Coupled Rotor-Fuselage Analysis with Finite Motions Using Component Mode Synthesis

This paper is concerned with the modeling of a rotor-fuselage system undergoing large angle maneuvers. The behavior of the elastic fuselage will be represented by a modal expansion, thereby greatly reducing the computational cost of the simulation. In this work, a floating frame approach is used. The total motion of the fuselage consists of the superposition of the rigid body motions of the floating frame and of elastic motions that are assumed to remain small. The proposed formulation makes use of a component mode synthesis technique that leaves the analyst free to choose any type of modal basis and simplifies the connection of the fuselage to other rotorcraft components. The proposed formulation is independent of the finite element analysis package used to compute the modes of the fuselage. It is also shown that in the absence of elastic deformations, the formulation recovers the exact equations of motion for a rigid body.