Global control of flexural vibration of a one dimensional structure using tuneable vibration neutralisers

Dayou, Jedol (1999) Global control of flexural vibration of a one dimensional structure using tuneable vibration neutralisers. University of Southampton, Doctoral Thesis.

Abstract

For the last few years, attempts have been made to use a tuneable vibration neutraliser, (TVN), for global control of vibration and radiation sound. The main reason for this has been to use an alternative method to active and passive control techniques. However, because the formulation that describes the behaviour of a structure with a TVN attached is complicated, there has been not much progress on the analytical approach in the investigation of the physical behaviour of such a system.

This thesis describes a simple analytical formulation that enables the prediction of the global vibration reduction. The methods are applied to a one-dimensional structure for simplicity of analysis and discussion. The formulation describing the behaviour of a structure with a single TVN attached has been simplified, which enables an expression for every single mode of global response of vibration to be written down. As a result, basic parameters that govern the optimum tuned TVN have been quantified. It is found that there is a threshold value of the ratio of the neutraliser mass to the neutraliser damping ratio, beyond which there is no further reduction in global response of the host structure. This threshold value has been identified as the optical value, and a mathematical expression is derived. As a consequence, there is a corresponding minimum achievable global response, and an expression for this is also derived.

Optimisation of the TVN parameters is also discussed in this thesis. By employing quadratic minimisation techniques that were originally developed for active control methods, an analogy called the passive-active analogy has been formulated. This analogy enables the determination of the required dynamic stiffness of a neutraliser that minimises the global response of the host structure. If the optical parameters described above are combined with this analogy, a TVN can be as good as the active method for tonal disturbances. The establishment of the active-passive analogy also means that some of the theoretical work in active control can be applied for global vibration control using a TVN.

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