Active control of microvibrations for equipment loaded spacecraft panels

During the last two decades, there has been a dramatic increase in research into the active control of vibrations, especially for aerospace applications. Microvibrations (i.e. small amplitude vibrations in the frequency range 0 - 1 kHz) have, however, received relatively little attention due, in the main, to the low level of disturbances they induce. The new generation of space-borne optical instruments and microgravity experiments are very sensitive to disturbances however, and they require stability levels against microvibrations that can only be achieved through the use of active control schemes. Analysis and design of active control schemes requires realistic yet computationally feasible models to represent the dynamics of the structure under consideration.This thesis develops a systemic procedure for the development of such models in the case of a commonly encountered spacecraft component: an equipment loaded panel. The various pieces of equipment are mounted on active or passive suspensions and resonators are used to represent internal dynamics, arising from flexible circuit boards for example. The panel itself, which transmits vibrations from sources to receivers, is controlled through piezoelectric patches, with each patch acting as either a sensor or an actuator. Once the particular configuration under consideration is specified, its equations of motion are derived here by using Lagrange's equations of motion with the bare panel vibration mode shapes used as Ritz functions.An essential prerequisite to control related analysis is clearly to verify that the model obtained is indeed 'an adequate' description of the underlying dynamics. Here the model is verified against those produced by other techniques for the same configuration. This confirms that this procedure can produce models which are a suitable basis for detailed controller design/evaluation studies.