One of the many design aspects of modern railway vehicles isto ensure good ride quality by reducing the vibration amplitudes of the car body which are typically present in light-weight structures.
The excitation of these vibrations is mainly caused by geometric track irregularities which generate varying wheel-rail contact forces.
The conventional design approach is to minimize the propagation of the dynamic wheel forces to the elastic car body.
This is usually achieved by a careful design of the secondary suspension in vertical as well as transversal direction.
Instead of this passive solution, active control concepts can be employed to generate an active or semi-active secondary suspension system(Foo & Goodall, 2000; Stribersky, M¨ uller, & Rath, 1998).
There, due to the mass of a railway car body, large actuators and considerable
power consumption are major drawbacks.
Moreover, any active concept which directly acts on the suspension may affect the
safety of the vehicle against derailment.
Another solution to reduce the dynamic wheel-rail contact forces are active steering
strategies (Mei, Nagy, Goodall, & Wickens, 2002), but this concept can only marginally alleviate the accelerations in vertical direction.
All these methods may be referred to as vibration isolation