Purpose
The purpose of this paper is to develop an improved adhesion model to better reproduce the low adhesion condition of the anti-skid control for rail vehicles under braking condition.
Design/methodology/approach
In view of the low adhesion characteristics for rail vehicles under braking conditions, the Polach adhesion model was improved based on the sliding power and sliding energy. The wheel–rail low adhesion model suitable for braking condition was given. The analysis of braking anti-skid control under emergency braking condition was carried out through the co-simulation, and compared with the test data; the effectiveness and practicability of the improved low adhesion model were verified.
Findings
The results showed that the improved adhesion model is simple and efficient and the parameters involved are less, and it can be directly applied to the real-time simulation of anti-skid control in the process of train braking.
Originality/value
This paper can provide a theoretical reference for the reasons of change and improvement of adhesion between wheel and rail caused by the adjustment of braking force under anti-skid control, which can fulfill a need to the study of sliding energy on the contact surface, the removal effect of pollutants on the wheel–rail surface and the improvement and recovery of adhesion caused.
Peer review
The peer review history for this article is available at: https://publons.com/publon/10.1108/ILT-07-2020-0244/
Abstract. The performance of the braking system has an important influence on the safe operation of the train. In this paper, the AMESim simulation software is used to simulate the pneumatic valve unit (PVU) for the direct electro-pneumatic braking system controlled by the microcomputer. And the correctness of the model is verified by the simulation of the service braking and the emergency braking. At the same time, the vehicle dynamics model is built in the MATLAB/Simulink environment, and the AMESim pneumatic valve model is combined with the simulation to verify the effectiveness of the anti-skid logic. The simulation results from the service braking and emergency braking can be drawn that the PVU for the direct electro-pneumatic braking system controlled by the microcomputer is consistent with the response of the real system, which verifies the correctness of the PVU model. It can be seen from the simulation results that the anti-skid control logic can achieve the control requirements, and can achieve the stability of the anti-skid effect in the event of a continuous sliding. The results of this study provide an effective model base for the design of the actual vehicle braking system and solutions to the fault.
Purpose -This paper aims to deduce a set of theory computational formula, and optimize and improve the heat conductivity of vias in printed circuit boards of electrical power apparatus. Design/methodology/approach -The authors adopted numerical simulation and experimental measurement to verify the reliability of this formula. Findings -Research result showed that 0.45 mm was the optimal bore diameter of vias; the conductivity had no obvious improvement when filling material was FR4 or Rogers, but if it was filled with texture of high thermal conductivity like soldering tine, the conductivity would improve a lot; the plating thickness of vias had a greater influence on thermal conductivity. Originality/value -Through the theory computational formula, this paper studied the influence of aperture of vias, filled materials and thickness of copper plated on vias on thermal conductivity.
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