Dynamic Characterization and Stability of a Large Size Multibody Tiltrotor Model by POD Analysis

A great level of flexibility and accuracy can be gained by employing a multibody approach as the modeling strategy for servo-aeroelastic analyses of rotating wing aircraft. However, the resulting models are often large, in terms of degrees of freedom, and fully nonlinear, making the dynamic characterization phase cumbersome and computationally demanding. Moreover, non-minimal set formulations such as the one used here to express the equations of motion may cause the rise of spurious eigen-values. This paper presents the application to a tiltrotor model of a technique which associates the POD (Proper Orthogonal Decomposition) methodology, to reduce the impact of the model large dimensions, with standard dynamic system identification methods, to efficiently circumvent the complexity usually associated with the development phase of flexible multibody models. The same technique is also employed to assess the periodic motion aeroelastic stability of the tiltrotor.