Dynamic Inversion Flight Control Laws for Automatic Transition of Tilt-Rotor/Wing Aircraft

This article presents the development and demonstration of dynamic inversion (DI) flight control laws for the automatic transition of tilt-rotor/wing aircraft from hover to cruise flight. The DI control laws employ a multiloop architecture without requiring gain scheduling; however, feedback linearization must be scheduled based on the aircraft's linearized dynamics, which depend on variables such as airspeed and nacelle angle. A generic multirotor/wing simulation model is adapted to represent four configurations: a Bell XV-15-like tilt-rotor, two eVTOL aircraft resembling the Joby S4 and Archer Midnight, and a tilt-wing aircraft similar to the NASA Tilt Wing. The XV-15-like model is validated against US Army/NASA flight-test data and existing models. The simulation models are trimmed and linearized across speed increments from hover to cruise, and model-order reduction methods are applied for control design. The DI control laws are shown to comply with frequency-domain-based stability, performance, and handling quality specifications in selected flight conditions. Closed-loop simulations using the full-order nonlinear dynamics of all configurations demonstrate successful automatic transitions from hover to cruise with accurate forward speed tracking and minimal off-axis response.