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EP-3802192-B1 - METHOD FOR MANAGING BRAKING IN A DEGRADED ADHESION CONDITION FOR A TRAIN

EP3802192B1EP 3802192 B1EP3802192 B1EP 3802192B1EP-3802192-B1

Inventors

  • FREA, Matteo
  • IMBERT, Luc

Dates

Publication Date
20260513
Application Date
20190531

Claims (9)

  1. A method for managing braking in a degraded adhesion condition for a train including at least one railway vehicle, comprising the following steps: - setting a target deceleration value (D obb ) to be reached by the train; this target deceleration value (D obb ) allowing the train to reach a zero traveling speed within a target stopping distance (Dis obb ); - applying a non-degraded braking force (F nd ), via at least one braking means of the train, the value of which is calculated to obtain the target deceleration value (D obb ); - checking the presence of a degraded adhesion condition between the railway vehicle and the rail; wherein the method further comprises: - when a degraded adhesion condition is not detected, maintaining the application of the non-degraded braking force (F nd ), which will allow the train to reach the target deceleration value (D obb ) within a first time (t1) and allow the train to achieve accordingly a zero traveling speed within the target stopping distance (Dis obb ); - when a degraded adhesion condition is detected, executing the following steps: - by means of sliding control means, causing the aforesaid braking means to apply a degraded braking force (F d ) lower than said non-degraded braking force (F nd ) and coinciding with the maximum braking force applicable in such degraded adhesion condition; - activating recovery means arranged to positively influence the train deceleration, until the at least one railway vehicle has left the degraded adhesion condition to return again to a non-degraded adhesion condition; such recovery means being adhesion recovery means or braking means not dependent on adhesion and allowing the train to reach the target deceleration value (D obb ) within a second time (t2), greater than the first time (t1), which would allow the train to reach a zero traveling speed within a degraded stopping distance (Dis deg ) greater than said target stopping distance (Dis obb ); - determining a compensation deceleration value (D comp ) as a function of the degraded stopping distance (Dis deg ) due to the difference between the degraded braking force (F d ) and the non-degraded braking force (F nd ); the compensation deceleration value (D comp ) being arranged to allow the train to reach a zero traveling speed within the target stopping distance (Dis obb ); - applying by means of the at least one braking means and/or the recovery means arranged to positively influence the deceleration of the train, a compensation braking force, greater than the non-degraded braking force and calculated as a function of the compensation deceleration value (D comp ), so as to allow the train to reach the compensation deceleration value (D comp ) and to reach a zero traveling speed within the target stopping distance (Dis obb ).
  2. A method for managing braking in a degraded adhesion condition for a train according to claim 1, wherein the target stopping distance (Dis obb ) is calculated as a function of an initial traveling speed of the train, of an average deceleration value obtained through the average of the deceleration values obtained from the instant in which the non-degraded braking force (F nd ) is applied, up to the moment wherein the train reaches a zero traveling speed, and a target braking time obtained through the ratio between the initial traveling speed of the train and said average deceleration value.
  3. A method for managing braking in a degraded adhesion condition for a train according to claim 2, wherein the target stopping distance (Dis obb ) is calculated by the following formula: Dis obb = Initial speed ∗ target braking time − 1 2 Average deceleration ∗ target braking time 2
  4. A method for managing braking in a degraded adhesion condition for a train according to any of the preceding claims, wherein the compensation braking force is lower than a maximum braking limit.
  5. A method for managing braking in a degraded adhesion condition for a train according to any of the preceding claims, further comprising the step of: - providing a signal to the train driver or to a specific control infrastructure when the compensation braking force exceeds the value of non-degraded force (F nd ).
  6. A method for managing braking in a degraded adhesion condition for a train according to any of the preceding claims, wherein the degraded stopping distance (Dis deg ) is calculated at certain instants of time by the following formula: Dis deg t = ∫ 0 t ∫ 0 t Dec t dt − ∫ 0 t Dis obb dt dt where Dis deg ( t ) is the degraded stopping distance (Dis deg ) measured at the time t, Dec ( t ) is an instantaneous deceleration value measured at the time t and Dis obb is the target deceleration value (Dis obb ).
  7. A method for managing braking in a degraded adhesion condition for a train according to any of the preceding claims, wherein the adhesion recovery means comprise at least one sandbox or one magnetic shoe.
  8. A method for managing braking in a degraded adhesion condition for a train according to any of the preceding claims, wherein the braking means not dependent on the adhesion comprise at least one magnetic track brake or eddy current brake.
  9. A method for managing braking in a degraded adhesion condition for a train according to any of the preceding claims, wherein said train braking means comprise an electromechanical brake and/or an electro-pneumatic brake and/or an electrodynamic brake and/or a pneumatic brake and/or a hydraulic brake.

Description

Technical sector The present invention is, in general, in the field of braking management methods for a railway vehicle; in particular, the invention refers to a method for managing braking in a degraded adhesion condition for a train that includes at least one railway vehicle. Prior art Conventional brake management systems, under degraded adhesion conditions, base their operation on open-loop or closed-loop controls using, inter alia, the following measurement and/or feedback quantities: braking force, work of the braking force, wheel-rail adhesion, etc. For example, document WO2016207078 describes the possibility of using braking force, documents WO2012076523, WO2012052381, WO0071399 describe the possibility of using the work of the braking force, EP2918459 describes the possibility of using the wheel-rail adhesion engaged during braking, and the possibility of using the acceleration of the vehicle is also known. The aforesaid quantities may be measured and/or distributed and/or controlled at different levels, i.e. at the single axle level, at the railway wagon level (multiple axles) and at the train level (multiple railway wagons). Depending on these quantities, conventional brake management systems act accordingly on a plurality of devices, including, inter alia, the devices responsible for applying the braking force and the devices responsible for improving the adhesion conditions of the rail or of the wheel-rail contact. For example, the devices responsible for applying the braking force are pneumatic disc brakes (EP brake), pneumatic tread brakes (EP tread brake), electrodynamic brakes (ED brake), magnetic track brakes (MTB). On the other hand, the devices responsible for improving the conditions of adhesion of the rail or the wheel-rail contact are, for example, a sandbox or a magnetic shoe (MTB). In conditions of degraded adhesion, since it is not possible to apply a nominal braking force on all axles, the braking management systems described above intervene with a series of strategies and/or devices, the objective of which is to return the vehicle to an instantaneous deceleration as close as possible to or equal to a target deceleration. The expression 'nominal braking force' refers to a braking force which enables a 'target deceleration' to be achieved, i.e. the level of instantaneous deceleration which, if maintained throughout the braking period, enables the train to stop its travel within a target stopping distance. Therefore, the conventional systems described above focus mainly on the instantaneous deceleration of the vehicle and have as their objective the achievement of the aforesaid target deceleration. This type of approach presents a fundamental problem. Under degraded adhesion conditions, at best, it will be possible to reach the target deceleration after a certain delay with respect to the start of braking. The delay is due to a time necessary for the aforesaid systems to detect the conditions of degraded adhesion, to activate the devices described above and to give them time to act. At such point, following this delay, the target deceleration will be achieved. Disadvantageously, this target deceleration will no longer be sufficient to reach the target stopping distance and, as a result, the stopping distance of the train will increase relative to the envisaged target. Taking a practical example, supposing a railway vehicle traveling 160 km/h, when at a time t=0 braking is activated, the target deceleration will be 1 m/s2. Decobb=1ms2 In a dry rail scenario, i.e. in a condition of good adhesion, the full "nominal braking force" may be applied. The vehicle will then reach the target deceleration of 1 m/s2 and maintain it throughout the braking process. Figure 1 shows the deceleration time profile in this condition. As may be seen in this figure, the train will stop its travel within the target stopping distance, in this example equal to 990 m. This stopping distance value may be easily calculated by tracing the example condition back to the case of uniformly accelerated motion: Stoppingtime=initialspeedaveragedeceleration Stoppingdistance=initialspeed∗Stoppingtime−12averagedeceleration∗Stoppingtime2 Figure 2 shows a braking curve that relates the speed of the vehicle to the distance traveled. In a contaminated rail scenario, i.e. where there is a contaminant on the rail, e.g. water, oil, wet leaves, etc., it follows that the wheel-rail adhesion is degraded. Considering the use, in this scenario, of a conventional braking management system according to the prior art described previously, in the first instance, it is not possible to apply the full nominal braking force, and therefore it is not possible to achieve the target deceleration of 1 m/s2. In the light of this gap in force and/or deceleration and/or adhesion, the conventional brake management systems described above activate strategies and/or devices for the recovery of adhesion which, at best, bring the deceleration of the vehi