Transition flight modeling and control of a novel tilt tri-rotor UAV

Abstract

A novel tilt tri-rotor unmanned aerial vehicle (UAV) which combines the vertical flight capability of a helicopter and forward flight performance of an airplane is proposed. The two front rotors are able to tilt from the vertical to the horizontal position, however, the third rotor is fixed in the aft fuselage with a small angle. The nonlinear dynamic model of tilt tri-rotor UAV is given by the equations of Newton-Euler. By balancing flight conditions in transition mode where there are redundant controls, the transition corridor is obtained. To resolve the attitude control problem of tilt tri-rotor UAV, we proposed an improved control allocation based on the rotational speeds of three propellers and the tilt angles of two front rotors. Besides, the structure of PID controller including inter loop and outer loop is developed. Simulation results during full envelope flight are presented, and the success of the modeling carried out as well as the control strategy designed are demonstrated.