Experimental study of local and modal approaches to active vibration control of elastic systems

Summary Two different methods, local and modal, are suggested to control systems with distributed parameters, each of them having its own advantages and drawbacks. The aim of the present research is to carry out experiments aiming in comparison of these 2 methods for the problem of suppression of forced bending vibrations of a thin metal beam. Two pairs of piezoelectric sensors and actuators are attached to the beam in each control system considered. Their locations are chosen so as to provide the most efficient measurement and excitation of the first and second vibration modes of the beam. Frequency methods of the automatic control theory are employed to design stable control systems that can efficiently suppress bending vibrations of the beam with the first and second resonance frequencies. As a result, control systems with the desired performance are created on the basis of both local and modal methods. The obtained modal system works efficiently for both resonances, whereas the local systems demonstrate appropriate performance either at the first or at the second resonance frequency only. This difference is due to the fact that in the case of modal control, each control loop corresponds to a particular vibration mode and can be designed to provide optimal performance at the required frequency. The performed benchmark study demonstrates the advantages of the modal method over the local one for the cases where it is necessary to suppress vibrations in the frequency range that contains more than one resonance frequency of the control object.