Train speed supervision systems, namely ATP systems (Automatic Train Protection) principles use a comparison between actual train speed and reference values evaluated as a function of train position and usually referred to as braking curves. Their definition requires a preliminary knowledge of braking models that allow the conversion of the general parameters affecting the braking performance of a train into a deceleration profile as a function of time and speed. The guaranteed deceleration values used to calculate braking curves are obtained by applying a proper safety factor to the nominal deceleration depending on train characteristics. Train actual deceleration may differ from the nominal one due to the variability of several parameters: the safety factor has to take into account such variability and to guarantee that the train can comply with the imposed speed constraints with an appropriate safety margin. This study allows evaluating the probability that the real deceleration is smaller than the one used in the basic braking model and then that the real stopping distance is longer than the one calculated by the braking model. This model can then be used to tune the value of the safety margin in order to obtain a certain reliability, defined in probabilistic terms. The numerical procedure used to simulate the braking performance is based on the Monte Carlo method that is a method for iteratively evaluating a deterministic model using sets of random numbers as inputs, often used when the model is complex, nonlinear, or involves several parameters. The paper starts from previous studies developed for some types of passenger and freight trains and extends the proposed model to high-speed trains. The paper presents the main features and the implementation of a deterministic model used to describe high-speed train deceleration, then the probability distributions of input parameters affecting the braking distance will be presented and discussed. The results of this model will be compared with some experimental data.
Models of high speed train emergency braking deceleration for the definition of automatic train protection intervention curves
2012
17 Seiten, 5 Bilder, 2 Tabellen, 8 Quellen
Aufsatz (Konferenz)
Datenträger
Englisch
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