Nonlinear order reduction of structural dynamic aircraft models. (Q2713511)

New methods for nonlinear order reduction of structural dynamic aircraft models, described by nonlinear differential equations, have been developed. The methods are based on singular perturbations, weak couplings and cost functionals for selecting the physical states of the reduced order model. By introducing a formally affine nonlinear model structure, the cost functional vector optimization yields closed expressions for the reduced order system. Making use of Lagrange multipliers, even constraints with regard to the reduced order system can be considered, only extending these closed expressions. This leads to the notion of smaller and control oriented realization. Moreover, a unified approach to structural dynamic aircraft modeling for load analysis and for structural dynamic control is developed, which allows to apply the new reduction methods directly to both problems. The methods are applied to a structural dynamic aircraft model in order to achieve a very low order model suited for structural dynamic controller design.