Keywords: mechanical semi-active control, curving performance, mechanical velocity sensor, hydraulic bush, railway vehicle, MATLAB/Simulink.

A semi-active control method using a mechanical device within a radial beam is proposed in order to solve the contradiction between hunting stability and curving performance for the traditional railway vehicles. As is well known, the requirements for the primary longitudinal stiffness for the hunting stability and curving performance are in conflict [1]. For the hunting stability purpose the primary longitudinal stiffness should be large in value, but for the curving performance purpose this value should be small. To achieve a practical implementation, a mechanical device together with a hollow hydraulic bush design is invented based on the velocity feedback. With the device, when the vehicle's speed is lower than a certain value (named the switch velocity in the paper) the primary longitudinal stiffness becomes very soft, for example less than 3 MN/m; but when the speed reaches a relatively higher value the primary longitudinal stiffness becomes very hard, for example about 19 MN/m. The range of these stiffness values will satisfy the basic need for the low-speed vehicles. The design schemes of the device are presented in detail in this paper.

With the aim to evaluate the improvement effects, of the device, to the curving performance, models of the traditional railway vehicle and a vehicle with hydraulic bushes are established using MATLAB/Simulink. Assuming the railway vehicles run through the two curves with different radiuses at speeds of 50Km/h and 80Km/h respectively, simulations are carried out. Taking the leading wheel as the object of study, which is always in the most serious situation when steering, some curving performance indices are recorded, including the lateral displacement of the leading wheel set, the attack angle of the leading wheel set, the lateral creep force of the leading outer wheel, the friction work of the leading outer wheel, and the derailment coefficient of the leading wheel set. The simulation results also show that, compared with the traditional vehicle, the vehicle with hydraulic bushes has a better curving performance, and it can run through curves more smoothly. Finally, the paper presents the further investigations for future practical use of the device.

1

Y.S. Hu, "Dynamics of Railway Vehicles", China Railway Press, Beijing, China, 2009.

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