Investigation on the safety of 30,000-ton combined train with different lag times of slave control locomotives

To investigate the influence of the lag time in braking response of the slave control locomotives caused by the LOCOTROL wireless synchronous control system on the longitudinal impulse of the train, a 30,000-ton heavy-haul train model was established. The model is in the form of '1+1+1+1'. The simulation accuracy of the air braking system was verified by comparing with static tests. A dynamic model consisting of two HXD1 locomotives and a 100-type couple was established for study the middle locomotive's running safety. Results show that, under normal transmission delays, the lag time in the braking response of the slave control locomotives is approximately 2–3 s. The lag time significantly influence the coupler force and its distribution law. During emergency braking, the lag time increased from 0 s to 6 s, and the maximum coupler force increased by 1877.1 kN. Among the three slave control locomotives, the one positioned in the middle has the greatest impact on the coupler force, while the one closest to the leading locomotive has the least impact. When the lag time reaches 5 s, the middle locomotive's coupler becomes unstable. Increasing the lateral stiffness of the secondary suspension is beneficial for enhancing the locomotive's ability to stabilise the coupler.