Conversion control of a tilt tri-rotor unmanned aerial vehicle with modeling uncertainty

The tilt-rotor unmanned aerial vehicle (TRUAV) has vertical take-off and landing and high-speed flight capabilities through conversion and reconversion modes, thereby presenting wide application prospects. This article presents a compact tilt tri-rotor UAV. For flying in the conversion mode, the TRUAV needs to realize the transition of two control logic and two kinds of actuators in both of the rotor and fixed-wing modes, achieving the control of the multi-input multioutput, input nonaffine, and nonlinear multichannel cross-coupling UAV system. Furthermore, the lateral dynamics of a tilt tri-rotor UAV is more unstable for unpaired rotors. These system characteristics present a great challenge to conversion control. To solve these problems, the nonlinear dynamic model of the vehicle in the conversion mode is provided. Furthermore, a cascade control system consisting of position control, velocity control, angle control, angular velocity control, and control mixer is proposed. The simulation result of the control system shows steady flight and a fast transition in the conversion mode with modeling uncertainty in case of no wind