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CBTC braking curve calculations - CAN BERK - 16-07-2019
Hello everyone, I am trying to calculate GEBR and braking curve The safe braking model is the method used to determine the minimum separation between trains. IEEE 1474.1 defines it as: “An analytical representation of a train’s performance while decelerating to a complete stop, allowing for a combination of worst-case influencing factors and failure scenarios. A CBTC equipped train will stop in a distance equal to or less than that guaranteed by the safe braking model.” (IEEE CBTC standard 1474.1, section 3.1) That’s a mouth full. Translation: the safe braking model is the calculated distance to stop a train, under the worst-case failure, without colliding with an obstacle in front. Which static dynamic train parameters to use? What do I need to pay attention to when calculating? How do I test? Thank you. RE: CBTC braking curve calculations - Peter - 19-07-2019
(16-07-2019, 11:08 PM)CAN BERK Wrote: Hello everyone, First, a caveat - I am not a CBTC braking expert, so my comments are general on the sort of thing I believe the examiners look for, not specific CBTC answers. When you say you are trying to calculate the braking curve, what question are you looking to answer and what information is provided? Not sure what mean "Which static dynamic train parameters to use" - do you mean static or dynamic? Taking a leaf out of the comments on the past papers for various other modules, the examiners will not be looking for definite particular values, so when you ask about train parameters to use, are you looking for a list of the sort of parameters or values for them? I would suggest that you want to be looking for the former but with an understanding of what typical values might be (and more importantly, why that is a typical value and what would be the implication of varying from that). Depending on what the question is that you are looking to answer, the things that you need to think about when calculating are those things that are going to be important in addressing the risk associated with the activity. Some things may well cause variability but if that is a known variability within a given range, you can take account of that. Some things may be measurable / detectable and can therefore be controlled, others may be external or uncontrollable and so present more of a problem. As for how to test - once you have a model, that will be based on parameters being between limits. If the requirement is that a train meets those, you can test those independently. If you are talking about how the overall model performs, that will be more tricky to do physically, particularly if there are many variables which give you too many scenarios. You will need to look at proving your model using analytical techniques in which case you are likely to come up with the outcome being with a range with a different level of confidence. The wider risk analysis will then need to look at whether the chances of being outside the required range presents an intolerable level of risk or can be reasonably improved. Peter RE: CBTC braking curve calculations - tfc82 - 25-09-2019
Thanks Peter, found your response useful. This seemed like quite a good primer on braking curve implementation on ETCS, might be of interest: https://www.era.europa.eu/sites/default/files/activities/docs/introduction_to_etcs_braking_curves_en.doc |