Steering of Flexible Multibody Models with Application to the Simulation of Maneuvering Flight

Nonlinear flexible multibody dynamics enables the high-fidelity simulation of rotorcraft vehicles. In this work we focus on the problem of simulating extreme maneuvering flight conditions. In fact, limiting design factors such as maximum loads, vibrations, noise, etc. are encountered in the maneuvering flight case and at the boundaries of the flight envelope. The approach here proposed is based on a multiscale approach. A coarse level flight mechanics model of the vehicle is used for solving a generalized trajectory optimization problem that yields the flight path and the controls that fly the vehicle along it. This problem is formulated as an optimal control problem, but it is manageable at a reasonable computational cost since only a coarse model with few degrees of freedom is used. The computed controls are then used for steering a fine scale aeroelastic model which is based on finite element non-linear multibody dynamics. Matching of the trajectories flown by the two models is here obtained by means of parameter identification of the flight mechanics model. Selected critical rotorcraft maneuvers are analyzed in order to demonstrate the effectiveness of the proposed methodology.