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 c ontrol of structural vibration transmission. Five different active con trol strategies have been studied for the reduction of structural powe r transmission from a source to a receiver via a number of active moun ts. The effects of transducer errors and the problems created by the p resence 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 con trol strategies at the junctions connecting the mounts to the plate: t he cancellation of out-of-plane velocities, the cancellation of out-of -plane forces, the cancellation of the power due only to the out-of-pl ane velocities and forces and the minimization of the sum of squared o ut-of-plane velocities and weighted square forces. The control of tota l power gives the best results under ideal conditions but, for realist ic cases, characterized by measurement errors and flanking paths, the cancellation of velocity or force is more effective than the active co ntrol of measured power. The minimization of the sum of squared veloci ties and weighted squared forces gives a particularly interesting resu lt since the performance of the active control system is then almost t he same as that of minimizing total power and this performance is not sensitive to measurement errors or flanking paths. (C) 1997 Academic P ress Limited.