Modelling and control of a smart auxiliary mass damper equipped with a bragg grating

This paper presents the results of a key activity of a large research project in the aeronautics field, funded by the European Community under the Sixth Framework Programme, namely the modelling and control of a magnetostrictive actuator to be used for broadband vibration and noise control. The developed auxiliary mass damper is designed in order to meet the demanding requirements of the application at hand, especially in terms of weight reduction and force capability. The specifications are successfully satisfied using an inertial resonant actuator concept based on a nonlinear amplification mechanism of the seismic mass displacement. The nonlinearities of the actuator highly affect the problem of its adoption within the active feedback control system devoted to vibration and noise reduction of the controlled structure. In order to overcome the limitation and negative effects of these nonlinearities within the main control system, the actuator is equipped with an optical sensor based on a Bragg grating used for a low-level control loop aimed at imposing a desired linear behaviour to the actuator itself. A preliminary modelling and characterization of the dynamic behaviour of the actuator is performed taking into account also the hysteretic nonlinearity exhibited by the active material as well as the nonlinear dynamics of the mechanical actuator structure. A model-following control algorithm, designed on the basis of an experimentally identified dynamic model, is adopted as the low-level control algorithm. Experimental results show the effectiveness of the approach and its validity as the first step to be taken during the design phase of the complete noise and vibration control system.