High frequency spatial vibration control for complex structures

When attempting to actively control the vibration of a complex structure subjected to unknown complex disturbance forces, how the controller performs can be primarily influenced by four factors: the frequency bandwidth to be controlled, the accuracy of the structural modelling, the robustness of the controller, and the extent to which the disturbance can be quantified. Each consideration can be separately addressed through the application of appropriate techniques or approaches that are not part of the original control system design. The difficulty confronting the control system designer is to find a way of combining all of these separate techniques into a unified approach. The current work outlines techniques that can be used to address each consideration and how the techniques can be combined to produce a robust, fixed bandwidth controller for which the lower frequency limit for control can be any frequencies larger than 0 Hz. It is shown how Subspace Model Identification can be used to obtain the system dynamics through experiment. There is also a description of the spatial input/output control approach, which provides a conceptualisation of the structure's global displacement and the contribution of the global disturbance on the structure. It is shown how combining these two theories enables an experimental model to be defined, which could be used to achieve global vibration attenuation for the system in question. Finally this work provides results from a vibration control experiment on an irregularly shaped shell for specified frequency bandwidth, to demonstrate the effectiveness of the global vibration attenuation control approach proposed.