Modal Representations in Control/Structure Interaction

When examining control/structure interaction problems, a standard method for representing the structure is to choose a truncated set of normal modes calculated from either a finite element or a distributed parameter model. However, the normal modes can neglect important static information about the structure. Using a set of fixed interface modes results in a much more accurate closed-loop model, even when coupled with relatively low bandwidth controllers. The fixed interface modes are calculated with control input degrees of freedom held fixed and can be calculated using standard finite element software. Illustrative examples include a simple hinged beam and a complex model of the Phase I Space Station configuration.