Research Of Quadrotor UAV Flight Attitude Control

The quadrotor is a kind of six degree of freedom UAV, which can be used to take off and landing aircraft, its maneuverability is strong, the stability is high, the operation is simple and so on, which makes it very popular in the field of civil and military. But the quadrotor UAV is a typical system with strong coupling and nonlinear, it is easy to be disturbed by outside environment, which makes it difficult to accurately model, so, the control of the quadrotor UAV has become relatively difficult. In this thesis attitude control algorithms are designed,and the correctness and effectiveness of the proposed algorithm are verified by simulation experiments under the condition of the system parameter perturbation and external disturbance.The main contents of this paper include:(1) The establishment of the quadrotor UAV dynamic model. Firstly, The system structure and flight principle of the quadrotor UAV are analyzed. using Euler angles as description of the attitude derived coordinates of the carrier to the ground coordinate system transformation matrix. Finally, the nonlinear equations of the quadrotor UAV are derived from the Euler dynamic equation and the mass center motion.(2) The quadrotor UAV attitude backstepping adaptive control. The quadrotor UAV attitude controller is designed by backstepping method which based on Lyapunov stability criterion, and the adaptive control law is added to the backstepping method. The dynamic estimation model error and external disturbance are used to increase the robustness of the system. Finally, the validity of the model is verified by simulation experiments. The results show that the tracking error is large when the external torque disturbance is disturbed, and the control performance is better in rest time.(3) The quadrotor UAV attitude backstepping sliding mode control. The backstepping control and sliding mode control are combined to design the attitude controller of the quadrotor UAV. The sliding mode control can force the system to move in accordance with the "sliding mode" state trajectory, which can better solve the problem of controlling the system parameters and the system’s robustness. The results show that the system can solve precision of adaptive backstepping controller when the system is disturbed by the parameters and the external disturbance, but this controller has the problem of “chattering”.(4) The quadrotor UAV attitude L2 robust adaptive control. According to the mathematical model of the quadrotor UAV, the L2 robust controller is derived by using backstepping method, and the L2 robust control and adaptive control are combined, the adaptive control can dynamicly estimate external interference and enhance system robustness,then design the fitness function and use the improved differential evolution algorithm to optimize the parameters of the controller. The results show that when the system is disturbed by the parameters and the external disturbance, the system is robust and can solve the problems in above two methods.In this thesis, a nonlinear model of quadrotor UAV is established, and attitude controllers are designed, which provide an important theoretical basis for the future research of quadrotor UAV.