Research on flight control of tilt tri-rotor uav in transition mode

The full-flight envelope of a tilt tri-rotor UAV encompasses three distinct modes: rotor mode, transition mode, and fixed-wing mode. Due to the unique three-rotor configuration of the aircraft, attitude stabilisation control in rotor mode must integrate the motion of the tilting rotors, resulting in control coupling across multiple channels. When the tilt tri-rotor UAV operates in transition mode, both rotor control and fixed-wing control are active simultaneously, introducing a control allocation challenge that complicates stable flight control during this phase. This paper proposes a flight control system architecture for a tilt tri-rotor UAV based on a commercial open-source flight controller. At the strategy level, the design includes a rotor tilting path planning approach and a stabilisation strategy for mode transition. At the controller level, dedicated controllers are developed for both rotor mode and transition mode. For the control allocation layer, the study investigates a rotor-mode control allocation mechanism based on tilt angles, as well as a low-level control allocation algorithm that integrates controllers from both rotor and fixed-wing modes. Finally, the feasibility of the transition flight control system is validated through simulations, covering the entire flight process from rotor mode to transition mode and then to fixed-wing mode.