Hiro-o Yamazaki

Effect of wheel-slip prevention based on sliding mode control theory for railway vehicles

It is important to consider the robustness when designing brake control systems, because of the models uncertainties that result from the nonlinear characteristics of wheel-to-rail adhesion forces and brake material friction coefficients. This paper presents the experimental results from the new wheel-slip prevention control using nonlinear robust control theory. The authors performed experiments for the proposed wheel-slip prevention control to compare it with the conventional control laws. The experimental results proved the comparative effectiveness of the proposed control and showed high brake performance under nonlinear characteristics of brake dynamics.

Evaluation of braking behaviour for train drivers using phase-plane trajectories

This study analyses braking behaviour of train drivers and estimates drivers’ mental condition using a train simulator. The velocity deviation recognised by drivers is defined by the difference between the present vehicle velocity and the desired velocity that enables the vehicle to stop at the desired position if the present deceleration is kept constant. Observing the relation between the velocity deviation and the braking operation enables the detection of abnormal driving behaviour. The phase-plane trajectory of the velocity deviation and the brake command with mental workload indicates a large velocity deviation and repetition of the braking operation, while the trajectory without mental workload indicates that both the velocity deviation and the brake command gradually approach the origin of the coordinate axes.

Effects on braking distance from the use of traction fluid as a wheel/rail lubricant

Mineral oil and other lubricants are commonly applied to the gauge corner of high rails to avoid wheel/rail interface wear on railways. Although not directly applied to the top of the rail, these lubricants sometimes end up on this surface, and the relatively low coefficient of friction they produce can cause slipping or sliding at the wheel/rail interface during vehicle acceleration or braking. It has been reported in the literature that the application of traction fluid (a modern technique involving the use of a synthetic lubricant) produced a higher coefficient of friction than that of a conventional wheel/rail interface lubricant. In this study, tests were performed using traction fluid to evaluate its influence on a vehicle’s braking distance and other important performance elements from a practical point of view. The results of the braking performance evaluation carried out on a braking test stand showed that the braking distance increase with synthetic traction fluids was roughly one-half of that observed with conventional wheel/rail lubrication oil. This suggests the potential of using traction fluid as a wheel/rail lubricant.