Aeroservoelastic Flight Dynamics and Control of Lift Plus Cruise Electric Vertical Take-Off and Landing Vehicle in Forward Flight

Abstract

This paper presents an aeroservoelastic modeling approach for NASA Lift+Cruise electric vertical take-off and land- ing (eVTOL) aircraft in forward flight. A trim analysis for forward flight is performed in CHARM. A mode shape extraction is performed to construct the mode shapes and elastic axes from a NASTRAN model of the Lift+Cruise vehicle. An aeroelastic model is developed using Theodorsen's theory to capture unsteady aerodynamics. The aeroelastic model is coupled to a rigid-body flight dynamic model of the Lift+Cruise vehicle. A closed-loop servo-actuator model is developed for each of the control surfaces and collective pitch of the push fan. A linearized aeroservoelastic state-space model is formulated by coupling the aeroelastic model, flight dynamic model, and servo-actuator models together. An altitude command longitudinal flight controller and a stabilizing lateral-directional flight controller to stabilize the unstable spiral mode are designed using the LQR method.