A finite state aerodynamic model for a lifting surface in incompressible flow

An aerodynamic model necessary for a state equation of an aeroelastic system is proposed. The system is assumed to be a lifting surface in incompressible flow. The model consists of a nonmemory component and a memory component. The former is directly expressed by generalized coordinates. The latter is approximately expressed by using augmented system which is strictly proper and of finite dimension. The augmented system is constructed from Marcov parameters which are derived from an appropriate numerical computation of unsteady aerodynamics. A simple example is given to illustrate the approximation properties of the model. The characteristics of the model are: 1) no complex parameters are necessary to determine the model, 2) system stability of the model is easily guaranteed, and 3) accuracy of the model is good in both the high- and lowfrequency regions.