Rail Brake Deceleration Limiting for Low-Friction Conditions
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Solution Overview
Problem
Existing brake systems for rail vehicles struggle to maintain predictable braking results under varying environmental conditions such as wetness, snow, or ice, due to changes in friction coefficients between brake components.
Innovation Solution
A brake regulating device with a limiting device that independently controls the deceleration manipulated variable, allowing it to deviate from the target deceleration value by a maximum positive or negative control excursion, which can be selected independently of the control unit's behavior and adjusted based on target deceleration values, braking time, and environmental conditions.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If a control circuit is used to adjust braking force based on actual deceleration feedback, then braking predictability is improved, but the system cannot compensate for extreme friction coefficient changes under environmental influences like wetness, snow or ice
Solution Approach 1:
The patent applies dynamics by making the control excursions time-dependent and asymmetric. The limiting device dynamically adjusts the maximum positive and negative control excursions based on braking time, allowing the system to adapt its response characteristics over time. This resolves the contradiction by enabling the control system to handle varying friction conditions through time-varying control parameters rather than fixed symmetric limits
Solution Approach 2:
The patent changes the control parameters by introducing asymmetric maximum positive and negative control excursions that can be independently selected. The limiting device modifies the manipulated variable within asymmetric bounds, allowing different control efforts in positive and negative directions. This parameter change enables better adaptation to environmental conditions where friction coefficients vary, resolving the contradiction between reliability and adaptability
2Device complexity
If symmetric control excursions are used around the target deceleration value, then control simplicity is maintained, but optimum braking results cannot be achieved under changed friction properties
Solution Approach 1:
The patent directly applies asymmetry by introducing a limiting device that enforces asymmetric maximum positive and negative control excursions. The asymmetric control limits allow different control efforts in positive and negative directions, which is essential for compensating for changed friction properties under environmental influences. This asymmetric structure resolves the contradiction by sacrificing some control symmetry to achieve better braking performance and reliability
Solution Approach 2:
The patent makes the control excursions time-dependent, allowing the asymmetric control parameters to evolve during the braking process. The limiting device dynamically adjusts the control effort within asymmetric bounds based on braking time, providing adaptive control that maintains reliability while managing complexity through structured time-varying parameters
3Speed
If the control unit freely adjusts the manipulated variable to minimize deceleration deviation, then response speed is improved, but control instability increases under variable friction coefficients
Solution Approach 1:
The patent applies beforehand cushioning by pre-defining asymmetric maximum positive and negative control excursions in the limiting device. These pre-established bounds act as protective constraints that prevent the control system from making excessively large or unstable adjustments. By cushioning the control adjustments within predetermined asymmetric limits, the system maintains fast response while preventing instability under variable friction conditions
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 solution ensures optimum braking results even under challenging conditions by limiting control excursions and adjusting them based on specific conditions, thereby compensating for reduced friction caused by environmental factors.
Implementation Method 1
Environmental influences such as, in particular, wetness, snow or ice reduce a coefficient of friction of the friction partners of these brakes
Data Source
AI summary
A brake system, brake regulating method and device for a rail vehicle use an input for a target deceleration value (äset), an input for an actual deceleration value (atrain), and an output for a deceleration control variable value. The deceleration control variable value (a0Ut) is set by a regulating unit to minimize a deviation between the actual deceleration value (atrain) and the target deceleration value (aset). The brake regulating device uses a limiting device, which limits the deceleration control variable value (aout) independently of the regulating unit such that the deceleration control variable value (aout) deviates from the target deceleration value (aset) maximally by a maximum negative control stroke to lower values or maximally by a maximum positive control stroke to higher values. The invention additionally relates to a braking method and a brake system for a rail vehicle.