Distributed control of beams by electric transmission lines with PZT actuators

The aim of the paper is to propose a distributed control technique based ou. the modal coupling between a beam and an Electric transmission line with PZT actuators; these last behave as capacitances in the electric line and contribute to beam stiffness because their end-points are restrained along tile beam; we call the described system piezoelectro-mechanical (PEM) beam. Structural control by means of concentrated devices often requires high voltages and high inductances this fact is particularly serious when one has to deal with PZT actuators; in order to overcome the problem we propose a device in which tile control action is distributed along the beam. We found that the line inductance and the line resistance behave as electric "taps" respectively for the electro-mechanical modal coupling and for the damping efficiency: we found a bounded region in the hue impedance plane in which the energy exchanged between the beam and the electric line is maximum and therefore the control strength is maximum. By means of already available PZT actuators we obtain very high damping ratios fur mechanical vibrations (delta similar or equal to 0.1)(1). We only investigated a simple case of passive control in damping vibration, but several active control applications are conceivable: it seems to us that such control technique is more efficient than those already proposed in the literature characterized by the use of actuators supplying concentrated forces.