Research On Flight Control Of Small Unmanned Aerial Vehicle Based On Backstepping

With the rapid advancement of modern science and technology,the miniaturization of(UAV)unmanned aerial vehicle has become more and more common.As a kind of UAV,the small-rotor UAV can achieve low-altitude,low-speed,hovering and heading remains unchanged flight performance.In addition,it can complete the corresponding tasks in a small area and space.It is due to the superior flight performance that the small-rotor UAV has been widely developed and applied in both agricultural and military fields.However,the small-rotor UAV is a strictly nonlinear,underactuated and strongly coupled system,and there is unmodeled dynamics in the system model.In addition,the system may be affected by actuator failure or external uncertain interference.Not only that,the shape and structure of the small-rotor UAVs vary widely,and their dynamic characteristics are extremely complex and uncertain.These characteristics bring great difficulties and challenges to the research of the small-rotor UAV.In this thesis,an in-depth theoretical study on the flight control algorithm problem of a small rotorcraft UAV is carried out,and further experimental verification is carried out.First,the Newton-Eulerian equation is applied to describe the dynamic model of a small-rotor UAV.Second,the nonlinearity and the uncertainty of the model of the small-rotor UAV system,and the actuator failure are studied and analyzed.Then,an adaptive control method based on Backstepping is proposed by using fuzzy logic system.It is proved by Lyapunov stability theory that all signals in the closed loop system of small-rotor UAV are semi-globally uniformly ultimately bounded(SGUUB).The fuzzy logic system is used to approximate the uncertainty in the system model and to deal with the dead zone problem of the actuator,so as to improve the flight performance and tracking accuracy of the small-rotor UAV.A three-degree-of-freedom(3-DOF)helicopter experimental platform is further used to verify the proposed control algorithm.In order to reduce the conservativeness of the above methods and analyze the underactuated and strongly coupled characteristics in the small-rotor UAV system,this thesis continues to use the fuzzy logic system to propose an adaptive control method with disturbance observer based on Backstepping technology.The disturbance observer is used to observe the external uncertain disturbances of the small-rotor UAV system and to compensate the estimation error caused by the use of the fuzzy logic system,thereby improving the robustness of the small-rotor UAV system.In addition,command filtering techniques will be used to deal with the negative impact of the use of Backstepping technology.A small quadrotor UAV was used to verify the effectiveness of the proposed control method.Finally,by analyzing and comparing the experimental results,the proposed control method can control the flight of the small-rotor UAV and improve the robustness of the system.