Research And Design Of Flight Control Method For Unmanned Aerial Vehicles

The vigorous development of the industry of unmanned aerial vehicles(UAVs)is an important manifestation of the rise of both China and the aviation industry of China.UAVs have begun to be widely used in some parts of military,commercial,industrial,agricultural and daily activities.The quadrotor unmanned aerial vehicle is the most typical one of various types of UAVs.However,with the deepening of the popularity of UAVs,the severity of accidents caused by their failure will be amplified,especially in the controller failure.Therefore,related topics such as controller fault diagnosis and structural health management have received much more attention.The quadrotor UAV is taken as the research object in the research where the attitude control is regarded as the core carried out in this paper,to provide data samples in normal flight for accurate diagnosis results,and improve the controller to fundamentally reduce the chance of controller failure that can provide a guarantee for the stable operation of UAVs.For the second-order nonlinear,high-coupled,underactuated system of the quadrotor,the dynamics and control model are firstly established with the Newton-Euler equation.Then the backstepping controller with secondary PID method,which is developed based on the traditional backstepping control method is put forward.Next the backstepping sliding mode controller is developed based on the former backstepping controller.Finally,the fractional-order backstepping sliding mode controller is designed by combining the fractional-order calculus theory and the method used before.All the three controllers have been proved to be stable and effective under Lyapunov theorem and MATLAB/SIMULINK simulation experiments.The relationship among them and the performance of each three controller are also compared and analyzed in detail in this paper.In the simulation experiment,the controlled states can reach the desired value within two seconds and remain stable under the backstepping controller.Besides,the value of the feature point at stable period of the backstepping height controller is approximately equal to the actual gravity of the UAV.So it can be told that the controller is fast,accurate,stable and in line with the actual characteristics.In the anti-disturbance experiment,the state deviation caused by the disturbance can be reduced up to 95% relative to the backstepping controller under the same disturbance condition by adjusting the coefficient of the sign function of the backstepping sliding mode controller.It shows that the introduction of the sliding mode control method can indeed improve the controller's robustness to disturbances.While the response speed of the controller can be increased by 25%,and the system chatter caused by the sliding mode control method can almost be suppressed by 100% under the fractional-order saturation function backstepping sliding mode controller,due to the introduction of fractional-order saturation function.It further improves the performance of the controller.In the final position tracking experiment,the errors of direction x and y which are strongly coupled can be limited to 5%,and the error of direction z which is weekly coupled can be limited to 0.3% under the fractional-order saturation function backstepping sliding mode flight control system designed in this paper.It proves the effectiveness and correctness of this system.