Research On Modal Switching And Cruise Mission Planning Of Tilt-rotor UAV

Tilt-rotor aircraft is a new type of aircraft that combines the flight characteristics of fixed-wing and quad-rotor aircraft.An research on tilt-rotor aircrafts has roused in the field of aerospace since the 1980s because of its characteristics of vertical take-off and landing(VTOL)and high cruising speed,etc.It is difficult to establish an accurate mathematical model and design a reasonable controller due to the complex structure of the tilt-rotor aircraft,the strong coupling of the system and the characteristics of multi-modal flight.In this research,the research object is a novel tilt-rotor UAV with four rotors and the front dual tilt-rotor(DTR)are tiltable.The study goal is to achieve flight modal stable switching and cruse mission planning.The main work is as follows:In this research,the force and torque of each part of the fuselage are analyzed according to the DTR's force characteristics and aerodynamics.The inertial coordinate system,rotor coordinate system and body coordinate system were established.The dynamic model of DTR UAV was established by using Newton-Euler formula.The dynamic model of VTOL and modal switching phase is finally established according to the different flight modals of the UAV.And both the models are simplified based on the assumptions.The VTOL attitude controller was designed using the classical quadrotor flight strategy and PID control method was used based on the established dynamic equations for the VTOL phase.The numerical result shows the fixed-point take-off was realized and the attitude was also stabilized.The backstepping method is used to stabilize the subsystem gradually and finally design a nonlinear controller that can achieve a stable transition of modal switching according to the strong coupled and underactuated characteristics for the modal switching phase.The simulation results demonstrate the effectiveness of the controller for the switching phase.Finally,the linear temporal logic(LTL)theory is used to plan the cruise mission for the tilt-rotor UAV.The flight environment model of the tiltrotor is established and converted into a scalable weighted switching system.The cruise mission is described by the LTL formula and converted into a Buchi automaton using the LTL2B A tool.The switching system and the Buchi automaton are made into Cartesian products to generate the Product automaton.The particle swarm optimization algorithm is used to optimize the path of the tilt-rotor UAV under flight constraints.Through simulation experiments,this scheme enables the tilt-rotor UAV to effectively complete the established cruise mission and maintain the stability of the attitude.