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S. Popprath, A. Schirrer, C. Benatzky, M. Kozek, J. Wassermann:
"Experimental modal analysis of an actively controlled scaled metro vehicle car body";
Talk: ICSV14, 14th International Congress on Sound and Vibration, Cairns, Australia; 2007-07-09 - 2007-07-12; in: "Proceedings of the 14th International Congress on Sound and Vibration", (2007), ISBN: 9780733425165; Paper ID 805, 8 pages.

This paper deals with the experimental modal analysis of an actively controlled scaled laboratory
model of a flexible metro vehicle car body. To investigate such a control system a 1/10-
scaled laboratory model of a metro vehicle car body has been built. Control forces are applied
to the structure by two piezoelectric stack actuators mounted in specially designed consoles,
which are bonded to the side members of the structure. The car body itself is suspended in a
test bed frame by four coil springs to obtain a free-free suspension configuration. An electrodynamic
shaker is used to generate broad band excitation forces, which in real operation enter
the structure at the application points of the secondary suspension system. The state feedback
controller and the observer are designed by an LQR-based modal weighting procedure implemented
in Matlab/SIMULINK. To investigate the reduction of the amplitudes of the shaker
induced vibrations a non-contact measurement utilizing a laser scanning vibrometer is applied.
In order to verify the achieved performance, open and closed loop disturbance-displacement
transfer functions and the mode shape corresponding to specific natural modes are identified by
an experimental modal analysis. Since the ride quality is mainly influenced by the lowest global
vibration modes, the investigation is focused on the first torsional mode and a low vertical bending
mode of the car body.