Autonomous Takeoff And Landing Control Of Fixed-wing UAV Based On ADRC

With the rapid development of electronic technology and the richness and perfection of control theory,UAVs have gradually integrated into people’s lives.Compared with manned aircraft,small fixed-wing UAVs have superior maneuverability,more compact size and low price,so they have been used more and more in military and civilian applications,such as battlefield reconnaissance,surveillance,surveying and mapping,traffic management and so on.The working process of a fixed-wing UAV can be divided into three phases,launch segment,mission flight,and recovery segment.The autonomous flight technology of fixed-wing UAVs flying on air routes is relatively mature,but the process of autonomous take-off and landing is still difficult.Since the process of take-off and landing is more complicated,and UAVs are easy to be disturbed by gusts,crosswinds and ground effects,the higher requirements are difficult points for the UAV to achieve autonomous control.The quality of the fixed-wing UAV’s autonomous take-off and landing process determines the quality of the aircraft’s mission.So,the autonomous takeoff and landing process of small fixed-wing UAVs are carried out specific research in this thesis.In this thesis,the nonlinear model of the airborne flight segment and the ground-slip segment is established according to the different force conditions of the fixed-wing UAV in the air and ground.And the model is linearized by small perturbation theory.And simplify the transfer function of the longitudinal movement of the UAV,laying the foundation for the following model identification and controller design.The control strategy is crucial to the safety of the autonomous take-off and landing process of the UAV.Therefore,control strategy is designed in this thesis.The autonomous take-off process is divided into three stages,three-wheeled run,two-wheeled run and off-ground climb.The autonomous landing process is divided into four stages,approach flight,sliding flight,pull-up and ground-slip deceleration.And control law of autonomous takeoff and landing are designed.Combined with the prototype,the autonomous control process of the take-off segment is designed,and the landing trajectory and specific parameters are designed for the landing segment.Since the aerodynamic parameters of the UAV are difficult to measure,the method of model identification to identify transfer function model of the longitudinal channel is used in this thesis.To improve the control performance of the takeoff and landing and improve the ability of resisting disturbance,an auto disturbance rejection controller based on the takeoff and landing process is designed in this thesis.PID controller and active disturbance rejection controller are designed for the identified model and simulated by Simulink.It is verified that the auto disturbance rejection controller has stronger anti-interference ability.Finally,autonomous takeoff and landing flight experiment is conducted in this thesis.Based on the subject flight engineering hardware platform,the software of the autonomous takeoff and landing flight control system is designed.And the reliability of the software design is verified based on the X-plane semi-physical simulation platform.Finally,the autonomous takeoff and landing flight experiments of the prototype are carried out,and the control effects of the three processes of autonomous takeoff,air flight and landing are analyzed.It is verified that designed strategy and controller of the autonomous takeoff and landing in this thesis have good control effects.