Objectives: Degraded adhesion between wheel and rail can impose restrictions on rail operations. Currently, these restrictions are mitigated by means of operational measures and/or by the adoption of a defensive driving style by train drivers. Even so, they usually have a negative impact on punctuality and/or operational stability/capacity. When considering future ATO, especially at GoA3/GoA4 level, it is essential that technical solutions rather than drivers should be capable of identifying and managing such situations. With this in mind, Knorr-Bremse is currently developing solutions such as an improved wheel slide protection system (WSP) supplemented by a train-wide Adhesion Management (ADM) system. Both solutions are associated with the Reproducible Braking Distance (RBD) development program, which also includes a new kind of Deceleration Control (DCC) system. Furthermore, magnetic track brakes (MTBs) can improve braking performance in conditions of degraded adhesion. The study aims to show the effectiveness of the new system functions in different rail conditions. Beyond, the influence of the MTB on overall braking behavior is analysed. DB Systemtechnik will use the findings to devise a mathematical model. Methodology: To achieve the above objectives, joint test runs were carried out in spring 2022 as part of the Shift2Rail (PIVOT2) technology initiative under the HORIZON 2020 European Research Framework Programme. As in previous trials in 2019, a DB Class 605 diesel multiple unit converted into a test train called “advanced TrainLab” (aTL) was used for these test runs. The test runs concentrated on validating the WheelGrip adapt function, the ADM functions, and their interaction. In addition, MTB behavior and conditioning effects in different rail conditions were investigated. For the test runs, additional braking system components were installed to perform the functions under investigation. The main parameters adjusted during the vehicle tests included rail conditions (dry, water/soap, oil, and paper tape simulating black leaf layer) and the configuration of the braking and adhesion management systems (various WSP settings, different ADM modes). Most tests were performed as emergency brake applications at starting speeds between 60 and 120 km/h. Results: Compared with existing WSP systems, the new WheelGrip adapt algorithm maintained the same braking performance in regular low adhesion (“UIC”) conditions, while showing improved performance in extremely low adhesion conditions (initial adhesion <5%). The use of the advanced train-wide ADM function in conjunction with sanding systems resulted in even shorter stopping distances. The test run findings served to confirm the results of previous tests, including tests on Knorr-Bremse’s ATLAS test rig. As MTBs can also influence the adhesion between wheel and rail, their rail-conditioning effect was investigated as well. The main points of observation were both the effect on the same vehicle while braking (“MTB to wheelset”) and the effect on following traffic (“train to train”). Different effects were identified depending on the third-body layer. On a paper-tape track preparation, the MTB-to-wheelset effect was a drying effect which improved the wheel/rail adhesion resulting in a better deceleration performance. The train-to-train effect (adhesion improvement) with the MTB activated was better than using friction brakes only. The braking force of the MTB itself showed a fairly rapid increase to levels comparable with those achieved in non-contaminated conditions. The train-to-train effect on an oil-based preparation was almost identical with and without the MTB. Further overruns did also not significantly increase the MTB’s own braking force. Limitation of the studies: The range of initial braking speeds and consequently the findings and quantitative conclusions of the study are limited to speeds up to 120 km/h. Conclusion: In conclusion, it can be asserted that the inclusion of an MTB in the braking system not only provides additional braking force, but also further improves the performance of other types of brakes acting on the downstream wheelsets (of both the same and following trains). The reliability of the adaptive response of the WheelGrip adapt function and the resulting improvement in adhesion utilization in extremely low adhesion conditions were demonstrated on a multiple unit train. The data obtained will be used in the further development of the Knorr-Bremse solutions, and also in the configuration of the wheel slide protection test rig used by DB Systemtechnik to support certification tests.
Dr.-Ing. Marcus Fischer, Expert Standardisation, Partnerships and Special Projects, Knorr-Bremses SfS; Dipl.-Ing. Thomas Rasel, Expert Control Functions, Knorr-Bremses SfS; Dipl.-Ing. Bernhard Ebner, Project Assistant, Christian Doppler Laboratory for Enhanced Braking Behaviour of Railway Vehicles, Institute of Mechanics and Mechatronics, TU Wien; Dipl.-Ing. Felix Kröger, Test Engineer, DB Systemtechnik GmbH, Minden; Mr. Sebastian Heinz, Head of Testing Brakes and Couplers, DB Systemtechnik GmbH, Minden