Gabbert U., Lefevre J., Nestorovic T., Laugwitz F., Schmidt G.

In the paper an overall numerical design approach for an active vibration and noise control of thin-walled smart structures is presented. The vibration and noise control can be managed by attaching the structure with distributed piezoelectric ceramic patches. A controller unit processes the signals of the sensor patches and generates the required voltages for driving the actuator patches in order to reduce the undesired vibration modes as well as the acoustic noise level. The simulation of such smart structural systems requires an overall virtual model, which includes the passive structure, the acoustic fluid, the piezoelectric actuators and sensors as well as the control algorithm. For the numerical modelling and analysis a finite element approach has been developed. Besides the standard structural finite elements the simulation software includes special active finite elements, which include the fully coupled electromechanical field equations for modelling piezoelectric patches (active 3D elements and layered shell elements), 3D acoustic fluid elements, developed on the basis of a velocity potential as well as the vibro-acoustic coupling. Because of the large number of degrees of freedom of such coupled FE model, a modal truncation technique based on a complex eigenvalue analysis is performed in order to create an adequate model for controller design purposes. After transforming the model into the state space form, the Matlab/Simulink software can be used to design and simulate an appropriate controller. In the paper first the theoretical basis is presented in detail. Then an acoustic wooden box covered with an aluminium plate and attached with a number of piezoelectric patches is investigated numerically as well as experimentally. The aluminium plate is excited by a shaker and the piezoelectric patches are used to actively control the vibration and noise level inside the wooden box. The experimental und numerical results are compared and discussed in detailed.