G.A.U.S., Mech. Eng. Dept., Univ. of Sherbrooke, Sherbrooke, PQ J1K 2R1, Canada
Sensing approaches used in active structural acoustic control (ASAC) are mainly concerned with monitoring acceleration, velocity or displacement of the structure, typically by means of accelerometers or PVDF, thereby eliminating the need for far-field acoustic sensor(s). The radiation of the structure is estimated from this information, either directly or from a model of the radiating structure. The direct approach has the advantage of not being dependent on the accuracy of any model. A new sensing strategy is herein presented, in both direct- and model-based approaches, where the estimation of acoustic radiation involves monitoring the strain field of the structure. Such information is directly given by fiber optics sensors, for example, so that significant gain is expected at this level. Two approaches are presented using strain information. The first formulation is obtained by integrating by parts the Rayleigh's formula. Dependence on boundary conditions then appears and has to be dealt with. The second formulation utilizes a finite-difference scheme in order to estimate, from the strain information, the displacement field in Rayleigh's formula. Simulations are performed using a given displacement field and the two formulations are compared in order to evaluate their effectiveness for use in active control schemes.