Decentralised velocity feedback control of structures

Abstract

This thesis investigates algorithms that allow the tuning of multiple, single loop feedback controllers in a decentralised arrangement that reduces the global vibration of the structure.  Ideally, this controller should be tuned on the basis of the local properties of the structure and, when applied at multiple locations to the same structure, achieve performance comparable to a centralised controller.

Constant gain velocity feedback is a decentralised control strategy known to be effective at controlling vibrations and requires only the feedback gain to be set appropriately.  Because there are no analytical solutions for the optimal feedback gain, approximations of the gain were considered.  For a beam, approximations on the basis of a few modes performed almost as well as a centralised, dynamic controller but the gains could not be set consistently on the basis of the mobility in a multi-channel set-up.  On a plate, setting the gain to match the impedance of an infinite plate performed well and it is shown that this gain can be calculated from the local mobility in both single- and multi-channel set-up.  Tuning the gain to maximise power absorption performed well, but may be difficult to realise in the multi-channel set-up and can be sensitive to the spectrum of the excitation.

On the basis of a carefully selected model of sound radiation, controllers were also designed to minimise sound radiation.  Decentralised velocity feedback controls were found to perform almost as well as LQG control.  Strategies that minimised the vibration performed less well at controlling radiated noise, but still provided useful performance.

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