Influence of Cyclic Pneumatic Brake on the Longitudinal Dynamics of Heavy-Haul Combined Trains

Heavy-haul transportation plays a significant role in railway freight. Limited by the complex topography and resource distribution, China’s heavy-haul railways contain a great number of long downward slopes, which is the main challenge for heavy-haul combined trains. Constrained by the pneumatic brake system of the train, cyclic pneumatic brake needs to be applied to provide adequate braking capability, when the train is running on a long and steep downward slope. The subject of this work is 20,000-tonne heavy-haul combined trains, consisting of 1 locomotive $+$ 105 wagons $+$ 1 locomotive $+$ 105 wagons with end of train device (abbreviated as 1 $+$ 1 $+$ EOT). The test data show that the switching process from service lap to brake release is quite dangerous when applying cyclic pneumatic brake. During the brake release process, the asymmetric forces on the front and rear vehicles can result in the exacerbation of longitudinal forces. This paper establishes a simulation model of the heavy-haul combined trains’ cyclic braking process. Meanwhile, we focus on the release process of the cyclic pneumatic brake, and investigate the effect of the initial speed of dynamic braking adjustment, value and time of dynamic braking application, and differentiated collaborative control of leader and follower locomotives on the longitudinal train dynamics (LTD). The comparison of these simulation results reveals how differentiated collaborative control strategy works on the longitudinal dynamics of heavy-haul combined trains, laying the foundation for the optimization of longitudinal dynamic performance during cyclic pneumatic brake.