Active structural acoustic control:: Numerical modeling, robust controller design and experimental validation

Payload protection against noise induced vibrations in rocket fairings is an important issue. In the work presented here, active structural acoustic control using an H-infinity-controller together with piezoceramic sensors and actuators attached to the structure and interior microphones is investigated as an approach to this problem. For this a generic experiment has been set up. One objective of the work is to find and validate a method for getting accurate low-order parametric models for controller design based on finite element calculations. Therefore parameter estimation methods are applied to measured data as well as to numerical simulation data. A comparison of both yields information about the accuracy of the numerically calculated frequency responses. Due to uncertainties in the finite element model and time varying parameters, the robustness of the closed-loop system is an important design criterion. The most critical perturbations are variations of natural frequencies due to temperature-induced prestresses. The perturbations and uncertainties can be modeled by using linear fractional transformations. Robust stability and performance properties of the closed loop are investigated, both analytically and experimentally. These analyses allow a statement about the necessary accuracy of the numerical model and about the achievable performance.