Robust Full-Envelope Flight Control Design for an eVTOL Vehicle

View Video Presentation: https://doi.org/10.2514/6.2021-0254.vid This manuscript considers the flight control design for an electric Vertical Take-Off and Landing (eVTOL) vehicle, whose configuration is based on the fixed-wing Cessna 182 mounted with additional tilting rotors to provide helicopter flight characteristics. The control design for such vehicle exploits advanced robust control strategies (H∞ design methods) to offer a single control law covering over a wide range of flight conditions in each operation mode (helicopter and airplane). The stability metrics, in addition to the frequency and time domain properties of the linearised closed-loop, are examined before the controllers are tested on the nonlinear model to enhance confidence. The transition between the 2 operation modes is controlled based on a feedforward scheduling technique typical for tilt-rotor configurations. The performance of the proposed control laws is tested in a whole flight simulation performed on the nonlinear model. We observe that the control outcome is successful, in the sense that no significant changes in the flight properties are recorded during the transition period, and the H∞ controllers are able to stabilise the vehicle and follow the reference signals quickly. The control methods in this work are appealing in a practical context because of the lower implementation requirements, more accurate robustness measures and more transparent design process.