The problem of active control of sound radiated by thin walled structures using arrays of spatially discrete piezoceramic sensors and actuators is addressed. A general methodology for the design of structure-radiated noise controllers is developed and presented. This methodology utilizes well tested commercial finite elements modeling (FEM) packages to perform structural discretization, and is applicable to any flexible structure. The FE model includes coupled-field electro-mechanical elements and structural-acoustic interaction. This allows the investigation of the adaptive structure and its acoustic environment as a coupled dynamic system, with the results being instrumental in the initial design stages of the controlled structure. The discretized structure is presented in state space, with the sensors/actuators mass and stiffness included in the model. The sensor/actuator models are incorporated into the output (measurement) and input (control) matrices, respectively. The acoustic power radiated by the structure into the far field is expressed as a quadratic form of the system states, and this forms the basis of an acoustic cost function. A linear-quadratic controller is constructed using this cost function, and its performance is evaluated using several numerical simulations of the controlled structure. The methodology presented in the paper is applied to a simply supported beam, where the sound radiated by the beam into the far-field is shown to be effectively controlled.
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