Comfort improvement in railway vehicles with piezoelectric stack actuators

Piezoelectric stack actuators (PSAs) are compact mechatronic devices that can be used to mitigate structural vibrations in mechanical systems. This paper proposes a systematic investigation of the potential benefits of using these devices in the car body of a railway vehicle to reduce car body resonance effects caused by specific combinations of vehicle speed and track irregularity wavelengths, providing a detailed assessment of performance for both passive and active operation of the actuators over the entire range of operational speed of interest. Two mathematical models of a high-speed railway vehicle are defined: a simplified model with 7 degrees of freedom considering the effect the car body's first bending mode, and a multibody model considering the car body as a deformable body through modal synthesis. Both these models are integrated with a PSA model, and an LQG control strategy is defined for the active operation mode. The results obtained confirm that the benefits provided by the PSA are particularly relevant at specific resonance speeds and prove the superior performance of actively controlled PSAs compared to passive (shunted) ones. The importance of the length of the PSA coupling arm as a design parameter of the actuation system is also highlighted.