MPC-Based Longitudinal Control Design for a Fixed-Wing VTOL UAV in Transition Flight

In this study, control design on transition flight between hover and cruise mode of a Lift and Cruise (LC) type of fixed-wing Vertical Takeoff and Landing (VTOL) Unmanned Aerial Vehicle (UAV) is considered. The aircraft is required to generate sufficient airspeed to cruise under trim angle condition at the end of the transition mode. To deal with the nonlinearities and mutual interference between the lift generation of fixed-wing and vertical rotors, cascaded control design based on Nonlinear Model Predictive Control (NMPC) approach is proposed. In the outer-loop, desired trajectories of pitch angle and forces exerted by vertical and horizontal rotors are generated by solving on-line optimal control problem. The desired attitude control is accomplished in the inner-loop by Dynamic Inversion (DI) methodology. The numerical simulation results show that the proposed controller provides faster transition and achieves the trim condition compared to our previous work.