Model-based control of plate vibrations using active constrained layer damping.

In this thesis, the author presents a numerical and experimental study of the
application of active constrained layer damping to a clamped-clamped plate. Piezoelectric
actuators with modal controllers are used to improve the performance of vibration
suppression from the passive constrained layer damping treatment.
Surface damping treatments are often effective at suppressing higher frequency vibrations
in thin-walled structures such as beams, plates and shells. However, the effective
suppression of lower frequency modes usually requires the additional of an active vibration
control scheme to augment the passive treatment. Advances in the technologies associated
with so-called smart materials are dramatically reducing the cost, weight and complexity of
active structural control and make it feasible to consider active schemes in an increasing
number of applications. Specifically, a passive constrained layer damping treatment is
enhanced with an active scheme employing a piezoceramic (PZT) patch as the actuator.
Starting with an established finite element formulation it is shown how model updating and
model reduction are required to produce a low-order state-space model which can be used
as the basis for active control. The effectiveness of the formulation is then demonstrated in
a numerical study.
Finally, in the description of the experimental study it is shown how modes in the
frequency range from 0 to 600 Hz are effectively suppressed: the two lowest modes
(bending and torsional) through active control, the higher modes (around ten in number)
by the passive constrained damping layer. The study'S original contribution lies in the
experimental demonstration that given a sufficiently accurate model of the plate and
passive constrained damping layer, together with a suitable active feedback control
algorithm, spillover effects are not significant even when using a single sensor and single
actuator. The experimental traces show, in some instances, minor effects due to spillover.
However, it can be concluded that the presence of the passive layer introduces sufficient
damping into the residual modes to avoid any major problems when using only the
minimum amount of active control hardware.