OPTIMAL PLACEMENT OF MICROPHONES AND PIEZOELECTRIC TRANSDUCER ACTUATORS FOR FAR-FIELD SOUND RADIATION CONTROL

This paper presents an optimization solution technique to determine th e optimal locations of piezoelectric transducer (PZT) actuators and fa r-field microphone sensors for active structural acoustic control in c onjunction with the use of least-mean-square (LMS) feedforward control algorithm. A simply supported beam in an infinite rigid baffle subjec t to an harmonically excited point force is considered. The piezoceram ic patches are adhered to the beam and act as control transducers, whi le microphones located in the far field are used as error sensors. The objective function is first defined as the total radiated sound power , The design variables which are the locations of PZT actuators and mi crophone sensors are then identified and determined. The genetic algor ithm (GA) incorporated with the use of linear quadratic optimal contro l theory (LQOCT) to calculate the control voltages to the actuators is adopted to solve the optimization problem. Results show that the opti mally placed PZT actuators and microphone sensors can perform better s ound radiation control than the arbitrarily selected ones. In particul ar, for off-resonance excitation cases the optimized PZT actuators and microphone sensors can efficiently control the sound radiation and el iminate the control spillover. The control mechanisms of PZT actuators and microphone sensors are demonstrated through the studies of radiat ion directivity patterns and beam displacement distributions as well a s the wave-number analysis. The effect of the number of microphone sen sors are also presented. The use of optimally positioned PZT actuators and microphone sensors can efficiently achieve structural sound radia tion control. (C) 1996 Acoustical Society of America.