Contrôle actif du bruit par minimisation du débit volumique de structures : analyse et expériences

Abstract
The active control of structurally radiated sound requires in general a large number of error sensors on the vibrating structure. A simple control strategy, using only one error signal -the volume velocity of the structure- has recently been proposed. Such a strategy allows (i) to control all the structural modes that are monopole radiators at low frequencies (i.e., with a high radiation efficiency), (ii) to keep the control set-up simple (only one information is to be minimized). The volume velocity is measured using piezoelectric PVDF strip. The shape of the PVDF strip is determined in such a way that the output signal from the PVDF sensor is directly proportional to the volume velocity induced by the structure on which it is bonded. Using a modal approach, the sensor shape is shown to depend only on the structure and sensor characteristics. However, it is independent of the excitation and the frequency. For a simply supported beam, the shape of such a PVDF sensor is shown and experimental validations are presented for the measure of the volume velocity. Active control was then implemented with this PVDF error sensor and piezoceramic actuators for different frequencies of excitation, using a one-channel feedforward adaptive LMS algorithm. Results show that sound radiation can be efficiently attenuated using this strategy when the system is driven "on-resonance". However, when the system is driven "off-resonance", the axial effects induced by the asymmetric piezoceramic actuators limit the control efficiency.