1. Electro-hydraulic actuator with fail-safe function for steering system

A problem with existing bogie angle linked steering trucks has been than it is more difficult to effectively reduce the lateral force in transition curves than in circular curves.

We developed an electro-hydraulic actuator which was able to reduce the lateral force in transition curves while preventing the reverse steering action which is the largest problem of the active steering system.

The developed actuator, in addition to offering large generative force, high responsiveness and good maintainability is also small enough to be fitted to existing steering bogies.

From the result of the running test on a test line using an existing steering truck equipped with the developed actuator, we confirmed that the new steering system was able to reduce the average of the outer lateral force in the entry transition curve approximately by 60% (Fig.1).

In order to avoid rise of the lateral force in the failure situation such as a reverse steering command, we devised the fail-safe hydraulic circuit which was able to switch mechanically using the vehicle dynamics when running through a curve section (Fig.2).

From the result of a bench test, we confirmed that the steering force was not generated in case of a reverse steering command (Fig.3).