capability without requiring separate dedicated control systems for different braking types.
2Ease of operation
If slip-based control is used for wheel slip protection, then braking control can be implemented, but optimal frictional contact is not always guaranteed since maximum friction occurs at different slip values under different conditions
Solution Approach 1:
The system dynamically adapts the target slip value based on real-time friction conditions rather than using a fixed slip threshold. The control logic continuously monitors friction indicators and adjusts the optimal slip point accordingly, allowing the system to maintain optimal frictional contact across varying track conditions such as dry rails, wet rails, or leaves on rails, where the maximum friction occurs at different slip values.
Solution Approach 2:
The system changes the control parameter from a fixed slip-based threshold to a dynamic target slip value that is continuously adjusted based on friction conditions. By monitoring friction indicators and adapting the target slip parameter in real-time, the system ensures optimal frictional contact is achieved regardless of environmental conditions that would otherwise require different fixed slip thresholds.
3Productivity
If braking distance is reduced under good track conditions, then transport capacity increases, but stochastic variations in braking distance increase due to friction variations between brake pad and brake disc
Solution Approach 1:
The system implements feedback control by continuously monitoring friction conditions between the brake pad and brake disc and adjusting the braking force accordingly. This closed-loop control mechanism detects variations in friction coefficients and compensates for them in real-time, reducing stochastic variations in braking distance while maintaining short braking distances under good track conditions, thereby enabling increased transport capacity with consistent and predictable braking performance.
4Reliability
If maximum braking force is utilized under adverse track conditions, then braking distance is minimized, but the system must accurately determine optimal slip values which vary with wheel-rail contact conditions
Solution Approach 1:
The control system performs self-adjustment by automatically detecting friction conditions and determining the optimal slip value without requiring external intervention or complex predefined lookup tables. The system uses real-time friction indicators to self-correct and adapt the braking control parameters, enabling accurate optimization of braking force under varying adverse track conditions while keeping the control logic relatively simple and intuitive.
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
This approach minimizes stochastic variations in braking distance, enabling precise and adaptive braking control that maximizes traction under poor conditions and reduces safety margins, thus enhancing train frequency and network capacity.
Implementation Method 1
the braking distance under good track conditions is primarily determined by the friction between a brake pad and a brake disc
Data Source
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Figure 3~4
AI summary
The invention describes a method for the computer-implemented control of an electrodynamic or electropneumatic braking system of a rail vehicle with a control loop. The braking system comprises an actuator assigned to at least one wheel of the rail vehicle, wherein the control loop, during operation of the rail vehicle, processes a requested target frictional contact (ftarget) at a current time step k between the wheel and a rail and outputs a time-discrete target braking quantity (Mk+1) at a subsequent time step k + 1, which is supplied to the braking system as an input variable.At each time step k, a braking force change (ΔMk) is determined from one or more time steps during the operation of the rail vehicle from the requested target frictional contact (fsoll), a currently utilized actual frictional contact (fist,k) and its derivative (ḟist,k), and a derivative of a current slip (ṡk), which is superimposed on the current braking quantity (Mk).