Dynamic Modeling And Controller Design Of Coaxial Tilt-rotor UAV

As a remotely controlled unmanned aerial vehicle,UAV can perform complex and danger-ous tasks and play an important role in civil,military and other fields.As missions become more diverse,demands on UAVs increase.The coaxial tilt-rotor UAV has the ability of vertical take-off and landing,hovering in the air and the ability to fly forward quickly.It has A pair of coaxial rotors that can be tilted forward and backward,and a single rotor is installed at the tail to balance the pitching moment.The complex structure also complicates the dynamic modeling,control allocation and motion control of the coaxial tilt-rotor UAV.This paper studies these issues.The main research work is as followsFirst of all,according to the three-dimensional model of the coaxial tilt-rotor UAV,the relationship between the force and moment received by the UAV in the body coordinate system and the input of the actuator is analyzed,and the control allocation matrix is deduced.Then the nonlinear dynamic model of the UAV is established based on the Euler-Lagrange equation,including the position dynamic model and the attitude dynamic model.Secondly,based on the nonlinear dynamic model,the backstepping position controller and the backstepping attitude controller are designed to realize the trajectory tracking control of the UAV without interference.On this basis,considering the gust of wind in actual flight,etc.Exter-nal disturbance will affect the attitude stability of the aircraft,so the backstepping sliding mode control is designed to improve the robustness of the control system,and an adaptive law is in-troduced to estimate the upper limit of the disturbance online.The simulation results show that the adaptive backstepping sliding mode control can make the UAV’s attitude tracking error still converge in the presence of limited disturbance,and has good robustness.Thirdly,in order to meet the diverse task requirements,a nonlinear H∞controller is de-signed based on the nonlinear attitude dynamic model of the coaxial tilt rotor to realize the attitude tracking of the UAV in the presence of disturbance,so that the L₂gain from disturbance signal to output signal is bounded,and the output is not sensitive to disturbance signal,which makes the control system have better robustness,and the performance indicator can also be adjusted according to different demands.The simulation results show the effectiveness and robustness of the nonlinear H∞controller.Finally,the structure of the coaxial tilt-rotor UAV experimental platform is introduced in detail,The backstepping position controller and nonlinear H∞attitude controller that have been verified by simulation are embedded into the real aircraft to conduct ground bench experiments and The actual flight experiments,the experimental results verify the effectiveness and good robustness of the controller.