Recent developments in the use of structural actuators for decentralized active control

Abstract

With an array of ideal, dual, collocated actuators and sensors, decentralized feedback controllers can not only be unconditionally stable, but their performance in reducing vibration and, hence, radiated sound, can approach that of a centralized LQG controller [W. P. Engles et al., JASA 119, 1487–1495 (2005)]. They also have a modular architecture that scales well, even for very large structures. This paper discusses some of the problems that arise in practice when proof-mass or piezoelectric transducers are used instead of ideal force or moment-pair actuators in such decentralized controllers. Proof-mass actuators are attractive when generating significant forces, but their natural frequency must be well below the first structural resonance frequency for stable operation. Even when this is achieved, impulsive forces due to the actuators hitting their end-stops have recently been shown to potentially be an additional source of instability. Piezoceramic actuators can give significant control in thinner structures, but as well as controlling out-of-plane vibration, they also create in-plane motion in the structure that can couple into closely located strain sensors causing instability in feedback controllers. Novel arrangements of such transducers will be described in which the effect of in-plane coupling is minimized, thus significantly improving their performance.