Active suspension for a two-axle railway vehicle

Aim of this paper is to investigate how the ride quality of a two-axle railway vehicle with single-stage suspension might be improved by the use of active control, compensating for the lack of the double suspension stage, and thereby taking full advantage of vehicle lightweight construction. The basic requirement is to improve the ride quality on random track unevenness while keeping suspension deflection within acceptable levels when the vehicle negotiates deterministic track features such as a gradient. Two alternative active suspension configurations are considered. Skyhook damping and an LQG optimal control. Finally actuator dynamics are included in the analysis, to assess its impact on the overall success of an active suspension implementation. The paper shows that both skyhook and LQG control strategies offer significant improvements in ride quality and also that careful design of the actuators and their force control loops is essential.