Aeroservoelastic Flight Dynamic Modeling of Multi-Rotor eVTOL Aircraft

This paper presents an analytical formulation of aeroservoelastic-flight dynamic modeling of multi-rotor electric vertical takeoff and landing (eVTOL) aircraft in hover and transition flight. The method captures the analytical stability and control sensitivities of rotor unsteady aerodynamic loads about a trim solution due to the flexible airframe. The rotor aerodynamic forces include circulatory and non-circulatory components to account for unsteady aerodynamics. The circulatory forces are corrected for unsteady aerodynamics using the time-domain approximation of Theodorsen's function or alternatively the Leishmann's method. The integrated aeroservoelastic flight dynamic model includes the rigid-body aircraft flight dynamics, the structural dynamics of the flexible airframe, inflow dynamics, unsteady aerodynamics, blade pitch dynamics, and rotor dynamics. An analytical aeroservoelastic model of the NASA Lift+Cruise aircraft in hover is developed to illustrate the aeroelastic effect of the elastic airframe on the rigid-body modes of the aircraft.