Development and validation of a new code for longitudinal train dynamics simulation

Abstract

Longitudinal train dynamics have a significant impact on both safety and performance of railway systems. Numerical simulation of long heavy haul trains can thus provide essential information for the development of diagnostic and signaling systems as well as coupling elements and braking systems. Long trains are usually modeled by considering only the longitudinal degree of freedom and by adding extra resistant forces to represent the track curvature and gradients. The prediction of in-train forces represents the most critical aspect in modeling the longitudinal dynamics of long trains made up of several vehicles. In fact, coupling elements have non-linear force–deflection characteristics, with different behavior in loading and unloading states, thus featuring a hysteretic loop. Look-up tables storing data from experimental tests are generally used to model these elements; however, other strategies, such as fitting curves and white-box models are witnessed in the literature. Recently, an international benchmarking of longitudinal train dynamics simulator was established in order to compare the output results obtained by different models with the same input data. The research group from Politecnico di Torino performed the simulations using the multibody software Simpack, but computational inefficiencies and numerical divergences occurred. To overcome these issues, a new dedicated in-house code was developed in the MATLAB environment. The paper focuses on the description of this new code and its validation, which was carried out by performing the simulations according to the benchmark inputs and comparing the results with the outputs from the other participants.

Simulation of the Thermal Behavior of Cast Iron Brake Block during Braking Maneuvers

“…At this initial stage of the activity, the simple model briefly described above is developed to check the reliability of the monitoring system. However, an upgrade of the model is planned by combining a detailed multibody model of a single vehicle and a longitudinal train dynamics code, able to better simulate the vehicle dynamics behavior during braking operations [37][38][39][40].…”

The influence of resistant force equations and coupling system on long train dynamics simulations

“…The code was validated in previous works [49][50][51] on the four simulation scenarios proposed in the international benchmark of LTD simulators using the laws suggested by the benchmark for the computation of the resistant forces, see Table 1 and equations ( 3) and (6). The code validation showed that the outputs computed by the new code are in good agreement with the other simulators joining the benchmark.…”

Feasibility study of a diesel-powered hybrid DMU

“…Among other considerations, it should be highlighted that RB power represents part of the total braking effort since ED braking use is limited by the maximum braking power of motors and vehicle speed. The proposed LTD model is 1D, as common to most LTD simulators [34,35] and as suggested by the recently established international benchmark of LTD simulators [36,37]. The model considers both the gravitational force due to track slope and the propulsion resistance, which is the sum of rolling resistances and air resistances.…”