Control Research In Autonomous Landing Phase For A Fixed-wing UAV

The Unmanned Aerial Vehicle(UAV) is a kind of vehicle which is controlled by radio remote control and telemetry equipment for hand manipulation or airborne computer program for autonomous flight. Compared with manned aircraft, the UAV has characters of flexible maneuver ability, low requirement for takeoff and landing environment, strong survival ability, and UAV has become a hot spot in the field of aircraft research around the world. The whole working process of UAV includes launch, mission flight and recovery. The launch and flight technology of UAV have been relatively mature, but recycling is still a difficult problem in the development of UAV. This paper is a detailed study of the sample fixed-wing UAV’s autonomous landing process based on the summary of UAV recovery technology fields. The detail content includes dynamic modeling, flight performance analysis, autonomous landing strategy and route planning, controller design, system digital simulations and hardware in loop simulations.Wheeled autonomous landing has become the main way of recovery for the medium and large UAVs whose quality are more than 100 Kg. Wheeled autonomous landing is the progress of safe and smooth landing on the runway relying on navigation devices and flight control systems. Compared with wheeled autonomous landing of manned vehicle, the wheeled landing of UAV reduces the requirements for the runway. Compared with other landing ways of UAV, the wheeled landing has small overload which protects the body and machine equipment, shorten the preparation time of another takeoff and prolong the life.The aerodynamic parameters change greatly during landing flight near the ground, the location of the landing point is affected by the wind. The UAV should slow down and stop after touching the ground, ground taxiing could reduce the requirement for runway width if taxiing along the ground center line. Smooth of autonomous landing, precision of landing position and efficiency of lateral deviation correction are all put forward strict requirements for flight control system. Ground velocity, sinking rate and lateral deviation are the control targets in this paper, longitudinal internal model controller for landing flight, lateral internal model controller for landing flight and lateral internal model controller for ground taxiing are designed based on the internal model control(IMC) theory and the controllers are checked by system digital simulations. Considering the problem of the interaction between response characteristic and robust characteristic of IMC, adaptive internal model controller(AIMC) is proposed based on adaptive theory. Longitudinal adaptive internal model controller for landing flight, lateral adaptive internal model controller for landing flight and lateral adaptive internal model controller for ground taxiing are designed again, the self-tuning of the filtering parameters and the estimation of the controlled model parameters can improve dynamic performance and robustness of the system at the same time. System autonomous landing flight digital simulations indicate the landing accuracy achieves the scope of 30 m of forward or backward direction and 3m of lateral direction in the conditions of 6m/s of headwind or downwind and 10m/s of lateral wind. System ground taxiing digital simulations show the lateral position error is less than 1m and the heading error is less than 5° in the conditions of initial offset of 2m of lateral position and 5° of heading angle, or 8m/s of lateral wind. In the end, hardware in loop simulations are carried out, system digital simulations results are reproduced, system integrity and harmony are verified.