A brake hardware-in-the-loop simulation (HILS) system for a railway vehicle is widely applied to estimate and validate braking performance in research studies and field tests. When we develop a simulation model for a full vehicle system, the characteristics of all components are generally properly simplified based on the understanding of each component’s purpose and interaction with other components. The friction coefficient between the brake disc and the pad used in simulations has been conventionally considered constant, and the effect of a variable friction coefficient is ignored with the assumption that the variability affects the performance of the vehicle braking very little. However, the friction coefficient of a disc pad changes significantly within a range due to environmental conditions, and thus, the friction coefficient can affect the performance of the brakes considerably, especially on the wheel slide. In this paper, we apply a variable friction coefficient and analyzed the effects of the variable friction coefficient on a mechanical brake system of a railway vehicle. We introduce a mathematical formula for the variable friction coefficient in which the variable friction is represented by two variables and five parameters. The proposed formula is applied to real-time simulations using a brake HILS system, and the effectiveness of the formula is verified experimentally by testing the mechanical braking performance of the brake HILS system.
The braking system of a high-speed train has a crucial role for the safety of human mass transportation. However, it is hard to acquire design parameters of the braking system in the development stage of a new high-speed train. In this paper, we build a Hardware-In-the-Loop (HIL) system for the braking system of the Korean High-Speed Train (KHST) that is supposed to reach 350 km/h, and analyze the characteristics of the braking system of KHST (composed of 7 cars) via real-time simulations. In the HIL system that is built using a DSP board of dSPACE, the dynamics of the 7 car bodies and several bogies and characteristics of connecting devices between cars are considered individually. Simulation results show that the designed braking system of KHST is valid and satisfies design specifications.
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