Active isolation of structural vibration on a multiple-degree-of-freedom system .2. Effectiveness of active control strategies

This is the second of two companion papers concerned with the active control of structural vibration transmission. Five different active control strategies have been studied for the reduction of structural power transmission from a source to a receiver via a number of active mounts. The effects of transducer errors and the problems created by the presence of an uncontrolled flanking excitation acting on the receiver have been analyzed. Minimization of the total power transmitted to the receiver through the mounts has been compared with more practical control strategies at the junctions connecting the mounts to the plate: the cancellation of out-of-plane velocities, the cancellation of out-of-plane forces, the cancellation of the power due only to the out-of-plane velocities and forces and the minimization of the sum of squared out-of-plane velocities and weighted square forces. The control of total power gives the best results under ideal conditions but, for realistic cases, characterized by measurement errors and flanking paths, the cancellation of velocity or force is more effective than the active control of measured power. The minimization of the sum of squared velocities and weighted squared forces gives a particularly interesting result since the performance of the active control system is then almost the same as that of minimizing total power and this performance is not sensitive to measurement errors or flanking paths. (C) 1997 Academic Press Limited.