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Design and Analysis of an Active Tuneable Dynamic Vibration Absorber

High-level noise from modern industrial activities is raising more and more concerns nowadays. The presented research is focused on suppressing the noise radiation from structural frames in rotating machinery using an active structural acoustic source control strategy. To this end, an axisymmetric Piezo-Based Rotating Inertial Actuator (PBRIA) is proposed, which can be mounted on a rotating shaft. This differs from passive control strategies where damping materials, acoustic barriers or enclosures are used, as well as from active noise control strategies where acoustic actuators are used. Since a source control strategy is used, it also differs from techniques that directly apply control forces on the noise radiation surfaces, where tuned mass dampers, inertial actuators or piezoelectric patches are used. This way, a simpler control system with better performance can be obtained. In this research, the PBRIA is mounted on a rotating shaft close to the vibration source in order to interrupt the transmission of vibrations from the shaft through bearings and frames to the noise radiating surfaces. The benefit of this add-on approach is that it is relatively easy to be implemented in a practical setting as no major structural modifications are required, and the machine stiffness is not affected. Furthermore, the active element is not in a critical path of the machine such that a possible failure of the actuator does not necessarily affect the functionality of the machine. Two control strategies, adaptive-passive control and active control, are investigated in this thesis. For the adaptive passive control, external circuits are connected to the piezoelectric actuator in the PBRIA to adjust its electrical boundary conditions. The mechanical properties of PBRIA can be tuned through the piezoelectric effect, such that the response of the considered system is suppressed. For the active control strategy, the MIMO form of the standard Filtered Reference Least Mean Squares (FxLMS) control algorithm and its modified version are used, so that the force to be applied by the PBRIA is calculated numerically based on the observed error signals. Theoretical studies of both adaptive-passive and active strategies are performed in order to understand the working principles and to predict the control performance. Afterwards, experiments are conducted on an industrially relevant test setup in order to validate the theoretical analysis. The experimental results demonstrate the technical feasibility of suppressing the structure borne noise of rotating machinery using piezo-based rotating inertial actuators.

Vibration absorbers; Piezoelectric actuators; Active control; Active tuneable vibration absorbers

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