Semi-Passive Control Strategy using Piezoceramic Patches in Non Linear Commutation Architecture for Structural-Acoustic Smart Systems

The demands for novel smart damping materials can be summarized in: external power source not required for operation; device not needing to be tuned to a specific frequency; device operation not affected by changes in modal frequency; device suppressing vibration over a number of modes, weight and size minimized; self-contained unit device. This thesis focuses on these points and it shows that the dilemma between active and passive vibration control may be solved with a new approach, implementing a semipassive technique without penalties in terms of robustness and performance. Connecting a shunt circuit to a piezoelectric transducer leads to a simple and low cost vibration controller that is able to efficiently suppress unwanted structural vibrations: this is a way to fulfil the abovementioned demands. The objective of this work is to develop and validate by an experimental campaign a computational tool integrated with finite element Nastran software. An original 4-channel switched shunt control system has been realized using a tachometer device. The control system has been tested first of all on a simple cantilevered beam attaining a max vibrations reduction of 16.2 dB for the first bending mode. Further reference test article consisted of a 10 ply fibreglass laminate plate. A multimodal control has applied within a band range of 700Hz including the first seven modes. A maximum reduction of 16 dB has been found. Further numerical and experimental tests have been planned to extend the ability of the SSC to produce structural-borne sound reduction in acoustic rigid cavities for fluid-structure interaction problems. Numerical sound power radiation of an aluminium plate, controlled by synchronized switch system, compared with the experimental acoustic energy detected in acoustic room, has been planned in the ongoing activities.