Ride quality improvement ability of semi-active, active and passive suspension systems for railway vehicles

It is one of effective ways to increase the running speed of railway vehicles to make the railways more competitive with air transport while providing better safety. However, the high speed of the train would cause significant car body vibrations, which induce the following problems: the ride stability, the ride quality, and the cost of track maintenance. Thus various kinds of railway vehicle suspensions, which can be categorized as passive, active, and semi-active types, have been designed to cushion riders from vibrations. In this paper, it is aimed to investigate semi-active suspension systems using magnetorheological (MR) fluid dampers for improving the ride quality of railway vehicles. A full-scale railway vehicle model with seventeen degrees of freedom is proposed to cope with lateral, yaw and roll motions of the car body, trucks and wheelsets. The governing equations of the railway vehicle integrated with MR fluid dampers in the secondary suspension are developed and the LQG control law using the acceleration feedback is adopted, in which the state variables are estimated from the measurable accelerations with the Kalman estimator. The performance of the semi-active suspension system exploiting MR fluid dampers is compared with those of the active suspension system with linear and unconstraint actuators and the passive suspension system with springs and oil dampers. The results show that the semi-active suspension system with MR fluid dampers possesses a good ride quality improvement ability.