The LPV Modeling Method Research In Transition Mode Of Tilt-rotor Unmanned Aerial Vehicle

The tilt-rotor unmanned aerial vehicle(UAV)has the characteristics of vertical takeoff and landing and hovering ability of multi-rotor aircrafts.And the tilt-rotor UAV also has the outstanding characteristics of fixed-wing aircraft’s long flight duration,high speed and high flight efficiency.It has become a hot spot in the research field of UAV platforms.The transition mode between the helicopter mode and the fixed-wing mode is a key process for full process flight of the tilt-rotor UAV.During the transition mode,the flight speed of the UAV changes greatly,and the dynamic characteristics also change nonlinearly with large parameter change.The conventional controller design method based on the simplified model is difficult to adapt to the structural changes of the aircraft and has poor anti-interference ability.In view of this,this paper takes the tilt-rotor UAV in the transition mode as the research object,and carries out the research on the LPV modeling and control of the tilt-rotor UAV.Based on multi-body dynamics model,the LPV approach can realize the adaptive adjustment of the control law with the tilting process,which lays the foundation for stable control of the modal conversion process.The main work includes:(1)Multi-body dynamics modeling of the tilt-rotor UAV.Based on the analysis of the structure of the tilt-rotor UAV,the body and the rotors are regarded as rigid bodies,and the multi-rigid motion coordinate systems are established.Then,the force analysis and torque analysis of each rigid body are used to establish the motion functions.By analyzing the constraint relationships between rigid bodies and eliminating the influence of restraining reaction force and restraining counter moment,finally,the multi-body dynamics model of the tilt-rotor UAV with independent variables is established.(2)Physical parameter measurement and aerodynamic parameter simulation analysis.Firstly,the weight and size parameters of the rigid bodies of the tilt-rotor UAV are obtained by the physical measurement methods,and the moment of inertia of the aircraft is measured by the complex pendulum method.Then the motors and the engine are tested by the power system tester to obtain the tension coefficients and the anti-torque moment coefficients of the system.Finally,the CFD simulation method is used to measure the aerodynamic coefficients and the aerodynamic derivatives.Therefore,the parameter measurement of the multi-body dynamics model of the tilt-rotor UAV is completed.(3)Establishment of the LPV model in the transition mode of the tilt-rotor UAV.The tilting angle is selected as the scheduling parameter,and the trimming calculation is carried out under the selected tilting angles to determine the tilting corridor of the tilt-rotor UAV.Based on the equilibrium points of the UAV under given tilt angles,the linear parameter-varying model of longitudinal motion is obtained by using the Jacobian linearization method.(4)Performance verification of linear parameter-varying model in the transition process of the tilt-rotor UAV.Based on the linear parameter-varying model of the tilt-rotor UAV,the robust H-infinite gain scheduling controller is designed and the feasibility of the method is verified by the simulation analysis of the tilting process.