Optimization of Speed Curve for Energy-saving of Freight Train Based on Equivalent Gradient

With the development of the railway transportation and the increase in freight transport volume, the number of freight lines and freight trains are continuously increasing. How to effectively reduce the energy consumption of freight trains has become a research hotspot. This paper considers the length and weight of freight trains, and calculates the equivalent gradients of the lines. Using the train dynamics model, the ramps are divided into four types: steep uphill section, general section, downhill section and steep downhill section. At the same time, based on the optimal control strategy obtained by Pontryagin's Maximum Principle, three scenarios are studied and simulated. The first scenario is with a single steep uphill, the second is with a single downhill, and the third is the combination of steep uphill and downhill. This paper takes the train energy consumption and train punctuality as the optimization goals to design an optimization algorithm to find switching points of the optimal control strategy. The simulation results show that the speed curve after gradient equivalent optimization is smoother than that before gradient equivalent, and the optimized speed curve is easier to track by the train.